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The Journal of Clinical Endocrinology & Metabolism
Copyright © 2000 by The Endocrine Society
Vol. 85, No. 7
Printed in U.S.A.
Molecular Analysis of the Pendred’s Syndrome Gene and
Magnetic Resonance Imaging Studies of the Inner Ear
Are Essential for the Diagnosis of True
Pendred’s Syndrome*
LAURA FUGAZZOLA, DEBORAH MANNAVOLA, NADIA CERUTTI,
MOHAMED MAGHNIE, FABIO PAGELLA, PAOLO BIANCHI, GIOVANNA WEBER,
LUCA PERSANI, AND PAOLO BECK-PECCOZ
Institute of Endocrine Sciences, University of Milan (L.F., D.M., L.P., P.B.P.), Istituto Clinico
Humanitas (L.F., D.M., P.B.), Istituto Auxologico Italiano IRCCS (L.P.) and Ospedale Maggiore
IRCCS (P.B.P.), 20122 Milan; Departments of Internal Medicine (N.C.), Pediatric Sciences (M.M.), and
Otorhinolaryngology (F.P.), Policlinico S. Matteo IRCCS, University of Pavia, 27100 Pavia; and Third
Pediatric Clinic, HS Raffaele (G.W.), 20142 Milan, Italy
ABSTRACT
Pendred’s syndrome is a combination of congenital sensorineural
hearing loss and iodine organification defect leading to a positive
perchlorate test and goiter. Although it is the commonest form of
syndromic hearing loss, the variable clinical presentation contributes
to the difficulty in securing a diagnosis. The identification of the
disease gene (PDS) prompts the need to reevaluate the syndrome to
identify possible clues for the diagnosis. To this purpose, in three
Italian families presenting with the clinical features of Pendred’s
syndrome, the molecular analysis was accompanied by full clinical,
biochemical, and radiological examination. A correlation between ge-
I
N 1896, VAUGHAN Pendred first described a syndrome
combining congenital deafness and goiter (1). The definition of Pendred’s syndrome was further delineated in 1958,
when an iodine organification defect of thyroid hormone
synthesis was identified by means of a perchlorate discharge
test (2). The disease has an autosomal recessive pattern of
inheritance (3), and on the basis of clinical studies, it accounts
for 4 –7% of congenitally deaf children, being the most common cause of congenital deafness, which affects 1 in 1000
newborns (4). However, the incidence of the syndrome was
evaluated on the basis of clinical studies that were frequently
incomplete and underscored the fact that the phenotype of
patients with Pendred’s syndrome differs greatly among
families and even within the same family, leading to pitfalls
in the diagnosis (5–7). Indeed, goiter does not appear to be
an essential prerequisite for the diagnosis of Pendred’s syndrome, being absent in almost 50% of reported cases (3, 6,
8 –10). If present, it varies from a slight enlargement to a large
multinodular goiter, probably in relation to different degrees
Received November 15, 1999. Revision received March 22, 2000. Accepted March 29, 2000.
Address all correspondence and requests for reprints to: Paolo BeckPeccoz, M.D., Institute of Endocrine Sciences (Pad. Granelli), Ospedale
Maggiore IRCCS, Via F. Sforza 35, 20122 Milan, Italy. E-mail:
[email protected].
* This work was supported in part by grants from MURST (Rome,
Italy).
notype and phenotype was found in the only patient with enlargement
of vestibular aqueduct and endolymphatic duct and sac at magnetic
resonance imaging. This subject was a compound heterozygote for a
deletion in PDS exon 10 (1197delT, FS400) and a novel insertion in
exon 19 (2182–2183insG, Y728X). The present study demonstrates for
the first time the value of the combination of clinical/radiological and
genetic studies in the diagnosis of Pendred’s syndrome. The positivity
of a perchlorate discharge test and the malformations of membranous
labyrinth fit well with the recent achievements on the role of pendrin
in thyroid hormonogenesis and the maintenance of endolymph homeostasis. (J Clin Endocrinol Metab 85: 2469 –2475, 2000)
of iodine deficiency (11). Most patients are euthyroid, independently of the presence of goiter, but some show hypothyroidism, in general subclinical (6, 12). Thyroglobulin levels are elevated in the majority of tested cases (10, 13–15).
The onset of sensorineural hearing loss (SNHL) is generally prelingual (5), even if the course can be fluctuating and
progressive (3, 12, 14), leading to various degrees of deafness.
The first malformation associated with hearing loss was the
so-called Mondini cochlea (8, 16), in which the cochlea, due
to the deficiency of the interscalar septum, is constituted by
a normal basal turn and the upper two turns forming a
common cavity. However, more detailed and recent studies
show that this bony malformation is a common, but not
constant, feature of Pendred’s syndrome, thus drawing attention to the diagnostic value of malformations of the vestibular aqueduct (VA), endolymphatic duct (ED), and endolymphatic sac (ES) (6, 9). The VA is a bony canal that
extends from the vestibule to the petrous bone. The VA
enlargement is associated with fluctuating and sometimes
progressive SNHL (17) and is known as the most common
form of inner ear abnormality in the hearing-impaired population (18). It is present in about 80% of patients with a
clinical diagnosis of Pendred’s syndrome and is often associated with other hearing losses (19 –23), in particular the
large VA syndrome (LVAS). Through this bony canal courses
ED, which is a part of the membranous labyrinth and connects the sensory end organs for hearing (cochlea) and equi-
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FUGAZZOLA ET AL.
librium (vestibular apparatus) to the ES. The lumen of the
membranous labyrinth is filled with endolymph, a K⫹-rich,
Na⫹-low, positively polarized, hyperosmotic, protein-rich
fluid. The homeostasis in membranous labyrinth and the
secretion and resorption of endolymph are maintained and
regulated by the ED and ES cells (24). The recent application
of thin section high resolution magnetic resonance imaging
(MRI), showed ED and ES enlargements in 100% of patients
with a clinical, but not molecularly proved, diagnosis of
Pendred’s syndrome as well as with LVAS (9, 25, 26).
The disease gene, named PDS, has been mapped to chromosome 7q22-q31.1 and was fully characterized in 1997 (27).
PDS complementary DNA (cDNA) contains an open reading
frame of 2343 bp and encompasses 21 exons. By Northern
blot analysis it has been found to be highly expressed in the
thyroid, whereas weak signals have been observed in adult
and fetal kidney as well as in fetal brain (27). PDS expression
was also found in a human fetal cochlear cDNA library and
more recently in mouse endolymphatic duct and sac (27, 28).
The protein encoded by the PDS gene (pendrin) is predicted
to consist of 780 amino acids (molecular mass, 86 kDa) and
to contain an intracellular N-terminus, 11 transmembrane
domains, and an extracellular C-terminus. The initially hypothesized role of pendrin as a sulfate transporter has not
been confirmed by recent studies (29, 30). Indeed, pendrin
functions as a sodium-independent transporter of chloride
and iodide. In the last 2 yr, more than 30 different PDS
mutations have been found in Pendred families from different countries (11, 14, 27, 31–33) and more recently also in 7
LVAS families (34 –36).
The aim of the present study was to investigate the genotype-phenotype correspondence in 3 Italian families referred to our institution with a clinical diagnosis of Pendred’s
syndrome. In fact, the genetic studies reported in the literature are generally lacking a full clinical and radiological
evaluation (27, 31, 32); on the other hand, the specificity of
the inner ear malformations is not genetically confirmed (9,
25, 26). Furthermore, as PDS mutations have been described
in the literature with different nomenclatures, either starting
from the first nucleotide of exon 1, which is noncoding, or
from the ATG in exon 2, we unified them under the recent
nomenclature recommendations (37) to reveal possible clustering and/or “hot spot” regions.
Subjects and Methods
We studied five patients from three unrelated Italian families with
nonconsanguineous parents referred to us with a clinical diagnosis of
Pendred’s syndrome (Table 1). The affected members showed childhood
deafness due to a sensorineural defect and goiter, with positive perchlorate discharge test.
Family A comprises three affected brothers, 25 (female), 32 (female),
and 31 yr old (male) at the time of the present investigation, identified
as A1, A2, and A3, respectively. The affected member of family B is a
16-yr-old male (B1), and in family C, the proband is a 28-yr-old female
(C1).
The three brothers in family A, euthyroid at the neonatal screening,
developed goiter and hypothyroidism during the first months of life.
They began thyroid hormone substitutive therapy at 2– 4 months of age.
Patient B1 developed hypothyroidism without evidence of goiter during
the childhood, and l-T4 treatment was started at 5 yr of age. In patient
C1, goiter appeared soon after birth. Thyroid hormone levels constantly
remained in the normal range, whereas thyroid volume progressively
increased despite the administration of l-T4 therapy at TSH-suppressive
doses. Total thyroidectomy was performed at the age of 16 yr due to
esthetic problems. Histological examination showed a colloid goiter
without signs of malignancy.
In all patients the sensorineural hearing loss was diagnosed during
childhood. No patient had a history of vertigo. Patient A2 underwent
bilateral myringoplasty at 12 yr of age due to chronic otitis media. The
three families came from different Italian regions with moderate iodine
deficiency.
Clinical studies
Thyroid examination. Serum TSH, free T4, and free T3 levels were measured with the Axsym System (Abbott Laboratories, Abbott Park, IL),
thyroglobulin (Tg) was measured using Delfia human Tg (Pharmacia &
Upjohn, Inc./Wallac Oy, Turku, Finland), anti-Tg and antithyroperoxidase antibodies were determined using a Liaison Kit (Byk-Sangtec Diagnostica, Dietzenbach, Germany). Thyroid ultrasonography was performed using an AU5 Esaote (Genova, Italy) instrument with a 7.5-MHz
probe. A perchlorate test was carried out in all affected members; 2 h
after the administration of 7.4 megabecquerels 131I, 1 g KClO4⫺ was
administered, and the discharge was measured after 1 h. The test was
considered positive for a discharge rate of more than 10%.
Audiological examination. Hearing loss was assessed by pure tone audiometry. In each ear, the degree of hearing loss was classified by the pure
tone average at 0.5, 1, and 2 kHz as normal [0 –20 decibels (dB)], mild
(20 – 40 dB), moderate (40 – 60 dB), severe (60 – 80 dB), or profound
(⬎80 dB).
Radiological examination. To assess deficiency in the bony interscalar
septum of the cochlea (Mondini deformity) and to evaluate the VA, high
resolution computed tomography (CT) of temporal bones in the coronal
and axial planes was performed (1-mm contiguous sections). The vestibular aqueduct was considered enlarged when its diameter at the
midpoint between the common crus and the external aperture was 1.5
mm or more on thin CT sections (22).
High resolution, fast spin echo (FSE) T2-weighted MRI was performed (in axial and coronal planes) to study the membranous labyrinth
and, in particular, the ED and ES. The size of the normal ED at its
midpoint ranges from not visible to 1.4 mm (25). ES is rarely seen in
normal subjects despite high quality FSE MR images, and it is considered
enlarged when it is more than 2.5 mm (9, 25, 26). All of the images were
photographed individually and as a three-dimensional composite.
TABLE 1. Summary of clinical and molecular features of the five patients studied, all from nonconsanguineous families
Family
Age
(yrs)
A1
A2
A3
B1
C1
32
31
25
15
28
a
Thyroid
function
Hypothyroid
Hypothyroid
Euthyroid
IQa
Goiter
(mL)
80
70
55
90
92
12
25
50
8
45
131
I discharge after
perchlorate (%)
70
50
40
50
40
Sensorineural
hearing loss
Mild
Moderate
Moderate
Moderate
Severe/profound
WISC-R test.
Enlarged vestibular aqueduct (EVA).
c
Enlarged endolymphatic duct (EED) and enlarged endolymphatic sac (EES).
b
Mondini
cochlea
EVAb
EED and
EESc
PDS
mutations
No
No
No
No
No
No
No
Yes
No
Yes
No
Yes
GENETIC AND MRI STUDIES IN PENDRED’S SYNDROME
Genomic DNA analysis. DNA was extracted from whole blood by standard methods. All 21 PDS exons were amplified using primers flanking
each exon (27). Samples were subjected to 5-min denaturation at 98 C,
followed by 35 3-step cycles (55 C for 1 min, 72 C for 2 min, and 94 C
for 1 min) and 72 C for 10 min in a TouchDown Thermal Cycler (Hybaid,
Middlesex, UK). PCR products were directly sequenced after removal
of unincorporated deoxy-NTPs and primers using a GFX PCR DNA
purification kit (Amersham Pharmacia Biotech, Uppsala, Sweden). An
aliquot of 3–10 ng/100 bp of purified DNA and 3.2 pmol of either the
forward or reverse primer were used in standard cycle sequencing
reactions with ABI PRISM Big Dye terminators and run on an ABI
PRISM 310 Genetic Analyzer (PE Applied Biosystems, Foster City, CA).
The cycle-sequencing conditions consisted of 25 cycles of 96 C for 30 s,
50 C for 15 s, and 60 C for 4 min. One sequence read from each direction
across the entire coding region and including intron-exon boundaries
was obtained for each patient.
Analysis and revision of PDS gene mutations. All mutations reported previously have been uniformly classified according to the recent nomenclature recommendations, with the A of the ATG of the initiator Met
codon denoted as ⫹1 (37). Their localization on pendrin protein has been
analyzed, and either the involvement of point mutation-prone sites
(such as GC-rich regions or CpG dinucleotides) on cDNA or the presence
of cluster regions has been evaluated.
Results
Thyroid examination
After 2 months of l-T4 withdrawal, the three brothers of
family A showed severe hypothyroidism, with low free thyroid hormone levels and TSH values of 79 mU/L (patient
A1), 86 mU/L (patient A2), and 53 mU/L (patient A3). Serum
Tg levels on and off l-T4 were 8.4 and 290 ␮g/L in patient
A1, 550 and 11,380 ␮g/L in patient A2, 206 and 1616 ␮g/L
in patient A3. Patient B1 showed, before starting treatment,
very low free T3 and free T4 levels with high TSH levels (756
mU/L). Tg levels were not measured. Patient C1 before thyroidectomy had normal thyroid hormone levels, with TSH at
the upper limit of normal range (4.1 mU/L; normal range,
2.5– 4.5; Table 1). Anti-Tg and antithyroperoxidase (antiTPO) autoantibodies were negative in all cases.
Patients B1 and C1 have normal intelligence, whereas the
three brothers of family A have low intelligence (according
to WISC-R test; Table 1) (38).
Ultrasound examination showed a small simple goiter
(12-mL volume) in patient A1, a multinodular goiter (25 mL)
in patient A2, and a large multinodular goiter (50 mL), with
FIG. 1. High resolution CT scan of the
petrous temporal bones (axial view) in
patient C1. A, The vestibular aqueduct
is markedly enlarged, with a diameter
in the right ear of 2.9 mm at the midpoint between the common crus and the
external aperture (indicated by the arrow). B, Normal vestibular aqueduct
(1-mm diameter) in a normal subject
(indicated by the arrow).
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tracheal deviation in patient A3. Patient B1 had a normal
thyroid, whereas in patient C1 a large multinodular goiter (45
mL) was documented before total thyroidectomy (Table 1).
In all screened subjects, a positive perchlorate test was
found, with a discharge ranging from 40 –70% (Table 1).
Audiological examination
The otological examination revealed mild sensorineural
hearing loss in patients A1 and A2. Patient A3 and B1 showed
moderate hearing loss, and in patient C1 the degree of sensorineural hearing loss was severe in the right ear and profound in the left ear (Table 1).
Radiological examination
In the three members of family A and in patient B1 no
radiological malformations were found. In particular, no
Mondini cochlea or enlarged vestibular aqueduct (EVA)
were seen at CT scan, and no membranous labyrinth alterations were detected at FSE MRI (Table 1). Patient C1 had no
cochlear malformations, whereas an EVA was documented
bilaterally (2.9 mm right ear, 2.6 mm left ear; Fig. 1). At FSE
MRI, an enlarged ES (5 mm) and an enlarged ED (⬎2 mm)
were revealed in both ears (Fig. 2).
Mutation analysis
PDS sequence analysis of the entire 1–20 exons and of the
coding portion of exon 21 did not show any mutation in the
three members of family A and in patient B1. In patient C1
a compound heterozygous pattern was found: a single base
pair deletion at nucleotide 1197 in exon 10 (1197delT) and a
single base pair insertion at nucleotide 2182 in exon 19 (2182–
2183insG). In particular, the exon 10 deletion leads to a frame
shift at codon 400 (FS400) with the creation of a stop codon
at 431, and the G insertion of exon 19 results in a stop codon
(Y728X; Fig. 3). The FS400 mutation is located in the seventh
transmembrane domain of the protein, which will be deleted
for two and a half transmembrane domains and the entire
COOH-terminus, whereas the exon 19 insertion falls in the
final portion of extracellular C-terminus.
The mother of the patient was found to harbor the FS400
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FIG. 2. High resolution FSE T2weighted MRI scan of the petrous temporal bones in patient C1. Axial contiguous 1-mm images have been summated
into a single composite three-dimensional image. A, Endolymphatic duct and
sac are clearly enlarged in both ears with
diameters of more than 2 and 5 mm, respectively. The enlarged endolymphatic
sac (right ear) is indicated by the arrow.
B, MRI section in a control subject, where
the normal endolymphatic duct and sac
are difficult to identify.
FIG. 3. Sequence analysis of exons 10
and 19 in patient C1. A, The 1197 T
deletion in exon 10 is shown (arrow); the
resulting frame shift (FS400) with stop
codon at 431 is reported in the right part
of the figure. B, The G insertion between nucleotides 2182 and 2183 in
exon 19 (novel mutation) is shown (arrow); the resulting frame shift at codon
728 creates a stop codon (Y728X).
mutation. Her father and the two brothers refused to be
investigated.
Analysis and revision of PDS gene mutations
Until now, 35 different mutations in the PDS gene have
been described (11, 14, 27, 31–33), numbered either starting
from ATG in exon 2 or from the first nucleotide of exon 1. In
Fig. 4, all mutations are uniformly classified according to the
recent nomenclature recommendations and reported with
their exon distribution, including those associated with
LVAS (34, 36). Two mutations have been found in both
Pendred and LVAS families (32, 34). In Fig. 5, the position of
each mutation along the putative pendrin structure is shown.
The majority of the mutations (21 of 35, 60%) are missense
mutations localized in the 3rd, 4th, and 10th transmembrane
domains (n ⫽ 4); in the 3rd and 5th extracellular loops (n ⫽
5); in the 4th intracellular loop (n ⫽ 3); and in the COOHterminus (n ⫽ 9). Frame-shift mutations are a minority (14 of
35, 10 deletions and 4 insertions) and are localized in the 1st,
7th, 9th, and 10th transmembrane domains (5 deletions and
1 insertion); in the 1st and 3rd extracellular loops (1 deletion
and 1 insertion); in the 4th intracellular loop (1 deletion); and
GENETIC AND MRI STUDIES IN PENDRED’S SYNDROME
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FIG. 4. Distribution of all known PDS mutations along the open reading frame of the gene transcript. All but exons 1 and 21 are drawn to scale.
Several of the mutations reported have been observed in multiple families. Nucleotide numbers refer to the cDNA where the A of the ATG
initiation codon is denoted nucleotide ⫹1 and are in accordance with recent nomenclature recommendations (35). Mutations reported in the
literature with a numbering starting from the first nucleotide of exon 1 have been named again starting from ATG. The triangles indicate
mutations described in LVAS families; diamonds show mutations found in both Pendred and LVAS families. Arrows indicate intronic mutations.
The mutations described in the present paper are shown in bold.
Only four mutations (12%) were transitions in CpG
dinucleotides that are frequent sites of point mutations in
several other genes (39), and there were no mutations in
G-C-rich regions (defined as four or more consecutive Gs or
Cs) have been recorded.
Discussion
FIG. 5. Schematic representation of pendrin protein and the approximate position of mutations found in Pendred (circles) and LVAS
(triangles) families. Diamonds indicate mutations associated with
both Pendred and LVAS families. Black circles indicate the mutations
described in the present work. Numbers correspond to those indicated
in Fig. 4. As the effects of the two intronic splice site mutations on the
pendrin protein are not yet known, they are not included in this figure.
in the COOH-terminus (3 deletions and 2 insertions). Two
mutations occur in an intronic sequence (first nucleotide of
intron 7 and first nucleotide of intron 8), thus affecting the
splice donor sites. This analysis suggests that there is no
clustering in any particular domain of the PDS gene, even if
40% of the mutations are localized in the C-terminus of
pendrin.
The present study demonstrates for the first time the value
of the combination of clinical/radiological and genetic studies in the diagnosis of Pendred’s syndrome. Although in all
affected members from three unrelated Italian families, the
diagnosis of Pendred’s syndrome was based on classical
signs such as congenital sensorineural hearing loss associated with a positive perchlorate test, PDS mutations were
found in the only patient (C1) harboring malformations of
the inner ear. In this patient, a compound heterozygosity
pattern with an already described deletion in exon 10
(1197delT, FS400) and a novel mutation in exon 19 (2182–
2183insG, Y728X) was found; both mutations led to a truncate protein. The radiological examination showed bilaterally a wide enlargement of vestibular aqueduct on CT and of
endolymphatic duct and sac on MRI. It is worth noting that
the patient had a profound sensorineural hearing loss, confirming the existence of a correlation between the degree of
enlargement of the ES and the severity of the deafness (25),
and suggesting that the phenotypic spectrum of Pendred’s
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FUGAZZOLA ET AL.
syndrome associated with mutations in the PDS gene includes hearing impairment of a severe degree.
On the basis of these data we propose to redefine the
diagnostic criteria of Pendred’s syndrome, taking into account the recent achievements concerning the expression and
the putative role of pendrin. At the thyroid level, the consequence of an impaired pendrin function is the deficient
organification of iodide, probably due to the lack of iodide
transport across the apical membrane, where the protein has
been recently immunolocalized (40). The accumulation of
iodide into the thyroid cells leads to its discharge in response
to perchlorate administration, rendering such a test essential
to differentiate Pendred’s syndrome from nonsyndromic
hearing losses. At the inner ear level, a defect in chloride
transport could lead to an altered endolymph composition,
resulting in damage of the neuroepithelium and enlargement
of the membranous labyrinth structures with an osmotic and
toxic mechanism (41). As ED and ES continue to mature until
the age of 4 yr, their enlargement could lead in some cases
to an alteration of the surrounding bony structures, such as
the vestibular aqueduct and the cochlea. In accordance with
recent clinical studies (9, 25, 26), these findings underline the
higher diagnostic value of membranous labyrinth malformations compared to those of both Mondini cochlea and
enlarged vestibular aqueduct, which are recorded in about
20% and 80% of Pendred patients, respectively. Therefore,
the MRI study of the membranous labyrinth malformations,
along with perchlorate discharge test, should be performed
as primary examinations when Pendred’s syndrome is suspected. Finally, Qvortrup and co-workers (41) suggested that
ES in the rat resembles a thyroid follicle with a stainable
colloid substance occupying the lumen, and the chief cells of
the sac functioning like the follicular cells of the thyroid,
being able to synthesize, secrete, absorb, and digest proteins.
Besides this intriguing similarity, the recent findings of PDS
expression in both ED and ES (28) and the putative role of
pendrin in the maintenance of the endolymph homeostasis,
may explain why a single protein impairment can alter the
function of these two very different organs.
Similar to the findings we recorded in the two families
without PDS gene mutations, Coyle and co-workers (31)
recently reported eight families and seven sporadic cases
with a clinical diagnosis of Pendred’s syndrome based on the
association of congenital SNHL and positive perchlorate test,
but without PDS mutations or harboring only one PDSmutated allele. Mutations in regulatory or intronic sequences
of the PDS gene or involvement of other genes or interacting
genes may explain the above findings, especially considering
that the list of loci responsible for syndromic and nonsyndromic deafness continues to grow (42). Nonetheless, as Pendred’s syndrome appears to be a monogenic disease, although locus heterogeneity cannot be entirely excluded, and
no malformations of the membranous labyrinth have been
recorded in the two PDS-negative families described here, a
diagnosis based only on clinical ground (SNHL, goiter, positive perchlorate test) is no longer tenable. The differential
diagnosis should be focused on other diseases leading to
positive perchlorate test, such as other iodide organification
defects (TPO gene, other genes?) or Hashimoto’s thyroiditis.
Although the clinical features of our PDS-negative patients
at the thyroid level could be consistent with the above disorders, the congenital SNHL has never been described in
patients with TPO defects or in hypothyroid patients with
Hashimoto’s thyroiditis. Therefore, the diagnosis of true Pendred’s syndrome should be confined to patients presenting
with the classic clinical features along with positive perchlorate test, malformations of the inner ear, and PDS mutations with a homozygous or composite heterozygous
pattern.
The analysis of cDNA and protein localization for the 35
known PDS mutations unified under a unique nomenclature
(37) reveals no clustering in any particular domain of the PDS
gene, although the great majority of mutations (63%) are
located in the second half of the protein. The exon 10 frame
shift has been described, as 1421delT, in 3 Arabian families
living in Northern Israel and in 1 family from Lebanon (27,
32). Our findings confirm that FS400 is a common mutation,
although not restricted to the Middle East Arab population
(32).
Finally, no differences in the protein localization or type of
the mutation were seen among the cases reported as Pendred’s syndrome and those with a diagnosis of nonsyndromic LVAS, which lacks any thyroid involvement, as demonstrated by negative perchlorate test (34). It is worth noting
that recent studies demonstrate that the enlargement of ED
and ES are constant features of LVAS (26). Thus, it is tempting to speculate that PDS mutations are associated with a
variable phenotypic spectrum, not necessarily comprising
thyroid abnormality, but always characterized by membranous labyrinth malformations. At present, the genotypephenotype correspondence exists only in patients with alterations in the inner ear structures. High resolution CT and
MRI studies are thus mandatory to correctly diagnose Pendred’s syndrome and must be performed before engaging in
PDS genetic analysis.
Acknowledgments
We thank Drs. Luca Balzarini and Giuseppe Di Giulio for expert
advice in interpreting CT and MRI imaging and Mrs. Pasquala Ragucci
and Dr. Fabio Grizzi for skillful technical assistance.
References
1. Pendred V. 1896 Deaf-mutism and goiter. Lancet. 2:532.
2. Morgans ME, Trotter WR. 1958 Association of congenital deafness with goitre:
the nature of the thyroid defect. Lancet. 1:607– 609.
3. Fraser GR. 1965 Association of congenital deafness with goitre (Pendred’s
syndrome). Hum Genet. 28:201–249.
4. Gorlin RJ. 1995 Genetic hearing loss associated with endocrine and metabolic
disorders. In: Gorlin RJ, ed. Hereditary hearing loss and its syndromes. New
York: Oxford University Press; 337–339.
5. Fraser GR, Morgans ME, Trotter WR. 1960 The syndrome of sporadic goitre
and congenital deafness. Q J Med. 29:279 –295.
6. Reardon W, Coffey RA, Phelps PD, et al. 1997 Pendred syndrome–100 years
of underascertainment? Q J Med. 90:443– 447.
7. Vaydia B, Coffey R, Coyle B, et al. 1999 Concurrence of Pendred syndrome,
autoimmune thyroiditis, and simple goiter in one family. J Clin Endocrinol
Metab. 84:2736 –2738.
8. Johnsen T, Jorgensen MB, Johnsen S. 1986 Mondini cochlea in Pendred’s
syndrome. Acta Otolaryngol. 102:239 –247.
9. Phelps PD, Coffey RA, Trembath RC, et al. 1998 Radiological malformations
of the ear in Pendred syndrome. Clin Radiol. 53:268 –273.
10. Sheffield VC, Kraiem Z, Beck JC, et al. 1996 Pendred syndrome maps to
chromosome 7q21–34 and is caused by an intrinsic defect in thyroid iodine
organification. Nat Genet. 12:424 – 426.
11. Kopp P, Karamanoglu Arseven O, Sabacan L, et al. 1999 Phenocopies for
deafness and goiter development in a large inbred Brazilian kindred with
GENETIC AND MRI STUDIES IN PENDRED’S SYNDROME
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
Pendred’s syndrome associated with a novel mutation in the PDS gene. J Clin
Endocrinol Metab. 84:336 –341.
Johnsen T, Larsen C, Friis J, Hougaard-Jensen F. 1987 Pendred’s syndrome:
acoustic, vestibular and radiological findings in 17 unrelated patients. J Laryngol Otol. 101:1187–1192.
Billerbeck AEC, Cavaliere H, Goldberg AC, Kalil J, Medeiros-Neto G. 1994
Clinical and molecular studies in Pendred’s syndrome. Thyroid. 4:279 –284.
Cremers CWRJ, Bolder C, Admiraal RJC, et al. 1998 Progressive sensorineural
hearing loss and a widened vestibular aqueduct in Pendred syndrome. Arch
Otolaryngol Head Neck Surg. 124:501–505.
Friis J, Johnsen T, Feldt-Rasmussen U, Bech K, Friis T. 1988 Thyroid function
in patients with Pendred’s syndrome. J Endocrinol Invest. 11:97–101.
Mondini C. 1791 Opuscula caroli mundini: anatomica surdi nati sectio. Bononiae: De Bononiensi Scientarium et Artium Instituto atque Academia Commentarii; vol 7:419 – 428.
Hill JH, Freint AJ, Mafee MF. 1984 Enlargement of the vestibular aqueduct.
Am J Otolaryngol. 5:411– 414.
Mafee MF, Charletta D, Kumar A, Belmont H. 1992 Large vestibular aqueduct
and congenital sensorineural hearing loss. Am J Neuroradiol. 13:805– 819.
Chen A, Francis M, Ni L, et al. 1995 Phenotypic manifestations of branchiootorenal syndrome. Am J Med Genet. 58:365–370.
Abe S, Usami S, Shinkawa H. 1997 Three familial cases of hearing loss
associated with enlargement of the vestibular aqueduct. Ann Otol Rhinol
Laryngol. 106:1063–1069.
Griffith AJ, Arts A, Downs C, et al. 1996 Familial large vestibular aqueduct
syndrome. Laryngoscope. 106:960 –965.
Valvassori GE, Clemis JD. 1978 The large vestibular aqueduct syndrome.
Laryngoscope. 88:723–748.
Walsh RM, Ayshford CA, Chavda SV, Proops DW. 1999 Large vestibular
aqueduct syndrome. ORL. 61:41– 44.
Ferrary E, Sterkers O. 1998 Mechanisms of endolymph secretion. Kidney Int.
53:S98 –S103.
Harnsberger HR, Dahlen RT, Shelton C, Gray SD, Parkin JL. 1995 Advanced
techniques in magnetic resonance imaging in the evaluation of the large endolymphatic duct and sac syndrome. Laryngoscope. 105:1037–1042.
Okamoto K, Ito J, Furusawa T, Sakai K, Horikawa S, Tokiguchi S. 1998 MRI
of enlarged endolymphatic sacs in the large vestibular aqueduct syndrome.
Neuroradiology. 40:167–172.
Everett LA, Glaser B, Beck JC, et al. 1997 Pendred syndrome is caused by
mutations in a putative sulphate transporter gene (PDS). Nat Genet.
17:411– 422.
2475
28. Everett LA, Morsli H, Wu DK, Green ED. 1999 Expression pattern of the
mouse ortholog of the Pendred’s syndrome gene (Pds) suggests a key role for
pendrin in the inner ear. Proc Natl Acad Sci USA. 96:9727–9732.
29. Scott DA, Wang R, Kreman TM, Sheffield VC, Karnishki LP. 1999 The
Pendred syndrome gene encodes a chloride-iodide transport protein. Nat
Genet. 4:440 – 443.
30. Kraiem Z, Heinrich R, Sadeh O, et al. 1999 Sulfate transport is not impaired
in Pendred syndrome thyrocytes. J Clin Endocrinol Metab. 84:2574 –2576.
31. Coyle B, Reardon W, Herbrick JA, et al. 1998 Molecular analysis of the PDS
gene in Pendred syndrome (sensorineural hearing loss and goitre). Hum Mol
Genet. 7:1105–1112.
32. Van Hauwe P, Everett LA, Coucke P, et al. 1998 Two frequent missense
mutations in Pendred syndrome. Hum Mol Genet. 7:1099 –1104.
33. Cremers CWRJ, Admiraal RJC, Huygen PLM, et al. 1998 Progressive hearing
loss, hypoplasia of the cochlea and widened vestibular aqueducts are very
common features in Pendred’s syndrome. Int J Pediatr Otorhinolaryngol.
45:113–123.
34. Usami S, Abe S, Weston MD, Shinkawa H, Van Camp G, Kimberling WJ.
1999 Non-syndromic hearing loss associated with enlarged vestibular aqueduct is caused by PDS mutations. Hum Genet. 104:188 –192.
35. Abe S, Usami S, Hoover DM, Cohn E, Shinkawa H, Kimberling WJ. 1999
Fluctuating sensorineural hearing loss associated with enlarged vestibular
aqueduct maps to 7q31, the region containing the Pendred gene. Am J Med
Genet. 82:322–328.
36. Li XC, Everett LA, Lalwani AK, et al. 1998 A mutation in PDS causes nonsyndromic deafness. Nat Genet. 18:215–217.
37. Antonarakis SE, Nomenclature Working Group. 1998 Recommendations for
a nomenclature system for human gene mutations. Hum Mutat. 11:1–3.
38. Wechsler D. 1974 Manual for the Wechsler intelligence scale for children–
revised. New York: Psychological Corp.
39. Cooper DN, Yousoufian H. 1988 The CpG dinucleotide and human genetic
disease. Hum Genet. 78:151–155.
40. Royaux IE, Suzuki K, Mori A, et al. 2000 Pendrin, the protein encoded by the
Pendred syndrome gene (PDS), is an apical porter of iodide in the thyroid and
is regulated by thyroglobulin in FRTL-5 cells. Endocrinology. 141:839 – 845.
41. Qvortrup K, Rostgaard J, Holstein-Rathlou N-H, Bretlau P. 1999 The endolymphatic sac, a potential endocrine gland? Acta Otolaryngol. 119:194 –199.
42. Skvorak AB, Weng Z, Yee AJ, Robertson NG, Morton CC. 1999 Human
cochlear expressed sequence tags provide insight into cochlear gene expression
and identify candidate genes for deafness. Hum Mol Genet. 8:439 – 452.