Download The Case of the Newborn with Ambiguous Genitalia

case study [chemistry | immunology]
Principal Laboratory Findings
The Case of the Newborn
with Ambiguous Genitalia
Test
Qing H. Meng, MD, PhD, Stephen Hill, PhD, FCACB,
Gillian Luxton, MD, FCACB
Department of Pathology and Molecular Medicine, McMaster
University, Ontario, Canada
Hematology
WBC count
RBC count
Hemoglobin
Hematocrit
MCV
Differential:
DOI: 10.1309/FU9PBRKA5AHFV191
Patient
1-day-old baby.
Chief Complaint
Neonate was noted to have ambiguous genitalia.
Family History
The father is healthy. The mother (para 1, gravida 2) had a
Cesarean section for her first baby girl 3 years ago at 40
weeks gestation due to failure to progress following three
days of labor. The girl has been fine. The mother had no history of diabetes or hypertension.
Drug History
The mother did not take any medication during her most recent pregnancy. She had no history of drug abuse or contact
with any toxic chemicals.
Physical Examination
The baby weighed 3,925 grams with APGAR scores of 9 at
both 1 minute and 5 minutes after birth. Ambiguous genitalia
(clitoromegaly and partial fusion of the labioscrotal folds) were
observed. Cardiovascular and respiratory systems were normal.
Principal Laboratory Findings
[T1]
532
Questions:
1. What is(are) this patient’s most striking laboratory
result(s)?
2. How do you explain this patient’s most striking laboratory
test results?
3. What is the most likely diagnosis relevant to this patient?
4. Which additional laboratory test(s) are appropriate to order
on this patient and why?
5. What is the etiology of this patient’s condition?
6. How is this patient’s condition typically diagnosed?
7. How should this patient be treated?
Chemistry
Glucose
BUN
Sodium
Potassium
Chloride
Bicarbonate
Anion gap
TSH
Free T4
Cortisol (0800 h)
17-OH-progesterone
DHEA-S
“Normal”
Reference Range
14.8
4.16
11.1
39.9
78.3
9.0
4.1
1.3
5.5-15.5 x 103/µL
3.25-5.50 x 106/µL
10.5-14.0 g/dL
40-60%
70-95 fL
1.5-7.0 x 103/µL
2.0-8.0 x 103/µL
0.0-1.1 x 103/µL
79
5
130
5.8
100
18
12
1.8
2.6
1.0
34,500
822
50-80 mg/dL
4-12 mg/dL
135-145 mEq/L
3.5-5.5 mEq/L
95-105 mEq/L
22-30 mEq/L
5-14 mEq/L
0.5-5.5 µU/mL
0.8-2.7 ng/dL
5-23 mg/dL
20-140 ng/dL
26-444 µg/dL
WBC, white blood cell; RBC, red blood cell; MCV, mean corpuscular volume; BUN, blood
urea nitrogen; TSH, thyroid stimulating hormone; T4, thyroxine; DHEA-S, dehydroepiandrosterone-sulfate
Possible Answers:
1. The most striking laboratory results are markedly elevated
17-OH-progesterone, and dehydroepiandrosterone-sulfate
(DHEA-S) concentrations; elevated potassium; reduced
sodium, cortisol, and urea levels; low osmolality; and a normal anion gap.
2. The reduced cortisol level and accumulation of its precursor, 17-OH-progesterone, suggest 21-hydroxylase deficiency,
which is the most commonly seen enzyme deficiency in newborns with congenital adrenal hyperplasia (CAH). The accumulation of 17-OH progesterone may lead to the increased
formation of dehydroepiandrosterone (DHEA) and its metabolite, DHEA-S, by an alternate pathway. The increased DHEA
and DHEA-S concentrations lead to the peripheral synthesis
in the liver of androstenedione and testosterone, which,
together, are responsible for ambiguous genitalia, hirsutism,
and virilization in females. Lack of the 21-hydroxylase
enzyme blocks the pathways for both cortisol and aldosterone
production, the principal glucocorticoids and mineralocorticoids produced by the adrenal cortex. Aldosterone causes increased sodium ion reabsorption and potassium and hydrogen
ion excretion (Na+ ↔ K+ and Na+ ↔ H+ exchange) by the distal
convoluted tubules and collecting duct of the kidney. Aldosterone is essential for the homeostasis of plasma water,
sodium, and potassium ion concentrations. Aldosterone deficiency leads to hypovolemia, hyponatremia, hyperkalemia,
and metabolic acidosis. In early or mild aldosterone and cortisol deficiency, these biochemical changes may not be evident.
Severe cortisol deficiency may cause hypoglycemia.
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Medical History
Neonate delivered by Cesarean section under spinal anesthesia at 39 weeks of gestation. After delivery, the baby was assigned as a male by the obstetrician.
neutrophils
lymphocytes
monocytes
T1
Patient’s
Result
4. Serum aldosterone, plasma renin activity, serum
testosterone, plasma ACTH, and urinary pregnanetriol levels.
Low serum aldosterone concentration is expected in patients
with CAH, while plasma renin may be increased or decreased
depending on the type of enzyme deficiency present and the
degree of mineralocorticoid deficiency. In addition, serum
testosterone concentration is increased due to the decreased
cortisol and aldosterone levels in such patients and shunting
of cortisol precursors toward adrenal androgen production.
Moreover, cortisol deficiency leads to an elevated ACTH concentration, which increases further the levels of cortisol and aldosterone precursor substances and results in bilateral adrenal
hyperplasia (BAH). Measurement of urinary pregnanetriol (a
metabolite of 17-OH-progesterone) concentration is also useful in the diagnosis of CAH. Genetic testing for mutations in
the gene for the 21-hydroxylase enzyme is rarely necessary
for the diagnosis of classical forms of adrenal hyperplasia,
but is essential in the prenatal diagnosis of adrenal hyperpla-
©
sia. Subtle forms of adrenal hyperplasia associated with nonclassical forms of 21-hydroxylase deficiency and 3-beta-hydroxysteroid dehydrogenase deficiency often require a
Cortrosyn (synthetic ACTH) stimulation test to demonstrate
the abnormal accumulation of precursor steroids.
5. Several enzyme deficiencies can cause CAH [F1] and principal among these are: 21-hyroxylase, 11-beta-hydroxylase,
3-beta-hydroxysteroid dehydrogenase, 17-alpha-hydroxylase,
17,20-cholesterol-desmolase, and corticosterone 18-methyloxidase type II. Deficiency of the 21-hydroxylase enzyme
accounts for more than 90% of CAH cases.1 In this type of
CAH, there is increased production of progesterone, 17-OHprogesterone, DHEA, and androstenedione. Moreover, urinary concentrations of the metabolites of these substances
(eg, 17-ketosteroids and pregnanetriol) are increased, while
serum cortisol levels are decreased. The clinical symptoms of
CAH are exacerbated by the stress (and demand for cortisol)
of increased physical activity. The gene (CYP21) for the 21hydroxylase enzyme is located on chromosome 6p21, adjacent to the human leukocyte antigen (HLA) genes. This gene
is about 30 kilobases (kb) away from a pseudogene
(CYP21P), which is 98% homologous in structure with the
CYP21 gene; therefore, the minor differences between these
genes are sufficient to render the pseudogene inactive in the
production of functional 21-hydoxylase enzyme. Deficiency
of the 11-beta-hydroxylase enzyme causes 3% to 5% of all
cases of CAH and is associated with a characteristic elevation
of serum 11-deoxycortisol and deoxycorticosterone concentrations. In addition, urinary levels of 17-OH-corticosteroids
are also usually high. Because of the mineralocorticoid activity of deoxycorticosterone, patients with 11-beta-hydroxylase
enzyme deficiency exhibit salt retention, decreased plasma
renin activity, and hypertension with hypokalemic alkalosis.
The 11-beta-hydroxylase gene (CYP11B1) resides on chromosome 8q21. A neighboring gene (CYP11B2) codes for aldosterone synthetase, which catalyzes the conversion of
corticosterone to aldosterone in the zona glomerulosa of the
adrenal cortex. Mutations and deletions in the CYP11B2 gene
result in diminished aldosterone synthesis. Therefore individuals with a mutated CYP11B2 gene develop hyponatremia,
hyperkalemia, and dehydration. Deficiency of the 3-beta-hydroxysteroid dehydrogenase enzyme is indicated by an abnormal ratio of 17-hydroxypregnenolone to
17-hydroxyprogesterone and dehydroepiandrosterone to androstenedione concentration. The gene for 3-beta-hydroxysteroid dehydrogenase resides on chromosome 1p13.
Deficiency of the 17-alpha-hydroxylase, 17,20-lyase, and
17,20-cholesterol-desmolase enzymes result in virilization
of affected female infants and undervirilization of affected
male infants. A single gene (CYP17) mutation causes the deficiency in the activity of these enzymes. Moreover, steroidogenic acute regulatory protein (StAR) appears to be involved
in the transport of cholesterol across the mitochondrial membrane where it can be acted upon by the CYP450 system in
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3. Most likely diagnosis: Congenital adrenal hyperplasia.
Congenital adrenal hyperplasia is an inherited autosomal recessive disorder that occurs with a population frequency of
1:1,000. It is classified in 2 forms based on different clinical
presentations: classical and non-classical. The non-classical
form of CAH due to partial 21-hydroxylase deficiency is the
most common of all autosomal recessive diseases. The classical form of CAH due to hydroxylase deficiency occurs as a
result of the imbalance in the production of cortisol, aldosterone, and androgens.1 Too little cortisol during physical
stress can lead to low blood pressure and even death. The
lack of aldosterone production results in salt wasting. Excess
androgen production causes abnormal physical development.
The non-classical form of CAH is a milder version of the
classical form of this disease. Patients with nonclassical CAH
are not deficient in cortisol and aldosterone; however, they do
produce excess androgens. Salt wasting forms of adrenal hyperplasia are accompanied by low serum aldosterone concentrations, hyponatremia, hyperkalemia, elevated plasma renin
activity, hypovolemia, and hypotension. In contrast, hypertensive forms of adrenal hyperplasia (eg, 11-beta-hydroxylase
deficiency and 17-alpha-hydroxylase deficiency) are associated with suppressed plasma renin activity and often
hypokalemia. The diagnosis of CAH depends upon the
demonstration of inadequate production of cortisol and/or
aldosterone in the presence of accumulation of excess concentrations of precursor hormones. For example, the distinguishing characteristic of 21-hydroxylase deficiency is a very
high (usually exceeding 1,000 ng/dL) serum 17-OH-progesterone and urinary pregnanetriol (a metabolite of 17-OHprogesterone) concentrations in the presence of clinical
features suggestive of the disease (eg, a female with ambiguous genitalia, evidence of salt wasting, clitoromegaly, precocious pubic hair development, excessive growth, premature
phallic enlargement in the absence of testicular enlargement,
hirsutism, oligomenorrhea, and/or female infertility).
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Cholesterol
ACTH
17 OH'ase
17,20 Lyase
17,20 DLase
Pregnenolone
17-OH Pregnenolone
DHEA
Progesterone
17-OH Progesterone
Androstenedione
3 βSDH
21 OH'ase
Deoxycorticosterone
11-deoxycortisol
Testosterone
11 OH'ase
Cortricosterone
Cortisol
Estradiol
18 OH'ase
Aldosterone
the synthesis of pregnenolone which then is converted in various steroidogenic tissues into cortisol, aldosterone, or sex
steroids. A deficiency of StAR results in a global steroid deficiency state. Lastly, deficiency of corticosterone 18-methyloxidase type II is characterized by aldosterone deficiency
(low plasma aldosterone concentration) with chronic hyperkalemia and no abnormalities of sexual differentiation.
6. Prenatal diagnosis for 21-hydroxylase deficiency can be
performed using DNA analysis on fetal cells obtained from
amniotic fluid following amniocentesis or from chorionic villus samples (CVS).2 This technique will detect 95% of all
abnormal genes for CAH. Neonatal screening for 21-hydroxylase deficiency is sufficiently specific and sensitive to detect
almost all infants with classical CAH and some infants with
non-classical CAH. Analysis of 17-OH-progesterone levels in
dried blood spot samples obtained from newborns between
48 to 72 hours of age is the typical method for screening
newborns for CAH. A positive screening result must be confirmed by quantitative analysis of 17-OH-progesterone concentration, using a sensitive and specific method, in a second
serum/plasma sample, urine steroid analysis, or mutation
analysis of the CYP21 gene.
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7. Early (less than 9 weeks after last menstrual period) treatment of a pregnant woman carrying a CAH-affected fetus
appears to be somewhat successful in preventing the virilization of a female fetus with 21-hydroxylase enzyme
deficiency. However, more detailed guidelines for the use of
this treatment are needed. Infants with ambiguous genitalia
should be observed closely for any signs or symptoms of salt
wasting while the diagnosis of CAH is being established.
Such infants should undergo surgical evaluation in case corrective surgery is indicated.3 Moreover, newborns with dehydration, hyponatremia, hyperkalemia, or hypoglycemia must
be treated immediately to correct these symptoms. Glucocorticoid and/or aldosterone replacement therapy may be necessary depending upon what enzyme deficiency is involved and
whether cortisol and/or aldosterone synthesis is affected. A
new therapy using the combination of a glucocorticoid, a
mineralocorticoid, an aromatase inhibitor, and flutamide is
currently under investigation.2 A clitoroplasty was done on
this patient and her external genitalia progresses well. Our
patient has been on corticosteroid therapy and followed regularly by pediatric endocrinologists by monitoring 17-hydroxyprogesterone, renin, and electrolytes.
Keywords: congenital adrenal hyperplasia, 21-hydroxylase
enzyme deficiency, cortisol, aldosterone, 17-hydroxyprogesterone
1. New MI, Carlson A, Obeid J, et al. Prenatal diagnosis for congenital adrenal
hyperplasia in 532 pregnancies. J Clin Endocrinoal Metab. 2001;86:5651-5657.
2. Joint LWPES/ESPE CAH working group. Consensus statement on 21hydroxylase deficiency from The Lawson Wilkins Pediatric Endocrine Society
and The European Society for Paediatric Endocrinology. J Clin Endocrinol
Metab. 2002;87:4048-4053.
3. Lee PA. Genital surgery among females with congenital adrenal hyperplasia:
Changes over the past five decades. J Pediatr Endocrinol Metab. 2002;15:14731477.
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[F1] Pathway of adrenal steroid synthesis.
21 OH’ase, 21-hydroxylase; 11 OH’ase, 11β-hydroxylase; 18 OH’ase, 18-hydroxylase; 3βSDH, 3β-hydroxysteroid dehydrogenase; 17 OH’ase, 17αhydroxylase; 17,20 DLase, 17,20-cholesterol-desmolase.