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Larger than Life
Maria Thomas, a 5 year old girl, was brought to Urgent Care at the hospital because of a
painful swelling in her neck. The doctor who was on call that night, Dr. Anton, quickly
diagnosed it as swelling of the neck lymph nodes, a common side effect of a bacterial infection.
He took a throat culture, and told Mrs. Thomas to take Maria home, and that someone would call
with the results. The next day, Dr. Anton’s nurse called Maria’s house and told Mrs. Thomas
that the throat culture was negative for a strep infection. The nurse explained that it was
probably a viral infection, and that Maria should just wait it out with liquids and lots of rest.
One week later, Maria was brought back into Urgent Care. The swelling in her lymph
nodes had gotten worse; her neck was enlarged to twice the normal size. Her skin was showing a
slight yellowish color. She was also showing signs of listlessness and fatigue, and her heartbeat
was more rapid than usual. Dr. Anton was called in, and concerned with her newest symptoms
and that the swelling had not gone away, referred Maria to an oncologist, Dr. Stevens. Dr. Anton
also did a quick exam, and took a blood sample for lab analysis. The lab showed Maria was
severely anemic; her blood hemoglobin was only 6.5 mg/dL, much lower than the normal female
level of 12-15mg/dL. Her total bilirubin was 2.4 mg/dL, higher than the normal bilirubin count
of 0.3-1.9 mg/dL. Her pulse, at 125 beats/min, was also high for a 5 year old girl (normal
pediatric rate is 70-120 bpm).
That next week, Maria was admitted to the hospital and a biopsy was performed on her
neck. Mrs. Thomas was relieved to hear her daughter did not have malignant lymphoma; the
biopsy was negative. While an abnormal number of lymphocytes were present in her lymph
nodes, none of them were cancerous.
Puzzled, Dr. Stevens ordered an HIV screen to see if Maria was experiencing
opportunistic viral infection and went to grab some coffee, anticipating a long night. In the break
room, she ran into her friend and colleague Dr. Andry, an immunologist who worked in the lab.
Making small talk, Dr. Stevens told Dr. Andry about Maria. Dr. Andry asked if she could
examine Maria’s chart.
Thomas, Maria. Female, Age 5: DOB 11/06/95
5/12/00
Slight lymphadenopathy. Strep culture: negative
5/20/00
Severe lymphadenopathy
Dr. Anton
Dr. Anton
Listless, fatigued
Jaundice
Pulse: 125 beats/min (high)
BP: 94/56 (normal)
Blood labs-- Hemoglobin: 6.5 mg/dL (low)
Significant amount of red blood cell debris
from hemolysis
Polaroid of Maria’s lymph
node enlargement. From
Blood, vol 89, 1997.
5/27/00
Total bilirubin: 2.4 mg/dL (high)
Biopsy: negative
Dr. Stevens
Analysis of lymph nodes:
(From American Journal of Pathology, vol 153, 1998)
Histopathology of lymph
nodes: markedly
expanded by lymphocytes
Para cortex populated by
lymphocytes, plasma
cells, and immunoblasts
Dr. Andry decided to run an apoptotic assay on Maria’s lymphocytes that were taken
from the biopsy. The cells were incubated with and without an apoptotic stimulus, and then
propidium iodide was used to mark nonviable cells. The assay showed a significant decrease in
lymphocyte cell death, much less than the normal controls. Tables from Blood, vol. 89, 1997.
% Cell Loss
Maria Thomas
13
Normal control
87
Encouraged by this, she did an immunologic profile of Maria’s serum.
Serum Igs (mg/dL)
IgM
IgG
IgA
Maria Thomas
400
4020
1670
Normal control
37-200
523-1482
51-375
Meanwhile, the HIV test came back negative. Dr. Stevens was thoroughly frustrated by the time
Dr. Andry knocked on her door and said she knew just what was wrong.
1.) What is the cause of Maria’s symptoms (what disease does she have)?
a. What are the two genes in which mutations can cause this defect?
b. What are some common amino acid mutations?
2.) What does this defect do to the apoptotic pathway?
3.) What is causing Maria’s anemia? Her jaundice?
4.) Why does she have abnormal levels of immunoglobulins?
5.) How would this disease be treated?
Solution:
Maria is suffering from a genetic disorder called ALPS (autoimmune
lymphoproliferative syndrome). It is an autosomal dominant mutation in either the Fas
(CD95) or Fas ligand (CD95L) genes. Fas and Fas ligand play a very important role in
apoptosis, or programmed cell death. Lymphocytes, as part of the immune system, are
constantly dividing when presented with an antigen. Apoptosis is critical to maintaining
the homeostasis of lymphocytes through a signaling pathway. The Fas interaction with
its ligand sends a signal through to the “death domain”, a cytoplasmic region of Fas,
which recruits FADD, a signal protein. The binding of FADD to the death domain of Fas
initiates the cleavage of a procaspase to an active caspase, which leads to apoptosis
through proteolytic events. Without Fas or Fas ligand, the apoptotic pathway is not
finished because the signal is not created properly, leading to an accumulation of B and
T lymphocytes in lymph nodes and spleen. Some common amino acid mutations of the
Fas death domain are: Thr-225 to Pro, Leu-278 to stop codon, Arg-234 to Pro, and
Asp-244 to Val. Sequencing of Maria’s DNA indeed showed a mutation in Fas.
As a result of the excess lymphocytes, it is common in ALPS patients to have a
higher amount of antibodies circulating in the blood, which leads to autoimmune
disease. Anemia is commonly seen due to hemolysis of red blood cells; for Maria it is
the result of her own antibodies attacking her red blood cells. It is common to see
autoimmune attacks on kidneys, neutrophils, platelets, and phospholipids in ALPS
patients. A side effect of hemolysis is bilirubin, which causes jaundice when it builds up
from breakdown of heme groups (bilirubin is a yellowish color).
While ALPS is an autosomal dominant genetic defect, it is obvious that there are
other factors. If it is not a de novo mutation, then Maria’s mother or father must be a
carrier, yet neither of them shows any symptoms. Familial studies of ALPS patients and
their families show that it is common for a family member to have the Fas or Fas ligand
mutation and not present any symptoms.
There is no cure for ALPS currently, but it can be treated. Treatment with
prednisone drastically reduces swelling of lymph nodes, although not completely to
normal levels. Systemic corticosteroid therapy treats severe hemolytic anemia.
Interferon-alpha, IL-2, and cyclosporin can treat lymphoproliferative disease.
References
Autoimmune Lymphoproliferative Syndrome; ALPS #601859. [On-line]. Available
http://www3.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?601859.cs [2001, March 31].
Lim, Megan, and Straus, Stephen et. al. (1998). Pathological findings in human
autoimmune lymphoproliferative syndrome. American Journal of Pathology, 153,
1541-1550.
Martin, David, and Zheng, Lixin et. al. (1999). Defective CD95/APO-1/Fas signal
complex formation in the human autoimmune lymphoproliferative syndrome, type Ia.
Proceedings of the National Academy of Sciences of the United States of America,
96(8), 4552-4557.
Sneller, Michael and Wang, Jin et. al. (1997). Clinical, immunologic, and genetic
features of an autoimmune lymphoproliferative syndrome associated with abnormal
lymphocyte apoptosis. Blood, 89(4), 1341-1348.
WebMd. (2000). [On-line]. Available http://www.mywebmd.com.