kpmle2
Forum Guru
Topics: 95
Posts: 512
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A problem-based learning case being discussed
in class regards an immunodeficiency disorder
involving a 12-year-old boy. Shortly after he began
walking, he developed worsening instability
and imbalance until he was eventually confined
to a wheelchair at 9 years of age.
Additionally, he developed oculocutaneous
telangiectasias beginning at approximately 3
years of age. During the discussion of this patient’s
case, it is added that such patients commonly
have chronic sinopulmonary disease
and also have a high incidence of malignancy,
particularly lymphoreticular malignancies.
What is the mechanism of action responsible
for this patient’s condition?
(A) Absent respiratory burst
(B) Blocked lysosomal trafficking
(C) Defective DNA repair
(D) Defects in peroxisome function
(E) Impaired toll-like receptor signaling
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| Ali 200736
Forum Junior
Topics: 6
Posts: 78
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b
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| ngaybinhyen
Forum Guru
Topics: 23
Posts: 657
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 Good but ... tough one!
* Dx = Ataxia-telangiectasia (typical): complex syndrome with immunologic, neurologic, endocrinologic, hepatic, and cutaneous abnormalities
* AT mutation: 11q22–23
* Cells from patients as well as those of heterozygous carriers have increased sensitivity to ionizing radiation, defective DNA repair, and frequent chromosomal abnormalities
* The most prominent clinical features are progressive cerebellar ataxia, oculocutaneous telangiectasias, chronic sinopulmonary disease, a high incidence of malignancy, and variable humoral and cellular immunodeficiency
* selective absence of IgA: 50-80%, the most frequent humoral immunologic abnormality
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| docnit
Forum Senior
Topics: 8
Posts: 193
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other 3 defective DNA repair:
Bloom's
Fanconi's
Xeroderma pigmentosum
Fanconi and ataxia telengiectasia imp for usmle.
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| docnit
Forum Senior
Topics: 8
Posts: 193
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to dx ataxia..........look for gradual onset ataxia and appearance of telangiectasia...
they could give u a picture of ocular telangiectasias..as well.
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| ngaybinhyen
Forum Guru
Topics: 23
Posts: 657
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I'm impressed
Thanks, guys
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| kpmle2
Forum Guru
Topics: 95
Posts: 512
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Very good well done
The correct answer is C.
[Ataxia-telangiectasia
is a syndrome with cutaneous, immunologic,
neurologic, and endocrinologic abnormalities.
Patients have oculocutaneous telangiectasias
with progressive cerebellar ataxia that eventually
leads to confinement to a wheelchair, often
by the age of 10–12 years. Additional findings
often include a selective IgA absence with
low concentrations of IgE; IgM is often present
in the low-molecular-weight form. Ataxiatelangiectasia
is an autosomal recessive disorder
that is due to defective DNA repair and results
from a mutation in the ATM gene.
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| nightflight1945
banned
Topics: 32
Posts: 920
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Good one!
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| nitts2009
Forum Newbie
Topics: 1
Posts: 7
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Is it C?
Cuz its a mutation on chromosome 11!!
Any input?
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| nitts2009
Forum Newbie
Topics: 1
Posts: 7
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Oh ok!..
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