PATH - B- and T-cell disorders

Question 1

Severe combined

immunodeficiency

Answer 1

Several types including
defective *IL-2R gamma chain (most common, X-linked), *adenosine deaminase deficiency (autosomal recessive).

Failure to thrive, chronic
diarrhea, thrush

Recurrent viral, bacterial, fungal, and protozoal infections

TX: bone marrow
transplant (no concern for
rejection).

DEC T-cell receptor excision circles (TRECs).

Absence of thymic shadow
(CXR), germinal centers
(lymph node biopsy), and
T cells (flow cytometry).

Question 2

Ataxia-telangiectasia

Answer 2

Defects in *ATM gene–>failure to repair DNA double strand breaks–>cell cycle arrest

Triad: cerebellar defects
(Ataxia), spider Angiomas
(telangiectasia), IgA
deficiency

• INC AFP.
• DEC IgA, IgG, and IgE

Lymphopenia
cerebellar atrophy

Question 3

Hyper-IgM syndrome

Answer 3

X-linked recessive

Most commonly due to
defective *CD40L on Th cells-->class switching defect

Severe pyogenic infections
early in life; opportunistic
infection with Pneumocystis,
Cryptosporidium, CMV

• Normal or INC IgM
• DEC DEC DEC IgG, IgA, IgE.

Question 4

Wiskott-Aldrich syndrome

Answer 4

X-linked recessive

Mutation in *WAS gene

T cells unable to reorganize
actin cytoskeleton

WATER
Wiskott-Aldrich:
Thrombocytopenia
Eczema,
Recurrent infections.
 
INC risk of autoimmune disease and malignancy.

• DEC to normal IgG, IgM
• INC IgE, IgA

Fewer and smaller platelets.