Immunology

Question 1

2yo boy with R tibial osteomyelitis with abscess admitted. He has a history of pneumonia with empyema and his uncle have severe infections as a child. Bcx growing staph aureus. IgGAM are mildly elevated. Of the following enzymes, this patients infections are caused by deficiency of:
A) bruton tyrosine kinase
B) G-6PD
C) myeloperoxidase
D) nicotinamide adenine dinucleotide phosphate oxidase complex

Answer 1

D. NADPH oxidase complex
This is the enzyme defective in CGD, commonly x-linked, but some are AR (may not present til adulthood).

MPO often aymptomatic, can get candida infections. G6PD causes hemolytic anemia. Bruton TK def can’t generate mature B cells so will have agammaglobulinemia.

Question 2

15mo boy admitted for femoral osteomyelitis and his Bcx is positive for GPC. His first hospitalization was at age 2mo with strep pneumonia sepsis and meningitis and he was also admitted at age 9mo due to a. Aureus abscess. He has no significant family history and his NBS is normal.
On exam, temp 38, HR 145, he has enlarged tonsils and shorty cervical LAD. WBC 20, 43 segs, 2 bands, 43 lymph’s, CRP 2.3. What is the most likely diagnosis?
A) CGD
B) SCID
C) Toll like receptor defect
D) X-linked agammaglobulinemia

Answer 2

C. This is a deficiency of the innate immune system (so your adaptive immune system is still intact—CBC with mild elevated WBC, CRP mildly elevated, etc). CGD susceptible to catalase positive organisms (s. Aureus, listeria, pseudomonas, e. Coli), rarely get infections with strep species (catalase neg). SCID is tested for on NBS and CBC has lymphocytes. XLA often with family history but additionally, don’t present until 4-6months of age due to maternal IgG for the first 3 months (this baby presented at 2 months initially).

Question 3

How do you distinguish Wiscott-Aldrich Disease from ITP? (Both with marked thrombocytopenia)

Answer 3

WAS platelets are small while platelets are large or normal sized in ITP.

Question 4

4mo male who has recurrent infections, has low numbers of all Ig’s.
A) SCID
B) CVID
C) x-linked agammaglobulinemia
D) HyperIgM

Answer 4

C. Make no B cells (including IgM). X linked, so always male. If IgM only, would be D. CVID presents after age 2 with recurrent sinopulm infections or lymphoproliferative disease—will have low or normal B cells (may make them, they just don’t work). SCID is T cell
Failure so can’t measure with Ig’s.

Question 5

How do you treat CVID?
What are these patients at increased risk for?

Answer 5

1. IgG
2. Lymphoma

Question 6

Name 2 diseases associated with SCID.

Answer 6

1. DiGeorge
2. CHARGE (think of it as iCHARGE—can have the same thymic defects as in digeorge)