Problem: profoundly defective or absent T-cell and B-cell
function; small thymus, lymphocyte-depleted spleen
- Most severe of all the recognized
- Usually presents within first 6 months of life
- Baby is protected by passive immunity from mother for
about 3 mos, when maternal IgG finally wears out (T1/2 of IgG is 28 days,
effect lasts about 3 half-lives). At this time, normally, serum IgG starts to
become derived from baby. IgM and IgA are also baby-derived.
- 1st infection presents at 3
strep pneumonia, viral or other.
- Upon antibiotic treatment, the normal gut
flora is wiped out, and candida proliferates. Candidal enteritis ensues, and
FTT are common presenting symptoms.
- eczema and seborrhea
- May develop severe bacterial-GN sepsis, fungal-candidal,
aspergillus, P. jiroveci,or viral infections-CMV, disseminated
Two Major Types
- PPX: Bactrim
- ADA replacement (PEG-ADA)
- Il-2 replacement
- No live virus vaccines
- Prognosis: death in the 1st year
of life, unless BMT
Interesting Note: In normal
fetuses, after the 13th week of gestation the immune system works
well enough to reject foreign cells (including maternal). In SCID babies who are
not immunocompetent, the fetus cannot reject maternal blood, and will have
maternal cells in their body at birth. In boys, some cells may be XX (maternally
derived), in girls, looking at DNA fingerprinting (short tandem repeats), some
of momís cells may be present.