Findings:

A 4 month-old female infant with a history of diarrhea, severe diaper rash due to Candida, and oral Candida infection, presented with pneumonia due to Pneumocystis carinii.

The multiple yeast infections and Pneumocystis carinii suggest an immunodeficiency disease. The low lymphocyte count strengthens this possibility.

Children with severe immunodeficiency diseases are highly susceptible to infections and, if not treated, die of massive infection at an early age. The diseases can be acquired or can be caused by a defect in any of a number of genes.

Findings:

Nothing in the child's history or her mother's history suggested a risk of HIV infection

Based on the history, HIV infection seems to be a remote possibility. A sample was sent to the laboratory with a request for a PCR-based test for HIV RNA. There is no indication of HIV infection.

These results heighten the likelihood that this case is due to a genetic defect.

The most common form of inherited immunodeficiency is due to a defect in the interlukin-2 receptor gene, which is located on the X-chromosome. Since this patient is female, this does not seem to be a likely possibility. Two other types of immunodeficiencies are due to defects in enzymes of purine metabolism.

Findings:

To help pinpoint the enzyme that is defective, the clinical laboratory is asked to determine nucleotide levels in a 24hr urine sample. The results are: