412 COMPLETE ATYPICAL DIGEORGE SYNDROME TREATED BY THYMIC TRANSPLANTATION.

Background The 22q11 deletion syndrome is a relatively common genetic defect, with an estimated incidence of 1:3,000. Typically, this genetic defect is detected in screening children symptomatic with cardiac or velofacial abnormalities. Case Description We present a patient with normal cardiac and facial anatomy, presenting at 10 weeks of age with complete atypical DiGeorge syndrome. This diagnosis was made based on the presence of hypocalcemic seizures, the absence of naive T cells, 22q11 hemizygosity, and absent parathyroid function. The use of the term “complete” in “atypical complete DiGeorge syndrome” refers to the athymia indicated by the absence of naive T cells. Naive T cells are recent thymic emigrants that express the surface proteins CD45RA and CD62L. The patient had the atypical complete DiGeorge syndrome because he presented with chronic diffuse erythroderma associated with circulating oligoclonal T cells. Following aggressive antiviral and immunosuppressive therapy, the patient received a thymic stromal transplant. The post-transplant course was complicated by overwhelming CMV infection, subsequent multiorgan failure, and death. Implications for Practice This case emphasizes the diversity of the 22q11 phenotype and the potential severity of noncardiac and nonvelofacial abnormalities. Pediatricians must be aware that some children with classic findings of DiGeorge syndrome may also develop rash, lymphadenopathy, and expansion of oligoclonal T cells. These patients present a diagnostic challenge because they can be confused with patients with the less severe partial form of DiGeorge syndrome because of the presence of circulating T cells. The accurate diagnosis of athymia is critical to ensure optimal therapy for children with atypical complete DiGeorge syndrome.