Characterizing SCID in Bogota: A Single-Center Experience

Severe combined immunodeficiency (SCID) is a group of inborn errors of immunity that severely impair the immune system and lead to high susceptibility to infections. We present the cases of nine patients with SCID diagnosed at a pediatric referral center in Bogotá. Of the nine patients, seven (78%) were female and two (22%) were migrants. Consanguinity was reported in two cases, and one involved endogamy. The median age at diagnosis was 4 months and the median age at first infection was 2 months. Bacterial infections were documented in five patients, mostly due to Gram-negative organisms. Seven patients (78%) had BCGitis, three progressed to BCGosis. IgA and IgM levels were decreased in seven patients; total IgE was <15 IU/mL in all. IgG levels were low in all but one patient, reflecting maternal antibodies. Lymphoproliferative responses were severely decreased when tested. Seven cases were classified as “classical” SCID: five due to defects in IL2RG, IL7R, RAG1, RAG2, DCLRE1C, and ADA; two due to compound heterozygosity in RAG2 (one of whom presented with maternal T cell engraftment); and one secondary to a complete 22q11.2 deletion with athymia. There was one patient with leaky SCID secondary to ORAI1 mutations. All patients received immunoglobulin replacement, trimethoprim/sulfamethoxazole, fluconazole, and four-drug therapy for BCG (Bacillus Calmette–Guerin)-related disease. Acyclovir and palivizumab prophylaxis were given to 56% of patients. Two patients died before hematopoietic stem cell transplantation (HSCT) due to severe infections and one patient with 22q11.2 deletion was not a HSCT candidate. Colombia currently lacks a newborn screening program for SCID, leading to delayed diagnoses typically after severe infections during early infancy, frequently with organ involvement that negatively impacts survival. This case series highlights the clinical complexity and diagnostic challenges of SCID in a resource-limited setting, emphasizing the urgent need to guide public health policies for early detection and other strategies.