Case report on activated PI3K-delta syndrome.

Background: Activated phosphoinositide 3-kinase delta syndrome (APDS) [OMIM 615513] is an inborn error of immunity with autosomal dominant inheritance caused by a pathogenic variant in the PIK3CD gene. The prevalence ratio of APDS is < 1: 1,000,000 newborns. The main clinical features of APDS are sinopulmonary infections, benign lymphoproliferation, autoinflammatory disease, and a major risk of lymphoid neoplasms.

Clinical Case: A 17-year-old female with a history of pneumonia at 9 months of age subsequently developed recurrent respiratory tract infections, bronchiectasis, perforated otitis media, unilateral tonsillar lymphoid hyperplasia, pansinusitis, recurrent oral candidiasis, and chronic rhinitis. Laboratory studies reported persistent leukopenia and lymphopenia, low CD4 lymphocyte subpopulation, and persistently elevated immunoglobulin M immunoglobulin studies with values up to 692 mg/dL. An inborn error of immunity next-generation sequencing and multiplex ligation-dependent probe amplification analysis detected a heterozygous pathogenic variant in the PIK3CD gene, compatible with APDS. Treatment with monthly injectable gamma globulin and prophylactic antibiotics was started, allowing better control of the infectious processes.

Conclusion: This is the second case of APDS reported in Mexico in the literature. It is important to be aware of this condition to make a timely diagnosis, which requires a high clinical suspicion and immunological and genetic studies to provide adequate treatment and prevent complications.