Introduction: Adenosine deaminase (ADA) deficiency is a common form of severe combined immunodeficiency (SCID). The patients present in the first 6 months of life with manifestations of recurrent and opportunistic fungal, viral and bacterial infections, lymphopenia, and failure to thrive.
Case 1: A 27-day-old female referred due to suspicion of SCID, sister who died at 5 years old due to SCID. Began at 7 days of life with to pneumonia, requiring invasive mechanical ventilation, flow cytometry was taken, finding negative immunophenotype of T, B, and NK lymphocytes, and she was referred to this institution, admitting due to respiratory distress, antifungal treatment is started (history of BCG vaccination), as well as broad-spectrum antibiotics, in the immunological assessment, negative T, B and NK lymphocytes was found, decreased immunoglobulins, diagnosis of SCID is confirmed. Treatment with IV immunoglobulin at a replacement dose is started, exome sequencing is requested, with variant in ADA gene (c.320T>C, p.Leu10Pro; c.632G>A, p.Arg211His). Patient is enrolled in the transplant protocol, later follow-up is lost.
Case 2: A 3-month-old female referred due to a history of recurrent severe pneumonia, anemia, and thrombocytopenia with primary immunodeficiency suspected, admitted to hospital for respiratory distress. In the immunological assessment, we found immunoglobulin levels decreased for age and flow cytometry with a subpopulation of negative T and B lymphocytes and positive NK (uncommon immunophenotype), a diagnosis of SCID was integrated, management began with a broad-spectrum antibiotic and IV immunoglobulin at a replacement dose, complete exome sequencing was sent, finding a variant in the ADA gene (c.362+5_362+8del). Presents torpid evolution, is discharged after a month as maximum benefit.
Discussion: ADA deficiency should be diagnosed and treated on time because it has a fatal course due to severe and overwhelming infections, and most patients die within the first year of life unless therapeutic intervention is applied.