Late-Onset Autoimmune Lymphoproliferative Syndrome in a Costa Rican Woman

Autoimmune lymphoproliferative syndrome (ALPS) is a primary immune regulatory disorder (PIRD). This disease usually develops during childhood. However, atypically, some cases may have their onset in adulthood. We report the case of a 44-year-old woman with a history of autoimmune hemolytic anemia at 33 years old. The patient presented due to asthenia and a large, painful lymph node in the left axillary region for the last four months. Enlargement of the axillary and inguinal lymph nodes was found by mammography, breast, and abdominal ultrasounds. An excisional biopsy of the axillary lymph node conglomerate did not document immunophenotypical alterations of T or B lymphocytes but showed progressive transformation of germinal centers with reactive follicular hyperplasia. The lymph node cytometry did not show a malignant phenotype. The immunological work-up documented IgG and IgA hypergammaglobulinemia and slightly decreased IgM; the B cell immunophenotype documented a slight increase in CD21low B cells and decreased memory B cells. The blood count was normal. The T cell compartment evidenced 27% CD3⁺/αβ⁺/γδ^-/CD4^-/CD8^- of the total T CD3⁺ cells and 15% of the total lymphocytes. A pathogenic heterozygous variant in the FAS gene, exon 9, c.785T>A (p.Ile262Asn), was documented. This variant has not been previously described. This case highlights the importance of considering the diagnosis of ALPS even in adulthood. Genetic conditions such as incomplete penetrance or variable expressivity that depend on factors that are not entirely clear in ALPS, such as epigenetics and environmental factors, among others, could generate the onset of this disease in adulthood in a smaller number of patients.