Retrospective analysis of patients with severe combined immune deficiency: A 20-year Single center experience

Abstract: Severe combined immune deficiency (SCID) is a primary immunodeficiency characterized by impairment in the development and function of lymphocytes and could be a fatal disease if not treated with hematopoietic stem cell transplant in the first 2 years of life. There are differences in SCID diagnostic criteria between different primary immunodeficiency societies. This study aimed to retrospectively evaluate clinical and laboratory findings of the patients followed up with the diagnosis of 59 SCID at our clinic over the past 20 years to develop an algorithm to help diagnosis of SCID for the countries which high ratio of consanguineous marriage and haven’t started TREC assay in their newborn screening program. The mean age at diagnosis was 5.80 ± 4.90 months, delay in diagnosis was 3.29 ± 3.99 months. The most common complaint and physical examination findings were cough and eczematous rash (63%)/organomegaly (61%), respectively. ADA, Artemis, RAG1/2 deficiency were the most common genetic defects. Lymphopenia (87.5%) was the most frequent abnormal laboratory finding and below 3000/mm³ in 95% of the patients. CD3+ T cell count was 300/mm3and below in 83% of the patients. Although the diagnostic criterion for SCID is specified as a CD3+ T lymphocyte count below 300/mm3 by IUIS and lower total lymphocyte counts (under 3000/mm3) together with determination of genetic defects leading to SCID by ESID, profound lymphopenia might not occur in some genetic defects. Combination of ESID and IUIS criteria for diagnosis of SCID would be safety for the countries with high ratio of consanguineous marriage. Physicians should consider diagnosis of SCID in the patient under 2 years with severe infections together with lymphocyte count under of 3000/mm3.