Influence of clinical and immunophenotypic variants of severe combined immunodeficiency on severity and outcomes of opportunistic infections

Abstract

Severe combined immunodeficiency (SCID) is a primary immunodeficiency that presents with life-threating symptoms in early infancy and has poor prognosis if not promptly treated. Here we present an analysis of infectious presentation and its course depending on clinical and immunophenotypic form of SCID. This study is supported by the Independent Ethics Committee and approved by the Academic Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology. 54 patients were diagnosed with SCID in our center from 2012 to June 2020 and included to this study. The median age at diagnosis was 5.8 months. All patients were divided into 3 groups: classic SCID ( n = 31); Omenn syndrome ( n = 11); SCID with maternal fetal engraftment ( n = 12). To determine opportunistic infections severity, based on a number of infected organs at disease presentation, 3 groups were formed: with no infections or 1 infected organ, n=15; with 2 infected organs ( n = 15); with 3 and more infected organs ( n = 22). 22 of 46 BCG vaccinated patients (48%) developed BCG-infection: 16 local and 6 disseminated. There was no difference in severity of infections between 3 groups of SCID ( p = 0.22), with more severe infections found in patients older than 6 months of age at diagnosis. T- and NK-cell numbers lower than median level predisposed to severer infections in Omenn syndrome patients ( p = 0.041). There was a higher risk of BCG infections in classic SCID with low levels of NK-cells ( p = 0.009). 45 patients received allogeneic hematopoietic stem cell transplantation (HSCT). 9 patients died before HSCT and 21 after HSCT of infections and infections-related inflammatory syndromes. Though Т- and NKcells might have a role in protecting from severe infections, the early diagnosis is the most important factor of better prognosis of SCID patients.