Genetic carrier frequency in genes involved in inborn errors of immunity in the lebanese population.

Inborn errors of immunity (IEI) represent a heterogenous group of around 550 genetic disorders impairing the development and/or function of the immune system. Affected patients typically present with recurrent and/or opportunistic infections, often co-occurring with additional manifestations such as autoimmunity, atopy, and malignancy. Despite major advances in the field, IEI remain overlooked, particularly in underrepresented populations. In Lebanon, the burden of autosomal recessive diseases including IEI is significant due to consanguinity, yet poorly characterized. This study assesses the carrier frequency of pathogenic/likely pathogenic variants in 446 IEI-associated genes, using exome sequencing data from 960 Lebanese individuals referred for non-IEI indications. This revealed a total of 186 variants in 99 genes detected in 477 individuals, thus highlighting the burden of these conditions in this population. Genes involved in autoinflammatory diseases presented with the highest carrier rate (6.88%), consistent with previous reports of frequent MEFV variants in Mediterranean regions. In contrast, predominantly antibody deficiency (PAD) was among the least common categories in our cohort, unlike international registries that are enriched for clinically diagnosed PAD cases. Our findings highlight a substantial and likely underestimated burden of IEI in the Lebanese population and underscore the need for better genetic representation and national disease- tracking systems.