Familial hemophagocytic lymphohistiocytosis syndrome due to lysinuric protein intolerance: a patient with a novel compound heterozygous pathogenic variant in SLC7A7

Lysinuric protein intolerance (LPI) (MIM#222700) is a rare autosomal recessive defect in bibasic amino acid transport caused by pathogenic variants in solute carrier family 7 member 7 gene (SLC7A7). The symptoms begin after weaning from breast milk and include refusal of feeding, vomiting, and consequent failure to thrive. Some metabolic disorders, including LPI, are complicated by hemophagocytic lymphohistiocytosis (HLH); however, the frequency of HLH caused by inborn errors of metabolism is very rare in the HLH cohort. SLC7A7 consists of 11 exons, and has 66 known pathogenic variants. SLC7A7 is associated with HLH. Here, we report the case of a 32-year-old woman who presented with LPI and HLH. Genetic analysis revealed a novel compound heterozygosity in SLC7A7 with two pathogenic variants, c.713C>T (p. Sre238Phe) and c.625+1G>A (splicing acceptor site) inherited from her father and mother, respectively.