When a maternal heterozygous mutation of the CYP24A1 gene leads to infantile hypercalcemia through a maternal uniparental disomy of chromosome 20

International audienceBackgroundInfantile hypercalcemia is an autosomal recessive disorder caused either by mutations in the CYP24A1 gene (20q13.2) or in the SLC34A1 gene (5q35.3). This disease is characterized by hypercalcemia, hypercalciuria and nephrocalcinosis in paediatric patients.Maternal uniparental disomy of chromosome 20 [UPD(20)mat], resulting in aberrant expression of imprinted transcripts at the GNAS locus, is a poorly characterized condition. UPD(20)mat patients manifest a phenotype similar to that of Silver-Russell syndrome and small for gestational age-short stature.Case presentationWe report here the genetic and clinical characterization of a male child with a phenotype of infantile hypercalcemia, postnatal growth retardation, and minor dysmorphic features. Genetic analysis using a next generation sequencing panel revealed a homozygous pathogenic variant of CYP24A1. The absence of the variant in the father led to microsatellite segregation analysis, suggestive of UPD. SNP-array revealed a large terminal copy neutral loss of heterozygosity leading to CYP24A1 homozygosity. SNP-array data of parent–child trio confirmed a UPD(20)mat responsible for both infantile hypercalcemia and Silver-Russell syndrome-like traits.ConclusionThis is the first report of uniparental disomy of chromosome 20 revealed by infantile hypercalcemia related to CYP24A1 biallelic homozygous variants, underlying the importance of controlling allelic segregation in cases of homozygosity

Acute tubulointerstitial nephritis with or without uveitis: a novel form of post-acute COVID-19 syndrome in children

International audienceMultiorgan sequelae of coronavirus disease 2019 (COVID-19) beyond the acute phase of infection are increasingly described as clinical experience expands. In children, acute COVID-19 appears to be generally asymptomatic or mild. Yet, the multisystem inflammatory syndrome in children (MIS-C) may be a severe postinfectious complication following exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).1 During the first pandemic year, we observed a striking increase in the incidence of acute tubulointerstitial nephritis (aTIN) without or with uveitis (TINUs) among children. Causes of aTIN include drugs, infections, and systemic diseases, but often remain undetermined. The rare TINUs syndrome associating aTIN and uveitis is considered to result from a still ill-characterized immune-mediated process. The observed increased incidence of idiopathic aTIN/TINUs prompted us to examine whether SARS-CoV-2 might be the initial trigger