A novel SMARCAL1 mutation associated with a mild phenotype of Schimke immuno-osseous dysplasia (SIOD).

Background: Schimke immuno-osseous dysplasia (SIOD, OMIM #242900) is an autosomal-recessive pleiotropic disorder characterized by spondyloepiphyseal dysplasia, renal dysfunction and T-cell immunodeficiency. SIOD is caused by mutations in the gene SMARCAL1.

Case Presentation: We report the clinical and genetic diagnosis of a 5-years old girl with SIOD, referred to our Center because of nephrotic-range proteinuria occasionally detected during the follow-up for congenital hypothyroidism. Mutational analysis of SMARCAL1 gene was performed by polymerase chain reaction (PCR) and bidirectional sequencing. Sequence analysis revealed that patient was compound heterozygous for two SMARCAL1 mutations: a novel missense change (p.Arg247Pro) and a well-known nonsense mutation (p.Glu848*).

Conclusion: This report provided the clinical and genetic description of a mild phenotype of Schimke immuno-osseous dysplasia associated with nephrotic proteinuria, decreasing after combined therapy with ACE inhibitors and sartans. Our experience highlighted the importance of detailed clinical evaluation, appropriate genetic counseling and molecular testing, to provide timely treatment and more accurate prognosis.