A Distinctive Skeletal Phenotype in an Adult With IFITM5 -Associated Osteogenesis Imperfecta due to p.Ser40Leu Variant.

More than 100 patients have been reported with osteogenesis imperfecta due to disease-causing variants in IFITM5. Distinct features of this condition include ossification of the interosseous membrane and hypertrophic calluses. Most of them have a recurrent heterozygous variant in the 5'-UTR (c.-14C>T) of IFITM5. A few patients have a heterozygous missense variant in the first exon of IFITM5 [(c.119C>T) p.Ser40Leu]. These patients do not have the distinctive features that results from c.-14C>T variant. Fewer than 10 patients with the c.119C>T variant have been reported so far with most of them being diagnosed at birth or early infancy. We report a 45-year-old male from India with c.119C>T variant with very severe skeletal involvement.