Opsismodysplasia is an autosomal recessive skeletal disorder characterized by facial dysmorphism, micromelia, platyspondyly and retarded bone maturation. Recently, mutations in the gene encoding inositol polyphosphate phosphatase-like 1 (INPPL1) are found in several families with opsismodysplasia by a homozygosity mapping, followed by whole genome sequencing. We performed an exome sequencing in two unrelated Japanese families with opsismodysplasia and identified a novel INPPL1 mutation, c.1960_1962delGAG, in one family. The mutation is predicted to result in an in-frame deletion (p.E654del) within the central catalytic 5-phosphate domain. Our results further support that INPPL1 is the disease gene for opsismodysplasia and that opsismodysplasia has genetic heterogeneity.