Brachydactyly is a genetic condition leading to shortened or absent digits in hands or feet. It can occur independently or as part of syndromes. This case focuses on Brachydactyly type B, the rarest form. An 8-month-old from the Philippines was referred due to a missing third toe. Examination revealed a hypoplastic left third toe. X-rays confirmed the finding. Treatment options were discussed, including conservative therapy and follow up. Diagnosis involved history, examination, and imaging. Prenatal diagnosis is limited for isolated cases but useful for syndromic forms if a family mutation is known. Prognosis varies depending on the severity and associated syndromes. Currently there is no definitive treatment; management involves genetic counseling and therapy. Due to limited cases, Type B is underreported, highlighting the need for more research into its genetics.

Brachydactyly type B is an autosomal dominant disorder that is characterized by hypoplasia of the distal phalanges and nails and can be divided into brachydactyly type B1 (BDB1) and brachydactyly type B2 (BDB2). BDB1 is the most severe form of brachydactyly and is caused by truncating variants in the receptor tyrosine kinase-like orphan receptor 2 (ROR2) gene. Here, we report a five-generation Chinese family with brachydactyly with or without syndactyly. The proband and her mother underwent digital separation in syndactyly, and the genetic analyses of the proband and her parents were provided. The novel heterozygous frameshift variant c.1320dupG, p.(Arg441Alafs*18) in the ROR2 gene was identified in the affected individuals by whole-exome sequencing and Sanger sequencing. The c.1320dupG variant in ROR2 is predicted to produce a truncated protein that lacks tyrosine kinase and serine/threonine- and proline-rich structures and remarkably alters the tertiary structures of the mutant ROR2 protein. The c.1320dupG, p.(Arg441Alafs*18) variant in the ROR2 gene has not been reported in any databases thus far and therefore is novel. Our study extends the gene variant spectrum of brachydactyly and may provide information for the genetic counselling of family members.