Myhre Syndrome Presenting With Congenital Proximal Radioulnar Synostosis: A Case Report.

Myhre syndrome (MS) is a rare, autosomal dominant multisystem disorder. Clinical features include short stature, variable degrees of intellectual disability, distinctive facial dysmorphism, musculoskeletal abnormalities, cardiopulmonary disorders, and abnormal sexual development. We report on an 11-year-old male Taiwanese patient who was initially referred to our genetic counseling clinic due to congenital proximal radioulnar synostosis (PRUS) and clinical suspicion of mucopolysaccharidosis. A pathogenic heterozygous missense variant in SMAD4, c.1498A>G (p.Ile500Val), was subsequently identified, confirming the diagnosis of MS. This case demonstrates the typical clinical phenotype along with the unique finding of PRUS, which has not been previously reported in association with this syndrome. This report highlights PRUS as a rare skeletal manifestation, expanding the known clinical spectrum of MS and providing valuable insights for clinical recognition.