Spondylometaphyseal Dysplasia, Corner Fracture Type

Spondylometaphyseal dysplasia, corner fracture type (SMDCF) is a skeletal dysplasia characterized by short stature and a waddling gait in early childhood. Short stature may be present at birth or develop in early infancy. Individuals may present with short limbs and/or short trunk. Radiographic features include enlargement and corner fracture-like lesions of the metaphyses, developmental coxa vara, shortened long bones, scoliosis, and vertebral anomalies. Limited joint mobility and chronic pain are common. Vision impairment and glaucoma have been reported.

The diagnosis of SMDCF is established in a proband with characteristic clinical and radiographic features including short stature, corner fracture-like lesions, developmental coxa vara, and vertebral anomalies. Identification of a heterozygous pathogenic variant in COL2A1 or FN1 by molecular genetic testing can confirm the diagnosis if radiographic features are inconclusive.

Treatment of manifestations: Standard treatment for scoliosis per orthopedist; surgical treatment for coxa vara, genu valgum or varum, bowing of the tibia, leg length discrepancy, atlantoaxial instability per orthopedist; management of mobility issues and chronic joint pain by orthopedist and/or physiatrist and physiotherapist; management of vision impairment and glaucoma per ophthalmologist; management of psychosocial issues by a psychotherapist or referral to support groups. Surveillance: Annual evaluation by an orthopedist and/or physiatrist for scoliosis, other orthopedic complications, and mobility issues. Annual evaluation of intraocular pressure and blood pressure in individuals with FN1-SMDCF. Annual screening for psychosocial issues. Agents/circumstances to avoid: Contact sports if atlantoaxial instability is present; activities that cause joint strain in those with joint pain.

SMDCF is inherited in an autosomal dominant manner. An individual with SMDCF may have the disorder as the result of a de novo pathogenic variant. Each child of an individual with SMDCF has a 50% chance of inheriting the COL2A1 or FN1 pathogenic variant. If the SMDCF-causing pathogenic variant has been identified in an affected family member, prenatal testing for a pregnancy at increased risk for SMDCF and preimplantation genetic testing are possible.