Abstract
Multiple epiphyseal dysplasia type 1 is one of the most common autosomal dominant types of the genetically heterogeneous group of skeletal dysplasias characterized by impaired ossification of the epiphyses of long bones. To date, it is known that the disease is caused by heterozygous variants in the COMP gene and is characterized by a significant variability in the clinical manifestations. We report the first case of a patient with MED 1 caused by novel homozygous single nucleotide variant c.2170dupG (p.Val724Glyfs*20) in the COMP gene identified by whole-exome sequencing. The following segregation analysis in the family found a detected variant in heterozygous state in healthy consanguineous parents of the proband. Clinical and radiological examination revealed the atypical signs of epiphyseal dysplasia including limited range of extension and supination of both forearms, severe bilateral ulnar clubhand, plano-valgus deformity of the feet and generalized muscle weakness with gait disturbances. Among the clinical features, myopathic signs were the most prominent. The radiological and neurophysiological data can be helpful in the differential diagnostics with the congenital myopathies. The novel homozygous variant in the COMP gene that caused multiple epiphyseal dysplasia 1 with autosomal recessive inheritance can contribute to the more detailed description of genotype–phenotype correlations, which will allow research to understand better the role of the C-terminal domain of COMP.