The paper deals with a rare monogenic connective tissue disease from a group of fibrillinopathies with autosomal dominant inheritance — Beals syndrome caused by a mutation in the FBN2 gene. Attention is drawn to the high phenotypic similarity of this disease and Marfan syndrome (FBN1 gene mutation), which is associated with the almost complete identity of two proteins: fibrillin 1 and fibrillin 2.

The paper describes a clinical case of a child with Beals syndrome and the typical manifestations of the disease: asthenic constitution, arachnodactyly of the hands and feet, congenital contractures of the large and small joints, chest deformity, kyphoscoliosis, talpes, and crushed ears. The investigators made a differential diagnosis with other connective tissue diseases, such as Marfan syndrome, Stickler syndrome, Ehlers–Danlos syndrome, homocystenuria, and arthrogryposis. DNA diagnosis verified the Beals syndrome in the proband. Exon 28 in the FBN2 gene showed the previously undescribed missense mutation of c.3719G>A, resulting in the amino acid substitution of cysteine for tyrosine (p.Cys1240Tyr) in the structure of the protein fibrillin 2. A de novo mutation occurred. There is evidence for its pathogenicity in the development of the clinical symptoms of the disease. The problems of effective medical genetic counseling in this family are discussed.