Brachydactyly type E in two sibs with increased bone density and mental retardation. A new autosomal recessive syndrome?

Brachydactyly type E in two sibs with increased bone density and mental retardation. A new autosomal recessive syndrome?: We report on two sibs, a boy and a girl, with syndromic brachydactyly type E. Parents were first cousins. Facial dysmorphia was characterized by a flat occiput, a large forehead, hypertelorism, a long triangular nose, an everted lower lip, downslanting palpebral fissures and strabismus. They had marked shortening of the third, fourth and fifth fingers and of the third, fourth, and fifth toes. IQ was 16 in the boy, 63 in the girl. In both sibs ophtalmologic examination showed strabismus, absence of cataract and normal fundus and radiological findings disclosed increased bone density involving the skull, the vertebrae and the corticalis of the long bones. Neither ectopic calcifications, nor exostosic, nor osteomalacia, and nor osteotis fibrosa cystica were present. Investigations revealed that plasma calcium, phosphate, vitamine D, parathyroid hormone (PTH), response to exogenous PTH, and Gs activity were normal as well as renal and thyroid function. Molecular genetic studies failed to identify mutations in the GNAS 1 gene, in the PTH receptor gene and in the HOX D13 gene. Analysis of 2q showed that there was no deletion 2q37. Other known syndromes with brachydactyly type E and mental retardation were excluded. In conclusion we suggest that these two sibs with a combination of brachydactyly, mental retardation and increased bone density have a specific autosomal recessive syndrome.