Radioulnar Synostosis, Unilateral, With Developmental Retardation And Hypotonia

Clinical Features

Der Kaloustian et al. (1992) described a brother and sister born to nonconsanguineous French Canadian parents who presented with the same characteristic facial appearance, unilateral radioulnar synostosis, generalized hypotonia, and developmental retardation. Both had dolichocephaly with macrocephaly, a long narrow face, and a prominent nose. The radioulnar synostosis was of type 2, i.e., the fusion was located just distal to the proximal radial epiphysis and was associated with congenital dislocation of the radial head. See 179300.

Koc et al. (2008) reported 2 Turkish sibs, born of consanguineous parents, with clinical features similar to those described by Der Kaloustian et al. (1992). The proband was a 12-year-old girl with hypotonia and bilateral type 2 radioulnar synostosis apparent after birth. She had speech delay, delayed motor milestones, and an IQ of 63. Dysmorphic features included sloping forehead, deep-set eyes, wide nasal root and bridge, prominent columella, short philtrum, narrow palate, prognathism, dimples on the shoulders, cafe-au-lait spots, mild scoliosis, and lumbar lordosis. She also had long hyperextensible fingers and long toes. Echocardiography showed mild mitral valve prolapse and tricuspid deficiency. Her 10-year-old brother had mental retardation, mild hearing loss, and similar dysmorphic findings as his sister. However, he did not have radioulnar synostosis, which Koc et al. (2008) suggested may be a variable feature of this syndrome.