A congenital malformation syndrome that associates a complex syndactyly of the hands with malformations of the forearm bones and similar manifestations in the lower limbs. Fewer than 30 cases have been described, the majority of cases occurred in related families. The syndrome affects both the upper and lower limbs but, in general, the latter are less severely affected. Associated malformations (renal hypoplasia and vertebral and hemi-vertebral anomalies) have occasionally been reported. Mild facial dysmorphism has been described in isolated cases. The disease is transmitted as an autosomal recessive trait. Homozygous or compound heterozygous mutations of the LRP4 gene (11p12-p11.2) have been identified.