A congenital malformation with apparent shortness (or absence) of the middle phalanges of all digits and occasional fusion with the terminal phalanges. The proximal phalanges of the thumbs and big toes are short. Tendency to be of short stature in adulthood. Inherited as an autosomal dominant trait.

Brachydactyly type B2 (BDB2) is a subtype of brachydactyly characterized by hypoplasia/aplasia of distal phalanges in combination with distal symphalangism, fusion of carpal/tarsal bones, and partial cutaneous syndactyly (summary by Lehmann et al., 2007).

Proximal symphalangism-1A (SYM1A) is an autosomal dominant disorder characterized by ankylosis of the proximal interphalangeal joints, carpal and tarsal bone fusion, and, in some cases, conductive deafness (Strasburger et al., 1965). Genetic Heterogeneity of Proximal Symphalangism Another form of proximal symphalangism (SYM1B; 615298) is caused by mutation in the GDF5 gene (601146).

Carpenter syndrome is a rare autosomal recessive disorder with the cardinal features of acrocephaly with variable synostosis of the sagittal, lambdoid, and coronal sutures; peculiar facies; brachydactyly of the hands with syndactyly; preaxial polydactyly and syndactyly of the feet; congenital heart defects; growth retardation; mental retardation; hypogenitalism; and obesity. In addition, cerebral malformations, oral and dental abnormalities, coxa valga, genu valgum, hydronephrosis, precocious puberty, and hearing loss may be observed (summary by Altunhan et al., 2011). Genetic Heterogeneity of Carpenter Syndrome Carpenter syndrome-2 (CRPT2; 614976), in which the features of Carpenter syndrome are sometimes associated with defective lateralization, is caused by mutation in the MEGF8 gene (604267).