Brachydactyly type A1 (BDA1) is an autosomal dominant disorder characterized by shortening of the middle phalanges of the digits of the hand, with or without symphalangism. Mild short stature is often present. Considerable inter- and intrafamilial variability has been observed, with all or only some digits affected, and complete absence of the middle phalanx in some cases. Metacarpals may also be shortened, and clinodactyly, camptodactyly, and ulnar deviation have been reported. Some patients exhibit abnormalities of the feet (Zhu et al., 2007; Lodder et al., 2008; Byrnes et al., 2009; Vasques et al., 2018). Genetic Heterogeneity of Brachydactyly Type A1 BDA1B (607004) has been mapped to chromosome 5. BDA1C (615072) is caused by mutation in the GDF5 gene (601146) on chromosome 20q11. BDA1D (616849) is caused by mutation in the BMPR1B gene (603248) on chromosome 4q22.

Chitayat syndrome (CHYTS) is a rare condition characterized by respiratory distress presenting at birth, bilateral accessory phalanx resulting in shortened index fingers with ulnar deviation, hallux valgus, and characteristic facial features including prominent eyes, hypertelorism, depressed nasal bridge, full lips, and upturned nose (summary by Balasubramanian et al., 2017).