<unk>  is a form of acrocephalosyndactyly, a congenital disorder characterized by malformations of the skull, face, hands and feet. It is classified as a branchial arch syndrome, affecting the first branchial (or pharyngeal) arch, the precursor of the maxilla and mandible. Disturbances in the development of the branchial arches in fetal development create lasting and widespread effects. In 1906, Eugène<unk> , a French physician, described nine people sharing similar attributes and characteristics. Linguistically, in the term "acrocephalosyndactyly", acro is Greek for "peak", referring to the "peaked" head that is common in the syndrome; cephalo, also from Greek, is a combining form meaning "head"; syndactyly refers to webbing of fingers and toes. In embryology, the hands and feet have selective cells that die in a process called selective cell death, or apoptosis, causing separation of the digits. In the case of acrocephalosyndactyly, selective cell death does not occur and skin, and rarely bone, between the fingers and toes fuses. The cranial bones are affected as well, similar to Crouzon syndrome and Pfeiffer syndrome. Craniosynostosis occurs when the fetal skull and facial bones fuse too soon in utero, disrupting normal bone growth. Fusion of different sutures leads to different patterns of growth on the skull. Examples include: trigonocephaly (fusion of the metopic suture), brachycephaly (fusion of the coronal suture and lambdoid suture bilaterally), dolichocephaly (fusion of the sagittal suture), plagiocephaly (fusion of coronal and lambdoidal sutures unilaterally) and oxycephaly or turricephaly (fusion of coronal and lambdoid sutures). Findings for the incidence of the syndrome in the population have varied, with estimates as low as 1 birth in 200,000 provided and 160,000 given as an average by older studies. A study conducted in 1997, however, by the California Birth Defects Monitoring Program found an incidence rate of 1 in 80,645 out of almost 2.5 million live births. Another study conducted in 2002 by the Craniofacial Center, North Texas Hospital For Children, found a higher incidence of about 1 in 65,000 live births.
Apert syndrome
Down syndrome
Bardet–Biedl syndrome
Marshall–Smith syndrome
Prader–Willi syndrome
Ayazi syndrome
Smith–Magenis syndrome
13q deletion syndrome