259x259px One of the principle symptoms of<unk>  is growth retardation, caused by slow skeletal formation and results in individuals being below average height. Alopecia, or hair loss, is another key indication of<unk> . Their hair is typically thinly dispersed, and fragile, which often leads to baldness later in life. Similarly, tooth growth is stunted, with teeth failing to emerge form the gums or otherwise develop normally. Atrophy of the optic nerve occurs in approximately one third of individuals. This degradation leads to inhibited peripheral vision, and increased difficulty distinguishing colours. While not a defining feature, most sufferers of<unk>  have coarse facial features, and abnormal structure of the middle portion of their faces, typically coupled with a large forehead. Individuals with the disease tend to have depressed nose bridges, protruding ears, and abnormally thick lips, though these symptoms are not unique to this disorder. No direct correlation has been found between<unk>  and mental retardation, though cases of individuals having both have been reported. Due to the severity of the phenotype,<unk>  can be diagnosed very early on. Most cases can be diagnosed by 6 months of age, and most symptoms will be apparent by age 2.
GAPO syndrome
ATR-X syndrome
ATR-16 syndrome
GRACILE syndrome
MEDNIK syndrome
Kindler syndrome
Hecht Scott syndrome
ZTTK syndrome