Absent Tibia-Polydactyly-Arachnoid Cyst Syndrome

Absent tibia-polydactyly-arachnoid cyst syndrome is a very rare inherited multisystemic disorder initially recognized by Holmes et al. (1995). To this moment, this disorder is only reported in three siblings (two males and one female), who were also the first diagnosed patients. These siblings were born from first-cousin parents who had no musculoskeletal disorder and without exposure to any know teratogen. Although Holmes et al. recognized this syndrome for the first time, other similar musculoskeletal malformations were reported before them (Burn et al. 1984; Al-Awadi et al. 1987; Naguib and al-Awadi 1990). The cases reported before Holmes et al. had retrocerebellar cysts, which were not seen in any former case reports. Common malformations in these newborns were polydactyly and hypoplasia or absence of tibia. Neither of the parents or children had any mutation in HOXD10, C9, or A9 genes, which are crucial in the genesis and development of limbs and vertebras (Krumlauf 1994).