Athabascan brainstem dysgenesis syndrome (ABDS) and Bosley-Salih-Alorainy syndrome (BSAS) (MIM 601536) are allelic genetic diseases with overlapping clinical manifestations. They are caused by biallelic disease-causing variants in HOXA1 hence following the autosomal recessive mode of inheritance pattern. The primary clinical features include ocular motility disorder (horizontal gaze palsy/Duane anomaly), sensorineural deafness, variable cerebrovascular malformations, and motor developmental delay. However, patients of ABDS have additional phenotypes of central hypoventilation and intellectual disability, which distinguishes it from BSAS. Moreover, congenital heart disease (commonly conotruncal) and facial/bulbar weakness are other variable clinical manifestations of ABDS. ABDS has been described only in two Native American tribes (Navajo and Apache), whereas the majority of the patients with BSAS have been reported from Saudi Arabia, except four (two from India, one from Turkey, and one suspected possible BSAS phenotype patient of Navajo descent) patients from different geographical regions.
HOXA1