A variant of the alpha-thalassemia/mental retardation syndrome (ATR) without deletion of the short arm of chromosome 16, or without detectable molecular abnormalities of the alpha-globin complex. A form in which there is a deletion of the short arm of chromosome 16 is termed "alpha-thalassemia/mental retardation syndrome, deletion type" (q.v.). The phenotype of the nondeletion form comprises severe mental deficiency, facial abnormalities, short stature, genital deformities, and a mild form of hemoglobin H disease.
