thymic hypoplasia thymic hypoplasia thymic hypoplasia is a condition where the thymus is underdeveloped or involuted. thymic hypoplasiaspecialtymedical genetics causes there are various causes of thymic hypoplasia such as 22q11.2 deletion syndrome, charge syndrome, nude/scid and otofaciocervical syndrome type 2 (otfcs2), and ataxia telangiectasia.