Syndromic microphthalmia-12 is a rare disease characterized by bilateral small eyeballs (microphthalmia), lungs that are too small (pulmonary hypoplasia), and a defect or hole in the diaphragm that allows the abdominal contents to move into the chest cavity (diaphragmatic hernia). Other symptoms may include: Severe global developmental delay with progressive motor impairment due to spasticity and/or uncontrolled repetitive muscular contractions (dystonia), with or without abnormal quick movements that resemble dancing (chorea), Defects of the cerebellum (Chiari type I malformation) Accumulation of cerebrospinal fluid inside the brain (hydrocephaly), Severe feeding difficulties, Mild facial dysmorphism with broad nasal root and tip, and a very small chin (micrognathia), Severe language delay, Wheelchair-bound. Syndromic microphthalmia-12 is caused by mutations in the RARB gene. There is no specific treatment for this syndrome. The disease is microphthalmia, syndromic 12 (Monarch Disease Ontology identifier MONDO_0014229). Also known as: RARB syndromic microphthalmia, microphthalmia, syndromic type 12, syndromic microphthalmia caused by mutation in RARB.