hypomyelinating leukodystrophy 9 (Monarch Disease Ontology entry MONDO_0014506) can be described as follows. Any leukodystrophy in which the cause of the disease is a mutation in the RARS gene. Also known as: HLD9, RARS leukodystrophy, RARS-related autosomal recessive hypomyelinating leukodystrophy, hypomyelinating leukodystrophy type 9, leukodystrophy caused by mutation in RARS, leukodystrophy, hypomyelinating, type 9.