Pontocerebellar hypoplasia type 9 with a novel combination of compound heterozygous variants in AMPD2

Pontocerebellar hypoplasia type 9 (PCH9; OMIM#615809) is a rare autosomal recessive neurodevelopmental disorder caused by biallelic variants in the AMPD2 gene, which encodes adenosine monophosphate deaminase 2. PCH9 is characterized by progressive microcephaly, severe developmental delay, spasticity, hypomyelination, pontocerebellar hypoplasia, and a characteristic "figure-of-8" appearance of the midbrain on magnetic resonance imaging (MRI) 1 .