Biallelic variants in UGDH gene, also known as Jamuar syndrome (MIM #618792), are associated with developmental and epileptic encephalopathy. Affected individuals present with global developmental delay, speech impairment, intellectual disability and epilepsy. Less than 50 cases have been reported so far. However, based on data from gnomAD, it is estimated that the prevalence may range from 1 in 14 million to 1 in 2 million. In addition, there is a common homozygous pathogenic variant (p.Arg317Gln) identified in Saudi Arabian families.
Germline recessive mutations in one of the upstream enzymes UGP2 (MIM #618744), which belongs to the same pathway also brings about a comparable form of epileptic encephalopathy.