PLCB1lies on chromosome 20p12.3 and encodes phospholipase C beta 1, which plays a role in phosphoinositide signalling and calcium-dependent intracellular pathways. Reported pathogenic variants include homozygous deletions, compound heterozygous deletions plus splice variants, and homozygous nonsense variants, all consistent with loss of function. Available evidence supports a loss-of-function mechanism, with animal data suggesting that Plcb1 deficiency causes severe seizures and growth retardation, recapitulating the human phenotype. Diagnostic testing should include sequencing and copy-number analysis, because intragenic or larger deletions have been reported.
PLCB1