LMOD3 gene variant in familial periodic hypersomnolence.

INTRODUCTION: Kleine-Levin syndrome (KLS) is a rare and debilitating disorder presenting with periodic hypersomnolence, cognitive, psychiatric and behavioral disturbances. In the absence of biomarkers it can be difficult to diagnose. Rare LMOD3 variants in a family and in seven sporadic cases with KLS have been described. Here we report a patient and her family with an unclassified, familial, periodic central disorder of hypersomnolence (CDH) in whom the presence of a LMOD3 gene variant was assessed.

CASE DESCRIPTION: The female patient presented since early adulthood with recurrent episodes of hypersomnolence. Over more than 20 years of follow-up the diagnoses of idiopathic hypersomnia, KLS and hypersomnia associated with a psychiatric condition were made. The family history is positive for periodic hypersomnolence and psychiatric conditions. The patient, her symptomatic mother and her asymptomatic sister carried a Proline for Histidine substitution at codon 552 of the LMOD3-gene. This variant was previously reported in two sporadic KLS patients and its frequency in the general population is below 0.02%.

DISCUSSION: We report the association of periodic hypersomnia with a polymorphism of the LMOD3-gene in a patient with atypical KLS and a positive family history. Further research is needed to assess the pathological and predictive value of LMOD3 variants in KLS.