Kleine-Levin syndrome. Familial cases and comparison with sporadic cases.

OBJECTIVES To highlight the occurrence of familial cases and addresses, whether familial Kleine-Levine syndrome (KLS) presents the same spectrum of disease, as that seen in sporadic KLS.   METHODS Between September and December 2014, reports of familial cases of KLS were identified by searching the Library of Congress, PubMed, and Web of Science databases restricted to the English language, with no restriction on date of publication. All cases were reviewed to identify familial cases consistent with current diagnostic criteria for sporadic KLS.   RESULTS Six reviews and 11 case reports describing cases of familial KLS were identified. In 17 of the 29 familial cases identified, sufficient clinical details were described to be confident that these cases were familial and consistent with the description of KLS in the International Classification of Sleep Disorders 3rd edition (ICSD-3), and recent detailed reviews of sporadic KLS. CONCLUSION A significant number of familial cases of KLS have been described that are consistent with the ICSD-3 description of KLS, and indistinguishable from sporadic KLS. This suggests that study of familial KLS using modern genetic techniques may be useful in elucidating the pathogenesis of this rare condition.