Increased cerebrospinal fluid 5‐hydroxytryptamine and 5‐hydroxyindoleacetic acid in Kleine‐Levin syndrome

A 17-year-old man with the Kleine-Levin syndrome died unexpectedly of cardiopulmonary arrest during a period of autonomic instability that followed an episode of megaphagia. At autopsy, the only pertinent finding was mild depigmentation of the locus ceruleus and substantia nigra. Premortem CSF levels of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels were elevated. These findings indicate that many symptoms of the Kleine-Levin syndrome are a result of a neurotransmitter imbalance in the serotonergic pathway of the brainstem.