Precision Medicine for Idiopathic Hypersomnia.

Idiopathic hypersomnia (IH) is characterized by excessive daytime sleepiness despite normal or prolonged sleep. IH is distinguished from narcolepsy by the female predominance, severe morning inertia, continuous drowsiness (rather than sleep attacks), unrefreshing naps, absence of cataplexy, sleep onset in REM periods, and hypocretin deficiency. In IH, the multiple sleep latency test demonstrates low sensitivity, specificity, and reproducibility, compared with prolonged sleep monitoring. In some IH cases, an endogenous hypnotic peptide stimulating GABA receptors during wakefulness is suspected, which are improved by anti-GABA drugs. The benefits of modafinil, sodium oxybate, mazindol, and pitolisant were found in mostly retrospective studies.

IgG abnormality in narcolepsy and idiopathic hypersomnia.

BACKGROUND: A close association between narcolepsy and the Human Leukocyte Antigen (HLA)-DQB1*0602 allele suggests the involvement of the immune system, or possibly an autoimmune process. We investigated serum IgG levels in narcolepsy. METHODOLOGY/PRINCIPAL FINDINGS: We measured the serum total IgG levels in 159 Japanese narcolepsy-cataplexy patients positive for the HLA-DQB1*0602 allele, 28 idiopathic hypersomnia patients with long sleep time, and 123 healthy controls (the HLA-DQB1*0602 allele present in 45 subjects). The serum levels of each IgG subclass were subsequently measured. The distribution of serum IgG was significantly different among healthy controls negative for the HLA-DQB1*0602 allele (11.66+/-3.55 mg/ml), healthy controls positive for the HLA-DQB1*0602 allele (11.45+/-3.43), narcolepsy patients (9.67+/-3.38), and idiopathic hypersomnia patients (13.81+/-3.80). None of the following clinical variables, age, disease duration, Epworth Sleepiness Scale, smoking habit and BMI at the time of blood sampling, were associated with IgG levels in narcolepsy or idiopathic hypersomnia. Furthermore we found the decrease in IgG1 and IgG2 levels, stable expression of IgG3, and the increase in the proportion of IgG4 in narcolepsy patients with abnormally low IgG levels. The increase in the proportion of IgG4 levels was also found in narcolepsy patients with normal serum total IgG levels. Idiopathic hypersomnia patients showed a different pattern of IgG subclass distribution with high IgG3 and IgG4 level, low IgG2 level, and IgG1/IgG2 imbalance. CONCLUSIONS/SIGNIFICANCE: Our study is the first to determine IgG abnormalities in narcolepsy and idiopathic hypersomnia by measuring the serum IgG levels in a large number of hypersomnia patients. The observed IgG abnormalities indicate humoral immune alterations in narcolepsy and idiopathic hypersomnia. Different IgG profiles suggest immunological differences between narcolepsy and idiopathic hypersomnia.

Body mass index-independent metabolic alterations in narcolepsy with cataplexy.

STUDY OBJECTIVES: To contribute to the anthropometric and metabolic phenotyping of orexin-A-deficient narcoleptic patients, and to explore a possible risk of their developing a metabolic syndrome. DESIGN: We performed a cross-sectional study comparing metabolic alterations in patients with narcolepsy with cataplexy (NC) and patients with idiopathic hypersomnia without long sleep time. SETTING: University hospital. PATIENTS: Fourteen patients with narcolepsy with cataplexy and 14 sex and age-matched patients with idiopathic hypersomnia without long sleep time. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Metabolic parameters were evaluated by measuring body mass index (BMI), waist circumference (also with abdominal computed tomography), blood pressure, and daily calorie intake (3-day diary). Chronotypes were assessed through the morningness-eveningness questionnaire. Lumbar puncture for cerebrospinal fluid orexin-A determination and HLA typing were performed. Patients with narcolepsy with cataplexy (all HLA DQB1*0602 positive and with cerebrospinal fluid orexin-A levels < 110 pg/mL) had a higher BMI and BMI-independent metabolic alterations, namely waist circumference, high-density lipoprotein cholesterol, and glucose/insulin ratio (an insulin resistance index), with respect to patients with idiopathic hypersomnia without long sleep time (cerebrospinal fluid orexin-A levels > 300 pg/mL). Despite lower daily food intake, patients with narcolepsy with cataplexy displayed significant alterations in metabolic parameters resulting in a diagnosis of metabolic syndrome in more than half the cases. CONCLUSIONS: BMI-independent metabolic alterations and the relative hypophagia of patients with narcolepsy with cataplexy, as compared with patients with idiopathic hypersomnia without long sleep time, suggest that orexin-A influences the etiology of this phenotype. Moreover, considering that these dysmetabolic alterations are present from a young age, a careful metabolic follow-up of patients diagnosed with narcolepsy with cataplexy is mandatory.