Introduction:

Narcolepsy is an uncommon sleep disorder characterized by excessive daytime sleepiness, cataplexy, hypnagogic hallucinations, and sleep paralysis. It occurs in about 44.3 per 100,000 people1. Sleepiness is the core symptom in these patients and is seen in nearly all patients. Cataplexy is the second most common symptom; hypnagogic hallucinations and sleep paralysis are less common associations. Patients with narcolepsy usually present with a few of these primary symptoms; All symptoms rarely occur in the same patient simultaneously 1.
The International Classification of Sleep Disorders (ICSD-3) categorizes narcolepsy into two types: Type 1 narcolepsy (NT1), which is associated with cataplexy, and type 2 narcolepsy (NT2), which presents without cataplexy 2,3. Pathophysiologically, NT1 is differentiated from NT2 in that it is associated with the loss of hypocretin-producing cells in the lateral hypothalamus4. Thus, NT1 may be a distinct pathological entity from NT2 and idiopathic hypersomnia4. The neuropeptide hypocretin(also called orexin) plays a role in sustaining wakefulness and suppressing rapid-eye-movement sleep5. The loss of hypocretin-producing neurons thus results in loss of sleep continuity and breaks the border between sleep and wakefulness.
Narcolepsy may occur secondarily to other conditions (e.g. Parkinson’s disease, Niemann-Pick type C, and various vascular, neoplastic, or inflammatory lesions involving the lateral hypothalamic area)2. Numerous studies have postulated that narcolepsy may be an autoimmune disorder resulting in a loss of hypothalamic neurons expressing hypocretin5-8. Notably, almost all patients with NT-1 have the HLA DQB1*0602 variant that regulates T-cell immunity in viral and bacterial infections9.
On the other hand, COVID-19 has been associated with many neurological sequelae10. Since the incidence of narcolepsy has been previously shown to increase during the H1N1 pandemic in China and vaccinations11,12, researchers have called for particular attention to its occurrence in the setting of the current pandemic as a unique opportunity for a better understanding of its clinical and biological features13.
We present the case of a woman who presented with classical symptoms of narcolepsy that had started following her recovery from COVID-19. Since there are many immune-mediated presentations after COVID-19 infection10, we propose that our patients’ narcolepsy had para-infectious pathogenesis.