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IgLON5 disease is a rare autoimmune neurodegenerative condition with manifestations including REM/NREM parasomnias, sleep apnea, stridor, RBD, altered sleep initiation in addition to movement disorders, cerebellar/brainstem dysfunction, dysautonomia, cognitive/neuropsychiatric symptoms. Recently, sleep-related hypoventilation with alternating tachypneas associated with IgLON5 disease was reported in a case of patient after tracheotomy. Here we report first case of IgLON 5 disease with sleep-specific spontaneous sustained tachypnea in a patient without tracheotomy.

A 68-year-old man with sleep apnea who started having slowly progressive neurological symptoms including headaches, gait changes, insomnia, vivid dreams, dysarthria over 2 years. On exam, there were upward gaze impairment and propriospinal myoclonus. MRI brain/C spine, EMG, Neuropsychological testing, EEG were unremarkable, however CSF analysis was positive for IgLON5 antibodies. Treatment included a course of IV methylprednisolone, 5 plasma exchanges and rituximab. He was maintained on rituximab with residual symptoms.  Myoclonus did not respond to levetiracetam, clonazepam, zonisamide, baclofen. His sleep apnea and parasomnia were managed with BiPAP and clonazepam with some improvement. In-lab polysomnography (PSG) sleep study for this patient showed myoclonus involving upper body, mixed sleep apnea, an episode of confusional arousal indicating NREM parasomnia, and sleep-specific spontaneous tachypnea. Myoclonus episodes lasting less than 30 sec were observed during wakefulness or sleep arousals, and were associated with possible automatisms including clearing throat, making moaning sounds and with rhythmic activity on chin EMG. In contrast, a sustained period (2 hours) of spontaneous tachypnea with respiratory rate increased to 40s and transcutaneous partial pressure of carbon dioxide (PtcCO2) decreased to an abnormally low level of 32 mmHg. The patient was in sleep through this period.

IgLON5 disease has been associated sleep disturbances including sleep breathing disorders. Here we report a unique case of sleep-specific spontaneous tachypnea in IgLON5 disease in a patient without tracheotomy.