Introduction IgLON5 autoimmunity has four main clinical patterns; a sleep disorder, bulbar syndrome, PSP-like pattern and predominant cognitive impairment. Other manifestations include movement disorders, gait instability, dysautonomia and neuropsychiatric features [1-3]. Peripheral nervous system involvement has been occasionally reported [3,4]. We describe two cases of IgLON5 autoimmunity presenting with peripheral neuropathy.
Cases A 72-year-old lady presented with progressive distal lower limb numbness, paraesthesia, incoordination and gait disturbance. Associated features included fluctuating facial numbness, limb and trunk fasciculations, upper limb tremor, anxiety, episodic hyperventilation, nocturnal myoclonus and vocalisations in sleep. Nerve conduction studies (NCS) demonstrated demyelinating features in the lower limbs. Anti-IgLON5 antibodies were detected in cerebrospinal fluid. She was treated with IVIg, oral prednisolone, azathioprine and plasma exchange.
A 73-year-old man presented with worsening tremor. Evolving features included facial paraesthesia, imbalance, head ‘fogginess’, visual agnosia, constipation, insomnia, sleep utterances, somnambulism, nocturnal tremor and myoclonus. NCS showed a generalised demyelinating sensorimotor polyneuropathy. Neuropathy screen demonstrated anti-IgLON5 antibodies and IgG kappa paraprotein, leading to a new diagnosis of monoclonal gammopathy of undetermined significance (MGUS). IgLON5 autoimmunity was considered the likely explanation for the peripheral neuropathy, as sural nerve biopsy findings were not typical for MGUS-related neuropathy. He received IVIg, oral prednisolone, plasma exchange and Rituximab. During follow-up, he progressed to multiple myeloma and commenced lenalidomide and dexamethasone.
Conclusion Our two cases and the few published reports suggest an association of peripheral neuropathy and IgLON5 autoimmunity. We recommend cases of IgLON5 autoimmunity undergo routine neurophysiological studies.
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