Peripheral nervous system (PNS) involvement occurs in about 15% to 20% of neurosarcoidosis cases and can be categorized as large-fiber neuropathy (LFN), small-fiber neuropathy (SFN), or myopathy. LFN results from granulomatous infiltration and can present as symmetric or asymmetric polyneuropathy. Nerve biopsies often reveal noncaseating granulomas.

SFN in sarcoidosis is less understood and often involves painful dysesthesia and dysautonomia. Treatment is controversial, with mixed responses to standard therapies. Myopathy in sarcoidosis can present in various forms, including chronic myopathy, acute myositis, nodular disease, or isolated myalgias. Chronic myopathy is most common and often shows limited response to treatment if delayed. Acute myositis responds well to corticosteroids. Muscle biopsies are useful for diagnosis but less so for confirming myopathy in sarcoidosis with nonspecific symptoms. IBM can co-occur with sarcoidosis and is not responsive to immunotherapy, highlighting the need for accurate diagnosis to avoid ineffective treatments.

Reference: Dansereau B, Wang L. Neuromuscular Sarcoidosis: Peripheral Nervous System Manifestations. Practical Neurology. Accessed May 21, 2024. https://practicalneurology.com/articles/2024-apr/neuromuscular-sarcoidosis-peripheral-nervous-system-manifestations?c4src=home:feed