Introduction/aims: We aimed to describe the clinical phenotype, histopathological findings and overall survival (OS) of the immune-mediated neuromuscular complications of graft-versus-host disease (GVHD).

Methods: We conducted a retrospective chart review of adult patients presenting with immune-mediated neuromuscular complications of GVHD to Mayo Clinic, between April 2013 and July 2018.We collected clinical and laboratory characteristics, histopathological findings, response to treatment and survival data.

Results: We identified 20 patients with a mean age at presentation of 55 y. Mean time from transplant to neurological presentation was 14 mo. Myositis was the most common complication seen in 17 patients, manifesting with predominantly axial and/or proximal weakness. Eleven patients had a muscle biopsy showing diffuse perimysial, predominantly macrophagic infiltration in 10, 3 of them with perimysial perivascular lymphocytic collections, and endomysial and perimysial lymphocytic infiltration in 1. Only two patients had a neuropathic complication: one each with acute inflammatory demyelinating polyradiculoneuropathy and neuralgic amyotrophy. A single patient had a myasthenic syndrome presenting with fluctuating foot drop. Nineteen patients were treated and all responded to immunosuppressive agents; however, 11 had further GVHD flares requiring escalation of therapy. After a median follow-up of 83 mo, seven (35%) patients died: five from progressive GVHD and two from infections. The 5-y OS from time of transplant was 68%.

Discussion: Myositis is the most common immune-mediated neuromuscular complication of GVHD while peripheral neuropathy and myasthenic syndromes appear less common. The macrophage-predominant infiltration on muscle biopsy deserves further study to better clarify the role of macrophages in GVHD pathogenesis.