Clinical Characteristics of Myositis Associated with Graft-Versus-Host Disease

Recipients of allogeneic hematopoietic stem cell transplantation (HSCT) are at increased risk for inflammatory myositis; histological subsets reported include dermatomyositis, necrotising myopathy and chronic graft-versus-host disease (cGVHD)-related myositis. Though corticosteroids and various immunosuppressive therapies have been used, there is a lack of consensus guidelines dictating therapy.Recent evidence suggests the fascia as a preferential target in cGVHD myositis, with conditioning regimens promoting fascial microtrauma. Positron emission tomography (PET) can be a useful diagnostic tool, and case reports suggest that the Bruton's tyrosine kinase inhibitor ibrutinib may have therapeutic potential. Emerging therapies include targeted B cell depletion with rituximab, and extracorporeal photophoresis. Clinicians need to be vigilant for the development of inflammatory myositis post-allogeneic HSCT as most patients respond to treatment. Advances in immunohistochemistry to determine the dominant cell type and cytokine profile may enable targeted and individualised therapies.