Granulomatous Myositis as a Manifestation of Chronic Graft-Versus-Host Disease: A Case Series and Review of the Literature

Myositis and Its Mimics: Guideline Updates, MRI Characteristics, and New Horizons

Myositis is defined as inflammation within skeletal muscle and is a subcategory of myopathy, which is more broadly defined as any disorder affecting skeletal muscle. Myositis may be encountered as a component of autoimmune and connective tissue diseases, where it is described as idiopathic inflammatory myopathy (IIM). Myositis can also be caused by infections as well as toxins and drugs, including newer classes of medications. MRI plays an important role in the diagnosis and evaluation of patients with suspected myositis, but many entities may have imaging features similar to those of myositis and can be considered myositis mimics. These include muscular dystrophies, denervation, deep venous thrombosis, diabetic myonecrosis, muscle injury, heterotopic ossification, and even neoplasms. In patients with suspected myositis, definitive diagnosis may require integrated analysis of imaging findings with clinical, laboratory, and pathology data. The objectives of this article are to review the fundamental features of myositis, including recent updates in terminology and consensus guidelines for IIMs; the most important MRI differential diagnostic considerations for myositis (i.e., myositis mimics); and new horizons, including the potential importance of artificial intelligence and multimodal integrated diagnostics in the evaluation of patients with muscle disorders.

An Unusual Case of Hypercalcemia Due to Graft-Versus-Host Disease

Background/Objective

Hypercalcemia is a common disorder with a wide differential and is most commonly related to malignancy and hyperparathyroidism. Hypercalcemia is a rarely reported consequence of graft-versus-host disease (GVHD) and may be related to a granulomatous manifestation of the common stem cell transplantation procedure.

Case Report

A 67-year-old woman with a history of allogenic stem cell transplantation due to myelodysplastic syndrome presented to the bone marrow transplant clinic with dysphagia, muscle aches, and rash. She was found to have an extremely increased calcium and 1,25-dihydroxyvitamin D levels, which were ultimately corrected with administration of steroids and zoledronic acid.

Discussion

While uncommon, granulomatous disease can lead to hypercalcemia via the activation of 1α-hydroxylase within macrophages, which, in turn, activates 1,25-dihydroxyvitamin D leading to an increased serum calcium level. GVHD is a common, variably presenting complication of bone marrow transplantation. Granulomatous processes related to GVHD may mediate hypercalcemia in patients with both increased calcium and 1,25-dihydroxyvitamin D levels.

Conclusion

This is a rare cause of calcitriol-mediated hypercalcemia associated with GVHD. There have been cases of granulomas associated with GVHD, and this could potentially lead to ectopic production of calcitriol. We deemed GVHD to be a likely cause of the patient's calcitriol-mediated hypercalcemia because we did not find another etiology that fit the clinical findings. Physician awareness of this complication and the appropriate workup will allow future researchers to properly elucidate the etiology of this rare complication.

Granulomatous myopathy: Sarcoidosis and beyond

Non-necrotizing granulomatous inflammation is a rare but easily recognized histopathological finding in skeletal muscle biopsy. A limited number of diseases are known to be associated with non-necrotizing granulomatous myopathy. Once identified, a careful evaluation for evidence of extramuscular granulomatosis and other signs suggestive of sarcoidosis is warranted as about half of the patients have sarcoid myopathy. In addition, the presence of granulomatous myopathy should trigger a search for clinical and pathological clues of inclusion body myositis (IBM), which accounts for most of the remaining patients and can coexist with sarcoidosis. Recognizing the features of IBM in patients with granulomatous myopathy can potentially spare the patients from unnecessary exposure to immunosuppressive therapies. In patients whose granulomatous myopathy remain unexplained, further investigations should aim at identifying myasthenia gravis and other autoimmune disorders, especially those known to cause granulomatous inflammation in other organs. Laboratory investigations should include acetylcholine receptor, antimitochondrial, antineutrophil cytoplasmic, thyroglobulin, and thyroid peroxidase autoantibodies. In the appropriate clinical context, exposure to immune checkpoint inhibitors and chronic graft-vs-host disease can be causes of granulomatous myopathy. In cases of unexplained granulomatous myopathy, natural killer/T-cell lymphoma should be considered and careful histopathological examination for atypical cells and appropriate immunostaining is crucial. Identifying the etiology of granulomatous myopathy in each patient can guide appropriate treatment.

Rare forms of inflammatory myopathies - part I, generalized forms

INTRODUCTION

The idiopathic inflammatory myopathies traditionally comprise dermatomyositis, polymyositis, immune-mediated necrotizing myopathy, anti-synthetase syndrome, and inclusion body myositis. In this review, we aimed to cover the less common forms of generalized myositis.

AREAS COVERED

We identified rare forms of widespread myositis on the basis of list provided by the homepage of the Neuromuscular disease center of Washington University, USA and on the basis of the authors' knowledge. We searched PubMed® and EMBASE® for relevant articles on these forms with the aim of providing as much as possible information on their clinical manifestations as well as guidance on their work-up and treatment.

EXPERT OPINION

There is substantial heterogeneity among the various rare forms of generalized myositis in terms of their frequency and characterization. Some forms are reasonably well defined, while others may not represent truly well-defined diseases, but rather variants of other myopathies. The landscape of rare forms appears to have evolved over time, with some forms now being better characterized, while others, such as SARS-Cov-2- and immune checkpoint inhibitor-related myositis have come to the fore only in recent years. Knowledge about rare forms of myositis can aid in their recognition and treatment.