Abstract

Dermatomyositis is a common inflammatory myopathy with characteristic cutaneous findings. Panniculitis of dermatomyositis is considered a rare clinical manifestation. We highlight a case of a 68-year-old female with a known history of dermatomyositis, who presented to the dermatology clinic with tender subcutaneous nodules involving the chest, abdomen, axillae, upper arms, and thighs. These nodules had erupted progressively over one year, were causing significant discomfort, and were negatively impacting the patient’s quality of life. Patient was on methotrexate at the time of presentation with resolution of heliotrope rash and muscle pain. Further workup for underlying malignancy and internal organ involvement were negative to date. Differential diagnosis for these nodules included calcinosis cutis versus a neoplastic process. An 8-mm punch biopsy was performed, which demonstrated a mixed septal and lobular panniculitis composed of lymphocytes, histiocytes, multinucleated giant cells, foamy macrophages, eosinophils, and neutrophils. Fat necrosis was present, along with lipomembranous change and variation in adipocyte size. A colloidal iron highlighted an increase in mucin within the subcutaneous fat. With this constellation of pathologic findings, our patient was diagnosed with panniculitis of dermatomyositis. Here, we demonstrate a robust case of panniculitis of dermatomyositis and further describe the histopathologic features. We discuss the prognosis and treatment options. We go on to review the implications of particular pathologic findings, including the association of membranocystic change with treatment recalcitrance. Overall, it is important for dermatologists and dermatopathologists to be aware of this entity, in order to promptly diagnose and appropriately treat this condition.