Calcinosis in Adult-Onset Dermatomyositis: Metastatic or Dystrophic?

Abstract

An 89-year-old woman with adult-onset dermatomyositis presented with fatigue, abdominal pain, and leg swelling for two weeks. Physical examination revealed a tender, distended abdomen and lower extremities with pitting edema and purpuric lesions suggestive of leukocytoclastic vasculitis. Laboratory investigation revealed an elevated corrected calcium level (12.7 mg/dl), elevated 1,25 dihydroxyvitamin D (120 pg/ml) and parathyroid hormone (PTH) at the upper limits of normal (22 nLEq/ml); PTH-related protein and phosphorus levels were normal. Chest radiography demonstrated extensive subcutaneous and muscular calcifications, most prominent in the shoulders (Fig. 1). Computed tomography of the abdomen showed a 9-cm retroperitoneal mass (Fig. 2), ultimately diagnosed as B-cell lymphoma. The patient passed away in the hospital while awaiting hospice arrangements. Figure 1. Chest radiograph, demonstrating diffuse subcutaneous and muscular calcifications in the shoulders (arrows). Figure 2. Computed tomography scan of the abdomen, demonstrating a 9-cm retroperitoneal lymphoma (arrows). Our patient’s deep tissue calcium deposition was consistent with metastatic calcinosis, which occurs in normal tissue secondary to elevated serum calcium levels.1 In this case, hypercalcemia was predominantly mediated by increased extrarenal production of 1,25-dihydroxyvitamin D (calcitriol) by malignant lymphocytes.1,2 The lack of complete PTH suppression suggests a degree of parathyroid autonomy, which was not felt to be significant. By contrast, the calcinosis typical of dermatomyositis, dystrophic calcinosis, occurs in damaged tissue in the setting of normal calcium levels, and is rare in adult-onset dermatomyositis.3,4