Adult-Onset Anti-NXP2 Dermatomyositis and MGUS triggered by COVID-19 vaccination: A clinical pharmacist’s report

Abstract

A 35-year-old previously healthy male developed progressively worsening proximal muscle weakness and pain shortly after receiving the Covishield COVID-19 vaccine, initially presenting with low back and bilateral thigh pain followed by rapid progression to quadriparesis and significant functional impairment. Laboratory evaluation revealed markedly elevated creatine phosphokinase, anti–NXP2 antibody positivity, and MRI findings consistent with inflammatory myositis with subcutaneous involvement. Despite comprehensive autoimmune and malignancy screening being largely negative, serum immunofixation identified a monoclonal IgM lambda gammopathy of uncertain significance. The patient was treated with intravenous immunoglobulin, corticosteroids, and supportive care, resulting in significant clinical and biochemical improvement. Three years later, he experienced a relapse with proximal weakness and characteristic skin changes, which responded well to high-dose steroids and rituximab. This case illustrates severe adult-onset anti–NXP2 antibody-positive dermatomyositis temporally associated with COVID-19 vaccination and complicated by monoclonal gammopathy, highlighting the need for vigilant long-term monitoring for relapse and malignancy, and the importance of timely immunosuppressive therapy to achieve favorable outcomes.