A CASE OF AUTOIMMUNE NECROTISING MYOSITIS

ABSTRACT

Introduction An 88-year-old previously independent lady presented with progressive proximal weakness of all limbs and multiple falls for 10 months. Her swallowing got difficult lately. She lost weight gradually in that duration but denied any other symptoms suggestive of malignancy. PMH—Hypothyroid, Mild cognitive impairment Drg History—Atorvastatin for years. Stopped in this admission. On examination, she showed signs of proximal muscle weakness and areflexia in both upper and lower limbs without muscle tenderness. She had no facial nor eye muscle weakness. Sensory functions were intact. There were no rashes. Investigations CK 2000 TSH 24 Inflammatory markers, white cell counts—non-significant Vitamin D—18 CT-Chest Abdomen Pelvis, CT-colonography—No evidence of malignancy Paraneoplastic antibodies—Negative Anti-OJ and anti-Ro52 Antibodies—positive ENA profile—negative Anti-RNP—equivocal HMG-CoA reductase antibodies (HMCR)—Positive. Progress Prednisolone was commenced and gradually increased to 60 mg once a day but there is no significant improvement clinically though creatinine kinase level had improved. She was unfortunately infected with COVID-19 infection in the stay which delayed the plan for muscle biopsy and EMG. It affected the plan for Intravenous Immunoglobulins and was later decided to be non-beneficial due to high risks of thromboembolic events and superimposed infections. Steroid was later switched to methotrexate. She was discharged to a rehab unit. Conclusion Necrotising Autoimmune Myopathy is a rare form of idiopathic inflammatory myopathy. Risk factors include statins, cancer, connective tissue diseases, autoimmune diseases, and infections such as HIV2. Diagnosis includes clinical features, serum creatine kinase, HMG CoA reductase antibody (HMGCR-Ab), electromyography, and muscle biopsy. The first-line treatment options are steroids and immunosuppressive agents. Early use of immunoglobulin achieves good outcome. It is still under investigation for the recommended choice for immunosuppressive therapy and the duration of the therapy.