Paraneoplastic necrotizing myopathy in a woman with breast cancer: a case report

Paraneoplastic necrotizing myopathy is a rare disorder, described as a proximal, symmetrical, and rapidly progressing myopathy that is manifested as a paraneoplastic syndrome. Diagnosis is established via histological examination of the muscle biopsy.

We present the case of a 53-year-old woman, born in Guinea-Bissau, with a history of locally advanced breast cancer, diagnosed ten months previously. The patient had experienced a progressively proximal muscle weakness of the lower extremities, which led to a total inability to walk. Upon neurological examination, the patient showed muscle weakness and atrophy in both proximal lower extremities without myalgia. Muscle strength was graded according to the Medical Research Council Scale as 2 out of 5 in the bilateral iliopsoas muscle, and 4 out of 5 in the bilateral quadriceps femoris. The deep-tendon reflexes were hypoactive. The laboratory examination showed increased values of serum creatinine kinase and myoglobin. An electromyogram showed an incomplete interference pattern during voluntary contraction in the iliopsoas and quadriceps femoris. The motor nerve conduction was 44.1 m/s and 44.3 m/s in the right and left tibial nerves, respectively, and 46.5 m/s and 46.1 m/s in the right and left peroneal nerves, respectively. The sensory motor nerve conductions and the compound motor action potential amplitudes were normal. These findings, despite not being specific, suggested a myopathy. Consequently, a muscle biopsy was performed. A biopsy specimen showed myopathic changes that were characteristic of a necrotizing myopathy.

Treatment for this syndrome consists of controlling the tumor, and providing corticoid therapy. This led to the partial remission of the neurological manifestations.