Paraneoplastic Myositis Associated With Lung Adenocarcinoma, an Unusual Presentation

Document Type

Conference Proceeding

Publication Date

5-21-2023

Publication Title

American Journal of Respiratory and Critical Care Medicine

Abstract

Introduction: Paraneoplastic syndromes are clinical manifestations caused by systemic effects of malignancy and not related to direct invasion, obstruction, or metastasis. It is essential to develop an acumen to suspect these syndromes as it may lead to early diagnosis before clinical manifestations of direct invasion become apparent. We report a patient who presented with profound muscle weakness and hyponatremia leading to subsequent workup showing lung adenocarcinoma. Case: Patient is a 69-year-old female with past medical history significant for chronic obstructive pulmonary disease, degenerative joint disease, and a longstanding history of smoking. She presented with acute on chronic upper and lower extremity weakness that had become so severe that she was unable to move. CT & MRI of the left lower extremity demonstrated findings of myositis and fasciitis. Left leg biopsy showed chronic inflammation. Autoimmune workup and creatine phosphokinase (CPK) were unremarkable. Laboratory studies were significant for hyponatremia. Workup for hyponatremia was consistent with SIADH (Syndrome of Inappropriate Antidiuretic Hormone) and it resolved after tolvaptan. Based on clinical presentation, there was a suspicion of underlying Malignancy. Imaging studies revealed a spiculated right middle lobe lung mass concerning for carcinoma. Biopsy of the lung was completed; findings were consistent with primary lung adenocarcinoma. Rheumatology suspected muscle weakness was from paraneoplastic myositis. She was treated with steroids but showed only minimal improvement in her weakness. It was explained to the patient that the myositis was unlikely to improve without treatment of the lung cancer. The patient opted against cancer treatment. The patient's condition continued to deteriorate, and her clinical course was complicated by a pneumothorax, atrial fibrillation, and pleural effusions leading to respiratory failure. The patient was transitioned to hospice and passed away. Discussion: Neuromuscular manifestations of cancer are common, disabling, and can be multifactorial. Lung cancer, particularly small cell cancer, is commonly associated with paraneoplastic neurological syndromes. These syndromes can involve the spinal cord, dorsal root ganglia, neuromuscular junction, peripheral nerves, and muscle fibers. Autoimmune panels to check associated antibodies, muscle biopsy, and electromyography are important tests that can help elucidate the pathology. Notably, a normal CPK does not exclude myositis. The symptoms of these syndromes are not particularly known to improve with immunosuppressive treatment but demonstrate improvement after cancer treatment. In this case, the findings of SIADH and muscle weakness triggered lung cancer workup This case highlights the importance of physical exams and biochemistry in identifying underlying pathological conditions.

Volume

207

Issue

1

Find It @ Sladen

Share

COinS