本個案為一位60歲女性，過去有甲狀腺癌開刀的病史。因半年來逐漸感到全身無力至本院家醫科門診就診。無力的情形是以四肢近心端的肌肉無力為主，沒有皮膚病灶的表現；血液肝功能檢查(GOT/GPT)與肌酸磷激(CPK)皆為異常上升，且肌電圖與肌肉切片病理報告確定有肌肉病變與肌肉發炎的證據，因此診斷為多發性肌炎，並給予類固醇治療。

多發性肌炎與皮肌炎皆為特發性發炎性肌病變的一種，主要特色為四肢近端肌肉無力與肌肉發炎，診斷上除了病史詢問與理學檢查外，通常還需要實驗室檢驗、肌電圖與肌肉切片檢查的輔助。由於全身無力為家醫科門診常見主訴之一，於看診時可特別注意是否有近端肌肉無力的情形。

A 60-year-old female with a past history of thyroid cancer developed progressive proximal muscle weakness for six months with no skin rash. She was hospitalized because of elevated aspartate transaminase (AST), alanine transaminase (ALT), and creatine phosphokinase (CPK), and electromyography (EMG) and muscle biopsy revealed respectively myopathic change and inflammatory infiltration, leading to the definite diagnosis of polymyositis. The patient was then treated with corticosteroids and reported favorable responses.

Polymyositis and dermatomyositis are classified as idiopathic inflammatory myopathies, which are characterized by proximal skeletal muscle weakness and muscle inflammation. General weakness, one of the most common chief complaints of patients visiting family physicians, should be evaluated carefully to check if there is proximal skeletal muscle weakness.