Amyopathic dermatomyositis in Hong Kong - association with nasopharyngeal carcinoma

Background Amyopathic dermatomyositis (ADM) is a rare variant of dermatomyositis (DM) in which there is no apparent muscle involvement at initial presentation, but clinical and laboratory evidence of myopathy may appear later. Like DM, it has a known association with malignancy. Objective To record the occurrence of ADM in Hong Kong during the period from January 1988 to June 1996, and to establish the types of carcinoma with which it is associated. Methods The records of all patients diagnosed with ADM in three major dermatology clinics in Hong Kong were retrospectively studied to confirm the diagnosis and to look for any associated malignancy at any stage of the disease. Results Between 1988 and 1996, six patients in Hong Kong (five men and one woman; mean age, 50 years) fulfilled the criteria of ADM, During a follow-up period ranging from 20 to 90 months (average, 35.6 months), none developed any evidence of myositis. Associated malignancy was found in the five male patients. There were three cases of nasopharyngeal carcinoma (NPC), one case of non-small cell carcinoma of the lung, and one case of metastatic carcinoma of the cervical lymph node of unknown primary. No carcinoma had developed in the female patient during a follow-up period of 90 months. Conclusions There is a strong association between ADM and NPC in Hong Kong.