Hypomyopathic Dermatomyositis Associated with Interstitial Lung Disease and Good Response to Mycophenolate Mofetil: Case-based Review

Hypomyopathic dermatomyositis (HDM) is a rare form of dermatomyositis (DM). Interstitial lung disease (ILD) associated with clinically amyopathic DM (CADM-ILD) or hypomyopathic DM (HDM-ILD) is a rare condition with a more unfavorable prognosis than ILD associated with classic DM (CDM-ILD). There is no effective treatment for HDM-ILD. A 62-year-old woman with a 6-month history of chronic polyarthritis and myalgia presented skin lesions characteristic of DM (erythematous lesion on extensor surface of elbows, Gottron's papules, V-neck sign) with no clinical muscle impairment (global muscle strength: grade 5). Muscle enzymes (creatine kinase, lactic dehydrogenase, and aldolase) and electroneuromyography (ENMG) were normal. Computed tomography of the chest revealed ILD. Magnetic resonance imaging and muscle biopsy revealed subclinical muscle impairment. High doses of corticosteroids were used without success. As an alternative, 1500 mg/day of mycophenolate mofetil (MMF) was combined with low doses of prednisone, and the patient demonstrated a good clinical response after 3 months of this combination. Twenty-five months after initiating treatment, ILD remains in remission with the use of MMF and a low dose of prednisone. Therefore, MMF can be a good option for the treatment of HDM-ILD.