Interstitial lung disease in amyopathic dermatomyositis, dermatomyositis and polymyositis

This study investigated interstitial pneumonia associated with amyopathic dermatomyositis, dermatomyositis and polymyositis, paying particular attention to muscular and/or cutaneous manifestations and their chronology relative to lung involvement. Patients included four males and 13 females, aged 51.7+/-10.8 yrs, who had surgical lung biopsy. Diagnoses included dermatomyositis (10 patients), polymyositis (four patients) and amyopathic dermatomyositis (three patients). Solitary respiratory manifestations preceded the onset of any skin or muscle disease in four cases (24%). Reticular and ground glass opacities were the most frequent computed tomography (CT) findings. Pathological review showed nonspecific interstitial pneumonia (eleven, 65%; cellular, two; cellular and fibrotic, five; fibrotic, four), usual interstitial pneumonia (two), organising pneumonia (two), lymphocytic interstitial pneumonia (one), and unclassifiable interstitial pneumonia (one). Nonspecific interstitial pneumonia was the most common histological pattern of interstitial pneumonia in patients with amyopathic dermatomyositis (three of three) and in patients with respiratory symptoms as the initial clinical manifestation of the connective tissue disease (three of four). Survival at 5 yrs was 50%. This study shows the clinician should remain alert to potential muscular or cutaneous manifestations whenever a pathological diagnosis of nonspecific interstitial pneumonia is made.