Objectives: Interstitial lung disease is a life-threatening complication of many systemic autoimmune diseases with diverse clinical and histopathological features. Among them, lymphocytic interstitial pneumonia (LIP) is mainly associated with primary Sjögren's syndrome (pSS). A case of a middle-aged man with LIP, anti-Ro/La, anti-Scl70 autoantibodies and overlapping histopathological features of pSS and systemic sclerosis (SSc) is presented and discussed.
Methods: A 65-year-old man complaining for easy fatigue and dry cough was evaluated. Physical examination revealed bibasilar crackles on auscultation. Imaging tests showed areas of centrilobular nodules with tree-in-bud sign on the medial lobe of the right lung. Pulmonary function tests demonstrated small airways disease. Laboratory evaluation revealed elevated ESR and CRP, ANA titre >1/320, positive Ro52, Ro60 and La autoantibodies but also, weakly positive anti Scl70 autoantibody.
Results: Right lobe lung biopsy showed diffuse fibrosis with altered alveolar architecture and diffuse infiltration of alveolar septa by lymphocytes and mast cells. Ectopic germinal centres were disclosed, adjacent to the small bronchi causing lumen obstruction and validated after the demonstration of CD23 expression, specific for follicular dendritic cells. Biopsy of minor salivary glands revealed intense periductal fibrosis with limited round cell infiltrates, not fulfilling the histopathological criteria for pSS. The diagnosis of LIP was established and the patient received corticosteroids with poor response. Subsequently he was treated with rituximab with satisfactory results.
Conclusions: This case with LIP and disease-specific autoantibodies for pSS and SSc teaches the complexity and overlapping nature of both diseases, extending from autoimmune epithelitis with ectopic germinal centres to fibrosis-related SSc. It points out the significance of the affected tissue biopsy, which may uncover the different disease phenotypes. To this end, treatment with anti-CD20, acting at the crossroads of the pathogenetic mechanisms of both diseases may serve as a first choice therapy.