D103-20 Identical Twins With Non-identical Interstitial Lung Diseases

Abstract Introduction Interstitial lung disease (ILD) is a heterogeneous group of diseases characterized by interstitial inflammation and fibrosis of the lung parenchyma. Sjogren’s syndrome (SS) is a known autoimmune cause of ILD with a strong female preponderance, with pulmonary manifestations seen in up to 20% of the cases. Case An 82-year-old ex-smoker (twin #1) with a 20 pack-year smoking history presented with 1 month of exertional dyspnea and cough after an initial upper respiratory tract infection. Symptoms were refractory to several courses of outpatient antibiotics. He also reported several weeks of dry eyes and dry mouth; endorsed mold exposure at home; and required hospitalization for acute hypoxic respiratory failure with imaging evidence of multifocal ground-glass opacities (GGO) and areas of fibrosis with traction bronchiectasis. Treatment with antibiotics and steroids resulted in initial clinical improvement, but symptoms recurred after completion of a 2-week steroid taper. Follow-up CT chest was concerning for organizing pneumonia (OP) with confluent GGOs. An extensive autoimmune workup was negative except for weakly positive antinuclear antibody (ANA) 1:40. A pulmonary function test (PFT) was ordered but never completed. Interestingly, the patient has a monozygotic twin brother (twin #2) who lives with him. He presented a month after the initial presentation of twin #1 with similar complaints except for the absence of dry eyes. Imaging demonstrated diffuse GGOs with cystic lung disease and labs revealed positive ANA 1:320 and SS-A antibodies. He was treated for SS and lymphocytic interstitial pneumonia (LIP) with a course of steroids. PFT showed mild simple restriction and moderate reduction in diffusion capacity. He also showed initial improvement, but symptoms recurred upon the completion of steroids. Since both the patients declined rheumatology evaluation and invasive workup with bronchoscopy or biopsy, a prolonged course of steroids was started after shared decision-making with subsequent clinical and radiological improvement. Discussion Most common ILD caused by SS is nonspecific interstitial pneumonia (45%). However, other forms of ILD such as usual interstitial pneumonia (16%), LIP (15%), and OP (11%) are also seen. Studies have identified several human leukocyte antigen (HLA) molecules and non-HLA regions which have been implicated in the disease. While there have been reports of SS in monozygotic twins, it has almost always been in adolescent patients. This makes the diagnosis of SS-related ILD in our elderly monozygotic twin brothers (one seropositive and the other seronegative) unique and reportable. They will likely need long-term immunosuppressants with serial outpatient follow-up. This abstract is funded by: None