C41-41 Vanishing Volumes: A Case of Shrinking Lung Syndrome in Systemic Lupus Erythematous

Abstract Introduction Shrinking lung syndrome (SLS) is a rare pulmonary manifestation of systemic lupus erythematosus (SLE) characterized by dyspnea and restrictive physiology without parenchymal lung disease. Underlying pathophysiology remains unknown, although it is felt to be secondary to multifactorial diaphragmatic dysfunction. Case description 58-year-old woman with established SLE/Sjögren overlap syndrome complicated by nephritis on hydroxychloroquine and osteoporosis presented with progressive dyspnea on exertion, confusion, and pleuritic chest pain. No prior history of thoracic surgery was noted. Upon admission, SpO2 was 55% on room air; she was afebrile and hemodynamically stable (BMI 32.42 kg/m²). Physical examination demonstrated perioral cyanosis, increased work of breathing, decreased lung sounds at bilateral bases, and no jugular venous distention, wheezing, or proximal muscle weakness. Venous blood gas (VBG) revealed pH 7.17 and pCO2 82. Clinical presentation and laboratory findings were consistent with acute hypoxic and hypercapnic respiratory failure requiring admission to the medical intensive care unit. Laboratory tests showed normal hemoglobin (13.8 g/dL) and elevated CRP and ESR to 16.9 mg/L and 74 mm/hr, respectively. Subsequent focused evaluation demonstrated normal TSH, CK, and aldolase levels, a negative myositis panel, and a negative acetylcholine receptor antibody. CT chest was notable for elevation of the left hemidiaphragm and right-sided pleural thickening, without interstitial changes or focal consolidation. Bedside spirometry demonstrated restriction (FEV1 16% predicted, FVC 18% predicted, FEV1/FVC 89%). She had a reduced inspiratory pressure (NIF -28 cmH2O). Fluoroscopic sniff test showed slightly decreased bilateral diaphragmatic excursion without diaphragmatic paralysis. Brain MRI revealed an incidental Chiari malformation; cervical spine MRI was unrevealing. Despite noninvasive positive pressure ventilation, hypercapnia persisted. Patient was started on prednisone ∼0.5 mg/kg along with AVAPS (VT 510 mL, EPAP 6 - 10 cm H2O, PS 15 - 25 cm H2O, RR 18). She was discharged from the hospital on 3 L/min of oxygen at rest. Given history of osteoporosis, rituximab 1000 mg (2 infusions every 6 months) was started as a steroid-sparing agent, and prednisone was gradually weaned. 12 months after initial presentation, her FVC improved to 34% with normalization of MIP to -57 cmH2O (83% predicted). Her venous pH was normal at 7.33 with a pCO2 of 53. She no longer required oxygen at rest. Discussion SLS diagnosis is clinical and radiographic, requiring systematic exclusion of interstitial and neuromuscular causes of restrictive lung disease. Treatment is not standardized, but corticosteroids along with steroid-sparing agents remain the mainstay and are often effective. This abstract is funded by: N/A