TOPIC: Pulmonary Manifestations of Systemic Disease
      TYPE: Medical Student/Resident Case Reports
      INTRODUCTION: IgG4-Related Disease (IgG4-RD) is a recently recognized chronic fibroinflammatory disease that can be difficult to diagnose. We present a case of a fifty-one-year-old female diagnosed with IgG4-RD despite normal serum IgG4 levels.
      CASE PRESENTATION: A fifty-one-year-old female with history of chronic kidney disease stage 2, membranous glomerulonephropathy (MGN), Type 2 Diabetes Mellitus, Hypertension, and Rheumatoid Arthritis was referred to pulmonology for evaluation of abnormal findings on CT. She was diagnosed with MGN three years prior to presentation and her renal function improved with cyclophosphamide 50mg and prednisone 60mg daily. Two years later she was admitted to an outside hospital for acute hypoxic respiratory failure secondary to presumed PNA, resulting in intubation. She recovered and the decision was made to discontinue her cyclophosphamide due to concerns of pneumonia. Six months later her kidney function began to worsen resulting in a repeat kidney biopsy. Pathology showed glomeruli positive for IgG4 and negative for PLA2-R. During this time, she lost 20 pounds within 3 months and had CT C/A/P done to rule out malignancy. The CT showed diffuse ground glass infiltrates, for which she was referred to pulmonology. Repeat high resolution CT showed thickening of the interstitium mainly in the subpleural areas of the bilateral lungs with lower lung predominance, consistent with ILD. Of note, serum IgG4 levels returned normal.
      DISCUSSION: IgG4-Related disease (IgG4-RD) is a rare immune-mediated disease that can affect multiple organs. Clinical presentation may include any of the following: autoimmune pancreatitis, head/neck gland tumors, retroperitoneal fibrosis, glomerulonephropathy, and ILD. Diagnosis of IgG4-RD should not be solely based on serum IgG4 levels since the levels can be normal in up to 30% of cases. Diagnosis can be established with clinical suspicion and histopathological analysis of tissue biopsy. IgG4-RD has no established incidence or prevalence as there are no reliable studies likely due to disease being recently recognized or under diagnosed.
      CONCLUSIONS: IgG4-RD should be considered as a differential diagnosis in patients with ILD and nephropathy, despite a normal serum IgG4 level. Delay of diagnosis and treatment could be life-threatening as in our patient with multiple episodes of acute hypoxic respiratory failure requiring intubation.
      REFERENCE #1: Opriţă R, Opriţă B, Berceanu D, Diaconescu IB. Overview of IgG4 - Related Disease. J Med Life. 2017;10(4):203-207.
      REFERENCE #2: Legatowicz-Koprowska M. IgG4-related disease: why is it so important?. Central European Journal of Immunology. 2018;43(2):204-208. doi:10.5114/ceji.2018.77391.
      DISCLOSURES: No relevant relationships by Prangthip Charoenpong, source=Web Response
      No relevant relationships by Cesar Davila-Chapa, source=Web Response
      No relevant relationships by Diana Song, source=Web Response