First in, but Not Best Dressed

A 59-year-old gentleman presented with maculopapular exanthem, acute kidney injury, and eosinophilia post use of amoxicillin. He was diagnosed with drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome. His RegiSCAR score at diagnosis was 5. He was treated with high-dose prednisolone, as well as mepolizumab, as part of a clinical trial. One year later, the diagnosis was revisited during clinic review, and IgG4 levels were arranged after reviewing the renal biopsy at diagnosis with evidence of lymphoplasmacytic inflammatory infiltrate, though immunohistochemical stain was inconclusive. The IgG4 levels were significantly elevated. He received rituximab induction and achieved clinical remission. One year afterward, he presented with acute liver function test derangement, with gamma-glutamyl transferase (GGT) 1,020 U/L, alkaline phosphatase (ALP) 197 U/L, alanine aminotransferase (ALT) 200 U/L, and aspartate aminotransferase (AST) 139 U/L. He had associated eosinophilia, elevated C-reactive protein, and elevated serum IgG4 levels. Magnetic resonance cholangiopancreatography (MRCP) did not reveal evidence of hepatobiliary disease. We commenced high-dose prednisolone 75 mg daily and a two-dose course of rituximab 1,000 mg. Rapid improvement in liver function tests was observed, with resolution of eosinophilia and significant reduction in IgG4 subclass levels. High-dose prednisolone was weaned off within four weeks. It is unclear whether DRESS and IgG4-related disease sequentially affected the patient or whether there was a unifying diagnosis. Further workup is being conducted to assess these possibilities and will be presented at the clinical grand round.