Asymptomatic pleural thickening with effusion as the only manifestation of IgG4-related disease

Immunoglobulin G4 (IgG4)-related disease is a systemic fibroinflammatory disorder that can affect almost any tissue. Isolated IgG4 pleural disease is a rare manifestation and, when present, is usually described in patients presenting with dyspnoea. We present a case of asymptomatic isolated IgG4 pleural effusion and highlight that IgG4-related disease should be remembered as a differential diagnosis in patients with pleural effusion and pleural thickening, even if asymptomatic and without any other organ involvement.