Relapsing polychondritis (RP) and immunoglobulin G4–related disease (IgG4-RD) are rare multi-organ immune-mediated diseases. Both can present with nonspecific symptoms of fatigue, weight loss, arthralgia, raised inflammatory markers, or chronic anemia, and diagnostic delay is common. Early recognition and diagnosis are important to minimize morbidity and risk of incapacity as both diseases have a potentially good treatment response.