We present a case about a 25-year-old male patient suffering from a rare genetic disorder called Mizuho haemoglobin. He was admitted to the Intensive Care Unit with acute liver and renal failure. During admission he also developed a cardiac tamponade twice. Finally he received a liver transplantation. Hereafter the patient stabilised and his liver and renal functions improved. His symptoms could not be explained solely by his known disease. After searching the literature, similarities between his symptoms and a rare complication of sickle cell disease were found. Molecular diagnostics showed that the patient also suffered from Gilbert’s syndrome. Due to his chronic haemolysis, symptoms of this other disease were masked. This stresses the importance of always looking for other causes if symptoms or changes cannot be explained by a known rare disorder.