Paroxysmal cold haemoglobinuria in an adult with chicken pox.

Paroxysmal cold haemoglobinuria (PCH) is an autoimmune disorder characterized by intravascular haemolysis causing haemoglobinuria. It is due to a biphasic haemolysin known as the Donath-Landsteiner antibody, which binds specifically to the P antigen of red blood cells at low temperatures, leading to complement activation and red cell lysis at 37 degrees C. PCH is a rare disease which predominantly affects the paediatric population, occurring mostly during viral infections. We report on what is possibly the first case of PCH in an adult to be precipitated by chicken pox infection.