Donath Landsteiner is seen in -

Paroxysmalcoldhaemoglobinuria (PCH). In PCH, the cold antibody is an IgG antibody (Donath-Landsteiner antibody) which is directed against P blood group antigen and brings about complement-mediated haemolysis. Attacks of PCH are precipitated by exposure to cold. PCH is uncommon and may be seen in association with teiary syphilis or as a complication of ceain infections such as Mycoplasma pneumonia, flu, measles and mumps HARSH MOHAN Textbook of pathology 6th edition pg no 313