Definition of Paroxysmal cold hemoglobinuria (PCH):

PCH is a rare blood disorder caused when a person is exposed to the cold, and the immune system makes proteins called antibodies that destroy red blood cells.

Causes, incidence, and risk factors:

Paroxysmal cold hemoglobinuria only occurs in the cold, and affects mainly the hands and feet. Antibodies are formed that attack one type of blood cell. These antibodies attach (bind) to red blood cells and to proteins in the blood (called complements) that destroy cells. The blood cells are destroyed when they move through the body and get rewarmed. As the cells are destroyed, the part of red blood cells, called hemoglobin, which carries oxygen is released into the blood and passed in the urine.

The disease has been linked to secondary syphilis, tertiary syphilis, and other infections (diseases caused by viruses or bacteria). Sometimes the cause is unknown.

People with this disease often get better quickly and do not have symptoms between episodes. Usually, the attacks end as soon as the affected cells stop moving through the body. The risk factors are infection with a virus and syphilis. The disorder is rare.