Paroxysmal cold hemoglobinuria (PCH) is a rare type of anemia characterized by the premature destruction of healthy red blood cells by autoantibodies. The disorder is classified as an autoimmune hemolytic anemia (AIHA), an uncommon group of disorders in which the immune system mistakenly attacks healthy red blood cells. Autoimmune diseases occur when the body's natural defenses against foreign organisms destroy healthy tissue for unknown reasons. Normally, red blood cells have a life span of approximately 120 days before they get removed by the spleen. In individuals with PCH, red blood cells are destroyed prematurely and sometimes suddenly (paroxysmally). Many reports emphasize that PCH is an unusual disease. However, in recent years, PCH has become recognized as one of the most common causes of acute AIHA in young children. The reason why acute transient PCH appears to be a more common type of childhood AIHA than it was thought to be several decades ago is uncertain, but probably relates to greater awareness of the disorder and more frequent use of the Donath-Landsteiner test (see Diagnosis section ), especially in children with acute AIHA with hemoglobinuria.
PCH was first described as a distinct disorder in the medical literature in 1872. The specific antibody associated with the disorder (Donath-Landsteiner autoantibody) was first described by Drs. Donath and Landsteiner in 1904.
A majority of cases of PCH recorded in the early medical literature were associated with late syphilis or congenital syphilis. In the early 1900s over 90 percent of patients with chronic PCH had a positive test for syphilis and approximately 30 percent showed clinical evidence of the disease. With the effective treatment of syphilis and the virtual elimination of the congenital form, "classical" syphilitic PCH is now an extremely rare disorder, as is chronic PCH. It was in patients with the chronic form of PCH that exposure to cold resulted in a paroxysm of hemoglobinuria.
In modern times, PCH is almost always encountered as an acute transient syndrome in young children with a recent history of a viral illness, so that paroxysms resulting from cold exposure are rarely encountered. Thus, although this type of AIHA is known as PCH, the words paroxysmal and cold are generally not relevant to the disorder as it is manifest in the modern era. As children with PCH do not usually have hemolysis directly related to exposure to the cold (e.g., they continue hemolysis when in a warm hospital environment), it has been suggested that a better term might be Donath-Landsteiner test positive hemolytic anemia.