Associations:
(1) syphilis
(2) viral infections, which is the usual cause for young children with PCH
(3) advanced age
Clinical features on exposure to cold:
(1) chills
(2) fever
(3) malaise
(4) abdominal pain
(5) back pain
(6) leg pain
(7) hemolysis with hemoglobinuria
Features of the Donath Landsteiner antibody:
(1) It usually has anti-P specificity.
(2) It is an autoantibody so the patient's cells will test positive.
(3) It binds complement when the blood is chilled to less than 15°C, then hemolyzes the blood after the blood is warmed to 37°C.
(4) It is not active at 20°C or 30°C so does not interfere with crossmatching.
(5) It is an IgG antibody that binds at low temperature and dissociates at higher temperatures. It may only be detectable on red blood cells if the blood is kept cold. At higher temperatures only complement may be detected.
(6) An eluate performed on red blood cells tested at room temperature will be negatve since the antibody is only bound in the cold.
