The disease has been associated with secondary syphilis , tertiary syphilis , and viral infections. Sometimes the cause is unknown.
Attacks follow warming after exposure to cold.
Hemoglobin is released in the blood and passed in the urine as blood cells are broken down. Recovery from the attacks occurs very quickly, and people with this disease do not experience symptoms between episodes. Usually, the attacks end as soon as the sensitized cells are gone from the circulation. The risk factors are viral infection and syphilis . The disorder is rare.