Sickle cell anemias are chronic hemolytic diseases that may induce three types of acute accidents: severe anemia, severe bacterial infections, and ischemic vasoocclusive accidents (VOA) caused by sickle-shaped red blood cells obstructing small blood vessels and capillaries. Many diverse complications can occur.

Severely increased amount of excretion of protein in the urine, defined as 3.5 grams per day or more in adults and 40 mg per meter-squared body surface area per hour in children.