For vaso-occlusive crisis:
Stress
Cold weather
Dehydration
Hypoxia
Infection
Acidosis
Alcohol intoxication
Pregnancy
Exertional stress
For aplastic crisis:
Parvovirus B19 infection
Folate deficiency
Stress
Cold weather
Dehydration
Hypoxia
Infection
Acidosis
Alcohol intoxication
Pregnancy
Exertional stress
Parvovirus B19 infection
Folate deficiency
Sickle cell crisis
Vaso-occlusive pain crisis
Aplastic crisis
Bony infarction
Dialysis disequilibrium syndrome
Dactylitis
Hemolytic uremic syndrome
Avascular necrosis of femoral head