Acute sequestration crisis is caused by obstruction of the splenic sinusoids with sickled cells. It most commonly presents in children between 6 months and 2 years although it has been reported into the early twenties. Signs and symptoms include the rapid onset of fatigue, listlessness, pallor, abdominal pain, and splenomegaly. Infection is a common precipitant and can mask the symptoms. CBC will result an acute drop in hemoglobin,  and possible thrombocytopenia and leukopenia. The reticulocyte count will be normal or high. Emergent treatment consists of rapid correction of the intravascular volume and oxygen carrying capacity with a transfusion of packed red blood cells. If blood is not immediately available, volume expansion with isotonic saline can temporize the patient. Approximately 50% of patients with acute sequestration will experience another episode within a few months. It is commonly recommended that a splenectomy be preformed after 1-2 episodes. Splenectomy is commonly delayed until after the age of two due to the infection risk with encapsulated organisms.

Jason Fixler, Lori Styles. Sickle cell disease, Pediatric Clinics of North America.  Dec 202 Volume 49, Issue 6

Pediatric Emergency Medicine, Jill M. Baren, 1st ed.  pg 900,902