A 2-year-old boy with sickle cell anemia is brought to the emergency department by his parents due to pallor and decreased responsiveness. Yesterday, the patient had abdominal pain and less energy than usual. This morning, he looked pale and the parents had difficulty awakening him. The patient has had no fever, vomiting, diarrhea, or rashes. He takes daily folic acid and prophylactic penicillin against pneumococcal infection. Temperature is 36.7 C (98.1 F), blood pressure is 70/30 mm Hg, pulse is 158/min, and respirations are 44/min. On physical examination, the patient appears pale and is asleep but is briefly arousable to painful stimuli. Examination reveals a 3/6 systolic ejection murmur throughout the precordium and clear breath sounds. Abdominal examination demonstrates marked splenomegaly, and the patient grimaces with palpation of the left upper quadrant. Capillary refill is >3 seconds, and the extremities are cyanotic and cool to the touch. Which of the following laboratory profiles would most likely be seen in this patient?
Acute, severe anemia in sickle cell disease | ||
Cause | Reticulocytes | Key features |
Aplastic crisis | ↓ |
|
Splenic sequestration crisis | ↑ |
|
This patient with sickle cell disease (SCD) has a markedly enlarged spleen and signs of shock (eg, tachycardia, hypotension), findings consistent with a splenic sequestration crisis, or red blood cells pooling in the spleen. Splenic sequestration is a common complication of SCD in younger patients whose spleens have not yet become fibrotic from recurrent vaso-occlusion and infarction (ie, autosplenectomy).
Red blood cell sequestration in the spleen leads to severe, acute anemia and splenic engorgement, resulting in clinical findings of pallor, flow murmur, left upper quadrant pain, and splenomegaly. If untreated, splenic sequestration can progress to hypovolemic shock, as a significant portion of the total blood volume is trapped in the spleen. Classic laboratory findings include severe normocytic anemia, compensatory reticulocytosis, and thrombocytopenia (as platelets are also trapped in the spleen). Treatment includes correction of hypovolemia with isotonic fluids, small-volume transfusions, and eventual splenectomy.
(Choice A) Bone marrow suppression, most commonly from viral infection, can result in decreased reticulocyte count and thrombocytopenia. Patients often have signs of pancytopenia (eg, pallor, petechiae/bruising) after or during viral infection (eg, fever, rash, upper respiratory symptoms). This patient with sickle cell anemia and a rapidly enlarging spleen more likely has splenic sequestration crisis.
(Choice B) Aplastic crises in SCD arrest erythrocyte production and result in severe anemia. Reticulocyte counts are low, and platelet counts are typically normal (although a slight decrease is sometimes seen due to bone marrow involvement). Symptoms often develop after infection with parvovirus B19, which presents with nonspecific flulike symptoms and a classic erythema infectiosum rash, neither of which is seen in this patient.
(Choice C) Laboratory findings in iron deficiency anemia may include thrombocytosis and a decreased reticulocyte count due to inadequate iron stores. Patients are typically asymptomatic.
(Choice E) At baseline, patients with SCD typically have a normal platelet count, but the reticulocyte count is elevated due to chronic hemolysis. Some patients develop thrombocytosis following autosplenectomy. During acute splenic sequestration crisis, platelet trapping typically results in thrombocytopenia.
Educational objective:
Splenic sequestration crisis, or pooling of red blood cells in the spleen, in sickle cell disease presents with signs of severe, acute anemia (eg, tachycardia, pallor, shock) and splenomegaly in young patients. Laboratory testing demonstrates normocytic anemia, reticulocytosis, and thrombocytopenia.