Sequestration crisis in sickle cell anaemia

Sequestration crises results from trapping of large amounts of red cells in the spleen and sometimes in the liver (1).

Acute splenic sequestration is one of the important causes of early mortality in children with SCD (2).

In homozygos (HbSS) patients the life time prevalence of acute splenic sequestration is reported to be between 7%-30%.

• it may be seen as early as 8 weeks of age although usually an initial event is seen in toddlers
• in HbSC and HbS/thalassaemia patients the initial event tends to occur later in life (even into adulthood) (2)

During a crisis the sequestered sickle cells cause the spleen to become grossly enlarged. This is more common in infancy as repeated sequestration and infarction of the spleen during childhood gradually results in an auto- splenectomy. There is marked pallor with cardiovascular collapse due to loss of effective circulating volume (2).

A patient with a sequestration crisis is usually severely anaemic (2-3 g/100 ml), but the reticulocyte count will be high, in contrast to the aplastic crisis where the reticulocyte count is low or zero.

Sequestration crises also occur in pregnant women.

Immediate management of sequestration crises is aimed at correcting hypovolaemia with emergency blood transfusion. The subsequent management depends on the recurrence rate of splenic sequestration and may include observation, chronic transfusion and splenectomy (3).

The important features are:

• sequestration crises recur
• splenectomy is curative - and is recommended after two episodes
• educating the parents about the proper management is vital, particularly in the developing world

Similar sequestration episodes may occur in the liver in adults.

Reference:

• (1) Okpala I. The management of crisis in sickle cell disease. Eur J Haematol. 1998;60(1):1-6
• (2) Ballas SK, et al. Definitions of the phenotypic manifestations of sickle cell disease. Am J Hematol. 2010;85(1):6-13.
• (3) National Institute of Health. National heart, lung and blood institute, Division of blood diseases and resources. The management of sickle cell disease.