Acute chest syndrome in a child with sickle cell crisis

Clinical History

A patient presented with respiratory symptoms and anaemia.

Imaging Findings

A patient with a known history of sickle cell anaemia presented with a chest pain, cough, fever and leukocytosis. Her haemoglobin when measured was 7.2g/dl. PA and lateral chest radiographs were also performed.

Discussion

Sickle cell anaemia (SCA) is a hereditary form of haemolytic anaemia in which an abnormal beta-globin chain (HbS) is synthesised. The disease is inherited as an autosomal recessive condition. The heterozygotic form is known as sickle cell trait. Geographically, HbS is commonly present in Sub-Saharan Africans, and it is found in 8-13% of African-Americans. Patients with homozygous HbS (i.e. SCA) get affected by severe haemolytic anaemia punctuated by crises. The acute chest syndrome (ACS) is one of the more common complications of SCA and is fatal found to be in 10%–25% of children aged less than 10 years. Recurrent ACS leads to pulmonary arterial hypertension and cor pulmonale.Patients who are affected present with acute chest pain, fever and leukocytosis. They have varying degrees of anaemia and hypoxaemia. The aetiology of ACS is unclear. Some authors suggest that it could be due to pulmonary thromboses and infarction, others say that pulmonary intravascular sickling could be responsible. Pulmonary infection is believed to be a less likely cause. The chest radiograph in ACS shows patchy uni- or bilateral lower lobe infiltrates. There may be associated uni- or bilateral pleural effusions. The severity of the chest radiograph findings in ACS mirrors the severity of the patient's clinical condition. However, the radiographic abnormalities may not be visible several days after the patient presents. It is difficult to differentiate between pulmonary infarction and infection based on chest radiographs. Thin section CT can be used to diagnose microvascular occlusion in ACS with a reasonable degree of accuracy (sensitivity 84%, specificity 97% in one study). A paucity or absence of small vessels near pulmonary opacities suggests a vaso-occlusive rather than an infectious crisis. The use of V/Q scans in ACS proves to be unhelpful, but a negative gallium scan would again favour a diagnosis of pulmonary infarction rather than of infection. Other diagnostic features of SCA that may be visible on the chest radiograph include the cardiomegaly of severe anaemia; hepatomegaly due to haemolysis and extramedullary haematopoiesis; a calcified, auto-infarcted, tiny spleen; and paravertebral soft tissue masses due to extramedullary haematopoiesis. Visible bony changes of SCA include avascular necrosis of the humeral head; sclerosis of the humeri and ribs due to old bone infarcts; and a thickening of the ribs due to marrow hyperplasia. The vertebral bodies have a characteristic H-shape (codfish, Lincoln-log) due to infarction of the central portions of the end plates. Patients with ACS are treated empirically with oxygen, rehydration, analgesia and broad spectrum antibiotics. Those with a marked fall in haemoglobin levels may be transfused with packed red cells. Exchange transfusions are reserved for severe cases. Both arterio-venous and veno-venous ECMO have been used in cases of life-threatening ACS with some success. Our patient recovered from this crisis, but was known to have had at least one further episode of acute chest syndrome.

Differential Diagnosis List

Final Diagnosis

Acute chest syndrome in sickle cell anaemia.

URL:	https://eurorad.org/case/2146
DOI:	10.1594/EURORAD/CASE.2146
ISSN:	1563-4086