**13.2.4 Sickle cell disease**

Sickle cell disease is the most common hereditary blood disorders. It occurs almost exclusively among black americans and black africans, related with the presence of a mutated form of hemoglobin, hemoglobin S. Bone and joint problems are the most common manifestations. Distinguishing sickle cell crisis with possible bone marrow infartion from osteomyelitis is a challenge (Shammas, 2009; as cited in Connolly et al., 2007). Bone marrow scan with 99mTc-sulfur colloid plus conventional bone scan may be used in the evaluation of sickle cell disease, but it should be done within the first 7 days after the pain onset to be helpful in the differential diagnosis (Shammas, 2009). If the bone marrow scan is abnormal at the site of pain, followed by normal or decreased uptake on conventional bone scan, infarction is the likely diagnosis. Increased uptake in blood pool and delayed images on conventional bone scan is more suggestive of osteomyelitis (Shammas, 2009; as cited in Gilday, 2003).
