Sickle cell disease

What it is

The sickle cell is a sickle-shaped RBC, and the shape comes from polymerization of hemoglobin S. The sickle cell disorders named are HbSS and HbSC.

How it presents

When hemolysis increases, pallor, jaundice and a non-tender palpable hepatosplenomegaly appear. The baseline is already abnormal, so it is the move away from baseline that matters. In one described admission a baseline hemoglobin of 9g/dL with a reticulocyte count of 200x10^9/L moved to hemoglobin 8.5g/dL, reticulocytes 210x10^9/L, WBC 14x10^9/L, platelets 120x10^9/L, and bilirubin 210 with a direct bilirubin of 120, against a normal 11.5-15.5 g/dL, 20-150x10^9/L, 2.2-10x10^9/L, 140-400x10^9/L, 0-17 umol/L and 0-4 umol/L.

How it is diagnosed

The Sickledex test is positive. The blood film shows many target cells. Hemoglobin variant analysis gives the pattern, and on HPLC sickle cell anemia HbSS runs HbA 0% with HbS 90-95%, while sickle cell trait HbAS runs HbA above 50% with HbS under 40%. A worked example beside that rule is worth holding: a positive Sickledex test, many target cells on the film and a variant analysis of Hb A 55%, Hb S 41%, Hb F 2% and HbA2 4, in a young man with leg pain, swelling and tenderness in the anterior aspect of the shin, no transfusions in the past and a strong family history of sickle cell disease, is sickle cell trait - not sickle cell anemia HbSS, not sickle cell/B+ thalassemia, not sickle cell disease with hereditary persistence of Hb F and not sickle cell disease HbS OArab. Its Hb S of 41% sits just above the under 40% of the rule above it, and both stand as written. Target cells, the codocytes with a bull's eye on the dried film, are not tied to sickle cells alone: they are also listed with liver disease, hemoglobin SC, thalassemia, iron deficiency and asplenia.