Sickle Pathology

Polymerization allows deoxygenated hemoglobin to exist as a semisolid gel that protrudes into the cell membrane, distorting RBCs into sickle shapes. Sickle-shaped RBCs increase blood viscosity and encourage sludging in the capillaries and small vessels. Such obstructive events lead to local tissue hypoxia and accentuate the pathologic process. 

The (Cu,Zn)-SOD levels in erythrocytes of normal human subjects are fairly constant 461 46 (standard deviation) gg/g hemoglobin. Results are also reported for several pathological conditions Small differences were e.g. observed in erythrocytes with on the average a 19 % decrease in patients with Duchenne muscular dystrophy and a 20% increase in black alcoholics in contrast with white alcoholics Sickled erythrocytes showed significantly higher levels of (Cu,Zn)-SOD 170 % on the average of those of normal erythrocytes Tumor cells as a rule seem to have lower or zero levels of (Mn)-SOD... 

Figure 2-5. Pathologic changes in sickle cell diseases. Vaso-occlusion is a combination of exposure of phosphatidylserine on the red cell membrane, activation of vascular endothelial cells, activation of leukocytes, and a state of increased coagulability. From Steinberg, 1999. Copyright 1999, Massachusetts Medical Society. All rights reserved.

There are many abnormal or mutant hemoglobins, some of which cause pathological conditions. One is sickle-cell hemoglobin (HbS), in which the glutamate residue in the sixth position of the normal human hemoglobin (HbA) /3 chain has been replaced by valine. This position, referred to as /36, is on the outside of the hemoglobin molecule. Individuals who... 

A 30-year-old man with schizophrenia developed priapism for 8 hours after taking chlorpromazine for 3 years (13). He was taking no other medications and there were no other pathological findings a complete blood count and sickle cell screen were normal. Aspiration of blood from the corpora cavernosa, followed by saline irrigation led to complete detumescence. 

Song, J., Pathology of Sickle Cell Disease. Thomas, Springfield, Illinois, 1971. 

It appears, therefore, that while some of the details of this picture of the sickling process are as yet conjectural, the proposed mechanism is consistent with experimental observations at hand and offers a chemical and physical basis for many of them. Furthermore, if it is correct, it supplies a direct link between the existence of defective hemoglobin moleeules and ibe pathological consequences of sickle cell disease. 

Table 2I.I. Classification of musculoskeletal conditions that may present with pathological fractures in children. Several conditions could be included in more than one category. For example, sickle cell disease is both a congenital and developmental disorder as well as haematopoietic. For the sake of simplicity each disorder is only included once in the overall classification...

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