The amount of bone marrow increases, leading to fragile bones and tower skull. The heart also enlarges to try to improve oxygen transport by pumping more blood. The anemia itself causes weakness and poor mental and physical development. The abnormal sickle cells are collected in the spleen which enlarges and becomes fibrotic. Most serious are problems caused by clumping of sickle cells, which tends to clog capillaries and cause local failures of blood supply.
Patients often have episodes of severe abdominal or joint pain as a consequence.
The lack of adequate blood supply causes kidney damage, strokes, heart damage and frequent cases of pneumonia. The only remedy for years was blood transfusions, but this provided only temporary relief and leads to accumulation of toxic levels of iron. Long term consequences of using these compounds have yet to be determined. More promising may be the use of bone marrow transplant or introduction of cells from fetal tissues that do not induce antibody responses, but these are also experimental treatments at this time.