Q: I was diagnosed with sickle cell trait from birth. My parents were told that people with this trait don't get sick and have nothing to worry about. My doctors say that I don't need to take medication regularly. Is this true?

A:Sickle cell anaemia is an inherited disease of the blood, which is characterized by chronic anaemia and periodic episodes of pain. It is caused by an error (mutation) in the gene that controls haemoglobin synthesis. The mutation leads to synthesis of sickle haemoglobin (Hb S) instead of normal adult haemoglobin (Hb A) resulting in deformed (sickle-shaped) red blood cells. Two genes regulate haemoglobin synthesis. If an individual inherits copies of the defective gene from both parents, he/she will have sickle cell anaemia while individuals inheriting only one defective sickle haemoglobin gene from one parent will not have the disease, but will carry the sickle cell trait. Individuals with sickle cell trait generally have no symptoms, but they can pass the sickle haemoglobin gene on to their children Sickle cell trait is not considered a disease because complications are usually rare and mild. But under some unusual circumstances complications related to polymerisation of deoxy-haemoglobin S may occur. This can be so in urinary tract infection in women, gross haematuria, complications of hyphema, splenic infarction at high altitude or exercise or exertional heat illness. Conditions that cause hypoxia, acidosis, dehydration, hyperosmolality, hypothermia, or elevated erythrocyte 2,3-DPG can transform silent sickle cell trait into a syndrome resembling sickle cell disease with vaso-occlusion due to rigid erythrocytes. Determination that a clinical syndrome is due to sickle cell trait rather than a subtle form of sickle cell disease is difficult. Compound heterozygous sickle cell disease can be mistaken as uncomplicated sickle cell trait, particularly when an unusual globin variant is involved (other variants of beta or alpha globin that produce undiagnosed sickle cell disease). Sometimes it may be due to phenotypes with increased 2,3-DPG or with arterial desaturation which increases the rate of polymerisation of haemoglobin S sufficiently to convert a patient with sickle cell trait into phenotypic sickle cell disease.