Just 100 kms away from Mumbai lives a tribal family in the grip of dreaded sickle cell disease (SCD) or sickle cell anemia. Sugana (belonging to the Warli tribe) had been suffering from this disease for a long time, but was diagnosed only last year at a health camp. Her daughter Rani (6), too, suffers from the disease, while her year-old son, Raja, is yet to be tested. All she knows about the disease is that it is a serious blood disorder, typically inherited from the patient’s parents.
India has the highest number of sickle cell gene carriers in the world, accounting to more than 50 per cent globally. According to Indian Council of Medical Research, 20 per cent of children with sickle cell disease die by the age of two and 30 per cent of children with this disease (in tribal community) die before they reach adulthood.
Sickle Cell anaemia
It is a genetic disorder resulting from inheritance of abnormal haemoglobin genes from both parents. Red blood cells (RBC) with normal haemoglobin are generally round. In SCD patients, the haemoglobin molecules are abnormal, which make their RBC sickle- or crescent-shaped. These RBC die prematurely, which can lead to anaemia. Further, the abnormal RBC gets stuck in small blood vessels, slowing down the passage of blood and oxygen, leading to severe pain,jaundice, anaemia and recurrent infections.
A person having two copies of the abnormal gene has SCD, while a person having only one copy of the abnormal gene is said to be a carrier (sickle cell trait). Carriers don’t have the disease, but can pass the defective gene to their children.
Sharing an insight on SCD, Dr Sheetal Sharda, clinical geneticist at a genomics-based diagnostics and research company in Bengaluru, says, “This disease is mainly associated with malaria-endemic areas and African lineage. SCD has significant implications such as higher morbidity and mortality, poor quality of life and lower life expectancy. Of 18 crore tribal population, approximately 1.80 crore people are carriers of SCD, while 14 lakh people suffer from it.”
The only cure for SCD is bone marrow transplantation. In this procedure, the patient is transplanted with bone marrow from healthy, genetically compatible sibling donors. However, only less than 20 per cent of children with this disease have a healthy, matched sibling donor. Gene therapy promises a cure, but is still in experimental stages.
In India, newborn screening programmes for SCD among tribal and non-tribal populations have only recently been initiated during the last three-five years in south Gujarat, Maharashtra, Chhattisgarh, Odisha and Madhya Pradesh. In case of newborns detected with SCD, the disease may express its severity only after a particular age and a timely course of medication and vaccines.
Carriers are known to develop splenic infarct at high altitudes, impaired renal concentrating abilities, and intermittent micro- and macroscopic hematuria.Based on various national programmes by the state governments, the awareness regarding the SCD and the prevention strategies are being accepted. They are now more open to carrier screening and preconception counselling. “Genetic counselling plays an important role in helping the patients understand the disease, its management and implications. The prevalence of these disorders has been reduced drastically in many countries through carrier screening and premarital/peri-conceptional genetic counselling. In India, population screening followed by genetic counselling is a well-accepted option,” says Dr Sharda.
Carrier screening: It is a simple blood test which can be done either before marriage or before planning a baby. It helps to diagnose if you or your partner has sickle cell trait, and the chances about you passing it on to your baby.
New born screening: All babies are screened at birth for sickle cell anemia and for early management of disease. This will reduce the morbidity and mortality associated with it. If undetected, it can lead to life-threatening complications and early death.
Prenatal diagnosis: This helps find out whether a couple’s foetus is affected. It also helps in pre-implantation genetic diagnosis to a couple opting for IVF (in vitro fertilisation) in order to test their embryo for sickle cell anaemia before transplantation.