There are around 10,000 known genetic disorders and with the advancements in genetic testing, many more genetic disorders are coming to the fore and patients are getting the right medical advice and treatment.
The incidence of individual genetic disorders is rare but collectively, there are over 300 million patients living around the world with an undiagnosed genetic disorder. Most countries define rare diseases in context to their own population, health care system and resources. Many times, it is also defined in absolute terms or in terms of prevalence per 100,000 people. But when we flip the same definition the other way around and ask those living/suffering with the condition we realize how frustrating to live with these conditions can be. Many describe the battle on two fronts “one is not knowing what exactly is wrong and second is dealing with a world where very few people understand what you are up against”. Several others describe it as a “Lifelong detective mission”.
In India genetic diseases are seen as a chronic, serious lifelong disease or disorder with a prevalence of less than 1 per 1000. However, owing to the epidemiological data to define genetic diseases in terms of prevalence rate are limited. To overcome this, a hospital-based ‘National Registry for Rare Diseases’ has been initiated by ICMR by involving centres across the country that are involved in the diagnosis and management of rare genetic diseases.
The prevalence of Genetic Disorders.
According to the WHO the prevalence of genetic defects are at about 5% of all births and that holds true for India as well. When we translate it to actual numbers 1.7 million birth annually. The government doesn’t have a collated number of those living with genetic disorders, however there are several estimates that put that number at around 72mn. A study conducted through the March of Dimes Birth Defect Foundation, in 2006, reported the birth defect prevalence in India as 64.4 (per 1000 live births). Other estimates by Rao and Ghosh (2005) report that 1 out of 20 children admitted to hospital has a genetic disorder that ultimately account for about 1 out of 10 childhood deaths.
Major genetic disorders by prevalence in India include Beta thalassemia, Cystic Fibrosis, Spinal Muscular Atrophy, and Down syndrome.
Do Indians have high risk and why?
India is the second most populous country in the world. The socioeconomic and demographic factors lead to a large percentage of genetic anomalies. Even today the enduring practice of in-community marriages increase the number of carriers of genetic diseases. Consanguinity rates in India vary from 1% to 4% in the northern region to 20-30% in the southern region. In addition, the disease-causing genes for the same disease are different between communities (genetic heterogeneity). Many of us may be carrying a copy of defective gene without any symptoms but when we pass it to our offspring it may they can show symptoms because our life partner may also carry a copy of defective gene. This phenomenon is known as Recessive Inheritance. This occurs when both parents, who do not have the disease, pass along the disease causing gene(s) to the child. Due to intra-community marriages and consanguinity, Indian populations have accumulated these genetic defects. According to a multi-centre study conducted by Mohanthy D in 2012, there are around 3 carriers in 100 people (age 17-37) for Beta Thalassemia. When we consider the 2500 recessive genetic disorders, there is a possibility that every one of us is a carrier for at least one of the genetic disorders.
Symptoms of a genetic disorder can manifest at birth or later in life. For example, some types of Muscular Dystrophy symptoms can manifest in childhood and some other types even after 50 years. In late onset genetic disorders the defective genes would have been passed on to the next generation by the time the symptoms manifest.
Treatment and Prevention
Some of the genetic disorders can be treated, and the treatment depends on the severity of the disorder itself. In certain cases, like in congenital birth defects surgery may be used to help repair anatomical congenital disorders. In cases where the gene has mutated and not able to produce the enzyme doctors offer enzyme therapy. Some of the genetic diseases such as Phenylketonuria can be managed by dietary supplements or customised diets.
It has to be noted that majority of the genetic disorders can be prevented by utilizing the advanced genetic diagnosis technologies to detect causal gene mutations. Non-invasive prenatal genetic testing can be used to detect possible chromosomal defects in the foetus at early stages. Genetic carrier screening for at risk couple before conceiving. Genetic screening can be performed for at risk children. With many of the Indians planning a single child, it would be prudent to have a better family planning to lead healthy life.