The 5 most common human genetic diseases

Guido Putignano
Yealthy
Published in
5 min readSep 15, 2022

The completion of Human Genome Project in 2003 has helped to identify genes associated with many genetic diseases. As a result, scientists were able to develop genetic testing which could confirm a diagnosis or a carrier state of the disease or predict future illness or even a response to therapy. There are currently over 2000 genetic tests available. Many human diseases have a genetic component to them. There are over 6,000 genetic disorders, many of which are fatal or severely debilitating. A genetic disease is caused when a mutation occurred in DNA.

Source: Stanford.edu

Genetic diseases can be divided into 4 major groups:

(1)Single-gene mutation.

(2)Multiple genes mutations.

(3)Chromosomal changes.

(4)Mitochondrial mutations.

As scientists discover the secrets of the human genome (the complete set of human genes), nearly all diseases have a genetic component. Some diseases are caused by mutations that are inherited from the parents and are present in an individual at birth, like sickle cell disease. Other diseases are caused by acquired mutations in a gene or group of genes that occur during a person’s life. Such mutations are not inherited from a parent but occur either randomly or due to some environmental exposure (such as cigarette smoke). These include many cancers, as well as some forms of neurofibromatosis.

These are 5 common human genetic diseases:

Down Syndrome

Typically, the nucleus of an individual cell contains 23 pairs of chromosomes, but Down syndrome occurs when the 21st chromosome is copied an extra time in all or some cells. After detailed prenatal screening tests, like blood tests, that detect quantities of chromosomal material and other substances in a mother’s blood. Physicians can determine, with high accuracy, whether or not a child will be born with Down syndrome. When a person is diagnosed with Down syndrome, they are likely to exhibit varying levels of mild to severe cognitive delays. Other markers of Down syndrome include a higher disposition for congenital heart defects, low muscle tone, smaller physical stature, and an upward slant to the eyes. Also, the older a mother is at the time of birth, the more likely the child is to have Down syndrome.

Thalassemia:

Thalassemia is an inherited blood disorder in which the body makes an abnormal form of haemoglobin. Haemoglobin is the protein molecule in red blood cells that carries oxygen. The disorder results in excessive destruction of red blood cells, which leads to anaemia. Anaemia is a condition in which your body does not have enough normal, healthy red blood cells. Thalassemia is inherited, meaning that at least one of your parents must be a carrier of the disorder. It’s caused by either a genetic mutation or a deletion of certain key gene fragments. Thalassemia minor is a less serious form of the disorder. There are two main forms of thalassemia that are more serious. In alpha thalassemia, at least one of the alpha globin genes has a mutation or abnormality. In beta thalassemia, the beta globin genes are affected. Each of these forms of thalassemia has different subtypes. The exact form you have will affect the severity of your symptoms and your outlook.

Symptoms of Thalassemia:

The symptoms of thalassemia can vary. Some of the most common ones include bone deformities, especially in the face. Another symptom is the dark color of urine. The patient also feels fatigued and tired. Other than that, abnormal and delayed growth of different parts. Not everyone has visible symptoms of thalassemia. Signs of the disorder also tend to show up later in childhood or adolescence.

Cystic fibrosis:

Cystic fibrosis is an inherited condition that causes sticky mucus to build up in the lungs and digestive system. This causes lung infections and problems with digesting food. Symptoms usually start in early childhood and vary from child to child, but the condition gets slowly worse over time, with the lungs and digestive system becoming increasingly damaged. Treatments are available to help reduce the problems caused by the condition and make it easier to live with, but sadly life expectancy is shortened.

Symptoms of cystic fibrosis include recurring chest infections, wheezing, coughing, shortness of breath and damage to the airways (bronchiectasis), difficulty putting on weight and growing, jaundice diarrhea, constipation, or large, smelly poo, bowel obstruction in newborn babies (meconium ileus). People with the condition can also develop several related conditions, including diabetes, thin, weakened bones (osteoporosis), infertility in males, and liver problems.

Tay-Sachs Disease:

Tay-Sachs disease is a rare inherited disorder that progressively destroys nerve cells in the brain and spinal cord. The most common form of Tay-Sachs disease becomes apparent in infancy. Infants with this disorder typically appear normal until the age of 3 to 6 months, when their development slows, and muscles used for movement weaken. Affected infants lose motor skills such as turning over, sitting, and crawling. They also develop an exaggerated startle reaction to loud noises. As the disease progresses, children with Tay-Sachs disease experience seizures, vision and hearing loss, intellectual disability, and paralysis. An eye abnormality called a cherry-red spot, which can be identified with an eye examination, is characteristic of this disorder. Children with this severe infantile form of Tay-Sachs disease usually live only into early childhood [6]. Tay-Sachs disease is broken down into the classic or infantile form, the juvenile form, and the adult or late-onset form. In individuals with infantile Tay-Sachs disease, symptoms typically first appear between three and five months of age. In individuals with the late-onset form, symptoms may become apparent anytime from adolescence through the mid-30s.

Sickle cell anemia:

Sickle cell anaemia (sickle cell disease) is a disorder of the blood caused by inherited abnormal haemoglobin (the oxygen-carrying protein within the red blood cells). The abnormal haemoglobin causes distorted (sickled appearing under a microscope) red blood cells. The sickled red blood cells are fragile and prone to rupture. When the number of red blood cells decreases from rupture anaemia is the result. This condition is referred to as sickle cell anaemia. The irregular sickled cells can also block blood vessels causing tissue and organ damage and pain. Sickle cells cause swelling in the hands and feet and lead to joint pain that feels like arthritis and also causes a decrease in red blood cells (Anemia) As of today, there is no cure for sickle cell anaemia. However, some treatments have reduced the death rate among children and the levels of pain caused by the disease.

Above mentioned disease can be cured by gene therapy (Source: http://pixshark.com/somatic-gene-therapy-diagram.htm)

References:

[1] https://www.labroots.com/trending/infographics/8833/10-common-genetic-diseases.

[2] https://www.genome.gov/For-Patients-and-Families/Genetic-Disorders.

[3] https://online.regiscollege.edu/blog/information-5-common-genetic-disorders.

[4] https://www.healthline.com/health/thalassemia#symptoms.

[5] https://www.nhs.uk/conditions/cystic-fibrosis.

[6] https://medlineplus.gov/genetics/condition/tay-sachs-disease.

[7] https://rarediseases.org/rare-diseases/tay-sachs-disease.

[8] https://www.medicinenet.com/sickle_cell/article.htm.

[9] https://my.clevelandclinic.org/health/diseases/4579-sickle-cell-anemia.

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Guido Putignano
Yealthy
Editor for

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