20 of the worst hereditary conditions

We inherit a lot of who we are from our parents and extended family, some good and some bad. Unfortunately, in some cases, serious and potentially debilitating diseases are passed along through family bloodlines. Here are 20 of the worst hereditary conditions.



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Alcoholism

American Addiction Centers reports that children of alcoholics have a twofold to fourfold increased chance of struggling with alcohol abuse as they get older. And according to a study by the National Institute on Alcohol Abuse and Alcoholism, inherited genes can account for 40% to 60% of why a certain individual becomes addicted to alcohol.



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Heart disease

The University of Ottawa Heart Institute notes that several cardiac disorders can be inherited, such as arrhythmias, congenital heart disease, and high blood cholesterol. One such abnormal heart rhythm, Brugada syndrome, is recognizable, and if it’s detected in one family member, chances are others carry the same gene. Coronary artery disease leading to heart attack, stroke, and heart failure can also run in families.



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Breast cancer

According to the American Cancer Society, around 5% to 10% of breast cancer cases are thought to be hereditary, the most common being an inherited mutation in the BRCA1 or BRCA2 gene. On average, a woman with this type of gene mutation has about a 7 in 10 chance of getting breast cancer by age 80, and the risk goes up if more family members are affected.



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Duchenne Muscular Dystrophy

According to the Muscular Dystrophy Association, the Duchenne form of muscular dystrophy is hereditary in nature; a mutated gene on the X chromosome was identified as the cause in 1986. The condition occurs when a specific protein is absent from muscles, causing damage and progressive weakness. Each son born to a woman with the mutation has a 50% chance of inheriting the flawed gene and thus having Duchenne muscular dystrophy. Daughters have a 50% chance of inheriting the mutation and being a carrier. Girls do not usually experience the full effects of the condition the way boys do.



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Huntington’s disease

The Mayo Clinic notes that Huntington’s disease is an inherited condition caused by a defect in a single gene, and each child in the family of a person with the defect has a 50% chance of inheriting it. The disorder causes the degeneration of nerve cells in the brain and a wide range of movement, cognitive and psychiatric issues.



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Hemophilia

According to the World Federation of Hemophilia, the bleeding disorder is often inherited from one or both parents; only about 30% of people with hemophilia did not get it from their parents’ genes. Since the defective gene is on the X chromosome, most hemophiliacs are male, but women can also be both carriers and sufferers of the abnormal bleeding condition.



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Colour blindness

The National Eye Institute reports that as many as 8% of men and 0.5% of women with Northern European ancestry have the common form of red-green colour blindness, and the most common form is inherited. The responsible gene is on the X chromosome, which explains why men are much more likely to be colourblind than women. Inherited colour blindness can be present at birth, begin in childhood, or not appear until adulthood.



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Lactose intolerance

NHS notes that the most common worldwide cause of lactose intolerance (primary lactase deficiency) stems from an inherited genetic fault that runs in families. There is also a rare condition known as congenital lactase deficiency found in newborn babies who produce little or no lactase. This occurs when both parents have a copy of the faulty gene.



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Cystic fibrosis

According to Stanford Medicine, cystic fibrosis is an inherited genetic disease that occurs when both parents pass on the gene. If only one gene is passed along, the person becomes a carrier of the disease, and parents have a 25% chance of having another child with cystic fibrosis. The disease causes persistent lung infections and limits the ability to breathe over time due to the creation of thick mucus in various organs.



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Sickle cell disease

The American Society of Hematology reports that as many as 100,000 Americans have this inherited blood disorder, which causes the production of abnormal hemoglobin, C-shaped red blood cells, and symptoms that include pain, infections, organ damage and other disabilities. Both parents must have either sickle cell disease or sickle cell trait to pass along the disease.



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Thalassemia

NHS notes that thalassemia is a group of inherited conditions that affect hemoglobin, causing sufferers to produce little or none of the substance, which makes them extremely anemic. Faulty genes are the culprit for thalassemia; a child has a 1 in 4 chance of being born with the condition if both parents possess them.



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Fragile X syndrome

According to the World Health Organization, Fragile X syndrome is the single most common inherited cause of mental impairment. It affects 1 in every 3,600 males and 1 in every 4,000 to 6,000 females worldwide. The syndrome is caused by a “fragile” site at the end of the X chromosome, which results in a wide range of behavioural and cognitive symptoms. Carrier females have a 30% to 40% chance of giving birth to a developmentally challenged male child and a 15% to 20% chance of having an afflicted female child.



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Hemochromatosis

The Canadian Liver Foundation notes that hemochromatosis is an inherited disease in which a person’s body absorbs too much iron from their diet. This results in iron being stored in places like the heart and pituitary gland. Hemochromatosis is hereditary. Sufferers will have inherited two defective genes, one from each parent, and siblings of an affected individual have a 25% chance of getting it.



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Marfan syndrome

The Mayo Clinic notes that Marfan syndrome is an inherited disorder that affects connective tissue in the human body, most commonly the heart, eyes, blood vessels and skeleton. People with this condition often have disproportionately long arms, legs, fingers and toes, and are usually tall, thin and have scoliosis. Most people who have Marfan syndrome inherit it from a parent: children have a 50-50 chance of inheriting the defective gene.



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Spinal muscular atrophy

According to the Muscular Dystrophy Association, spinal muscular atrophy affects the part of the nervous system that controls voluntary muscle movement, mostly located in the spinal cord. The disease leads to the loss of muscle mass and nerve cells, impacting motor function. If both parents are carriers of the genetic flaw located on chromosome 5, each pregnancy carries a 25% risk of producing a child with the disease.



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High cholesterol

Johns Hopkins Medicine reports that familial hypercholesterolemia (FH) occurs due to a genetic defect on chromosome 19. The inherited disorder makes it harder for your body to remove “bad” cholesterol from your blood. This drastically increases the risk of heart attack or stroke at a very early age. If both parents have the FH trait, children will also have it, and there’s a 50% chance they will pass it on to their children as well.



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Down syndrome

In the vast majority of cases, Down syndrome is not inherited. However, the Mayo Clinic notes that about 3% to 4% of children with Down syndrome have translocation, which can be passed from parent to child. In these rare cases, the mother or father has some rearranged genetic material from the affected chromosome 21 on another chromosome, but no extra genetic material. This means the parent has no signs or symptoms of Down syndrome, but can pass this unbalanced translocation on to children, which causes the genetic disorder.



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