8 Common Gene-Linked Disorders

According to Elizabeth Corwin, Ph.D., author of “Handbook of Pathophysiology” there are around 4,500 diseases due to single gene disorder alone. Single gene disorders are diseases which are a result of a mistake made in one gene. In addition to the single gene disorder, there are the genetically transmitted diseases which are a result of mistakes caused by several genes. A genetically transmitted disease is caused by some genetic disorder like abnormalities in the genome or some congenital condition. They are usually rare and affect one person in several thousands or million.

Here are some “common” genetically transmitted diseases:

  1. Cystic Fibrosis:

Cystic fibrosis (Located on human chromosome 7, the CFTR gene), or CF, is an inherited disease of the secretory glands. Secretory glands include glands that make mucus and sweat. CF mainly affects the lungs, pancreas, liver, intestines, sinuses and sex organs. A defect in the CFTR gene causes this disease. This gene makes a protein that controls osmosis in the cells. In people who have cystic fibrosis, this gene makes a defective protein that doesn’t work well. This causes thick sticky mucus and very salty sweat. Unfortunately, this disease has no cure though with some medicines and respiratory treatments the patient’s lifespan can be increased.

  1. Huntington’s disease:

Huntington’s Disease (Caused by the mutation of HTT  gene located on the chromosome 4) causes the degeneration of the nerve cells in the brain and central nervous system.  This hereditary condition is the autosomal dominant disorder, meaning that children have a 50-percent chance of developing it and passing it along to their own children if one of their own parents has it. Treatment aims to limit the course of the disease. HD typically shows itself when the individual is between 30 and 40-years old—however, rare forms begin in childhood. Symptoms of HD include uncontrolled movement (chorea), difficulty in swallowing, behavioral changes, difficulty in balancing and walking, memory, speech, and cognitive loss.

  1.  Down Syndrome:

Down Syndrome, a common chromosomal abnormality where the most common form of Down’s syndrome is known as Trisomy 21, a condition where individuals have 47 chromosomes in each cell instead of 46 that affects approximately 1 in 1000 newborns (particularly in older expectant mothers), results when an extra copy of genes occurs on chromosome 21. Although Downs can be detected by prenatal testing,  babies affected typically show the following features at birth—decreased muscle tone in the face, developmental delays, and heart and digestive system defects.

  1. Duchenne Muscular Dystrophy:

Inherited in an X-linked recessive pattern. Males have only one copy of X-chromosome from their mother and one copy of the Y chromosome from their father. If their X chromosome has a DMD gene mutation, symptoms of Duchenne Muscular Dystrophy typically show themselves before the age of 6. The condition causes fatigue and weakness of the muscles, which starts in the legs and then gradually progresses to the upper body, leaving individuals wheelchair bound by the age of 12-years-old. For some reason, the condition affects mostly boys with symptoms such as heart and respiratory difficulties, deformity of the chest and back, and potential mental retardation.

  1. Sickle Cell Anemia:

Sickle cell disease is caused by a mutation in the hemoglobin-Beta gene found on chromosome 11. Sickle cell anemia (SCA) occurs when red blood cells are unable to carry adequate oxygen throughout the body due to their deformation—healthy red blood cells are disc-shaped, but those with SCA have crescent-shaped red blood cells).  SCA can only occur a few times in one lifetime and is often present in those of African, Mediterranean, Caribbean, South and Central American, and Middle Eastern descent. This genetic disease is extremely painful, causing abdominal, chest, and bone pain, fatigue, shortness of breath, accelerated heart rate, delayed puberty, stunted growth, fever, and leg ulcers. Pain medication, rounds of folic acid, kidney dialysis, and blood transfusions can help ease some symptoms.

  1. Thalassemia:

Thalassemia refers to a collection of genetic blood disorders. It occurs when hemoglobin (oxygen-carrying molecules in the blood) can’t become synthesized by red blood cells. A Thalassemia often leads to an anemia (which typically occurs with decreased hemoglobin in the blood) and causes similar symptoms to occur—like fatigue, an engorged spleen, bone pain, a propensity to broken bones, shortness of breath, lack of appetite, dark urine, jaundice (a yellowing of the skin and whites of the eyes), and liver dysfunction.

  1. Celiac disease:

This digestive, genetic disorder inflicts patients with gluten intolerance—basically those afflicted with Celiac Disease are unable to digest any products or food containing gluten (i.e., foods processed from wheat and related grain). If left undiagnosed, the disease will often lead to malnutrition and dehydration due to severe diarrhea. Additional signs of the condition include abdominal bloating and digestive pain.

  1. Bloom’s Syndrome:

Bloom syndrome is inherited as an autosomal recessive genetic trait. The defective gene has been mapped to chromosomal locus 15q26.1 and is responsible for encoding a protein known as BLM. A single mutation, known as blmAsh, is responsible for almost all cases of Bloom syndrome among Ashkenazi Jews, they are the most prone ethnicity to Bloom’s Syndrome, with the genetic condition afflicting one in 110 in cases where parents carry the affected DNA and transmit it to a biological child. Bloom’s Syndrome increases the risk of certain types of cancer in childhood, as well as chronic pulmonary disease and type 2 diabetes. Additional indicators include smallish stature, sun-sensitive skin, a bloated nose, a high-pitched voice, face rash, and a narrowing of the face.

References-

http://www.asgct.org/about_gene_therapy/diseases.php

https://www.cff.org/What-is-CF/About-Cystic-Fibrosis/

https://ghr.nlm.nih.gov/condition/huntington-disease

http://www.ndss.org/Down-Syndrome/What-Is-Down-Syndrome/

https://www.nlm.nih.gov/medlineplus/ency/article/000705.htm

http://www.nhlbi.nih.gov/health/health-topics/topics/sca

https://www.nlm.nih.gov/medlineplus/ency/article/000587.htm

http://www.webmd.com/digestive-disorders/celiac-disease/celiac-disease-topic-overview

https://ghr.nlm.nih.gov/condition/bloom-syndrome

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