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

Breast Cancer and the Genes Behind it

Before we delve into the topic of breast cancer and the genes behind it, let’s first brush up on our basics, what is cancer? Cancer is the name given to a collection of related diseases. In all types of cancer, some of the body’s cells begin to divide without stopping and spread into surrounding tissues.It can start almost anywhere in the human body, which is made up of trillions of cells. Normally, human cells grow and divide to form new cells as the body needs them. When cells grow old or become damaged, they die, and new cells take their place.When cancer develops, however, this orderly process breaks down. As cells become more and more abnormal, old or damaged cells survive when they should die, and new cells form when they are not needed. These extra cells can divide without stopping and may form growths called tumors.

 

Now that we know what exactly cancer is, let’s discuss breast cancer, as we can figure from the name, the majority of this cancer’s victims are females, with their risk of getting it increasing with age. One in eleven women gets breast cancer at some point in their lives. While there are quite a lot of factors which increase the chances of a lady getting breast cancer, One that increases the chances the most is inheriting it via your parents. Breast cancer caused by inheriting a changed gene is called hereditary cancer. We all inherit a set of genes from each of our parents. Sometimes there’s a change (called a mutation) in one copy of a gene which stops that gene from working properly.

There are several genes for which inherited changes may be involved in the development of both breast and ovarian cancer. These are genes which normally control cell growth and prevent a woman getting breast or ovarian cancer. Some of these are genes that you may have heard are BRCA1 and BRCA2. Their names come from the abbreviation of ‘breast cancer 1’ and ‘breast cancer 2’. Both men and women can inherit a change in these genes.If a woman has inherited a change in one of these genes, she has a higher chance of breast or ovarian cancer but that doesn’t mean she’s certain to get cancer. Less than 5% of all breast and ovarian cancers can be explained by an inherited gene change in BRCA1 or BRCA2.

Breast-Cancer

Like all cancers, if found early, it can be promptly treated. Any change in the size or shape of the breast, a lump in or close to the breast,any change in the nipple, such as a discharge

What exactly are BCRA1 and BCRA2? BRCA1 and BRCA2 are human genes that produce tumor suppressor proteins. These proteins help repair damaged DNA and, therefore, play a role in ensuring the stability of the cell’s genetic material. When either of these genes is mutated or altered, such that its protein product either is not made or does not function correctly, DNA damage may not be repaired properly. As a result, cells are more likely to develop additional genetic alterations that can lead to cancer.

Abnormal BRCA1 and BRCA2 genes may account for up to 10% of all breast cancers or 1 out of every 10 cases.

 

Are genetic tests available to detect BRCA1 and BRCA2 mutations?

Yes. Several different tests are available, including tests that look for a known mutation in one of the genes (i.e., a mutation that has already been identified in another family member) and tests that check for all possible mutations in both genes. DNA (from a blood or saliva sample) is needed for mutation testing. The sample is sent to a laboratory for analysis. It usually takes about a month to get the test results.

As the saying goes, “Knowledge is power” And the saying is especially true in this case, for you now hold the power to potentially cure yourself of this cancer if you treat it at the right time. Regular tests, along with a healthy lifestyle can ensure that your risk of getting this cancer is at a minimum.  

References-
https://www.cancervic.org.au/genetics-breast-cancer

http://www.cancer.gov/about-cancer/causes-prevention/genetics/brca-fact-sheet

http://www.breastcancer.org/risk/factors/genetics

Breast Cancer and the Genes Behind it