HEREDITARY HEMOCHROMATOSIS Coco DelVecchio Period 4

What is the disease?

Hereditary hemochromatosis (HHC) is a genetic disorder in which the body fails to regulate the absorption of iron from the diet, resulting in damaged tissue and organs.

There are two types of HHC: Primary (hereditary) and secondary hemochromatosis. This presentation will focus solely on primary hemochromatosis because it is the genetic disease, and secondary is not.

The gene HFE is most responsible for the cause of this particular disease. HFE consists of two common mutations: C282Y and H63D. The HFE gene has a sequence made up of 343 amino acids. Two missense mutations in the HFE gene, which can be found on chromosome 6, were discovered. The more important one was a single mutation of guanine to adenine at nucleotide 845, later causing the substitution of tyrosine for cysteine in the amino acid sequence. This is known as the C282Y mutation. The other is the H63D mutation. HFE also produces a "343-residue type I transmembrane glycoprotein", which is a protein used to modulate iron uptake.

Inheriting both of these genetic mutations causes a person to be more susceptible to hereditary haemochromatosis. This type of inheritance pattern is referred to as autosomal recessive.

Symptoms of Hereditary Hemochromatosis

Hereditary hemochromatosis is usually detected at birth, but symptoms often occur later in life, at approximately ages 50-60 for men, and above 60 for women. This is because women above 60 stop menopause, causing the iron levels in blood to increase.

Common HHC Prognoses

Short-Term

Joint and abdominal pain, weakness, and fatigue.

Long-Term

Heart and liver failure, diabetes, and impotence.

Statistics & Research

Hemochromatosis is one of the most dangerous and deadliest genetic diseases in the world. When left untreated, like most illnesses, the results can be fatal. Many risk factors play into the chance of obtaining HHC or not, such as gender, age, family history, and even ethnicity.

About 1 in 200 people of European descent inherit hemochromatosis-causing genes. Hemochromatosis is not as common in ethnicities such as African-American, Hispanic and Asian-American.

1 in 9 people of European ancestry carry at least one copy of the defective gene for hemochromatosis. People with one copy of the gene have a 50% chance of passing it to the next generation.

Interestingly, people from Celtic origin are more susceptible to HHC than people from the rest of Europe. It is believed that hemochromatosis originated in Northern Europe about 60 to 70 generations ago, and has since spread throughout.

HHC is expressed more severely in males than in females, due to the fact that females have a continuous method for ridding excess blood from the body (menstrual cycle).

In America, 1 in 8 to 10 people have a single copy of the mutated gene. This means that they are simply carriers of the disorder and will be perfectly healthy, but still have the chance of passing it on to their son or daughter. However, an estimated 1.6 million Americans (0.5%) are believed to carry both gene copies for HHC, and half of them will develop complications later in life.

The gene HFE was discovered in 1996 by scientists in California and has since allowed an increased understanding of the disorder HHC.

“We believe this research will further the search for the factors that determine which people with the genetic markers for hemochromatosis go on to develop this very serious disease." – Bruce R. Bacon, M.D.

A study conducted on January 16th, 2008 shed new light on the incidence of the disease. Prior to this, scientists struggled to find what percentage of those with the C282Y mutation would go on to develop HHC. Their estimates seemed very low, all under one percent, but through recent studies, New England Journal of Medicine has discovered that the commonality of the iron overload disorder is much higher, more specifically among men. Researches continue to discover everything they can about HHC. In April of 2015, a study conducted by the Texas Tech University Health Science Center showed that hemochromatosis has the potential to trigger colonic inflammation and colon carcinogenesis, or more simply put, HHC can cause colon cancer.

Diagnoses and Treatment

Damage to tissues and organs from iron buildup can be prevented as long as hemochromatosis is diagnosed and treated early enough. Doctors diagnose HHC with the following blood tests:

  • TIBC: stands for total iron-binding capacity; measures the amount of iron that the blood is able to carry
  • serum ferritin: measures the amount of ferritin, a protein that contains iron
  • serum iron: measures iron concentration levels in the blood

Genetic testing or DNA analysis is also another method for detecting some cases HHC. Other times, doctors will need to perform a biopsy: taking a small liver tissue sample to look for iron changes in the cells.

HHC Treatments

Phlebotomy, the process of regularly drawing blood to lower the level of iron, is the most common treatment for iron overload disorder.

Citations

Frantz, Christopher N., M.D., editor. “Hereditary Hemochromatosis.” KidsHealth, Sept. 2014, kidshealth.org/en/parents/hh.html?WT.ac=ctg#. Accessed 5 Feb. 2017.

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Ganapathy, Vadivel. “Abstract 1557: The Iron-Overload Genetic Disease Hemochromatosis Potentiates Colonic Inflammation and Colon Carcinogenesis.” Cancer Research, American Association for Cancer Research, 1 Aug. 2015, cancerres.aacrjournals.org/content/75/15_Supplement/1557.short. Accessed 5 Feb. 2017.

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“Hemochromatosis.” Mayo Clinic, www.mayoclinic.org/diseases-conditions/hemochromatosis/home/ovc-20167289. Accessed 31 Jan. 2017.

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“Hemochromatosis - Causes, Symptoms, Diagnosis, Treatment & Pathology.” Youtube.com, uploaded by Tanner Marshall, M.S., 20 May 2016, www.youtube.com/watch?v=iUga3oM65Bc. Accessed 5 Feb. 2017.

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“Hereditary Hemochromatosis.” Genetics Home Reference, U.S. National Library of Medicine, 24 Jan. 2017, ghr.nlm.nih.gov/condition/hereditary-hemochromatosis#synonyms. Accessed 1 Feb. 2017.

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“Hereditary Hemochromatosis.” Vimeo.com, uploaded by George Bregante, Mar. 2016, vimeo.com/154775659. Accessed 5 Feb. 2017.

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“HFE hemochromatosis [ Homo sapiens (human) ].” NCBI Blast, National Center for Biotechnology Information, www.ncbi.nlm.nih.gov/gene/3077. Accessed 31 Jan. 2017.

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“Introduction to Genetic Haemochromatosis (GH).” Youtube.com, 28 May 2016, www.youtube.com/watch?v=DqAknj1rW_M. Accessed 5 Feb. 2017. This video was used for some images throughout the presentation.

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“Learning about Hereditary Hemochromatosis.” National Human Genome Research Institute, 23 Oct. 2012, www.genome.gov/10001214/learning-about-hereditary-hemochromatosis/. Accessed 5 Feb. 2017.

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Saint Louis University Medical Center. “Vital New Light Shed on Iron Overload Disorder.” ScienceDaily, 17 Jan. 2008, www.sciencedaily.com/releases/2008/01/080116191408.htm. Accessed 5 Feb. 2017.

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Whittington, Chris. “Genetics of Hereditary Hemochromatosis.” BC Medical Journal, 10 Dec. 2002, www.bcmj.org/article/genetics-hereditary-hemochromatosis. Accessed 5 Feb. 2017.

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Nicole DelVecchio
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