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HEREDITARY MONOGENIC DISEASES

           

Cystic Fibrosis

Cystic fibrosis develops due to mutations in the cystic fibrosis gene: the CFTR gene. To date, there are about 70,000 cystic fibrosis cases worldwide and each year 1000 new cases are diagnosed. Development of cystic fibrosis is much more common in individuals of European and North American origin than in individuals of Asia and Africa.

Symptoms usually appear during childhood, so if an early diagnosis is made, treatments can be started earlier and thus avoid later complications. The ACMG (American College of Medical Genetics) recommends testing the main cystic fibrosis mutations to those people who plan to have a child.

In tellmeGen we study the most frequent mutations that cause the development of cystic fibrosis. Our DNA test provides accurate information to detect if you or your familiars are cystic fibrosis carriers. To date, there is no cure for the disease, but several cystic fibrosis treatments can improve the patient quality of life.

WHAT IS CYSTIC FIBROSIS?

Cystic fibrosis is a monogenic disease (a type of rare inherited disease) caused by a mutation or alteration in the DNA. Cystic fibrosis causes accumulation of thicker and sticky mucus and sweat in many organs, affecting more severely the lung, the digestive system and the pancreas, being a potential life-threatening disorder if it is not adequately treated.

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What are the genes involved in cystic fibrosis?

CYSTIC FIBROSIS SYMPTOMS

CYSTIC FIBROSIS SYMPTOMS

The main cystic fibrosis symptoms are respiratory complications and digestive complications. Within the respiratory symptoms, cystic fibrosis can produce pulmonary obstruction leading to respiratory failure, nasal obstruction, intolerance to exercise, chronic bacterial infections leading to pneumonia, cough with blood, pneumothorax, respiratory insufficiency, etc.

Within digestive complications, cystic fibrosis can cause nutritional deficiencies, abdominal pain, intestinal infections, digestive failure, diabetes, weight loss, severe constipation, intestinal obstruction, biliary obstruction, etc. In addition to these main symptoms, cystic fibrosis may be associated with infertility, osteoporosis, hyper/hypotension, dehydration, etc.

In children and adolescents, symptoms of cystic fibrosis may produce a delay in growth (due to the difficulty of gaining weight), clubbing of fingers, salty-tasting skin, etc.

The sooner the patient has a cystic fibrosis diagnosis, the less impact it will have on the patient’s life since it will be possible to treat it more efficiently, therefore it is highly recommended that couples who plan to have a child undergo a cystic fibrosis genetic test.

CYSTIC FIBROSIS LIFE EXPECTANCY

Cystic fibrosis life expectancy of a patient promptly diagnosed is approximately 40 years (as opposed to a patient who has not been diagnosed early, whose life expectancy ranges between 5-10 years), and during the coming years it can be increased thanks to the advances in medicine.

Nowadays, cystic fibrosis life expectancy has increased greatly since the disease was described, due to an earlier-accurate diagnosis and to the development of new treatments in the latest years.

In many cases, affected individuals may manifest less severe forms of the disease, forms that may be asymptomatic during childhood and that manifest in adulthood. The key for a better quality of life is an early diagnosis, so the patient can be treated in an accurate and effective manner. For this reason, the DNA tests to detect cystic fibrosis mutations in progenitors and in the child are of high relevance.

CYSTIC FIBROSIS LIFE EXPECTANCY

CYSTIC FIBROSIS TREATMENT

Currently, there is no cure for the disease, but cystic fibrosis treatment enlarges the life expectancy and the quality of life of the patients. Antibiotics are used as a generalized treatment for respiratory tract and digestive system infections.

The antibiotics azithromycin, tobramycin, aztreonam and levofloxacin are mainly used for the control of respiratory infections. NSAIDs, steroids and cromolyn are used to treat inflammation of the respiratory tract.

To treat the problems of the digestive system, intestinal washes are used with solutions that unblock the intestinal tract, such as diatrizoate meglumine and diatrizoate sodium.

In addition to conventional treatments, there are other advanced treatments, such as ivacaftor (Kalydeco), lumacaftor and Orkambi (a combination of ivacaftor + lumacaftor), whose target is the gene responsible for the development of cystic fibrosis (CFTR).

The most advanced treatments consist of molecules that modulate this gene and to prescribe them it is necessary to know the mutations the patient presents, since these drugs are specific for each mutation. Cystic fibrosis definition cannot be complete without referring to the gene and inheritance pattern associated with the disease.

CYSTIC FIBROSIS GENE AND GENETICS

The cystic fibrosis gene is the so called CFTR gene: Cystic Fibrosis Transmembrane RegulatorThis gene produces a protein which function is to act as a channel that regulates the passage of chloride through other channels that exist in the cells that form the walls of the lung and other organs such as the intestine, pancreas, liver and in the reproductive system. These cells are involved in the production of mucus and other types of secretions.

CYSTIC FIBROSIS GENE AND GENETICS

WHAT CAUSES CYSTIC FIBROSIS?

Mutations in the cystic fibrosis gene cause this CFTR channel to work in a defective way, preventing the properly passage of chloride and water and thus causing a mucus much stickier and thicker than the normal. This abnormal mucus is the cause of the pulmonary obstructions producing infections and the cause of obstructions in other organs.

The development of this disease can only be understood if cystic fibrosis genetics is understood. CFTR gene is located at chromosome 7, at position 7q31.2. Cystic fibrosis disease develops when this gene is mutated and thus, the function of the chloride channel is defective. The most frequent mutation among patients with cystic fibrosis is the Phe508del mutation (F508del).

This mutation consists in the elimination of a small part of the gene that makes the amino acid phenylalanine, which is at position 508 of the protein, disappear.

This phenylalanine (Phe or F) is very important for the CFTR channel to be functional, and therefore this variant or mutation is pathogenic. In addition to the Phe508del mutation, the genetic test of tellmeGen provides information on the most common mutations that cause cystic fibrosis.

HOW IS CYSTIC FIBROSIS INHERITED?

Cystic fibrosis inheritance is autosomal recessive. It means that two copies of the mutation are needed to develop the disease: one copy in each chromosome (as opposed to autosomal dominant diseases, in which the presence of a single copy of the mutation is enough to develop the monogenic disease).

If both father and mother are carriers of the genetic disorder, the probability of having an affected child is of 25%. If only one of the parents is a carrier of the disease, the child can inherit the mutation but will not develop it.

HOW IS CYSTIC FIBROSIS INHERITED?

CYSTIC FIBROSIS TEST

In tellmeGen DNA test 68 mutations in the CFTR gene associated with the development of cystic fibrosis are analyzed. Among these 68 mutations are included those that are more common among people who are carriers or suffer from cystic fibrosis, such as Phe508del (F508del), Gly551Asp (G551D), Arg117His (R117H), Arg709Ter (R709X), Ser549Arg (S549R) or Gly542Ter (G542X).

The genetic analysis of the presence of mutations in the CFTR gene is a highly recommended tool for those individuals who are planning to have a child, or for those individuals who suspect they may be carriers or affected.

tellmeGen DNA test constitutes a quality screening to analyze the most common mutations of many diseases. Thanks to this informative test the client can know the risk of suffering a wide range of diseases, many of which have no cure at present and in which having an early knowledge of them will facilitate an adequate treatment, as is the case of cystic fibrosis.

GENE OR REGION STUDIED


  • CFTR