Without the condition and as such, treatment consists

Without doubt, Cystic Fibrosis is one of the mostwell known and most studied genetic diseases in modern medicine. Despite theextensive research surrounding the condition, there is currently no known curefor the condition and as such, treatment consists simply of alleviating the symptomsassociated with the illness, rather than addressing the underlying pathology ofthe respiratory tract and, to a lesser extent, the digestive and reproductivetracts(1) .

Unfortunately, Cystic Fibrosis is extremely common in the BritishIsles- more than 10,400 people in the UK suffer from the disease and it isthought that 1 in 25 of British people carry the faulty gene causing it, usuallyunknowingly(2). Meanwhile, Ireland has the highest incidence of cystic fibrosisin the world, with a whopping 1 in 19 Irish people being a carrier of thedisease (3).The genetics behind Cystic Fibrosis are wellunderstood. Cystic Fibrosis is an autosomal recessive inherited disorder,caused by a mutation of the gene on the long arm (the “q” arm) of chromosome 7in the region 7q31.2 (4). ‘Autosomal’ refers to the 22 non-sex chromosomes (5)and ‘recessive’ means that a faulty copy of the gene must be inherited fromboth the mother and the father in order for Cystic Fibrosis to be shown in theperson. If a single copy, from either the mother or father only was to beinherited, the individual would not show any of the diseases’ symptoms.

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However,that person would be a carrier of cystic fibrosis and could still pass themutation on to their own children in the future. Consequentially, geneticdiseases caused by recessive mutations, as in the case of Cystic Fibrosis, canlay dormant in families for many generations. If two carriers have children,the chance that any given child will inherit the genes required for CysticFibrosis follows Mendel’s Laws; these predictthat, in such a scenario, each child has a 25% chance of inheriting cysticfibrosis and each has a 50% chance of being an asymptomatic carrier of thedisease like his or her parents (6).Most commonly, the mutation associated with CysticFibrosis results in the deletion of the 508th amino acid that codes for aprotein called Cystic Fibrosis Transmembrane conductance Regulator (CFTR) (4). Innormal physiology, CFTR acts as a cAMP-dependent chloride ion channel pump inairway epithelia cells. However, in Cystic Fibrosis, The genetic mutation meansthat the body’s epithelial cells can’t pump chloride ions (Cl-) out of the celland into the lumens of the various tracts of the body. As a result, less wateris secreted from cells and viscous mucus is produced by the body (7).

In therespiratory tract, the thick mucus builds up on the inner lining of the lungs.White blood cells can become trapped in this mucus, rupture and make the mucuseven more viscous (6). As a consequence of the thick mucus, people with CysticFibrosis often experience wheezing, breathlessness and a persistent cough, astheir body attempts to remove the accumulated excess mucus. Furthermore, peoplewho suffer from Cystic Fibrosis also have an increased risk of contractingchronic infections, as the thick mucus provides an ideal environment forbacteria and fungi to proliferate. In the digestive system, the mucus producedprevents digestive enzymes from the pancreas reaching the small intestine. Thisis problematic as these digestive enzymes are responsible for the degradationof proteins. Bile salts are also often blocked on their way from the pancreasto the intestine as well, so the digestion of fats is often also incomplete. Thiscan result in nutritional deficiencies, as the body will be unable to absorbproteins, fats and fat-soluble vitamins.

Digestive symptoms of Cystic Fibrosisinclude the production of pungent, greasy stools, lack of weight gain andgrowth, intestinal blockage, (in new borns called ‘meconium ileus’) and severeconstipation. Finally, the vast majority of men who suffer from cystic Fibrosisare infertile. This is due to either the blockage of the vas deferens (the tubewhich connects the testes and prostate gland) due to mucus build up, or thefact that the vas deferens is completely missing. On the other hand, women withcystic fibrosis, while most often less fertile than other women, can still conceiveand may have successful pregnancies. Despite this, however, pregnancy is proneto worsen the symptoms of cystic fibrosis. (8)Receiving a diagnosis of cystic fibrosis has lastingconsequences for an affected individual, their family, and any potentialspouse. In most cases, a child who has the typical indicative clinical symptomsor a family history and positive sweat tests will confirm suspicions of cysticfibrosis. The diagnostic criteria are based on phenotypic evidence and havebeen useful in guiding clinical practice since the early 1960s (9).

Since 2003in Scotland and 2007 in the rest of the UK, all new born babies can be testedfor cystic fibrosis via the ‘heel prick test’. (10) When a baby is five toeight days old, their heel is pricked to collect a sample of four drops ofblood. The test is not specific to cystic fibrosis, and in fact tests for ninerare but serious conditions. It is also worth noting that a positive heel pricktest does not necessarily mean that a child has cystic fibrosis -as a result,confirmation tests are needed. This may include a sweat test or a genetic test.

(11) If a sweat test is conducted, and a sodium concentration of over 60 mmol/Lis discovered it is likely that a patient has Cystic Fibrosis.  Finally, other factors which may lead to adiagnosis include radiological features of bronchiectasis, the absence of vasdeferens and epididymis and raised blood immunoreactivity trypsin levels. (4)In conclusion, CysticFibrosis is one of the most debilitating conditions which modern society faces.Thankfully, the future looks bright for those with Cystic Fibrosis as morecomplex gene therapies are currently being developed which may put an end tothis life changing disease.

Nevertheless, there remains much more study to bedone with regards to the pathological basis of the body systems and furtherdevelopments in the field may unlock the secret to curing one of the worstdiseases known to mankind.

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