NUTR 4040 Study Guide - Final Guide: Cystic Fibrosis, Chronic Pancreatitis, Pancreas
6 Dec 2018
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Cystic Fibrosis
• Background:
o 1/3600 children born with CF, an autosomal, recessive genetic disorder
o Most common genetic defect is F508 mutation in cystic fibrosis transmembrane conductance
regulator (CFTR) protein. 5% of all Caucasians carry the CF gene
o CFTR is a chloride transporter found in the membrane of the epithelial cells of the lungs,
pancreas, liver, GI tract, genitourinary tract and skin
▪ In normal epithelial cells, the membrane allows the release of Cl from the cell,
creating and electrolyte imbalance that draws water out of the cell through osmosis.
Water keeps mucus moist and prevents infections
▪ If CFTR does not function, as is the case of CF, Cl does not get reabsorbed into
sweat duct cells. Cl therefore stays in the sweat ducts and attracts Na. The result:
sweat contains extra NaCl.
▪ Parent’s may say their baby tastes salty.
▪ And if CFTR does not function, movement of water into and out of cells is impaired.
This results in the accumulation of mucus which thickens and becomes sticky, due to
lack of water. With this mucus, cilia cannot function properly, and bacteria collect on
the cells, leading to infections
o Live to 40 and beyond (about ½)
• Pathophysiology
o Lungs: most seriously involved:
▪ CF causes mucus plugging of small- and medium-sized airways
• Leads to scarring, chronic infection, and inflammation (up to 80% of
patients eventually infected with P. aeruginosa. People with CF can infect
each other with this bug)
• ~50% of people with CF have symptoms which include a chronic cough and
wheezing
• Respiratory failure accounts for >90% of deaths in the CF population
▪ Patients with mild disease may only couch during exacerbation, but eventually,
cough becomes a daily occurrence, usually accompanied by sputum production.
▪ With disease progression, daily sputum increases in volume and becomes green to
tan in colour. Blood-streaked sputum no unusual in later stages of illness
• Infection indicated by the colour of sputum
▪ Patients experience increasing difficulty breathing due to mucus accumulation in
airways and as illness progresses, experience dyspnea on exertion and shortness of
breath
o Pancreas: *cysts*
▪ 85-90% of individuals with CF demonstrates pancreatic failure
• Pancreatic insufficiency occurs when >95% of the function or structure of
the exocrine pancreas has been lost
• Pancreatic insufficiency presents similarly to chronic pancreatitis.
▪ Caused by thick pancreatic secretions that block the pancreatic ducts
▪ Consequences of pancreatic insufficiency:
• Failure to secrete digestive enzymes therefore malabsorption is common.
This is especially the case for dietary fat, malabsorption of which leads to
steatorrhea.
• Failure to alkalinize pancreatic fluid, resulting in impaired gastric acid
neutralization
• Pancreatic atrophy may eventually lead to CF related diabetes, which affects
10-15% of people with CF over 20yr.
• Pancreatic-sufficient patients (10-15%) have much milder disease
progression, characterized by diagnosis at late age, more slowly progressive
lung disease, better growth, and a better survival rate.
o 10-20% of individuals who are pancreatic sufficient may eventually
develop pancreatic insufficiency. Slowly progressive chronic
pancreatitis is the cause.
o The liver: *fibrous*
▪ Liver disease is 2nd leading cause of death among persons with CF
• Occurs mainly in first decade of life; mean age of presentation between 7-
9yr.
▪ Caused by thick and sticky bile that causes blockages in the bile ducts of e liver, and
the surrounding tissue becomes damaged. This leads to cirrhosis.
▪ Routine physical exam reveals hepatomegaly
▪ Fibrosis, scarring and fatty deposits; often asymptomatic but increased risk for
fatigue, weight loss, jaundice
▪ Liver disease increases the risk of fat-soluble vitamin deficiency, particularly
vitamins D and K.
o The gut
▪ Steatorrhea secondary to fat maldigestion (caused in part by reduced secretion of bile
acids from the liver, reducing emulsification of fats) and fat malabsorption (caused
by the thick intestinal mucus which impairs nutrient absorption)
• Steatorrhea makes bowel movements bulky and greasy
▪ Esophagitis, caused by acid reflux with advanced lung disease (pressure from stiff
lungs), postural drainage during chest physio, and/or abdominal distension from gas
or hepatomegaly and/or splenomegaly. Frequency associated with pain, anorexia, and
vomiting after coughing bouts.
▪ Distal intestinal obstruction syndrome (DIOS)
▪ A partial or complete obstruction of the small intestine and sometimes the proximal
colon. A mix of feces, sticky secretions and food residue. It is so sticky that it
adheres to the intestinal mucosa and cannot be removed without causing bleeding.
▪ Seen in some adolescents and adults with pancreatic insufficiency. Caused by poor
compliance with enzyme therapy, sudden dietary changes and/or dehydration.
▪ DIOS causes recurrent, crampy abdominal pain; patients often find symptoms
exacerbated
o Growth/Development in Children
▪ Weight-for-age and height-for-age of Canadians with CF well under the 50th
percentile
▪ Increased risk for poor bone health due to:
• Failure to thrive
• Delayed puberty, so decreased bone modelling
• Malabsorption of Ca, Mg, vit D, vit K
• Reduced weight-bearing PA
• Inhaled corticosteroids
o Other
▪ Almost all men with CF are infertile, secondary to congenital bilateral absence or
abnormal narrowing of the vas deferens. Fertility in women with CF are unusually
normal.
▪ The excessive loss of salt in sweat makes people with CF intolerant to heat
▪ Gallstones common
▪ Cystic fibrosis-related diabetes (CFRD): with increasing survival of the CF
population comes an increased incidence of CFRD, caused by atrophy of insulin-
producing beta cells of the pancreas
Document Summary
Cystic fibrosis: background, 1/3600 children born with cf, an autosomal, recessive genetic disorder, most common genetic defect is f508 mutation in cystic fibrosis transmembrane conductance regulator (cftr) protein. 5% of all caucasians carry the cf gene: cftr is a chloride transporter found in the membrane of the epithelial cells of the lungs, pancreas, liver, gi tract, genitourinary tract and skin. In normal epithelial cells, the membrane allows the release of cl from the cell, creating and electrolyte imbalance that draws water out of the cell through osmosis. If cftr does not function, as is the case of cf, cl does not get reabsorbed into sweat duct cells. Cl therefore stays in the sweat ducts and attracts na. The result: sweat contains extra nacl: parent"s may say their baby tastes salty, and if cftr does not function, movement of water into and out of cells is impaired.
