Nutritional Diseases

CASE 7: Cystic Fibrosis and Malabsorption

Clinical History:

A 24-year-old woman has the homozygous ΔF508 mutation of the CFTR gene. She has had problems with respiratory tract infections since childhood. She has a chronic diarrhea with large amounts of foul-smelling stools. Her body mass index is 19. She is noted to have several contusions of varying ages, ranging from red to blue to purple to brown, scattered over her lower legs and arms. She has generalized muscle weakness. A neurologic examination shows absent deep tendon reflexes. She has reduced sensation to vibration and pain. MR imaging of her brain shows hyperintense areas of white matter with FLAIR mode and bright areas of spinal cord posterior columns with T2 weighting.

Laboratory findings include:

WBC count8150/microliter
Hgb13.2 g/dL
MCV94 fL
Prothrombin time24 sec (control 12.2 sec)
Partial thromboplastin time22.5 sec (control 23.1 sec)
Quantitative stool fat10 gm/day (normal <6) [note: laboratory technicians consider such specimens a form of bioterrorism]
  1. What underlying disease does she have?

  2. She has the most common mutation for cystic fibrosis.

  3. What problem in the gastrointestinal tract has resulted from this disease?

  4. She has malabsorbtion, mainly due to diminished pancreatic function.

  5. What nutrient deficiencies could she have?

  6. The increase in the stool fat (and the quality of the diarrheal fluid) indicates a major problem with fat absorbtion. Thus, she has malabsorbtion affecting fat. The fat soluble vitamins A, D, E, and K are dependent upon adequate fat absorbtion. Some vitamin D and K are made endogenously. These vitamins are stored to some extent in the liver, so dietary deficiencies of short duration are typically without effect. However, persons who have ongoing malabsorbtion, or very poor diets, or liver disease, are at risk for fat soluble vitamin deficiencies.

    The easy bruising suggests a coagulopathy. Vitamin K is a cofactor in carboxylation of glutamate residues of the coagulation factors II, VII, IX, and X which are synthesized in the liver. Her elevated prothrombin time is typical for vitamin K dependent factor deficiency (prothrombin is factor II).

    The neurologic problems could fit with vitamin E deficiency (B12 is ruled out by the lack of macrocytic RBC's, but one would want to check B12 and folate levels). Vitamin E deficiency is actually quite rare, but is possible in cases of ongoing malabsorbtion.

  7. What are dietary sources?

  8. Sources of vitamin D are discussed in the next case.

    Vitamin A is derived from foods containing carotenoids, typically yellow and orange vegetables but also dairy products, meats, and oils.

    Vitamin K can be made endogenously by bacteria in the intestine, and there is wide availability in many food sources, particularly fruits and vegetables. Vitamin K can also be given as an intramuscular injection or added to intravenous parenteral nutritive supplements.

    Vitamin E (as compounds known as tocopherols) is widely distributed in a variety of fruits, vegetables, grains, and meats, but fats and oils constitute the main source.

  9. Is there a therapy for her underlying condition?

  10. The loss of pancreatic acinar parenchyma cannot be reversed, but preparations containing pancreatic enzymes can be taken orally with meals. Vitamin A, D, and E supplements can be obtained, as well as multivitamins containing these nutrients. However, it is possible to develop vitamin A and D toxicities with excessive consumption of these vitamin supplements.