The pancreas of a 22-year-old Caucasian male with recurrent pulmonary infections and finger clubbing shows extensive exocrine gland atrophy and fibrosis. The pancreatic ducts are lined with squamous epithelium with areas of keratinization. The finding of squamous metaplasia in the pancreatic ducts is most likely related to a deficiency of:

Question

The pancreas of a 22-year-old Caucasian male with recurrent pulmonary infections and finger clubbing shows extensive exocrine gland atrophy and fibrosis.  The pancreatic ducts are lined with squamous epithelium with areas of keratinization.  The finding of squamous metaplasia in the pancreatic ducts is most likely related to a deficiency of:

Quizplus · Accepted Answer

Recurrent sinopulmonary infections and exocrine gland fibrotic atrophy in a young Caucasian are suggestive of cystic fibrosis (CF). In the pancreas, severe CF may cause total obstruction followed by complete fibrotic atrophy of the exocrine glands. The resulting pancreatic insufficiency can cause a deficiency of fat soluble vitamins. Avitaminosis A in particular may contribute to squamous metaplasia of the epithelial lining of pancreatic exocrine ducts, which are already injured and predisposed to squamous metaplasia by inspissated mucus. Normal levels of vitamin A and its metabolite, retinoic acid, are required to maintain orderly differentiation of specialized epithelia, including mucus-secreting columnar epithelium. When a deficiency state exists, the epithelium undergoes squamous metaplasia to a keratinizing epithelium. (Choices A and F) Riboflavin (vitamin B₂) and vitamin C are water soluble vitamins whose intestinal absorption is not affected by fat malabsorption. (Choice C) Vitamin D is a fat soluble vitamin. However, vitamin D deficiency would not cause epithelial squamous metaplasia. Instead, it could produce rickets in children and osteomalacia in adults. (Choice D) Vitamin E is a fat soluble vitamin. Deficiency of this vitamin could cause infertility and decreases in some serum phospholipids. (Choice E) Vitamin K is a fat soluble vitamin. A vitamin K deficiency could cause a coagulopathy (bleeding diathesis) secondary to inadequate vitamin K dependent clotting factors. Educational Objective: Recurrent sinopulmonary infections and exocrine gland fibrotic atrophy in a young Caucasian are suggestive of cystic fibrosis (CF). CF can lead to pancreatic insufficiency, fat malabsorption, and a deficiency of vitamins A, D, E and K. Vitamin A maintains orderly differentiation of specialized epithelia, including the mucus-secreting columnar epithelia of the ocular conjunctiva, respiratory and urinary tracts, and pancreatic and other exocrine ducts. Avitaminosis A can cause squamous metaplasia of such epithelia to a keratinizing epithelium.

The Pancreas of a 22-Year-Old Caucasian Male with Recurrent Pulmonary