A 17-year-old boy is seen in an emergency department with severe acute abdominal symptoms that suggest appendicitis. The patient had a similar episode previously that led to an appendectomy, but the appendix was free of inflammation at pathologic examination. On questioning,
the boy reports having had intermittent diarrhea with moderate chronic abdominal pain for several years, which he had been afraid to tell anyone about after having had a "normaI" appendix removed. On physical examination, the boy is noted to be thin, with short stature, and have a palpable fullness in the right lower quadrant of his abdomen. UItrasound examination of the abdomen shows some thickening of bowel mesentery, but no distinct masses. Colonoscopy demonstrates sharply demarcated segments of diseased bowel with patchy mucosal ulcersseparated by adjacent normal bowel involving both the distal ileum and right side of the colon.
Q 1
Which of the following is the most likely diagnosis?
/ A. Colon cancer
/ B. Crohn disease
/ C. Hirschsprung disease
/ D. Pseudomembranous colitis
/ E. UIcerative colitis
Q 2
Which of the following findings on right colon mucosal biopsy would be most suggestive of the patient's likely diagnosis?
/ A. Absence of nerve cell bodies in submucosa
/ B. Bacteria-Iaden pseudomembrane
/ C. Crypt abscesses
/ D. Neoplastic epithelial cells
/ E. Small granulomas
Q 3
The patient is treated initially with corticosteroids, and then these are tapered and he is switched to a maintenance therapy with sulfasalazine.
Sulfasalazine is an unusual medication that combines which of the following?
/ A. A histamine derivative and a beta blocker
/ B. A Iipoxygenase inhibitor and a penicillin derivative
/ C. A mast cell degranulation inhibitor and an anticoagulant
/ D. A salicylate derivative and a sulfonamide derivative
/ E. A serotonin antagonist and a proton pump inhibitor
Q 4
Several years later, the patient develops recurrent urinary tract infections with mixed flora bacteria isolated from the urine. This pattern
suggests that which of the following may have developed?
/ A. BIadder stone
/ B. Fistula
/ C. Kidney stone
/ D. Systemic immunosuppression
/ E. Urethral strictures
Q 5
At a still later date, the patient develops chronic lower back pain and is diagnosed with ankylosing spondylitis. Which HLA type has been
associated with this extracolonic manifestation?
/ A. HLA-B27
/ B. HLA-B35
/ C. HLA-Cw6
/ D. HLA-DR3
/ E. HLA-DR5
Q 6
Examination of the patient's legs reveals necrotic ulcers with ragged bluish-red overhanging edges together with areas containing plaques
with pustules. Which of the following is the most likely diagnosis?
/ A. Eruptive xanthomata
/ B. Lupus vulgaris
/ C. Raynaud's phenomenon
/ D. Psoriasis
/ E. Pyoderma gangrenosum
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Diarrhea Case 4 Answers
A1
The correct answer is B. This patient most likely has Crohn disease, as indicated by his chronic abdominal complaints and the distal small intestinal and colonic ulceration with skip lesions (normal bowel separating involved areas). In addition to the distal small intestine and colon, Crohn disease can affect the perianal area, entire small intestine, stomach, and esophagus. Crohn disease may present with chronic diarrhea with systemic complaints, acute abdomen, or extraintestinal manifestations. The peak incidence for onset of symptoms occurs between 14 to 24 years. Crohn disease is thought to be due to a genetic predisposition that leads to an autoimmune reaction in the intestine that may be triggered in response to an environmental, dietary, or infectious agent. About 1 in 6 people with Crohn disease have a relative with Crohn disease, or, less commonly, ulcerative colitis.
Hirschsprung disease (choice C) causes megacolon in young children.
Pseudomembranous colitis (choice D) is due to overgrowth of Clostridium difficile and is usually seen following treatment with broad-spectrum antibiotics.
Ulcerative colitis (choice E) usually extends from the rectum proximally and does not have skip lesions.
A2
The correct answer is E. Microscopic features of Crohn disease include transmural inflammation, small granulomas (most characteristic, but only present in about 50% of cases), and variable degrees of inflammation.
Absence of nerve cell bodies in submucosa (choice A) suggests Hirschsprung disease.
A bacteria-laden pseudomembrane (choice B) suggests pseudomembranous colitis;
Crypt abscesses (choice C) suggest ulcerative colitis.
Neoplastic epithelial cells (choice D) suggest colon cancer or neoplastic polyps.
A3
The correct answer is D. Acute exacerbations of Crohn disease can be treated with corticosteroids, but then the patient is usually switched to maintenance therapy with immunomodulating drugs, such as azathioprine and 6-mercaptopurine, or sulfasalazine or related drugs. Sulfasalazine has a sulfapyrine component, which is a sulfonamide derivative and a 5-aminosalicyclic acid (5-ASA) component, which is a salicylate derivative. Most of the drug activity appears to be related to the 5-ASA component, and most of the toxicity is related to the sulfapyrine, so alternatives to sulfasalazine, such as mesalamine, are being developed that preserve the 5-ASA activity without retaining the sulfapyrine component. The other answers are distracters.
A4
The correct answer is B. The patient has probably developed a fistula between the intestine and the bladder. Fistulas are a relatively common complication of Crohn disease. Surgery is used to correct recurrent intestinal obstruction and intractable fistulas, but may be unsatisfactory because of disease recurrence.
The other choices do not commonly complicate Crohn disease and would not specifically predispose for mixed flora infections.
A5
The correct answer is A. Ankylosing spondylitis is one of the seronegative spondyloarthropathies. It should be suspected in any young person complaining of chronic lower back pain and can be confirmed by radiographs or CT scans of sacroiliac joints. The disease usually progresses to involve the whole vertebral column, producing ankylosis and respiratory failure secondary to restrictive lung disease. HLA-B27 positivity has been associated with Crohn disease patients who develop extracolonic manifestations including ankylosing spondylitis, sacroiliitis, uveitis, and primary sclerosing cholangitis.
You should associate HLA-B35 (choice B) with vitiligo, duodenal ulcer, and subacute thyroiditis.
You should associate HLA-Cw6 (choice C) with psoriasis.
You should associate HLA-DR3 (choice D) with celiac disease, Goodpasture syndrome, type I diabetes mellitus, and systemic lupus erythematosus.
You should associate HLA-DR5 (choice E) with juvenile rheumatoid arthritis and pernicious anemia.
A6
The correct answer is E. Pyoderma gangrenosum can precede the onset of chronic inflammatory bowel disease. It is treated by systemic and topical corticosteroids. It may also be associated with myeloproliferative disorders and rheumatoid arthritis.
Xanthomata (choice A) may be located on the tendons on the back of the hands, the Achilles tendon and patellar tendon, buttocks, and back. They are usually yellow papules up to 5 mm in diameter. They suggest familial hypercholesterolemia.
Lupus vulgaris (choice B) is a progressive form of cutaneous tuberculosis occurring in a person with a moderate or high degree of immunity. The two types are the plaque form (a tiny reddish-brown, flat plaque that extends gradually) or the ulcerative form (scarring and ulceration over the areas of necrosis).
Raynaud's phenomenon (choice C) presents as cold and cyanotic digits along with atrophy of the finger pulp and, in severe cases, gangrene. It is an exaggerated physiological response wherein the fingers turn white, and then when rewarmed, will turn blue, and then red as part of rebound hyperemia. It may be associated with underlying connective tissue diseases such as systemic sclerosis.
Psoriasis (choice D) presents as a thick plaque-like scale that is usually silver or salmon-pink in color. It is usually well defined on the extensor surfaces of elbows or knees. It is often associated with asymmetrical arthropathy mainly involving the terminal interphalangeal joints.
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