MKSAP Quiz: Chronic intermittent nonbloody diarrhea
A 25-year-old woman is evaluated for chronic intermittent nonbloody diarrhea with associated abdominal cramping, burping, and bloating. Symptoms began several months ago. Following a physical exam and stool testing, what is the most likely cause of this patient's diarrheal illness?
A 25-year-old woman is evaluated for chronic intermittent nonbloody diarrhea with associated abdominal cramping, burping, and bloating. Symptoms began several months ago. She has a history of selective IgA deficiency with recurrent sinopulmonary infections. She has not taken antibiotics in the past 6 months.
On physical examination, temperature is 37.3 °C (99.1 °F); the vital signs are otherwise normal. On abdominal examination, bowel sounds are present with minimal diffuse tenderness to palpation.
Stool testing for occult blood is negative.
Which of the following is the most likely cause of this patient's diarrheal illness?
A. Clostridium difficile
B. Enterohemorrhagic Escherichia coli
C. Giardia lamblia
D. Listeria monocytogenes
E. Nontyphoidal Salmonella
MKSAP Answer and Critique
The correct answer is C: Giardia lamblia. This content is available to MKSAP 18 subscribers as Question 15 in the Infectious Disease section. More information about MKSAP is available online.
This patient with selective IgA deficiency most likely has chronic diarrhea due to a Giardia lamblia infection. Typical symptoms of Giardia include watery diarrhea that is fatty and foul smelling, bloating, crampy abdominal pain, flatulence, and nausea; fever is uncommon. In immunocompetent hosts, Giardia infection symptoms typically resolve within 2 to 4 weeks, but in patients with humoral immunodeficiency, such as hypogammaglobulinemia or selective IgA deficiency, Giardia infection may be prolonged because of impaired protection against Giardia adherence to the intestinal epithelium. Patients with selective IgA deficiency have impaired humoral immunity but no impairment in neutrophil, T-cell, or complement function. Infectious complications of selective IgA deficiency typically include recurrent respiratory tract infections and chronic diarrhea caused by Giardia.
Although Clostridium difficile can cause recurrent disease, this patient does not have a history of recent antibiotic use or any other risk factors for C. difficile infection such as advanced age, chemotherapy, gastrointestinal surgery, inflammatory bowel disease, or gastric acid suppression with proton pump inhibitors.
Enterohemorrhagic Escherichia coli (EHEC) infection is usually spread by ingestion of undercooked meat or fecally contaminated food. EHEC typically presents with bloody acute diarrhea, crampy abdominal pain, and no fever.
Listeria monocytogenes can cause an acute gastroenteritis syndrome associated with diarrhea, emesis, fever, headache, and nonbloody watery diarrhea associated with pain in muscles and joints. But such an infection typically lasts less than 2 days. Invasive complications of infection, including bacteremia and meningitis, are seen in conditions primarily associated with cell-mediated immune dysfunction such as pregnancy, use of glucocorticoids, and extremes of age (neonates or those older than 65 years).
Nontyphoidal Salmonella is the most common cause of foodborne illness. Infection usually results from ingesting fecally contaminated water or food of animal origin. Symptoms are typically self-limited and include crampy abdominal pain, fever, headache, nonbloody diarrhea, nausea, and vomiting. Severe invasive disease may occur in patients with cell-mediated immunodeficiency, but the clinical presentation is not significantly altered in selective IgA deficiency.
Key Point
- Patients with selective IgA deficiency are susceptible to Giardia lamblia infection, manifesting as abdominal cramping, bloating, and chronic diarrhea.