In this week’s Case Record of the Massachusetts General Hospital, a 34-year-old man was admitted to the hospital because of weakness, chronic diarrhea, and weight loss. Initial laboratory evaluation revealed a leukocytosis and hypokalemia. A diagnostic procedure was performed.
Cystoisospora is distributed worldwide, but infections are most common in tropical and subtropical areas. It is acquired through the fecal-oral route.
• What laboratory findings are suggestive of chronic malabsorption?
Features that are consistent with malabsorption in the context of chronic diarrhea include elevated fecal fat (normal range, <20%), anemia with thrombocytosis (suggesting iron deficiency), an elevated prothrombin time (suggesting vitamin K deficiency), macroovalocytes (suggesting vitamin B12 deficiency), a low-normal serum albumin level (consistent with protein loss or poor synthesis), and low total blood calcium and phosphorus levels.
• What are the clinical manifestations associated with severe hypokalemia?
Hypokalemia can be associated with neuromuscular features ranging from weakness and muscle cramping to full paralysis; the mechanism of action is thought to be due to potassium-related alterations of nerve action potentials. Clinical features include weakness, ileus electrocardiographic changes, and myopathy.
Morning Report Questions
Q: What are the most common infectious causes of chronic diarrhea?
A: Infectious causes of chronic diarrhea are usually protozoal, although bacterial overgrowth of the small intestine should be considered, as should chronic Clostridium difficile colitis and campylobacteriosis. Infection with microsporidia can result in chronic diarrhea, although usually in persons who have advanced acquired immunodeficiency syndrome or who are severely immunocompromised with other cell-mediated deficiencies. Chronic intestinal cryptosporidiosis and cystoisosporiasis could easily result in a wasting illness and chronic diarrheal process, but severe disease is usually be seen in persons with compromised cellular immunity, such as those with advanced HIV infection, although Cystoisospora belli (also known as Isospora belli) infection can cause chronic diarrhea in immunocompetent persons, where peripheral eosinophilia is often present. Intestinal amebiasis and balantidiasis can also cause chronic diarrhea. Chronic giardiasis caused by Giardia lamblia can cause chronic secretory diarrhea with malabsorption and does not require an underlying immunocompromised state.
Table 3. Causes of Chronic Diarrhea.
Q: How is the diagnosis of chronic diarrhea from Cystoisospora belli typically made?
A: A stool specimen should be examined for the presence of ova and parasites. If not found, greater sensitivity can be provided by using acid-fast stains and immunofluorescence assays. Antigen-detection assays exist only for Giardia and Cryptosporidia.