Microsporidium

Background

• Unicellular spore-forming parasitic protozoa that are found pervasively throughout the environment. Microsporidiosis most commonly affects immunosuppressed individuals and seldom has implications for the immunocompetent patient.

Clinical Features

Clinical manifestations are wide ranging and typically affect immunosuppressed hosts (e.g. HIV/AIDS, long-term steroid use, transplant and chemotherapy patients), travelers, children, and the elderly. The most common manifestation is copious diarrhea with volume depletion leading to electrolyte derangements.

Immunosuppressed patients:

• Profuse watery diarrhea with massive fluid loss
• Cholangitis and acalculous cholecystitis
• Disseminated infection
• Myositis

Immunocompetent patients:

• Self-limited diarrhea

Differential Diagnosis

• Microsporidiosis
• Cryptosporidiosis
• CMV (CD4 < 100)
• MAC (CD4 < 100)
• Adenovirus
• Isospora
• Giardia
• E. coli
• C. difficile

Acute diarrhea

Infectious

• Viral (e.g. rotavirus)
• Bacterial
  • Campylobacter
  • Shigella
  • Salmonella (non-typhi)
  • Escherichia coli
    • E. coli 0157:H7
  • Yersinia enterocolitica
  • Vibrio cholerae
  • Clostridium difficile
• Parasitic
  • Giardia lamblia
  • Cryptosporidium
  • Entamoeba histolytica
  • Cyclospora
  • Microsporidium
• Toxin
  • Staphylococcus aureus
  • Bacillus cereus

Noninfectious

• GI Bleed
• Appendicitis
• Mesenteric Ischemia
• Diverticulitis
• Adrenal Crisis
• Thyroid Storm
• Toxicologic exposures
• Antibiotic or drug-associated

Watery Diarrhea

• Enterotoxigenic E. coli (most common cause of watery diarrhea)
• Norovirus (often has prominent vomiting)
• Campylobacter
• Non-typhoidal Salmonella
• Enteroaggregative E. coli (EAEC)
• Enterotoxigenic Bacteroides fragilis

Traveler's Diarrhea

• Giardia lamblia
• Cryptosporidiosis
• Entamoeba histolytica
• Cyclospora

Evaluation

Work-up

• CBC
• Metabolic panel
• C. difficile toxin EIA
• Fecal WBC and RBC
• Lactoferrin
• Wet mount microscopy
• Stool culture

Evaluation

• It is important to differentiate bloody vs non-bloody and acute vs chronic diarrhea. Additionally helpful information includes recent antibiotic use, history of C. difficile, presence of nausea, vomiting, fevers, altered mental status, severe abdominal pain, and whether their diarrhea is distracting them from an additional problem.

Management

• Initial treatment consists of the ABCs
  • IV fluid resuscitation with LR or NS
  • Oral rehydrating solution for mild dehydration and tolerating PO intake
  • Address electrolyte derangements
• Albendazole 400 mg PO bid for 14-28 days in adults (15mg/kg PO bid for 7 days in children)
• Ondansetron or promethazine for nausea (avoid metoclopramide due to pro-motility effects)
• Loperamide for symptom reduction (contraindicated with bloody stool)

Disposition

• Discharge: immunocompetent or low risk patients with unclear etiology but normal examination findings after rehydration
• Admission: patients with life-threatening volume loss, failure to improve after resuscitation, electrolyte abnormalities requiring gradual and/or significant correction, toxic or ill-appearing, intolerant of PO intake or significant risk factors (CD4 < 100, chemotherapy, transplant, etc.)
• Pearl: Obtain contact information for patients PCP and specialist providers (oncology, infectious disease, rheumatology, etc). Consultation and coordination of care is especially important for patients with significant and relevant co-morbidities

External Links

• CDC-Microsporidiosis