Microsporidiosis overview

# Overview
Microsporidiosis is an opportunistic intestinal infection that causes diarrhea and wasting in immunocompromised individuals (HIV, for example). It results from different species of microsporidia, a group of protozoal parasites. In HIV infected individuals, microsporidiosis generally occurs when CD4+ T cell counts fall below 100. Microsporidiosis was first discovered in 1959 and its prevalence has increased in the late 20th century due to the worldwide spread of HIV. Immunodeficiency is the most common risk factor for developing microsporidiosis and leads to a worse outcome.
Microsporidiosis presents in many forms and can affect many systems. The most common form is intestinal microsporidiosis, which causes diarrhea and weight loss and can be complicated with nutritional deficiencies, weight loss, and acalculous cholecystitis. Diagnosis is confirmed by microscopic identification of the organism and positive PCR. The mainstay of therapy is HAART aiming for a CD4+ T cell > 100 cell/mcm.

# Historical Perspective
Phylum Microsporidia were first described in the 19th century, while the first human case was described in 1959. The number of cases increased after the spread of AIDS.

# Classification
There is no classification system established for Microsporidiosis.

# Pathophysiology
Microsporidia are a group of obligate intracellular parasitic fungi with more than 1,200 species belonging to 143 genera that infect a wide range of vertebrate and invertebrate hosts. They are characterized by the production of resistant spores that vary in size, depending on the species. After ingestion, microsporidia infect intestinal epithelial cells and cause chronic diarrhea with the possibility of distant spread. The microorganism can be visualized in stool samples using "Quick-Hot Gram Chromotrope technique."

# Causes
Microsporidiosis is an infection caused by microsporidia.

# Differentiating Microsporidiosis from other diseases
Microsporidiosis should be differentiated from other conditions that cause chronic diarrhea in immunocompromised patients.

# Epidemiology and Demographics
The overall prevalence is not accurately estimated especially in the whole population (because microsporidiosis is usually investigated in immunocompromised patients with correlating gastrointestinal symptoms to microsporidiosis. The disease is present worldwide. In HIV patients with diarrhea, microsporidia were the most commonly isolated organism, with a prevalence of 39%.

# Risk Factors
The most potent risk factor in the development of microsporidiosis is immunodeficiency. Other risk factors among immunodeficient patients include poor sanitation and contact with poultry droppings.

# Natural History, Complications, and Prognosis
If left untreated, immunocompetent patients resolve the disease completely within 2 weeks while immunocompromised patients might develop chronic diarrhea. Common complications of microsporidiosis include weight loss, dehydration, and acalculous cholecystitis. Prognosis is generally excellent in immunocompetent patients while immunocompromised patients are more vulnerable to developing chronic disease and complications.

# Diagnosis

## History and Symptoms
Symptoms of intestinal microsporidiosis include chronic diarrhea, abdominal pain, and weight loss.

## Physical Examination
Patients with microsporidiosis usually appear ill. Physical examination of patients with microsporidiosis is usually remarkable for weight loss, wasting and abdominal tenderness.

## Laboratory Findings
Laboratory findings consistent with the diagnosis of microsporidiosis include microscopic identification of the organism in fecal smears using chromotrope 2R method or Quick-Hot Gram Chromotrope technique, positive PCR, and positive serology using indirect immunofluorescence.

## Imaging Findings
There are no imaging findings associated with microsporidiosis.

# Treatment

## Medical Therapy
The mainstay of therapy for microsporidiosis in immunocompromised patients is highly active antiretroviral therapy (HAART). Albendazole and fumagillin have demonstrated consistent activity against other microsporidia in vitro and in vivo.

## Surgery
Surgical intervention is not recommended in the management of microsporidiosis.

## Prevention
Effective measures for the primary prevention of microsporidiosis include HAART, avoiding contact with poultry and avoiding swimming pools while secondary prevention strategies following microsporidiosis include continuing treatment indefinitely after ocular microsporidiosis and continued HAART for HIV patients.