Microsporidiosis Clinical Presentation

Updated: Feb 24, 2023
  • Author: Shirin A Mazumder, MD, FIDSA; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Patients may report the following:

  • Intestinal or biliary microsporidiosis

    • Chronic diarrhea (loose, watery, nonbloody)

    • Weight loss

    • Abdominal pain

    • Nausea

    • Vomiting

  • Disseminated microsporidiosis

    • Symptoms of cholecystitis, renal failure, and respiratory tract infections occur.

    • Patients with respiratory tract involvement may present with persistent cough, dyspnea, and wheezing.

    • Headache, nasal congestion or discharge, ocular pain, and loss of taste may indicate sinus involvement.

    • Patients with urinary tract involvement are frequently asymptomatic.

  • Ocular microsporidiosis

    • Foreign body sensation, eye pain, or both

    • Light sensitivity

    • Ocular redness

    • Excessive tearing

    • Blurred or decreased vision

  • Musculoskeletal microsporidiosis: Myalgia, generalized muscle weakness, and fever are common in patients with myositis and severe cellular immunodeficiency.

  • Dermatologic microsporidiosis: Microsporidia have been associated with a nodular cutaneous lesion in patients with HIV infection.

  • CNS microsporidiosis: Patients with microsporidiosis of the brain may experience seizures and headache.



Head, eyes, ears, nose, and throat (HEENT) examination

Patients with ocular involvement due to Encephalitozoon infection may develop conjunctival hyperemia. A slit-lamp examination may reveal keratoconjunctivitis, which is characterized by diffuse, superficial, punctate keratopathy. The infection frequently is bilateral in immunosuppressed individuals.

Corneal ulceration or corneal stromal keratitis is rare in patients with AIDS who have microsporidiosis. [13]  Retinal involvement has not been reported.

Those in whom microsporidiosis involves the sinuses may have nasal crusting or purulence, polypoid tissue, or thickened and granular-appearing mucosa.

Abdominal examination

Patients with intestinal or biliary microsporidiosis may have abdominal tenderness.

Clinical jaundice due to microsporidiosis is rare.

Severe wasting and signs of malnourishment are usually observed in patients with prolonged severe diarrhea.

Musculoskeletal examination

Muscle tenderness and generalized weakness may be noted in patients with microsporidiosis-related myositis.

Skin examination

A skin examination may reveal nodules or necrotic lesions.



Microsporidiosis is believed to be a zoonosis. Evidence suggests that microsporidia may be water-borne pathogens and may be transmitted from human to human. [14]

Most cases of microsporidiosis in patients with HIV infection occur in those with severe immunodeficiency.

Cases of microsporidiosis have been reported in individuals who are HIV negative and who are immunocompromised secondary to transplant surgery, prolonged steroid use, or undergoing chemotherapy.

Self-limited diarrhea due to microsporidiosis has been reported in immunocompetent travelers; waterborne transmission may play a role in these cases.