Continuing medical education
Tropical dermatology: Tropical diseases caused by protozoa

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Protozoan infections are very common among tropical countries and have an important impact on public health. Leishmaniasis is the most widely disseminated protozoan infection in the world, while the trypanosomiases are widespread in both Africa and South America. Amebiasis, a less common protozoal infection, is a cause of significant morbidity in some regions. Toxoplasmosis and pneumocystosis (formerly thought to be caused by a protozoan) are worldwide parasitic infections with a very high incidence in immunocompromised patients but are not restricted to them. In the past, most protozoan infections were restricted to specific geographic areas and natural reservoirs. There are cases in which people from other regions may have come in contact with these pathogens. A common situation involves an accidental contamination of a traveler, tourist, soldier, or worker that has contact with a reservoir that contains the infection. Protozoan infections can be transmitted by arthropods, such as sandflies in the case of leishmaniasis or bugs in the case of trypanosomiases. Vertebrates also serve as vectors as in the case of toxoplasmosis and its transmission by domestic cats. The recognition of the clinical symptoms and the dermatologic findings of these diseases, and a knowledge of the geographic distribution of the pathogen, can be critical in making the diagnosis of a protozoan infection.

Learning objectives

After completing this learning activity, participants should be able to recognize the significance of protozoan infections worldwide, identify the dermatologic manifestations of protozoan infections, and select the best treatment for the patient with a protozoan infection.

Section snippets

Leishmaniasis

Key points

  1. Many species of Leishmania are found worldwide and are transmitted by sandflies, producing cutaneous, mucocutaneous, or visceral disease.

  2. Coinfection with HIV may result in an atypical presentation of leishmaniasis, a lower response rate to treatment, a higher relapse rate, and a higher mortality rate.

  3. Clinically, CL can present as ulcers, nodules, papules, or as papulotuberous, verrucous, and lymphatic lesions.

  4. Diagnosis may be from detection of amastigotes in a tissue smear from a lesion or from

Cutaneous diseases caused by amebas

Key points

  1. Balamuthia mandrillaris is geographically restricted but causes potentially fatal disease; Entamoeba histolytica is found worldwide but primarily causes gastrointestinal disease with rare mucocutaneous manifestations.

  2. Clinically, cutaneous amebiasis usually presents as anogenital ulcers; Balamuthia usually presents as a granulomatous plaque of the central face.

  3. Diagnosis can be confirmed with biopsy with identification of trophozoites, or by serology, culture, or molecular techniques. Touch

Trypanosomiasis

Key points

  1. Three subspecies of Trypanosoma brucei are transmitted by the tsetse fly and cause sleeping sickness with occasional cutaneous manifestations in Africa; T cruzi is transmitted by reduviid bugs in the tropical Americas and causes Chagas disease.

  2. Clinically, African trypanosomiasis presents as a chancre followed by an eschar at the site of the bite. Lymphadenopathy progresses during the disease, and trypanids occur within 6 to 8 weeks. Cutaneous manifestations of Chagas disease include chagomas,

Toxoplasmosis

Key points

  1. Toxoplasma gondii is common worldwide; it usually causes systemic disease with rare cutaneous manifestations only in pregnant women and immunocompromised patients.

  2. Cutaneous manifestations of toxoplasmosis include hemorrhagic or necrotic papules.

  3. Diagnosis is made via biopsy and serology.

  4. Treatment includes sulfadiazine with pyrimethamine.

Toxoplasmosis is a worldwide infection caused by the protozoan parasite T gondii that belongs to the phylum Apicomplexa, subclass Coccidia. T gondii is an

Pneumocystosis

Key points

  1. Pneumocystis carinii (jirovecii) was once considered a protozoan but is now classified as a fungus; it primarily causes pneumonia and very rare cutaneous manifestations in immunocompromised patients.

  2. Cutaneous manifestations include erythematous or skin-colored papules or nodules usually in the ear or external auditory canal.

  3. Diagnosis of cutaneous pneumocystosis is obtained by biopsy.

  4. Therapy is usually with trimethoprin-sulfamethoxazole but can include pentamidine and atovaquone.

Pneumocystosis

Conclusion

Protozoan infections constitute public health and economic problems in many parts of the world, especially in tropical countries. In light of the significant morbidity and mortality of these infections, the WHO has acknowledged the importance of such diseases and has urged tropical countries to recognize the impact of such infections and improve the protozoan awareness, prevention, and treatment of them. Dermatologists should be familiar with protozoan infections because a recognition of the

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