Misnomer: 'Tropical' Dermatology

July 1, 2008

Dermatologists must look outside their regional communities for the source of unique symptoms. A history of tropical travel isn't always a precursor to tropical disease.

Key Points

Therefore, incidences of tropical diseases are increasing across the United States, Dr. Tyring says.

More Americans are traveling and working abroad, and large numbers of military troops are returning from overseas duty, bringing with them skin diseases rarely seen in the United States previously.

"Many/most skin problems in these patients ... are not related to their travel or national origin, but are the same disorders seen daily in persons who have never left their local communities," he tells Dermatology Times.

"You don't have to travel to these areas to get a tropical disease," Dr. Tyring says.

Doctors must look outside their regional boundaries for sources of unique symptoms.

Monkeypox

Serious cases of monkeypox were reported in the United States in 2003, although the disease is endemic to central Africa.

"The spread of monkeypox in Africa is thought to be due to the lack of vaccination against smallpox, because the vaccine that was used to protect against smallpox, i.e. vaccinia, gave cross-protection against monkeypox.

"Therefore, the lack of smallpox vaccination in the United States is also thought to have allowed the monkeypox virus to have spread among the patients in 2003," Dr. Tyring says.

Patients in Wisconsin adopted prairie dogs from Texas and, subsequently, presented with the virus they contracted from the prairie dogs - which had been housed next to Gambian rats - without ever leaving the United States.

Fortunately, Dr. Tyring says, absolutely "spectacular" healthcare took place to cure these first-ever cases of monkeypox in the United States.

Anthrax

In 2006, a patient in New York presented with cutaneous anthrax, contracted from animal hides he had imported from his homeland in Sierra Leone to make drums. He contracted the disease, even though he had not recently traveled outside the United States.

"The source of the infection was tropical, but the patient had not visited the tropics," Dr. Tyring says.

"Again, you don't have to travel to these countries to get these tropical diseases," he says.

From 'temperate' to tropical

Measles, rubella and chickenpox, once common childhood diseases in the United States, are all but obsolete in this country due to widespread vaccinations. However, these diseases are still major sources of morbidity and mortality in tropical countries. Consequently, they are making a comeback here.

These rare diseases are either brought here by individuals from other countries or by unvaccinated Americans who travel abroad, contract disease and bring it back.

"So, these are the opposite of tropical diseases being brought here that need to be examined," Dr. Tyring says.

Health problems in returned travelers

"Some studies suggest that one-third to two-thirds of returned travelers from tropical countries will experience some health problems," Dr. Tyring says.

Non-infectious sources of skin problems include sun exposure, cutaneous reactions to medications, exposures to marine or freshwater fish or invertebrates, stings, bites and reactions to plants.

Among non-infectious cutaneous problems unique to the tropics, Dr. Tyring cites podoconiosis, literally "dust in the feet," a non-filarial elephantiasis of the lower legs caused by walking barefoot in volcanic soil. According to Dr. Tyring, the aluminosilicates penetrate the skin.

Taking a history

When taking a patient history, the physician must take into consideration the patient's destination and length of stay, time since return, and time since development of signs and symptoms. Other considerations include vaccinations, medication, bites or stings, and occupational or recreational exposures.

"At the end, the bottom line is, the differential diagnosis of mucocutaneous lesions in the returned traveler, immigrant or adoptee should be based on the morphology of the lesions, history, lab tests and PE (personal experience)," Dr. Tyring says.