eMedicine Specialties > Dermatology > Fungal Infections

South American Blastomycosis

Author: Julie E Dixon, MD, FAAD, Private Practice, Ironwood Dermatology, Tucson, Arizona
Coauthor(s): Norman Levine, MD, Professor, Department of Medicine, Section of Dermatology, University of Arizona Health Sciences Center
Contributor Information and Disclosures

Updated: Apr 29, 2009

Introduction

Background

South American blastomycosis is a serious, systemic mycotic infection caused by the thermally dimorphic fungus Paracoccidioides brasiliensis. The fungus is endemic to countries in Central America and South America, most notably Brazil, Argentina, Colombia, and Venezuela, in regions classified as subtropical mountain forests. Infection with P brasiliensis is usually subclinical; however, the fungus sometimes proliferates, causing severe disease.¹

Two general forms of the disease exist: the subacute juvenile form and the chronic adult form. The chronic adult form accounts for more than 90% of cases. The lungs, skin, mucous membranes, and lymph nodes most frequently are involved. Other internal organs sometimes are affected. Also see Blastomycosis (pediatrics) and Blastomycosis (pulmonology).

Pathophysiology

P brasiliensis is a thermally dimorphic fungus that grows as a mycelium in nature and as yeastlike cells in tissue. Although P brasiliensis has been cultured from the soil, its natural habitat is not well understood. The disease is believed to be initially acquired through the inhalation of the fungus, as with other dimorphic fungi. After the inhalation of conidia, the fungus transforms into yeast cells within the alveolar macrophages. In most patients who are immunocompetent, infection is subclinical, and fungal growth is halted. However, in some patients, after an incubation period of weeks to decades, the fungus reactivates and disseminates, causing granulomatous disease in multiple tissues.² Most commonly, the lungs are affected, followed by the mucous membranes, skin, lymph nodes, and various internal organs.

Frequency

United States

The fungus is not endemic to the United States. A number of cases have been reported in patients who previously visited or resided in endemic areas.³

International

South American blastomycosis is restricted to Central America and South America, with about 80% of cases occurring in Brazil. About 6-50% of people living in endemic regions have positive paracoccidioidin skin test results, which indicate prior infection. Antibodies to P brasiliensis have been detected in 27% of blood donors in Brazil.⁴ Of the 90 million people living in endemic areas, approximately 10 million are infected, although exact figures are difficult to obtain.⁵

Mortality/Morbidity

• The mortality rate is high for both the chronic adult and subacute juvenile forms if untreated. With treatment, the mortality rate is 7-10% for children and 1-10% for adults.⁶
• In patients with HIV, the mortality rate is 30-45%.
• Complications generally result from fibrotic scarring that occurs during healing. Patients can have residual chronic lung, oral, nasal, pharyngeal, and laryngeal problems after the lungs or mucous membranes heal. If internal organs, such as the adrenal glands, are affected, chronic organ dysfunction (ie, Addison disease) can develop.

Sex

• The chronic adult form affects men more frequently than women, with a ratio of about 15:1. The fungus has receptors that bind estrogen. Binding of estrogen prevents the transformation of the mycelium into the yeast phase, which is necessary for tissue invasion. This inhibition has been hypothesized to explain the extreme sex differences despite the fact that equal numbers of men and women have positive paracoccidioidin skin test results and that equal numbers of prepubertal boys and girls have the subacute juvenile type.
• The subacute juvenile form affects both sexes equally.

Age

• Most patients are adult men aged 30-50 years.
• Children are affected in only 3-5% of cases.

Clinical

History

After the inhalation of conidia, the fungus transforms into yeastlike cells inside the alveolar macrophages. This transformation induces a nonspecific inflammatory response, which generally limits the disease at this point. Most patients have no signs or symptoms.

• Adult chronic
  • After a latency period of weeks to decades, some adults have a chronic progressive form of the disease. The skin, mucous membranes, lungs, and lymph nodes primarily are affected.
  • Constitutional symptoms include low-grade fever, malaise, and weight loss.
  • Mucous membrane symptoms include pain at ulceration sites. Oral lesions may lead to pain with eating or drinking. Laryngeal and pharyngeal lesions can cause dysphagia, hoarseness, or stridor.
  • Respiratory symptoms include cough; mucous production, which may be blood-tinged; and dyspnea. Symptoms due to involvement of other organ systems are sometimes seen, such as abdominal pain from gastrointestinal involvement or headache from central nervous system involvement.
• Juvenile subacute
  • After a brief latency period, some children have a subacute severe disseminated form of the disease. In children, the major target of South American blastomycosis is the reticuloendothelial system.
  • Symptoms include fever, asthenia, anorexia, malaise, weight loss, and diarrhea.
  • Mucous membrane and respiratory symptoms are unusual.
  • Most other symptoms are related to lymph node enlargement, suppuration, and sinus tract formation.

Physical

• Adult chronic
  • Mucous membranes⁷ : Approximately one half of patients with chronic disseminated disease seek medical attention because of mucocutaneous lesions. Oral, nasal, pharyngeal, and laryngeal lesions begin as papules or plaques, which ulcerate. The lesions typically have granulomatous, mulberrylike surfaces and most commonly occur on the lips, gingiva, palate, buccal mucosa, and tongue. Lesions progress over months and are painful. Gingival lesions cause the loss of teeth, which makes eating difficult. Lesions slowly enlarge and coalesce, increasing the difficulties. Conjunctivitis and ulcerative lesions of the perianal area occasionally occur.

• Skin: Skin lesions, which occur most commonly on the face, are polymorphous. They may be papular, nodular, ulcerated, papillomatous, or even tuberous. They most often arise from the direct extension of mucous membrane lesions. Occasionally, hematogenous spread results in widely scattered lesions and subcutaneous abscesses. Lymph node breakdown can lead to cutaneous fistulae. Without treatment, lesions gradually enlarge.

• Lymph nodes: Extensive lymphadenopathy develops. Numerous visceral and subcutaneous nodes may be involved through hematogenous and lymphatic spread. Cervical nodes are commonly affected. Nodes are hypertrophic, firm, and painful. They sometimes suppurate, forming sinus tracts or ulcers in the skin.
• Respiratory: Lung involvement occurs in 70-80% of patients. In 25% of patients with the chronic adult type of disease, the lungs are the only organ system involved. The clinical picture often resembles that of tuberculosis. Chronic dyspnea, cough, and sputum production develop.
• Other: Hepatosplenomegaly, caused by hepatic and splenic lesions, occurs in approximately 5% of cases. Central nervous system involvement, both meningitis and parenchymal granulomatous disease, is observed in 5-25% of patients and causes mental status changes and seizures.⁸ Occasionally, adrenal insufficiency due to the destruction of the adrenal glands is observed. Intestinal ulcerations and osteomyelitis are other infrequent manifestations.
• Juvenile subacute
  • Mucous membranes: Mucosal involvement is rare, but mucosal ulcerations occasionally occur.
  • Skin: Subacute disease may be associated with an acneiform eruption or subcutaneous abscesses. Sometimes, scrofuloderma is produced as a result of suppuration of the underlying lymph nodes.
  • Lymph nodes: Lymphadenopathy is prominent. Nodes may enlarge to such a point that infection with P brasiliensis may be confused with leukemia or lymphoma. Lymph nodes often suppurate and form sinus tracts to the skin. Mesenteric adenopathy may lead to bowel obstruction.
  • Respiratory: Pneumonia sometimes occurs.
  • Other: Cachexia, hepatosplenomegaly, adrenal insufficiency, osteomyelitis, and gastrointestinal problems may also occur.

Causes

• The disease is caused by the inhalation of the fungus P braziliensis. Animal-to-human and human-to-human transmissions do not appear to occur. Direct inoculation of the skin or mucosal surfaces is rare.
• Rural workers, particularly woodcutters, are more frequently affected because of their increased contact with the soil.
• Alcohol and possibly tobacco smoking is associated with disseminated disease.
• South American blastomycosis has been identified as an AIDS-associated opportunistic infection. Patients with AIDS usually have a form of the disease that closely resembles the juvenile subacute type.⁹
• Otherwise healthy patients who develop disseminated disease appear unable to mount a sufficient cellular immune response to the organism.

• Search for CME/CE on This Topic »

• Paracoccidioidomycosis (Infectious Diseases)
• Gastritis, Chronic (Gastroenterology)