A “laboa” most likely refers to Lacazia loboi, a fungus that causes a chronic skin infection called lobomycosis (also known as Jorge Lobo’s disease). It’s a rare tropical infection that produces firm, keloid-like growths on the skin, primarily affecting people who live or work in the Amazon rainforest and surrounding regions of Central and South America. The disease was first described in 1931, and the fungus behind it remains one of the most mysterious in medicine: scientists have never been able to grow it in a laboratory.
The Fungus Behind the Disease
Lacazia loboi is an obligate pathogen, meaning it can only survive inside living tissue. Unlike most disease-causing fungi, it has never been successfully cultured outside a host body. Everything researchers know about its biology comes from examining infected tissue samples. Under a microscope, the fungus appears as round or lemon-shaped cells about 6 to 12 micrometers in diameter, connected to each other by thin tube-like bridges. These chains of uniformly sized cells are the hallmark of lobomycosis and distinguish it from other fungal infections that can look similar.
The fungus contains a natural dark pigment in its cell walls and has a strong preference for cooler areas of the body, particularly the skin of the ears, elbows, shins, and ankles. It stays confined to the skin and the tissue just beneath it. Unlike many other fungal infections, it does not spread to internal organs.
Where Lobomycosis Occurs
The vast majority of human cases come from the Amazon rainforest, concentrated in the Brazilian states of Acre, Amazonas, and Pará. Cases also appear across the broader Amazon Basin in Peru, Colombia, Bolivia, Ecuador, Venezuela, Suriname, French Guiana, and Guyana. The disease primarily affects forest dwellers, farmers, miners, and others whose work brings them into regular contact with freshwater environments, soil, and vegetation.
Interestingly, a related form of lobomycosis also occurs in bottlenose dolphins along coastal waters. However, the evidence that dolphins can transmit the infection to humans is weak. Communities living near coastal areas with high rates of dolphin lobomycosis have not shown increased human cases, suggesting direct or indirect transmission between species occurs rarely, if at all.
How People Get Infected
The fungus enters the body through breaks in the skin. Documented routes of transmission include cuts, insect bites, snakebites, stingray injuries, and general abrasions on exposed skin. This explains why lesions tend to appear on areas like the ears, arms, and legs rather than on the trunk. People who work outdoors in tropical freshwater environments are at the highest risk. There is no evidence of person-to-person transmission.
What the Lesions Look Like
Lobomycosis starts as a small bump at the site of skin trauma. It can be superficial or deeper depending on the injury. From there, it progresses slowly over months to years into a firm plaque or nodule covered with smooth, shiny skin. The texture is fibrous and resembles a scar or keloid, which is why the keloid subtype is the most commonly recognized form of the disease.
The color of lesions varies. They can match the person’s natural skin tone or range from reddish-brown to a deep wine color, sometimes with visible tiny blood vessels on the surface. Color changes around the lesion are common, including lighter or darker patches. Five distinct subtypes have been described: infiltrated, keloidal, gummatous, ulcerative, and verrucoid (wart-like). Nodules are firm to the touch and can merge together over time. Most lesions are painless, though some cause abnormal skin sensations.
The ears are the single most common site, accounting for about 38% of cases. The upper limbs follow at 28%, then the lower limbs at 22%. Because lesions grow so slowly and don’t typically cause pain, people sometimes live with lobomycosis for years or even decades before seeking treatment.
How It’s Diagnosed
Diagnosing lobomycosis can be tricky because the lesions mimic several other tropical diseases, including leishmaniasis, leprosy, sporotrichosis, and other fungal infections. Wart-like lesions on the legs can resemble chromoblastomycosis, while ulcerated forms look similar to leishmaniasis. The definitive diagnosis comes from examining a skin biopsy under a microscope. The characteristic finding is chains of uniformly sized, round fungal cells connected by thin tube-like bridges. No other fungal infection produces this exact pattern, making it a reliable diagnostic marker once a biopsy is obtained.
Treatment Options and Challenges
Lobomycosis is one of the most difficult tropical infections to treat. No antifungal medication has proven effective against Lacazia loboi. The primary treatment recommended in the medical literature is surgical removal of the lesions, but outcomes are far from perfect. Recurrences are common, often because the fungus extends beyond the visible borders of the lesion. The frequent location of growths on the head and ears also creates functional and cosmetic challenges for surgery, and there is a small risk of accidentally spreading the fungus with surgical instruments.
Some treatment centers use a combination approach. One documented protocol involves wide surgical removal of lesions combined with antifungal medication, an anti-inflammatory drug, and cryotherapy (freezing with liquid nitrogen) applied every three months for two years. Even with this aggressive strategy, the disease can return. The inability to grow the fungus in a lab has been a major barrier to developing better treatments, since researchers cannot easily test new drugs against it.
Lobomycosis remains among the most neglected of tropical diseases. Its rarity, its confinement to remote populations, and the fundamental mystery of an organism that cannot be cultured have all contributed to slow progress in finding a cure.