Lobomycosis 

Updated: Apr 14, 2017
Author: Manuel Valdebran, MD; Chief Editor: Dirk M Elston, MD 

Overview

Background

Lobomycosis (lacaziosis) is a self-limited, chronic fungal infection of the skin endemic in rural regions in South America and Central America. Natives of the Brazilian rain forest call this disease miraip or piraip, meaning "that which burns."

Jorge Lobo first described this infection in the medical literature[1] as keloidal blastomycosis in a patient from the Amazon Valley of Brazil. Since the original report, lobomycosis has been reported in many South American countries, in North American travelers to endemic regions, closely related disease in two species of Atlantic dolphins, and in one marine park dolphin trainer.[2]

The condition was called Lobo disease in 1938, in 1958 the name lobomycosis was applied, and in 2005 the name lacaziosis was suggested.[3, 4, 5]

Three species names have been recommended: Loboa loboi[6] ; Paracoccidioides loboi[7] because of its antigenic relationship to Paracoccidioides brasiliensis; and Lacazia loboi[8] in deference to Lacaz, who contributed much to the knowledge of the disease. Other names that have been used are Glenosporella loboi and Blastomyces loboi. Based on recent molecular studies, the name Lacazia loboi is the current recommended name.[5] As is common in medical mycology, the name of the disease is taken from the genus of the etiologic agent, and therefore, lacaziosis has been proposed for the disease name rather than lobomycosis.[5]

Phylogenetic and genomic analyses indicate that it is a sister taxon of the human dimorphic fungal pathogen P brasiliensis and that both species belong to the order Onygenales.[5, 9, 10, 11]

Pathophysiology

The organism responsible for lobomycosis has yet to be cultured in vitro. The infection has been transmitted to an armadillo,[12] to the footpads and cheek pouches of golden hamsters,[13, 14] and to tortoises.[15] Live organisms have been maintained for 18 months in the footpads of BALB/c mice.[16, 17, 18] However, most of our knowledge of the etiologic agent of lobomycosis is derived from histopathologic, electron microscopic, and molecular studies.[5]

The fungus is abundant in lobomycotic skin lesions. It is a spherical intracellular yeast 6-12 μm diameter.[19] The fungus is remarkably homogeneous, with an average diameter of 9 μm. Although debate exists as to whether nuclei and organelles of fungal origin have been definitively identified,[19, 20, 21] 2 lines of evidence support the fungal nature of the etiologic agent of lobomycosis. First, immunologic studies show cross-reactivity of the antiserum obtained from patients affected by lobomycosis with several antigens prepared from cultures of P brasiliensis[22, 23] Second, sequence analysis of ribosomal RNA (rRNA) obtained from skin lesions in dolphins are highly homologous to rRNA sequences from the genus Cladosporium[24] and from P brasiliensis.[9]  Emerging data suggest that cetacean lacaziosis-like disease is related to L loboi, but more closely related to P brasiliensis and P lutzii.[2, 25]

L loboi is predominantly an intracellular pathogen. Organisms, singly or in chains, reside predominantly in macrophage vacuoles. They probably reproduce by budding; linear or radiating chains of as many as 20 organisms linked by tubules have been observed.[19] The melanin-containing birefringent 1-μm-thick cell wall[26] resists digestion by macrophages and may be central in contributing to the chronicity of the infection.[19]

The cytokines secreted in vitro by mononuclear cells of patients with lobomycosis showed increased interleukin-4 and interleukin-6 and decreased interleukin-2 production compared with mononuclear cells from normal patients. Mononuclear cells from patients with generalized disease produce higher levels of interferon-gamma than those from patients with localized disease. Taken together, these results suggest that mononuclear cells from patients with lacaziosis are predominantly of the Th2 profile. Further studies are needed to assess the significance of these observations.[27] When compared to healthy control subjects of the same ethnic group no human leukocyte antigen (HLA) susceptibility or resistance could be demonstrated in 21 patients with lobomycosis.[28] However, HLA-DR7 was found to be potentially protective.

The natural reservoir of L loboi is unknown. Its likely habitat is somewhere in the rural environment because of the observed distribution of the disease. Soil and vegetation seem to be likely sources of infection.

L loboi has also been recovered from lobomycotic lesions of the Guiana dolphin Sotalia guianensis from the Surinam River estuary[29, 30] and Tursiops truncatus dolphins in Florida, Hawaii, North Carolina, and the Bay of Biscay in Europe[31, 32, 33, 34, 30, 35] ; these findings imply that some aquatic reservoir also exists. 

Lobomycosis is similarly manifested in humans and in dolphins; the skin lesions and morphologic features of the organism are nearly identical, and at least one case of dolphin-to-human transmission has been documented.[32] However, the organism in dolphins is somewhat smaller than that seen in humans, and it may not prove to be identical.[36] In fact, a recent article suggests that transmission of any kind from dolphins to humans occurs rarely, if at all.[37]

Lobomycosis often develops at sites of minor trauma, but sometimes, no history of trauma can be recalled.[32] The disease has been associated with ear lesions in persons who carry natural materials on their shoulder, with snake and insect bites,[38] and in one case, with trauma associated with exposure to high-pressure falling water.[26] Human-to-human transmission has not been documented, though the inoculation of a tissue homogenate reproduced the disease,[39] and 1 case in Europe may have been caused by occupational exposure to an infected dolphin[32] . Murine-to-human transmission has been postulated but not proven.[40]

Once phagocytized, the organisms initiate a slow replication process, which may account for the slow incubation period and slow development of lesions. Transforming growth factor-β affects mononuclear function, inhibiting expression of interferon-gamma and nitric oxide.[41] In addition, interleukin (IL)–10 has been found to be importantly present in the dermis of affected individuals. Transforming growth factor-β and IL-10 inhibit the cellular immune response, thus altering the function of macrophages.[42]

Mechanisms for dissemination are unclear; however, newer lesions presenting adjacent to affected areas supports dissemination by contiguity or autoinoculation.[41] Although L loboi is generally considered a deep-seated mycosis, it has shown the potential for transepidermal elimination of infectious organisms.[43]

Dissemination within an individual also may occur by means of lymphatic spread.[44] Hematogenous dissemination has been proposed as a possibility, owing to a description of a patient presenting with testicular metastasis.[41]

Epidemiology

Frequency

United States

Only one case of lobomycosis has been reported in the United States. The patient was exposed to a waterfall in Venezuela years before presentation.[26]

International

Approximately 64% of all known cases have occurred in Brazil[27, 45] and though lobomycosis is uncommon, it occurs in as many as 8.5% of the members of some tribes indigenous to South America, for example, the Amoruas tribe of the Casanare state in Colombia and the Caiabi Indians of Brazil.[46, 47] The first report[48] of imported human lobomycosis in Canada was published in 2004 and in South Africa in 2008.[49]

Race

Other than a few tribes in South America (eg, the Amoruas, the Caiabi), no racial prevalence is known. One case has been reported in the United States, but the patient was exposed to a waterfall in Venezuela years before his or her presentation.[26] The case in Europe was reported in a handler of an affected dolphin.[32]

The disease has been reported in many areas: Costa Rica,[38] Panama,[50] Venezuela,[7] Colombia,[47] Guyana,[51] Surinam,[13] French Guyana,[52] Ecuador,[7] Peru,[53] Bolivia,[7] Honduras,[7] Mexico,[54] Holland,[32] the United States,[26] and Canada.[48]

The disease is usually found in areas higher than 200 m with tropical, humid, or subtropical forests; an average temperature of 24°C; and more than 2000 mm of annual rainfall.[44]

Sex

Lobomycosis is more common in men (68-92% of cases) than in women.[55]  The disease is most common in farmers, rubber workers, hunters, and prospectors.[56]  The high prevalence among women of some tribes is attributed to their active participation in farming activities.

Age

The age of onset is 1-70 years, with an average patient age of 38 years.[13]

Prognosis

Lobomycosis does not affect the general health of the patient. Current treatment is disappointing, and most patients continue to have lobomycosis unless it is surgically treated at an early stage. No deaths from lobomycosis have been reported. One patient in whom squamous cell carcinoma developed in a lobomycotic nodule later died from lung metastases.[57]

 

Presentation

History

Skin lesions develop slowly.[58] For example, the incubation time in the patient who acquired the disease from an affected dolphin was 3 months,[32] and the incubation period in the American who had traveled to Venezuela was 2.5 years.[26]

When a volunteer was inoculated with the etiologic agent, the lesion was 1 X 2 mm in the first month, and then it waxed and waned. At 5 months, the lesion was a 2- to 3-mm, red papule. At 15 months, it measured 1 cm, with a small telangiectasis. At 25 months, the lesion was 15 X 10 mm, and at 4 years, it measured 33 mm in diameter, and a 4-mm satellite lesion developed.[39]

Because of this slow growth, patients do not present for many years, or they may present only after the lesions become large. The lesions often begin as small papules or pustules, and they may occur at sites of minor trauma.[39]  The lesions may be mildly pruritic, or they may burn.[55]  Single lesions occasionally regress and form scars. However, the disease never disappears, and organisms are identifiable in the scar tissue.[59]  Aside from occasional lymphadenopathy, patients lack other systemic symptoms.[56] However, a recent case report describes a squamous cell carcinoma arising in old lobomycosis lesion scars.[60]

Physical Examination

The disease predominately affects exposed areas and extremities. Examples include the ears, buttocks, lumbosacral area, scapular area, elbows, and lower limbs.[61] The scalp and mucosae are spared.

Lesions, papules, or plaques are most often described as keloidal, but the adjectives gummatous, verrucous, or ulcerative have also been applied.[13]

Lesions have well-defined lobulated margins and are not attached to deeper structures.[62]

The epidermis may be shiny, atrophic, and discolored.[13]

The disease may spread proximally from the extremities and fungal cells have been found in the lymph nodes, indicating lymphatic spread.[47, 63]  Lymph nodes that drain the affected regions may be enlarged and infected with the organism in 0-25% of patients.[13]

See the images below.

Keloidal nodule on the leg. Courtesy of Dr Roberto Keloidal nodule on the leg. Courtesy of Dr Roberto Baruzzi, Sao Paulo, Brazil.
Lobomycosis in this patient appears as a flat plaq Lobomycosis in this patient appears as a flat plaque lesion. Courtesy of Dr Roberto Baruzzi, Sao Paulo, Brazil.
Separate keloidal lesions in a localized area. Cou Separate keloidal lesions in a localized area. Courtesy of Dr Roberto Baruzzi, Sao Paulo, Brazil.

Causes

Other than geography and possible implantation of organisms through skin trauma,[64] no predisposing factors have been identified.

Important data regarding the interplay among genetic, cultural, and geographic factors have been derived from studies of the Caiabi Indians of Brazil. After they relocated to a geographic area similar to their former one, no new cases have been reported. Furthermore, their original neighbors did not have similar prevalence rates.[65]

Immunodeficiencies appear to occur in patients with lobomycosis. These immunodeficiencies include a delayed skin allograft rejection, a failure to sensitize to dinitrochlorobenzene, and an anergy to Candida species.[66]  Whether the immunodeficiencies are primary and predispose patients to infection or secondary and the result of infection is not known. Based on the large number of fungal cells in the infected tissue and the disorganized cell arrangement in the granuloma, it has been hypothesized that patients with lobomycosis have immunoregulatory disturbances, which are likely to be specific and perhaps responsible for the lack of containment of the pathogen.[67]  One patient infected with the HIV has been reported to have lobomycosis.[68]

Complications

General complications may include the following:

  • Disfigurement
  • Ulceration
  • Superinfection of ulcerated lesions
  • Potential loss of function of affected areas in advanced cases

Two cases of squamous cell carcinoma have been reported in long-standing lesions.[57]

 

DDx

 

Workup

Laboratory Studies

Laboratory studies are not required.

Lesions can be gently scraped with a sterile scalpel blade and placed on a microscope slide with a coverslip with or without the use of 10% potassium hydroxide (KOH) or the use of a calcofluor preparation of strips of vinyl adhesive tape may demonstrate the yeast.[43, 48, 69]

An experimental research technique has been developed to determine the viability of L loboi to gauge success of therapy. The method uses fluorescein diacetate-ethidium bromide (FD-EB) vital staining and appears to be reliably sensitive and specific for viability determination of L loboi.[70]

Imaging Studies

Imaging studies are not required.

Other Tests

Other tests are not required.

Miranda and Silva have used vinyl adhesive tape (Scotch test) and direct microscopy to diagnose lobomycosis. This method presumably is possible because of transepidermal elimination of infectious organisms.[43] This test is an attractive, noninvasive, and inexpensive novel technique to diagnose L loboi infection, but additional research is needed to validate the method.

Procedures

Findings on skin biopsy are diagnostic.

Histologic Findings

Histologic examination reveals a granuloma with mostly histiocytes, multinucleated giant cells (average of 10 nuclei), asteroid bodies (ABs), and numerous fungal cells lined up in rows like a child's pop beads.[13, 67, 71] The identified inflammatory cells in a granuloma show the following frequency: CD68+ histiocytes > CD3+ T lymphocytes > CD4+ T lymphocytes > CB8+ T lymphocytes > CD57+ natural-killer cells > CD79+ plasma cells > CD20+ B lymphocytes.[67]

Granulomas are limited in distribution to the dermis,[56] and a delicate layer of collagen may separate the granuloma from the epidermis.[72] The epidermis can be normal, atrophic, or it may have pseudoepitheliomatous hyperplasia,[72] or its papillae may be short.[56]

Xanthomized histiocytes with clear or finely granular eosinophilic cytoplasm occasionally may be seen.[42]

Necrosis is rarely present.[46] Fungal cells are abundant in the macrophages.[19] The fungal cells are highlighted with Gomori Methenamine silver and periodic acid-Schiff stains.[48] Lymphocytes, plasma cells, and leukocytes are found in small numbers.[13] No nerve infiltration is present, and blood and lymphatic vessels are normal.[13]

The presence of intracellular ABs has been described in infiltrating giant cells in granulomatous conditions, including lobomycosis. These ABs have been confused with similar-appearing structures in pathologic specimens obtained from patients with sporotrichosis. Whereas ABs of sporotrichosis consist of a central yeast surrounded by eosinophilic spicules, ABs of lobomycosis are intracellular filamentous structures that contain lipid myelin figures.[73, 74]

See the image below.

Characteristic histologic appearance of the organi Characteristic histologic appearance of the organism. Courtesy of Dr Roberto Baruzzi, Sao Paulo, Brazil.

 

 

Treatment

Medical Care

To date, there have not been any investigations using pharmacological regimens; however, reports have described efficacy for certain regimens in nonsurgical candidates.

A case report described a therapeutic response to 1-year treatment with a combination of clofazimine at 100 mg/d and itraconazole at 100 mg/d.[75] Clofazimine alone improved the lesions in a few patients. Another case report described a patient in Peru who was cured after 27 months of posaconazole with no recurrence after 5 years of follow-up.[76]

Combination itraconazole and clofazimine has been used in the treatment of lobomycosis on the face, with no relapse after 3-year follow up.[77]

Patients with lobomycosis and concurrent leprosy respond to multibacillary therapy, with reduction of pruritus and the size of mycotic nodules.[78]

Surgical Care

The treatment of choice for patients with a localized, surgically amenable form of the disease is surgical excision.[79, 80] Recurrence at the excision site is not uncommon; however, if the disease is detected early, surgical excision may be curative.[72, 79] The major indication for excision is the prevention or correction of disfigurement.

In order to prevent recurrence, itraconazole with cryosurgery has been used successfully to treat relapsing cases.[81]

Diet

No specific dietary changes are required.

 

Medication

Medication Summary

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Antitubercular Agents

Class Summary

The goals of treatment are to shorten the clinical course, prevent complications, and prevent the development of latency and/or subsequent recurrences, These agents have bactericidal and bacteriostatic activity.

Clofazimine (Lamprene)

This agent is no longer commercially available in the United States; it is only available by obtaining an investigational new drug (IND), see Dosing Considerations. Use 100 mg/day PO.

Antifungals, Systemic

Class Summary

The mechanism of action of antifungal agents may involve an alteration of RNA and DNA metabolism or an intracellular accumulation of peroxide that is toxic to the fungal cell.

Itraconazole (Onmel, Sporanox, Sporanox Oral Solution)

Itraconazole has fungistatic activity. It is a synthetic triazole antifungal agent that slows fungal cell growth by inhibiting CYP450-dependent synthesis of ergosterol, a vital component of fungal cell membranes. Use 100 mg/d PO.

Posaconazole (Noxafil)

Posaconazole is a triazole antifungal agent. It blocks ergosterol synthesis by inhibiting the enzyme lanosterol 14-alpha-demethylase and sterol precursor accumulation. This action results in cell membrane disruption. Use 400 mg PO twice daily.