Keloidal blastomycosis: causes, symptoms, diagnosis, and treatment

Keloidal blastomycosis, also known as Lobomycosis or Lobo’s disease, is a cicatricial, verrucous, nodular, or even neoplastic plaques or masses caused by Lacazia loboi.


Causes

The pathogen is Lacazia loboi, a yeast cell with a diameter of 9 - 10μm, arranged in a chain. The disease is rare and may result from inoculation into human skin through snake bites or bites of insects such as mosquitoes and ticks. The disease can spread to other areas through autoinoculation, but does not involve organs.


Signs and Symptoms

Skin lesions are solitary or multiple, and more common on the face, especially the ears, as well as extremities, especially lower limbs, Initial symptoms are small, motile, cicatricial nodules under the epidermis, with light red to purplish red, smooth surface, with telangiectasis, with normal peripheral skin, without pain, with mild pruritus. Autoinoculation can occur with scratches. The old lesions can be manifested by ulceration, exudate, and scabs, probably verrucous. The disease develops very slowly.


Histopathology

The typical nodules are granulomas under the epidermis, which do not extend into the deep subcutaneous tissue, and epidermal atrophy is often present. Generally, fibrosis is absent, and granulomas contain histiocytes and giant cells. With the development of the skin lesions, the infiltration of giant cells can reach 40 - 80μm in size. There are about 10 yeast cells in a giant cell. The yeast cells are 7 - 12μm in diameter, and the cell wall is about 1μm. Several yeast cells are often connected together, and sometimes they can partially extend out of giant cells.


Diagnosis

On the basis of clinical findings, fungal microscopy, and histopathology, a diagnosis can be provided.


Treatment

Systemic sulfonamides, clofazimine, and antifungals such as itraconazole and fluconazole can be used, but amphotericin B is ineffective.

Early localized lesions can be treated with surgical excision, followed by antifungals.

Cryotherapy and CO2 laser therapy can also be considered.