OVERVIEW
Dark filamentous mycoses are a group of dark fungi causing skin, subcutaneous tissue or systemic infections, mostly in the tropics. Clinical manifestations include shallow ulcers, bruises, brownish-black spots, or warty growths, with slight itching or mild swelling and pain, or no symptoms. Diagnosis is confirmed by mycologic and histopathologic examination.
Etiology
Caused by a dark-colored fungus, which is found in plants and soil, and may be infected by implanting or inhaling fungal spores through skin breaks. It is an exogenous and conditionally pathogenic infection, and is most common in people who have frequent contact with plants and soil.
Symptoms
It may present as shallow ulcers, bruises, brownish-black spots, or warty growths, with slight itching or mild swelling and pain, and some may be asymptomatic. The subcutaneous tissue type often has isolated, deep subcutaneous or muscular abscesses or cysts of varying size. Systemic can be caused by dissemination of cutaneous or subcutaneous tissue type of dark filamentous mycosis to lymph nodes, lungs, brain and gallbladder, etc., or there is no skin damage, and the initial incidence is lymph node or blood dissemination. The subtypes are as follows:
1. Superficial skin type of dark filamentous mycoses
It can be manifested as shallow ulcers, bruises, brownish-black spots or warty growths, with slight itching or mild swelling and pain, and some may have no conscious symptoms. This type includes palm black spot and black hair nodule disease. Palm macules are brown to black non-scaly patches on the palms and metatarsals, occasionally spreading to the neck and chest. Black hair nodular disease is the formation of small ovoid nodules on the hair shaft, hard as a stone, black, rubbed with the fingers, as if sand grains. It mainly invades the hair, and to a lesser extent, it is also seen on the eyebrows and eyelashes.
2. Subcutaneous tissue-type dark filamentous mycoses
There are often isolated, deep subcutaneous or muscular abscesses or cysts, and the lesions may be as large as apricot kernels or several centimeters, or even large plaques on the whole chest. The skin is brownish-red or gray-black, with infiltration when looked at, and the surface is rough and usually unbroken. When biopsy, thin pus can be seen in the subcutaneous tissue, and there is exudate in the cyst.
3. Systemic dark filarial mycosis
This type can be caused by the skin or subcutaneous tissue type of dark filamentous mycosis spread to the lymph nodes, lungs, brain and gallbladder, etc., can also have no skin damage, the initial lymph node or blood dissemination. The onset of dark cerebral mycosis is rapid, and the prognosis is poor.
According to the manifestation of skin lesions, mycological examination and histopathological examination, the diagnosis is not difficult.
Examination
Brown and dark brown mycelia with yeast-like spores are seen microscopically by taking pus and tissue fluid. Cultures may grow brown and black fluffy or yeast-like colonies. Histopathology reveals mostly segregated, black-walled hyphae, 1.5 to 3 micrometers in diameter, with occasional branching or yeast-like budding spores, surrounded by inflammatory cells or multinucleated giant cells infiltrated by the hyphae, without thick-walled spores.
Diagnosis
The diagnosis of this disease is mainly based on clinical, fungal culture and histopathologic examination. It is not difficult to diagnose based on the manifestation of skin lesions, mycological examination and histopathologic examination.
Differential diagnosis
It needs to be differentiated from chromoblastomycosis, foreign body granuloma, cutaneous leishmaniasis, hyaline filamentous mycosis, etc. KOH examination, culture and histologic examination can confirm the diagnosis. Differential diagnosis with chromoblastomycosis and other pyogenic granulomatous diseases also depends on fungal culture identification.
Treatment
1. Local treatment
Surgical excision of limited skin and subcutaneous damage, as well as keratitis and sinusitis, is appropriate, but should be complete to avoid re-implantation of the fungus. In addition, localized heat therapy can be applied.
Topical antifungals are often effective in palmar melanosis, and keratolytic agents (e.g., 10% sulfur cream, 6% salicylic acid, 12% benzoic acid ointment or tincture) may also be applied. The common treatment for black hair nodular disease is to shave the hair or wash the hair daily, scrape the nodules by hand, and then use some antifungal agents to cure it. Can also be used with ketoconazole and selenium disulfide containing liquid washing hair.
2.Systemic treatment
Suitable for cases with systemic damage that cannot be removed by surgery. Most of the antifungal drugs are not sensitive, poor efficacy, the need for long-term, a large number of drugs.
Infections caused by vial mold, flucytosine, fluconazole and amphotericin B are more effective. Trichoderma infections are only sensitive to flucytosine, which can be combined with amphotericin B. Itraconazole, continued for more than 12 months, may be promising for the treatment of nonsurgically resected dark filamentous mycoses.
Prognosis.
Systemic dark filariasis has a poor prognosis and often results in death. Dietary caution should generally be exercised with seafood, eggs, legumes, and stimulating diets, and a light diet should also be used. Follow-up and repeated cultures and histopathologic examinations are necessary.