Lobomycosis is a chronic, localised, subepidermal infection characterised by the presence of keloidal, verrucoid, nodular lesions or sometimes by vegetating crusty plaques and tumours. The lesions contain masses of spheroidal, yeast-like organisms tentatively referred to as Loboa loboi. There is no systemic spread. The disease has been found in humans and dolphins and is restricted to the Amazon Valley in Brasil.
The initial infection is thought to be caused by traumatic implantation such as an arthropod sting, snake bite, sting-ray sting, or wound acquired while cutting vegetation. The lesions begin as small, hard nodules resembling keloids and may spread slowly in the dermis and continue to develop over a period of many years. Older lesions become verrucoid and may ulcerate. The disease may be transfered to other areas of of the skin by further trauma or autoinoculation. Thus the areas of involvement may become quite extensive. Lesions are usually found on the arms, legs, face or ears.
Lobomycosis showing extensive verrucoid lesions on the legs.
90% of cases are men, mostly in farmers and other high risk groups exposed to various harsh conditions as well as aquatic habitats.
1. Clinical material: Tissue sample obtained by curettage or surgical biopsy.
2. Direct Microscopy: (a) Tissue can be macerated and mounted in 10% KOH and Parker ink or calcofluor white mounts or (b) Tissue sections should be stained using PAS digest, Grocott's methenamine silver (GMS) or Gram stains.
Interpretation: The presence of chains of darkly pigmented, spheroidal, yeast-like organisms tentatively referred to as Loboa loboi is typical for lobomycosis.
GMS stained tissue specimen showing numerous darkly pigmented yeast-like cells, often in chains, 9-12 um in size.
3. Culture: The aetiologic agent known as "Loboa loboi" remains to be cultured.
4. Serology: There are currently no serological tests available.
5. Identification: Clinical features, geographic location and microscopic morphology are important.
The most successful treatment is for wide surgical excision of the affected area, however care must be taken to prevent contamination of surgical wounds, as relapse is common. Clofazimine at 100-200 mg/day has been used with varying results but it would appear that antifungal drugs are ineffective. The course of the infection is slow and chronic and the although not life threatening the prognosis is poor.
Ajello L and R.J. Hay. 1997. Medical Mycology Vol 4 Topley & Wilson's Microbiology and Infectious Infections. 9th Edition, Arnold London.
Kwon-Chung KJ and JE Bennett 1992. Medical Mycology Lea & Febiger.
Richardson MD and DW Warnock. 1993. Fungal Infection: Diagnosis and Management. Blackwell Scientific Publications, London.
Rippon JW. 1988. Medical Mycology WB Saunders Co.