Botryomycosis is a rare chronic bacterial infection that clinically and histologically mimics mycetoma, a fungal infection of the skin and subcutaneous tissues. Despite its name, which includes the suffix "-mycosis" typically associated with fungal diseases, botryomycosis is not caused by fungi but by bacteria, most commonly Staphylococcus aureus. Other bacterial agents reported in association with the condition include Pseudomonas aeruginosa, Escherichia coli, and Streptococcus species.
The infection typically presents as cutaneous or subcutaneous nodules, abscesses, or draining sinuses, often on the trunk, limbs, or head and neck region. Characteristic granules—similar in appearance to those seen in mycetoma—may be expelled from the lesions. These granules are composed of bacterial colonies embedded in an inflammatory matrix, rather than fungal elements.
Botryomycosis can occur in both immunocompetent and immunocompromised individuals, though predisposing factors such as trauma, diabetes, or chronic illness may increase susceptibility. Diagnosis is confirmed by histopathological examination showing colonies of bacteria in granules, along with positive bacterial culture. Imaging may be used to assess the extent of tissue involvement, particularly in deeper or systemic forms.
Treatment typically involves prolonged courses of antibiotics, chosen based on culture and sensitivity results, and may be combined with surgical debridement of affected tissue. Prognosis is generally favorable with appropriate therapy, though relapses can occur.
The term "botryomycosis" is derived from the Greek "botrys" meaning "bunch of grapes," referring to the grape-like clustering of bacterial granules observed microscopically, and "mycosis," a misnomer due to the historical confusion with fungal disease.
The condition is distinct from actinomycosis and eumycetoma, though differentiation may require microbiological and histological analysis.