Botryomycosis, pyoderma vegetans

Background

Botryomycosis is a rare condition, with few reported cases worldwide. Because it is so rare, there is confusion in the literature over the classification and definition of the illness. Some authors have suggested that cutaneous botryomycosis is a subtype of pyoderma vegetans, and propose these two conditions should be classified together. Other authors have suggested that actinomycosis and botryomycosis should be classified under the single term ‘granular bacteriosis’.

Botryomycosis is a chronic (slowly progressive) inflammatory response to a bacterial infection. Staphylococcus aureus is most commonly implicated, followed by Pseudomonas aeruginosa. Various other bacteria such as Proteus or Escherichia coli have also been isolated. Some form of trauma, surgery, or the presence of a foreign body usually precedes infection. Botryomycosis is more likely to occur in patients with impaired immunity, such as those with HIV infection, alcoholism, and diabetes mellitus.

Clinical features

Botryomycosis most commonly affects the skin. Infection may extend to the subcutaneous tissues, muscles, and bones.

It is rare for botryomycosis to affect internal organs. The lungs are the most commonly infected and usually there is a predisposing factor such as surgery or impaired immunity.

Botryomycosis skin disease presents as subcutaneous nodules (small solid lumps under the skin), large verrucous (wart-like) lesions, ulcers, and fistulae (small drainage tunnels). The lesions generally develop over several months and may drain pus. The pus may contain small yellow “grains” similar to the sulphur granules of actinomycosis.

Diagnosis

Botryomycosis can be difficult to diagnose. Features which suggest botryomycosis include:

• identifying typical bacteria and grains in pus or skin biopsy specimens
• culturing typical bacteria from biopsy specimens or swabs taken from ulcers or pus
• identifying characteristic microscopic features of biopsy specimens

Treatment

Botryomycosis is usually treated with long-term antibiotic therapy and surgical debridement. The choice of antibiotics depends on the type of bacteria involved.