What is malakoplakia?
Malakoplakia is a rare inflammatory tumour that occurs most frequently in the urinary bladder and less often other internal sites. However, there have been rare reports of skin involvement and even rarer cases affecting the tongue. It is probably an abnormal immune reaction to a localised bacterial infection, most commonly Escherischia coli.
Other bacteria reported causing malaplakia include Staphylococcus aureus, Pseudomonas aeruginosa, and Rhodococcus equi.
Who gets malakoplakia of the skin and tongue and why?
Malakoplakia of the skin has been reported in association with:
- Immunosuppression, such as organ transplant recipients
- Internal organ involvement with extension to the skin following surgery.
Malakoplakia of the tongue is very rare. It has presented in children and throughout adult life to extreme old age. Males appear to be more commonly affected than females. Unlike malakoplakia of the skin, there has been no apparent association with immunosuppression nor involvement of internal organs.
Malakoplakia is probably an abnormal response to bacterial infection, usually E. coli. There have been a number of theories proposed to explain this. A reduction in the messenger chemical, cyclic guanine monophosphate, has been noted within the tissue macrophages (immune cells). These cells fail to kill bacteria, with the formation of von Hansemann cells and the development of an abnormal inflammatory reaction.
What are the clinical features of malakoplakia of the skin and tongue?
Malakoplakia of the skin most commonly affects the perianal and genital area, presenting as asymptomatic, itchy or painful growths (tumours).
The skin lesions may be solitary or multiple, arranged in lines or across folds of skin. They are:
- Firm papules or nodules up to 2cm in diameter
- Skin-coloured, yellow or pink
- Smooth, sometimes with a central dimple or draining sinus.
The lesions may ulcerate.
Malakoplakia of the tongue usually causes a feeling of something in the throat affecting swallowing or a lump. Pain may be associated. Symptoms may be present for days, weeks or months. On examination, the single lesion is a yellow, pink or tan coloured soft tumour mass up to 4 cm in diameter, usually located on the base of the tongue.
How is malakoplakia diagnosed?
Diagnosis is made on the characteristic histology of a biopsy or excision specimen of the tumour.
The diagnostic feature is the presence of von Hansemann cells containing Michaelis-Gutmann bodies. These intracellular bodies stain positively for calcium and iron and, when fully developed, they resemble an owl's eye.
Bacterial culture will determine which organism is involved.
What is the treatment of malakoplakia of the skin and tongue?
Many tongue and skin lesions are biopsied or excised initially on suspicion of cancer or other unusual forms of inflammation. Wide surgical excision is not usually recommended.
Additional treatment is usually required as recurrence can occur after surgery. Options have included:
- Antibiotics – most commonly trimethoprim + sulphamethoxazole. The choice of antibiotic will depend on the causative organism. Clofazamine has been used successfully as it improves bacterial killing by white cells. Quinolones and rifampicin have good penetration of phagocytes (immune cells).
- Ascorbic acid (vitamin C)
- Reduction of immunosuppressive medications
Malakoplakia of the skin or tongue in isolation has an excellent prognosis. In some cases, there have been a spontaneous resolution. However, approximately 25% of cases with skin lesions have associated internal organ involvement, which can affect the outcome.