Malakoplakia is a less common chronic inflammatory disease caused by bacterial infection, more common in immunocompromised patients. The urinary tract is usually invaded, the most involvement is the bladder, followed by the kidney and ureter, and skin involvement is less common.
There are numerous pathogenic bacteria, mostly Escherichia coli, accounting for more than 90%, and others include Klebsiella, mycobacteria, and Rhodococcus equi. The pathogenesis is still unclear, but is associated with immunosuppression. After the bacteria are engulfed into the cells, the intracellular digestion defects of macrophages lead to weakened digestive ability, so that the bacteria cannot be completely digested. In addition, some bacterial components that cannot be digested by lysosomal enzymes of macrophages in the immunocompromised host are deposited intracellularly, resulting in the deposition of calcium and iron in the remaining bacterial glycolipids, thereby forming the characteristic Michaelis-Gutmann bodies in malakoplakia.
Signs and Symptoms
Malakoplakia can occur in persons of all ages, averagely aged 53 years. The disease is more common in immunocompromised patients with organ transplants, diabetes, lymphoma, long-term use of glucocorticoids, or rheumatoid arthritis. Skin lesions can be manifested by yellowish red papules, plaques, or ulcers, mainly in the perianal area, groin, gluteal sulcus, and abdominal wall, as well as draining sinus tracts adjacent to the urethra, perianal abscesses, painful abscesses of the thigh, and female genitals. Genitourinary malakoplakia is often similar to granulomas in the tumor, and are easily misdiagnosed as cancer.
Histological manifestations are foamy eosinophilic Hansemann macrophages, and intracellular calcified, concentrically layered cytoplasmic bodies are called Michaelis-Gutmann bodies. Discrete immunoblasts, neutrophils, and lymphocytes in the dermis can be seen. The Michaelis-Gutmann bodies are positive in PAS staining and are resistant to amylase, von Kossa staining can be used to reveal the deposited calcium, and Perls Prussian blue staining can be used to reveal deposited iron. In electron microscopy, Michaelis-Gutmann bodies are bacterial lysosomes that are not completely digested. Immunohistochemistry reveals positive anti-CD86 antibody, lysosome, and chymotrypsin.
Diagnosis is based primarily on clinical presentations and characteristic histopathological changes.
The treatment depends on the pathogenic microorganisms isolated from the lesions. Since the general medicine does not easily penetrate macrophages, the bacteria are not easily killed and are resistant to treatment. Fluoroquinolones such as ciprofloxacin and ofloxacin are more likely to infiltrate macrophages, thereby eliminating bacteria that are latent in the cells, so they are usually used for the treatment of this disease. The dose is 500mg twice daily for 3 - 6 months or longer. Auxiliary treatment is vitamin C. Nephrectomy is an optional treatment when the kidney is involved.