Malakoplakia is a rare inflammatory condition which makes its presence known as a papule

Papule

A papule is a circumscribed, solid elevation of skin with no visible fluid, varying in size from a pinhead to 1 cm.With regard to the quote "...varying in size from a pinhead to 1cm," depending on which text is referenced, some authors state the cutoff between a papule and a plaque as 0.5cm,...

, plaque

Plaque

Plaque or placque may refer to:* Commemorative plaque, a flat ornamental plate or tablet fixed to a wall, used to mark a significant event, person, etc.* Memorial Plaque, issued to next-of-kin of dead British military personnel after World War I...

 or ulceration

Genital ulcer

A Genital ulcer is an ulcer located on the genital area, usually caused by a sexually transmitted disease such as genital herpes, syphilis, chancroid, or thrush. Some other signs of having genital ulcers include enlarged lymph nodes in the groin area, or vesicular lesions, which are small, elevated...

 that usually affects the genitourinary tract. However, it may also be associated with other bodily organs. It was initially described in the early 1900s as soft yellowish plaques found on the mucosa of the urinary bladder

Urinary bladder

The urinary bladder is the organ that collects urine excreted by the kidneys before disposal by urination. A hollow muscular, and distensible organ, the bladder sits on the pelvic floor...

. Microscopically it is characterized by the presence of foamy histiocyte

Histiocyte

A histiocyte is a cell that is part of the mononuclear phagocyte system . The mononuclear phagocytic system is part of the organism's immune system...

s with basophilic inclusions called Michaelis-Gutmann bodies.

It usually involves gram negative bacteria.

Causes

Malakoplakia is thought to result from the insufficient killing of bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 by macrophage

Macrophage

Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...

s. Therefore, the partially digested bacteria accumulate in macrophages and leads to a deposition of iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 and calcium

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

. The impairment of bactericidal activity manifests itself as the formation of an ulcer, plaque or papule.

Malakoplakia is associated with patients with a history of immunosuppression

Immunosuppression

Immunosuppression involves an act that reduces the activation or efficacy of the immune system. Some portions of the immune system itself have immuno-suppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other...

 due to lymphoma

Lymphoma

Lymphoma is a cancer in the lymphatic cells of the immune system. Typically, lymphomas present as a solid tumor of lymphoid cells. Treatment might involve chemotherapy and in some cases radiotherapy and/or bone marrow transplantation, and can be curable depending on the histology, type, and stage...

, diabetes mellitus

Diabetes mellitus

Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...

, renal transplantation, or because of long-term therapy

Pharmacotherapy

Pharmacotherapy is the treatment of disease through the administration of drugs. As such, it is considered part of the larger category of therapy....

 with systemic corticosteroid

Corticosteroid

Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...

s.