The protozoan is in the smaller of its two forms, called an amastigote, which is round, non-motile, and only 3–7 micrometers in diameter. Inside the stomach of the sandfly, the amastigotes quickly transform into elongated and motile forms called the promastigotes. Promastigote is spindle-shaped, triple the size of the amastigote, and has a single flagellum that allows mobility. The promastigotes live extracellularly in the alimentary canal, reproducing asexually, then migrate to the proximal end of the gut where they become poised for a regurgitational transmission. As the fly bites, the promastigotes are released from the proboscis and introduced locally at the bite site.Once inside the human host, promastigotes invade macrophages. Inside the cells they transform back into the smaller amastigote form. The amastigotes replicate in the most hostile part of the macrophage cell, inside the phagolysosome, whose normal defensive response they are able to prevent. After repeated multiplication, they break down their host cell by sheer pressure of mass, but there is some recent speculation that they are able to leave the cell by triggering the exocytosis response of the macrophage. The daughter cells protozoans then migrate to fresh cells or through the bloodstream to find new hosts. In this way the infection is progressive, spreading to the hosts mononuclear phagocyte system, particularly the spleen and liver. The free amastigotes in peripheral tissues are then ingested by sandfly to enter another cycle. Regulatory T and B cells
The cell-mediated immunity (CMI) that kills Leishmania also produces inflammation. If the inflammation is excessive, it can cause tissue damage.
Granuloma faciale  is an uncommon benign chronic skin disease of unknown origin characterized by single or multiple cutaneous nodules, usually occurring over the face. : 836  Occasionally, extrafacial involvement is noted, most often on sun-exposed areas. Diagnosis
Skin biopsy for histopathology: 
Focal LCV, diffuse dermal neutrophilia with leukocytoclasia, tissue eosinophilia & perivascular fibrosis. Differential diagnosis
The disease mimics many other dermatoses and can be confused with conditions, such as sarcoidosis, discoid lupus erythematosus, mycosis fungoides, and fixed drug eruption. Treatment
Topical corticosteroid,
Intralesional corticosteroid,
Dapsone,
Colchicine,
Antimalarial,
Pulse dye laser,
Carbon dioxide laser. History
GF was first described in 1945 by John Edwin Mackonochie Wigley (1892–1962). See also
Cutaneous small-vessel vasculitis
List of cutaneous conditions

References


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