noun. 1  a. A cylindrical, usually metal casing containing the primer and charge of ammunition for firearms. 2  A case filled with high explosives, used in blasting. 3  A small modular unit designed to be inserted into a larger piece of equipment: an ink cartridge; a disposable cartridge of caulking compound. A removable case containing the stylus and electric conversion circuitry in a phonograph pickup.
Guttate psoriasis causes a rash formed of drop-shaped salmon-pink areas on the chest, arms, legs and scalp. Guttate psoriasis. Red drop-like lesions are found on the skin. Image courtesy of Dr Hon Pak.
In people with psoriasis, the skin cells grow too quickly. The exact cause of psoriasis is not completely understood, but genetic and immune system abnormalities are believed to play key roles in the condition. In psoriasis, cell turnover can happen in a matter of days. A faulty immune system signals an increased growth cycle of skin cells.