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.
No one knows the exact cause of psoriasis, but experts believe that itâs a combination of things. Something wrong with the immune system causes inflammation, triggering new skin cells to form too quickly. Normally, skin cells are replaced every 10 to 30 days. With psoriasis, new cells grow every 3 to 4 days.