Usually occurring in conjunction with nodules, cysts are considered severe acne lesions and are usually very painful. They penetrate the skin deeply, and usually result in scarring. Filled with bacteria, dead skin cells, and white blood cells, cysts are often severely inflamed and almost always cause scarring. When a nodule and a cyst occur together, it is often referred to as nodulocystic. Nodulocystic conditions are often only treatable with isotretinoin.