The two other forms, Borderline and Indeterminate, eventually grow into one of the two principle types. This type is found in patients without an immune resistance to the Mycobacterium leprae organism and is the widespread, anergic form of the disease. The organisms can always be found in enormous numbers in the deep layers of the affected skin. The disease then spreads up the nerves but does not adhere to them as in the Tuberculoid form. It very often spreads to the skin of the face, where it causes thickening and corrugation of the skin and a typical leonine appearance.
Soft nodules appear on the ears, nose, and cheeks and sometimes break down into discharging sores.
The nose often is teeming with bacilli, and this sometimes leads to destruction of the septum of the nose and the palate. The Lepromatous skin lesions involve cooler parts of the body surface and are characterized by massive collections of macrophages containing large numbers of acid-fast bacilli. This is the localized form of the disease and is due to a combination of bacterial proliferation and the immunologic responses of the host bacilli. These skin lesions consists of one or, at most, a few well-circumscribed skin lesions with profound anesthesia. Due to the body's immune system, which responds more intensely to presence of leprosy bacilli, this form of the disease is the most resistant.