[2][3] This debilitating form of leprosy begins to spread causing the eyebrows to disappear and spongy tumor like swellings appear on the face and body.

The disease attacks the internal organs, bones, joints and marrow of the body resulting in physical degeneration.

[4] Early detection of the disease is of utmost importance, since severe physical and neurological damage are irreversible even if cured (e.g. blindness, loss of digits/limbs/sensation).

Early infection is characterized by a well demarcated, usually pale, skin lesion which has lost its hair, and there may be many of these lesions if the infection is more severe (most commonly found on the cooler parts of the body such as the elbows, knees, fingers, or scrotum, as the bacteria thrive in cooler environments).

The disease is believed to be spread through respiratory droplets in close quarters like its relative Mycobacterium tuberculosis, and similarly requires extended exposure to an individual in most situations, so outsiders and healthcare workers are normally not infected (except with the most infective individuals such as those in the most progressed lepromatous forms, as those patients have the highest bacterial loads).