In 1893 Mibelli described under this name eccentrically spreading areas of hyperkeratosis with sharply elevated borders. the external surfaces of the feet, hands and neck, and the mucous membrane of the mouth are the usual sites. The initial lesion is a warty papule which slowly increases by peripheral growth, producing patches of varying size and shape. These patches are surrounded by a well-defined horny ridge or wall, the crest of which may exhibit a continuous or broken furrow. The furrow in turn will often contain a longitudinal cord-like ridge, black pin-head-sized points or conical warty elevations. While the area within the ridge may be normal, it is more commonly thickened and calloused or glossy and atrophied. The patches are usually circular at the onset but become irregular in outline as they grow. They may be raised or depressed and vary in size from a small coin to the width of a limb. Only one lesion may be present, but commonly they are multiple.
Etiology and Pathology. – The cause is not known but hereditary influences may be noted. While the disease is commonest in the first decade of life, it is a hyperkeratosis affecting the lower horny and upper rete layers.
Prognosis and Treatment. – The disease is benign but shows no tendency to spontaneous recovery. The electric needle has cured individual lesions and while surgical excision may accomplish the same purpose, scarring must be expected with the latter measure while it is slight in the former.