POROKERATOSIS OF MIBELLI
This is a rare, autosomal dominant defect of skin keratinization. Centrifugally spreading patches are surrounded by horny ridges, and there is central atrophy. Onset is usually in childhood, and lesions may occur anywhere on the skin, enlarge slowly, and are usually asymptomatic. Squamous cell carcinoma, Bowen’s disease, and basal cell carcinoma may develop in the keratoatrophodermic lesions, particularly on the extremities. X-ray treatment may increase the tendency to develop carcinoma. There are other rare forms of porokeratosis: disseminated superficial actinic porokeratosis and porokeratosis plantaris, palmaris, et disseminata, which are also inherited as autosomal dominant conditions predisposing to skin cancer but which occur more in adults and are more likely to be symptomatic. Sporadic cases also occur, and malignancy may be more common in sporadic cases. Males are more often affected than females (Gotz et al. 1999; Goerttler and Jung 1975).