Author: Vanessa Ngan, Staff Writer, 2003.
The term porokeratosis refers to skin lesions with a thinned centre surrounded by a ridge-like border called the cornoid lamella. The cornoid lamella is due to an expanding number of unusual keratinocytes (surface skin cells). Porokeratosis of Mibelli is one type of porokeratosis.
The cause is unknown. Occasionally there is a family history of porokeratosis of Mibelli or another type of porokeratosis such as linear porokeratosis or disseminated superficial actinic porokeratosis (DSAP), suggesting there is a genetic predisposition to the disorder.
Porokeratosis of Mibelli usually appears in childhood, but lesions may be present at birth or may first appear at puberty or later. Adult onset has been seen following suppression of the immune system by certain medications or illness.
Lesions start as small, light brown, scaly papules that may join into one or more plaques with irregular boundaries. Each plaque is separated from the surrounding skin by a warty rim with well-defined thin furrows running in its centre.
Porokeratosis of Mibelli most often affects the limbs, particularly the hands and feet, the neck and shoulders, the face and the genitals, although any part of the body may be affected including the mucous membranes.
Lesions may remain unchanged for many years or may slowly grow between long periods of inactivity. A skin cancer can develop within porokeratosis of Mibelli. This may be either a basal or squamous cell carcinoma, and is more likely to occur in older adults. If a lump or sore appears within a porokeratosis lesion, arrange for it to be reviewed by your dermatologist. It may require a biopsy or cutting out (excision).
The diagnosis of porokeratosis is sometimes made by characteristic features on pathology.
There is no known cure for porokeratosis of Mibelli and treatment is generally disappointing. However, the appearance may improve with the following measures:
Sun protection is very important as exposure to ultraviolet radiation may result in the development of skin cancer within the porokeratosis lesion.
See the DermNet NZ bookstore
© 2018 DermNet New Zealand Trust.
DermNet NZ does not provide an online consultation service. If you have any concerns with your skin or its treatment, see a dermatologist for advice.