What is linear porokeratosis?
Linear porokeratosis is an unusual skin condition that can be present at birth or not develop until adult life. Occasionally there is a family history of linear porokeratosis or another kind of porokeratosis such as disseminated superficial actinic porokeratosis (DSAP), suggesting a genetic predisposition.
The term porokeratosis refers to a roundish skin lesion with a thinned centre surrounded by a ridge-like border called the cornoid lamella. The cornoid lamella is due to an expanding proliferation of unusual keratinocytes (horny skin cells).
Features of linear porokeratosis
Numerous grouped patches arise in linear porokeratosis, each with the characteristic ridge on its border and central furrow. They are arranged in one or more lines along a limb or on one side of the trunk, head and/or neck, following a dermatomal distribution (i.e. along the pathway of a sensory nerve).
A skin cancer can develop within a linear porokeratosis patch. 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.
The diagnosis of porokeratosis is sometimes made by characteristic features on pathology.
Treatment of linear porokeratosis
There is no known cure for linear porokeratosis and treatment is generally disappointing. However, the appearance may improve with the following measures:
- 5-fluorouracil cream
- calcipotriol cream
- oral acitretin or isotretinoin
- carbon dioxide laser ablation
Sun protection is very important as exposure to ultraviolet radiation may result in the development of skin cancer lesions within the linear porokeratosis.