follow @PCDSUKCreated: 10th May 2013 | Last Updated: 8th November 2016
Introduction
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The term porokeratosis refers to skin lesions with a thinned centre surrounded by a ridge-like border called the cornoid lamella. They arise from clones of cells with varying degrees of dysplasia. There are a number of different types of porokeratoses, those best defined are described below. |
Clinical findings
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Distribution - depends on the type
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Isolated lesions (syn. porokeratosis of Mibelli)
- Familial lesions are autosomal dominant in inheritance and arise in childhood, sporadic lesions have a later onset
- Lesions are single or a few in number and can be large
- They are most common on the limbs, especially acral, but can affect any body site
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Linear porokeratosis
- Usually presents at birth or in childhood
- Multiple lesions arise in a linear fashion along the lines of Blaschko, most commonly along a limb or one side of the trunk or head and neck
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Disseminated superficial actinic porokeratosis (DSAP)
- This is the most common variety and arises in middle-aged individuals
- It is an autosomal dominant condition, but a history of chronic UV exposure also appears to be needed
- Lesions are predominantly found on sun-exposed areas of the legs, and less so the arms
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Isolated lesions (syn. porokeratosis of Mibelli)
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Morphology
- Lesions are annular with a well-demarcated, slightly raised keratotic rim known as a cornoid lamella. The centre may be scaly or thin and atrophic
- They grow gradually to between 3-10 mm. Grouped lesions will appear larger. Rarely, lesions of porokeratosis of Mibelli can be very large and are termed ‘giant’
Images
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Figure: 1 Porokeratosis of Mibelli - above the heel |
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Figure: 2 DSAP |
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Figure: 3 Linear porokeratosis |
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Figure: 4
Close-up of figure 3 |
Investigations
- The diagnosis is normally clinical
- Histological confirmation is occasionally needed - the biopsy needs to be taken from the scaly edge of the lesion and demonstrates the presence of the cornoid lamellae
Management
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General
- There appears to be no effective treatment, many have been tried
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For DSAP:
- Provide a patient information leaflet
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UV protection - although half of the children of affected individuals will have a tendency to develop DSAP, only some will go on to develop the condition, the risk is likely to be less for those with better UV protection
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Risk of malignant transformation
- Patients with DSAP appear to have a very low risk of malignant transformation
- Large lesions are said to have the highest malignant potential, and malignant change has also been reported in linear forms. SCC is the most common tumour
- Patients should be advised on UV protection and asked to report any changes or any new skin lesion that they do not recognise as normal