Porkeratosis

• may be congenital or acquired
• share a histopathological feature - a 'cornoid lamella' (thin column of parakeratotic cells) evidenct clinically as fine scaling around the periphery of the lesion
• mild atrophy occurs in the centre of the lesion
• congenital lesions - reticulate pattern and may be extensive
• aquired lesions - may be solitary and broad or multiple and scattered (disseminated superficial actinic porokeratosis - sunlight is believed to have an aetiological role)

Reference:

• (1) Smith LC et al. A guide to annular eruptions. Dermatology in Practice (April 2008); 16(1).