chapter  8
25 Pages

Other disorders of keratinization

Porokeratoses are chronic keratoatrophodermas of different clinical forms histologically characterized by columns of porokeratosis termed cornoid lamellae.

Clinical forms

Porokeratosis of Mibelli (plaque porokeratosis) ● Small asymptomatic keratotic papules enlarging gradually to form plaques with a

raised, wall-like border that resembles a dyke, and an atrophic depressed center (Figures 8.1 and 8.2)

● Solitary or a few lesions ranging in size from millimeters to many centimeters (giant porokeratosis) (Figure 8.3)

● Predilection for face and extremities, including the palms and soles (Figure 8.4)

Linear porokeratosis ● Linear, unilateral or diffuse coalescent keratotic papules, distributed along the

Blaschko’s lines, most commonly on the extremities (Figures 8.5-8.7) ● Loss of heterozygosity is relatively common, revealing exacerbation of the disease and,

rarely, malignant transformation

Punctate palmoplantar porokeratosis (Mantoux) ● Multiple 1-2-mm seed-like keratotic plugs surrounded by a thin raised border (Figures

8.8 and 8.9)

Disseminated superficial porokeratosis ● Widespread, uniform lesions not exceeding 1 cm in diameter occurring in both sun-

exposed and non-sun-exposed areas (Figures 8.10 and 8.11)

Disseminated superficial actinic porokeratosis ● Numerous pruritic papular lesions, enlarging centrifugally, confined to sun-exposed

areas ● Sparing of palms, soles and mucosal surfaces ● Exacerbations during the summer (Figure 8.12)

Onset is usually in childhood; the actinic form appears in the third or fourth decade.