Porokeratoses (overview)Q82.8

The term "porokeratosis" is used to describe a group of diseases with great genetic heterogeneity and clinical diversity, which is characterized by a superordinate pathogenetic principle, the formation of a focal, vent-shaped parakeratosis (so-called cornoid lamella). The name "porokeratosis" is undoubtedly a misnomer, as the "skin pore" is not the place of origin of the parakeratotic horny cone. However, it has found its way into international literature.

Clinically, the individual clinical pictures are characterized by the formation of keratotic papules with centrifugal growth and central atrophic flattening, resulting in characteristic, reddened, ring-shaped, horny papules or plaques with accentuated edges. In porokeratosis mibelli, map-like formations may also develop. In disseminated superficial porokeratosis, itchy, flat, often also annular papules and plaques are found, usually caused by actinic factors.

Characteristic is the histological phenomenon of the so-called " cornoid lamella", which is detectable in the area of the ring-shaped marginal ridge.

The following clinical variants with differing clinical morphology, acuity and localization have been described:

• Porokeratosis Mibelli (Porokeratosis 1)
• Porokeratosis plantaris, palmaris et disseminata (PPPD, Porokeratosis 2)
• Porokeratosis superficialis actinica disseminata (DSAP; porokeratosis types 3-9: uniform phenotype with numerous different genotypes)
• Superficial disseminated porokeratosis (SDP)
• Eruptive disseminated porokeratosis (EDP)
• Porokeratosis linearis unilateralis (linear porokeratosis, epidermal hamartoma)
• Porokeratosis punctata (PP)
• Porokeratosis punctata palmaris et plantaris is classified under the palmoplantar keratoses: palmoplantar keratosis punctate, type 2)

as well as some variants that require further confirmation

Other very rare clinical variants are (Le C, Bedocs PM 2021):

• Porokeratosis plantaris discreta
• Porokeratosis perforans
• Eruptive pruritic papular porokeratosis
• Reticular porokeratosis
• Giant porokeratosis
• Porokeratoma (Walsh 2007)
• Follicular porokeratosis (occurrence of cornoid lamellae in follicles; variant of disseminated actinic porokeratosis)
• Porokeratosis ptychotropica (inverse form localized in large folds and on genitalia).

m>f

Porokeratoses are associated with mutations in different gene loci (see classification).

The characteristic feature of porokeratoses is the so-called cornoid lamella, a columnar parakeratosis within an epidermis that is keratinized orthokeratotically.

Disease patterns summarized under the term "porokeratosis" with important distinguishing criteria

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