Porokeratosis is a specific disorder of keratinization that is characterized histologically by the presence of a cornoid lamella, a thin column of closely stacked, parakeratotic cells extending through the
stratum corneum with a thin or absent
granular layer.
[Freedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medicine''. (6th ed.). McGraw-Hill. .]
Types
Porokeratosis may be divided into the following clinical types:
* ''Plaque-type porokeratosis'' (also known as "Classic porokeratosis" and "Porokeratosis of Mibelli"
) is characterized by
skin lesion
A skin condition, also known as cutaneous condition, is any medical condition that affects the integumentary system—the organ system that encloses the body and includes skin, nails, and related muscle and glands. The major function of th ...
s that start as small, brownish
papule
A papule is a small, well-defined bump in the skin. It may have a rounded, pointed or flat top, and may have a dip. It can appear with a stalk, be thread-like or look warty. It can be soft or firm and its surface may be rough or smooth. Some h ...
s that slowly enlarge to form irregular, annular, hyperkeratotic or verrucous plaques.
[James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews' Diseases of the Skin: Clinical Dermatology''. (10th ed.). Saunders. .] Sometimes they may show gross overgrowth and even horn-like structures may develop.
[Familial disseminated plaque type porokeratosis with multiple horns and squamous cell carcinoma involving anal skin]
/ref> Skin malignancy, although rare, is reported from all types of porokeratosis. Squamous cell carcinomas have been reported to develop in Mibelli's type porokeratosis over partianal areas involving anal mucosa. This was the first report mentioning mucosal malignancy in any form of porokeratosis.
* ''Disseminated superficial porokeratosis'' is a more generalized processes and involves mainly the extremities in a bilateral, symmetric fashion. In about 50% of cases, skin lesion
A skin condition, also known as cutaneous condition, is any medical condition that affects the integumentary system—the organ system that encloses the body and includes skin, nails, and related muscle and glands. The major function of th ...
s only develop in sun-exposed areas, and this is referred to as '' disseminated superficial actinic porokeratosis''
* ''Porokeratosis palmaris et plantaris disseminata'' is characterized by skin lesions that are superficial, small, relatively uniform, and demarcated by a distinct peripheral ridge of no more than 1mm in height.[
* ''Linear porokeratosis'' is characterized clinically skin lesions are identical to those of classic porokeratosis, including lichenoid papules, annular lesions, hyperkeratotic plaques with central atrophy, and the characteristic peripheral ridge.][
* ''Punctate porokeratosis'' is a skin condition associated with either classic porokeratosis or linear porokeratosis types of porokeratosis, and is characterized by multiple, minute, and discrete punctate, hyperkeratotic, seed-like skin lesions surrounded by a thin, raised margin on the palms and soles.]
* ''Porokeratosis plantaris discreta'' is a skin condition that occurs in adults, with a 4:1 female preponderance, characterized by a sharply marginated, rubbery, wide-based papules.[ It is also known as "Steinberg's lesion".] It was characterized in 1970.
Genetics
Linear porokeratosis has been associated with mutations in the PMVK and MVD
The Ministry of Internal Affairs of the Russian Federation (MVD; russian: Министерство внутренних дел (МВД), ''Ministerstvo vnutrennikh del'') is the interior ministry of Russia.
The MVD is responsible for law enfor ...
genes.[Atzmony L, Khan HM, Lim YH, Paller AS, Levinsohn JL, Holland KE, Mirza FN, Yin E, Ko CJ, Leventhal JS, Choate KA (2019) Second-Hit, Postzygotic PMVK and MVD Mutations in Linear Porokeratosis. JAMA Dermatol ] The PMVK gene encodes the enzyme phosphomevalonate kinase and the MVD gene encodes the enzyme diphosphomevalonate decarboxylase.
Diagnosis
Pathology
Porokeratosis has a characteristic histomorphologic feature known as a ''cornoid lamella''.
Treatment
Dermabrasion
See also
* List of cutaneous conditions
*
References
External links
{{Medical resources
, DiseasesDB = 31356, 33408, 32454, 34839
, ICD10 = Q82.8
, ICD9 =
, ICDO =
, OMIM = 175860, 175800, 175850
, MedlinePlus =
, eMedicineSubj = article
, eMedicineTopic = 1059123
, MeshID = D017499
, Orphanet = 79358
, SNOMED CT = 400080004
Database of rare diseases
at Orphanet
NIH's Genetic and Rare Diseases Information Center
Genodermatoses
Rare diseases