Micrograph of early actinic keratosis with parakeratosis

Parakeratosis is a mode of

keratinization Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. It is the key structural material making up scales, hair, nails, feathers, horns, claws, hooves, and the outer layer of skin in vertebrates. Kera ...

characterized by the retention of nuclei in the

stratum corneum The stratum corneum (Latin language, Latin for 'horny layer') is the outermost layer of the epidermis (skin), epidermis. Consisting of dead tissue, it protects underlying tissue from infection, dehydration, chemicals and mechanical stress. It is ...

. In

mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It ...

s, parakeratosis is normal.Kumar, Vinay; Fausto, Nelson; Abbas, Abul (2010) ''Robbins & Cotran Pathologic Basis of Disease'' (8th ed.). Saunders. Page 1170. . In the skin, this process leads to the abnormal replacement of annular squames with

nucleated The cell nucleus (; : nuclei) is a membrane-bound organelle found in eukaryotic cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others including osteo ...

cells. Parakeratosis is associated with the thinning or loss of the granular layer and is usually seen in diseases of increased cell turnover, whether inflammatory or

neoplastic A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

. Parakeratosis is seen in the plaques of

psoriasis Psoriasis is a long-lasting, noncontagious autoimmune disease characterized by patches of abnormal skin. These areas are red, pink, or purple, dry, itchy, and scaly. Psoriasis varies in severity from small localized patches to complete b ...

and in

dandruff Dandruff is a skin condition of the scalp. Symptoms include flaking and sometimes mild itchiness. It can result in social or self-esteem problems. A more severe form of the condition, which includes inflammation of the skin, is known as s ...

. Granular parakeratosis (originally termed axillary granular parakeratosis) is an

idiopathic An idiopathic disease is any disease with an unknown cause or mechanism of apparent spontaneous origin. For some medical conditions, one or more causes are somewhat understood, but in a certain percentage of people with the condition, the cause ...

, benign, nondisabling cutaneous disease that manifests with intertriginous erythematous, brown or red, scaly or keratotic

papule A papule is a small, well-defined bump in the skin lesion, skin. It may have a rounded, pointed or flat top, and may have a umbilication, dip. It can appear with a Peduncle (anatomy), stalk, be thread-like or look warty. It can be soft or firm a ...

s and plaques. It presents in all age groups and has no established clinical associations. File:Histopathology of reactive hyperkeratosis.jpg, In contrast,

hyperkeratosis Hyperkeratosis is thickening of the stratum corneum (the outermost layer of the epidermis, or skin), often associated with the presence of an abnormal quantity of keratin,Kumar, Vinay; Fausto, Nelso; Abbas, Abul (2004) ''Robbins & Cotran Pathol ...

(pictured) may also show a heterogeneous stratum corneum, but a preserved granular layer is seen.

References

{{Clinical and histological nomenclature for skin lesions Dermatologic terminology

See also

References