Parakeratosis

{{Short description|Mode of keratinization characterized by the retention of nuclei in the stratum corneum}}

File:Micrograph of early actinic keratosis with parakeratosis.jpg with parakeratosis, with black arrows indicating one of multiple retained nuclei in the stratum corneum]]

Parakeratosis is a mode of keratinization characterized by the retention of nuclei in the stratum corneum.{{cite journal|last1=Brady|first1=Stephen P|title=Parakeratosis|journal=Journal of the American Academy of Dermatology|volume=50|issue=1|year=2004|pages=77–84|issn=0190-9622|doi=10.1016/S0190-9622(03)02801-9|url=https://www.jaad.org/article/S0190-9622(03)02801-9/pdf}} In mucous membranes, parakeratosis is normal.Kumar, Vinay; Fausto, Nelson; Abbas, Abul (2010) Robbins & Cotran Pathologic Basis of Disease (8th ed.). Saunders. Page 1170. {{ISBN|978-1-4160-3121-5}}. In the skin, this process leads to the abnormal replacement of annular squames with nucleated 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. Parakeratosis is seen in the plaques of psoriasis and in dandruff.

Granular parakeratosis (originally termed axillary granular parakeratosis) is an idiopathic, benign, nondisabling cutaneous disease that manifests with intertriginous erythematous, brown or red, scaly or keratotic papules and plaques. It presents in all age groups and has no established clinical associations.{{cite journal|last1=Scheinfeld|first1=NS|last2=Mones|first2=J|title=Granular parakeratosis: pathologic and clinical correlation of 18 cases of granular parakeratosis.|journal=Journal of the American Academy of Dermatology|date=May 2005|volume=52|issue=5|pages=863–7|pmid=15858479|doi=10.1016/j.jaad.2004.12.031}}

File:Histopathology of reactive hyperkeratosis.jpg|In contrast, hyperkeratosis (pictured) may also show a heterogeneous stratum corneum, but a preserved granular layer is seen.