title: Kenogen. A new phase of the hair cycle?
abstract: BACKGROUND
  A novel phenomenon has been described by the phototrichogram: the emptiness of the follicle after teloptosis. We called this phenomenon kenogen, from the Greek kappaepsilonnuóvarsigma, 'empty'.
  
  
  OBJECTIVE
  To describe the kenogen phase in its details.
  
  
  METHODS
  Analysis of the existing literature.
  
  
  RESULTS
  The original observation in 2 women was confirmed in 10 balding and non-balding males studied for 14 years in whom kenogen lasted about 4 months increasing up to about 7 months and affecting 80% of all hair cycles. In 2 women with progressing androgenetic alopecia studied for 2 years, kenogen involved 22% of the hair follicles, lasting from 3 months to 1 year. In a prepubertal boy studied for 1 year, it involved 8% of hairs and lasted about 2 months.
  
  
  CONCLUSIONS
  During kenogen, the hair follicle rests physiologically, but duration and frequency are greater in androgenetic alopecia, possibly accounting for baldness. In addition to the classical cycle, the hair follicle may follow an alternative route during which the telogen phase, not accompanied by a coincident new early anagen, ends with teloptosis leaving the follicle empty.
authors.affiliation: Department of Endocrinological and Metabolic Diseases, Section of Dermatology, University of Genoa, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Rebora
authors.forename: Marcella
authors.initials: M
authors.lastname: Guarrera
mesh_terms: D000505:Alopecia / Q000473:pathology* / Q000503:physiopathology; D002648:Child; D005260:Female; D006197:Hair / Q000254:growth & development*; D018859:Hair Follicle / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged