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May 2004

Teloptosis and Kenogen: Two New Concepts in Human Trichology

Author Affiliations

Copyright 2004 American Medical Association. All Rights Reserved. Applicable FARS/DFARS Restrictions Apply to Government Use.2004

Arch Dermatol. 2004;140(5):619-620. doi:10.1001/archderm.140.5.619

Recently, 2 new important concepts have been introduced in human trichology. They are exogen/teloptosis and kenogen. As it is customary when new concepts have to be accepted, some perplexity and confusion originated. We will try to clarify what exogen/teloptosis and kenogen mean and what importance they may gain in hair physiology and pathology.

Exogen is a term coined by Stenn1 and indicates the moment in which the club hair is shed from the follicle that is already occupied by a new terminal anagen hair. In Stenn's view, exogen, as the term suggests, is a new phase of the hair cycle. Its duration, however, is too short for deserving the privilege of a "phase" and, as Piérard-Franchimont and Piérard2 remarked, the term might rather suggest a biological exogenous process opposite to an endogenous one. They proposed instead the term teloptosis derived from the Greek τϵλος πτωση (falling off) to indicate the same phenomenon.