Background: Whilst there are several recognised explanations for persistent telogen-phase hair loss, for a proportion of cases, no clear underlying cause can be identified. These cases have been given the diagnostic label chronic telogen effluvium: a poorly characterised condition where there is legitimate uncertainty as to whether it represents a truly distinct disorder.
Objective: The aim of this review was to evaluate published cases of purported chronic telogen effluvium and how strongly they support its existence as a distinct disorder.
Methods: We systematically reviewed the literature identified from searching Embase, MEDLINE and Web-of-Science. An additional manual search was performed from the reference lists of publications identified. The review followed PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The Joanna Briggs Institute's checklists for case reports, case-series, case-control studies and analytical cross-sectional-studies were used to appraise the quality of identified articles.
Results: Eighteen studies (comprising five case-series, seven cross-sectional studies, three case-control studies, one case report, one quasi-experimental study and one diagnostic-accuracy study) were included for evaluation, containing 1628 cases. Eleven were rated of good quality. 97.5% of all cases were female. No studies documented that they had excluded all possible causes of telogen hair shedding. Only three studies (encompassing eight cases) featured a prospective follow-up. All eight studies that undertook biopsies reported a normal terminal to vellus hair ratio in the samples analysed. No studies objectively evaluated the influence of hair length or psychological distress/preoccupation on the likelihood of being diagnosed with chronic telogen effluvium.
Conclusions: The lack of a consensual consistent definition for chronic telogen effluvium is a significant limitation. Many cases presently labelled chronic telogen effluvium likely either represent early female pattern hair loss or incipient secondary telogen effluvium owing to an unidentified underlying secondary cause. Where triggering factors have been definitively excluded, hair shedding may represent an alteration in the hair cycle away from normal total asynchronous cycling. Some cases may also represent a preoccupation with normal hair shedding in anxious long-haired individuals.
© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.