Loose Anagen Hair Syndrome: A Scoping Review

Loose anagen hair syndrome (LAHS) is a rare, non-scarring alopecia that may occur sporadically or follow autosomal dominant inheritance. The objective of this study was to review the etiology, clinical presentation, diagnostic features (including trichoscopy, trichogram, and microscopy), natural history, and treatment outcomes of LAHS. A scoping review was conducted using MEDLINE, Embase, Web of Science, Scopus, and CENTRAL databases. Seventy-six studies, encompassing 425 patients with LAHS (mean age: 6.2 years), were included. Most patients were female (78.6%) with Type A LAHS (88.5%). The most common trichoscopic findings were follicular units containing single hairs (92.9%) and rectangular black granular structures (57.5%). Genetic associations included mutations in keratin genes (e.g., KRT32, KRT71, and related keratin family genes) and syndromic overlap, most prominently Noonan-like syndrome with loose anagen hair. 16.8% received treatment, primarily with topical minoxidil (88.2%). Complete resolution occurred in 14.7% of treated patients and two untreated patients. Evidence was limited predominantly to case reports and case series, with inconsistent follow-up data. LAHS should be considered in children presenting with diffuse shedding and easily extractable hair. Topical or oral minoxidil may be beneficial, but further studies are needed to clarify the natural history and comparative effectiveness of treatment.