Diffuse unpatterned alopecia: Practical diagnostic considerations

Diffuse unpatterned alopecia (DUPA) is a clinicopathologic phenotype of global follicular miniaturization with loss of donor dominance, rendering follicular unit excision/transplantation (FUE/FUT) unsafe. This review integrates clinical mapping, multi-zone trichoscopy, standardized trichometry/phototrichogram with AI-assisted counts, and horizontal-section histopathology to operationalize donor-area safety. Discriminants that consistently separate DUPA from diffuse effluvium and other overlap phenotypes include hair shaft diameter diversity (HSDD) ≥20% across vertex, parietal, and occipital zones with increased vellus proportion and single-hair follicular units, and phototrichogram evidence of miniaturization disproportionate to telogen shift. An occipital terminal:vellus ratio