Histological and Trichographic Differences Between Coat Types in Non-Alopecic Pomeranians and With Alopecia X

Background: Alopecia X (AX) is common in Pomeranians, and skin histological results support diagnosis. AX dogs may have shiny or woolly coats; the woolly type is implicated as a potential risk indicator. Objectives: To compare skin histological and trichographic results among Pomeranians with AX, and those unaffected by AX with woolly (W) and shiny (S) coat types. Animals: Seventy-two Pomeranians: 30 AX, 22 W, 20 S. Methods and Materials: Skin biopsies were analysed histologically; hair pluckings assessed by trichography and scanning electron microscopy (SEM), all blinded. Statistics evaluated follicular group counts, follicle numbers, hair types, anagen follicles and fragility events. Hair cycle staging was analysed descriptively. Results: AX dogs had fewer follicles per group (4.1) than W and S (both 5.1). Anagen stage dominated in S (60.2%), telogen in W (39.4%) and AX (39.8%). Kenogen and atrophic groups were more frequent in AX (4.7% and 10.0%, respectively) than W (1.4% and 3.4%) and S (2.0% and 1.5%). Hair fragility per 10 mg of hairs was highest in AX (85.3), followed by W (53.6) and S (26.3). Trichorrhexis nodosa ratios were for AX 12.39 (95% confidence interval [CI] 4.82–31.85) and W 3.60 (95% CI 1.37–9.94) compared to S. No differences in primary-to-secondary hair ratios were found between groups. SEM showed similar round hair morphology across groups. Conclusions and Clinical Relevance: Histological and trichographic findings in non-alopecic Pomeranians reveal coat-type differences, which should be considered when diagnosing AX.