Severe bilaterally symmetrical alopecia in a horse.
Authors: Kim D Y, Johnson P J, Senter D
Journal: Veterinary pathology
Summary
# Editorial Summary: Severe Bilaterally Symmetrical Alopecia in a Horse A 9-year-old Tennessee Walking Horse presented with extensive, non-inflammatory hair loss affecting the head, neck, shoulders, thighs and proximal limbs, whilst the trunk, distal limbs, tail and mane remained unaffected; localised scaling and crusting on the shoulder and back suggested a secondary complication. Histopathological examination revealed CD3+ T-lymphocyte infiltration around hair follicles, inner and outer root sheaths, and perifollicular regions, with immunohistochemistry confirming a T-cell mediated process consistent with alopecia areata; additionally, the crusted areas showed epidermal hyperplasia, parakeratosis and budding Malassezia yeasts. The diagnosis of concurrent alopecia areata with secondary Malassezia dermatitis highlights an important clinical relationship: the lymphocytic follicular damage characteristic of alopecia areata may compromise the skin barrier and alter the microenvironment, predisposing to opportunistic yeast colonisation. For equine practitioners, this case demonstrates that symmetrical, patchy alopecia warrant thorough dermatological investigation including histopathology and immunophenotyping, and that successful management may require addressing both the underlying immune-mediated hair loss and any secondary microbial infections rather than treating visible scaling and crusting as a primary condition.
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Practical Takeaways
- •Alopecia areata should be considered in differential diagnosis when horses present with symmetrical hair loss and mild pruritus; skin biopsy with immunohistochemistry and fungal assessment is needed for definitive diagnosis.
- •Secondary Malassezia infections commonly occur in areas of follicular inflammation from alopecia areata, so addressing both the autoimmune component and yeast colonization may be necessary for management.
- •The pattern of hair loss (sparing of mane, tail, and distal limbs) can aid clinical recognition of this condition.
Key Findings
- •A 9-year-old Tennessee Walking Horse presented with extensive bilaterally symmetrical alopecia affecting head, neck, shoulder, thigh, and proximal limbs while sparing trunk, distal limbs, mane, and tail.
- •Histopathological examination revealed CD3+ T lymphocytic infiltration of hair bulbs and follicular regions consistent with alopecia areata.
- •Secondary Malassezia dermatitis was identified on affected areas with scale and crust, suggesting alopecia areata may predispose to opportunistic yeast colonization.