Prevalence of infiltrative lymphocytic mural folliculitis in equine inflammatory skin diseases.
Authors: Yasuda K, Scott D W, Erb H N, McDonough S P
Journal: Equine veterinary journal
Summary
# Editorial Summary Infiltrative lymphocytic mural folliculitis (ILMF)—characterised by lymphocyte infiltration into the epithelium of hair follicles—had been documented only sporadically in equine dermatology, prompting Yasuda and colleagues to establish its true prevalence across various inflammatory skin conditions. Through histopathological examination of skin biopsies from 250 horses with diagnosed inflammatory dermatoses alongside 27 clinically healthy controls, the researchers identified ILMF in 82% of diseased specimens whilst observing it in none of the healthy skin samples. Although this high prevalence across multiple disease presentations limits ILMF's value as a specific diagnostic indicator, its complete absence in normal skin establishes it as a consistently abnormal finding that warrants clinical attention. For farriers, vets, and other equine professionals, this distinction matters: whilst ILMF alone cannot pinpoint a particular diagnosis, its presence on biopsy confirms inflammatory pathology and rules out purely mechanical or non-inflammatory causes of skin disease, potentially streamlining differential diagnosis and directing further investigations toward immune-mediated, infectious, or parasitic aetiologies rather than investigating structural or traumatic mechanisms alone.
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Practical Takeaways
- •ILMF is a common histopathological finding in equine skin disease but cannot be used to differentiate between specific inflammatory dermatoses
- •Detection of lymphocytic infiltration in hair follicles on skin biopsy confirms abnormality and supports inflammatory skin disease diagnosis, but further investigation is needed for specific condition identification
- •Absence of ILMF in healthy equine skin makes it a useful marker of skin pathology, even though it lacks specificity for particular conditions
Key Findings
- •ILMF was present in 82% of diseased skin specimens from 250 horses with inflammatory dermatoses
- •ILMF was not detected in any of the 27 physically healthy control skin specimens
- •ILMF occurs across a wide variety of equine inflammatory dermatoses, indicating low diagnostic specificity
- •Presence of lymphocytes in equine hair follicle epithelium should be considered abnormal despite lack of diagnostic specificity