Assessment of the ‘no eosinophils' rule: are eosinophils truly absent in pityriasis lichenoides, connective tissue disease, and graft‐vs.‐host disease?

Abstract

Eosinophils are often present in the inflammatory infiltrate of an interface dermatitis, but the diagnostic specificity of eosinophils in interface dermatitis has not been formally evaluated. We retrospectively identified 97 examples of interface dermatitis with clinically confirmed diagnoses, including lupus erythematosus (LE), lichen planus, pityriasis lichenoides (PL), graft‐vs.‐host disease (GVHD), dermatomyositis (DM) and drug reaction. Diagnoses were clinically confirmed by at least two dermatologists. Slides were reviewed in a blinded fashion by at least two dermatopathologists. The average eosinophil count per 10 ×200 (×20 objective) fields was lowest for PL (0.2), DM (0.3), GVHD (0.4), and LE (0.5) [defined as Group 1] and was higher for lichen planus, drug reactions, erythema multiforme (major and minor) and viral exanthems [defined as Group 2]. Distinction between Group 1 and Group 2 was maximized using an eosinophil count cutoff of 1.1. In conclusion, eosinophils are usually rare to absent in PL, DM, most forms of LE and GVHD. While final interpretation requires a composite assessment of all features, our results suggest that the presence of even a single eosinophil within nine or ten ×20 fields argues against a diagnosis of PL, DM or LE. Sharon VR, Konia TH, Barr KL, Fung MA. Assessment of the ‘no eosinophils' rule: are eosinophils truly absent in pityriasis lichenoides, connective tissue disease, and graft‐vs.‐host disease?

The significance of eosinophils in hypertrophic lichen planus

“…Dermatopathologists should be aware of this phenomenon to raise the appropriate differential diagnosis when faced with a case of lichenoid interface dermatitis with eosinophils. Similarly, a recent report of eosinophils in interface dermatitis describes eosinophils in cases of both LP and lichenoid drug reaction . Although the subtype of LP cases was not reported in that study and no statistical analysis was performed, the findings support our conclusion that LP and especially hypertrophic LP should be considered in cases of lichenoid interface dermatitis with eosinophils …”

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“…This condition results from a complex and intricate pathobiology sustained by interactions between the donor and host innate and adaptive immune responses. A number of lymphocyte subsets (naive, memory, Treg, Th1, Th17, NK, …) are involved, as well as eosinophils, mesenchymal stem cells and the monocyte-macrophage lineage including Factor XIIIa+ DD [26–30]. …”

Cutaneous Lupus Erythematosus With Histopathologic Changes Restricted to the Acrosyringia

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