Dermal hypersensitivity reaction: a PCR-confirmed pattern of herpetic dermatitis

The role of eosinophils in the differential diagnosis of inflammatory skin diseases

Eosinophils are known to be present in inflammatory skin diseases, but their diagnostic utility is not well established. Upon review of the published status of lesional eosinophils, several categories were identified. 1) Lesional eosinophils highly characteristic such that, in their absence, the pathologist may question the diagnosis. These include arthropod bite reactions and scabies, urticarial dermatitis, and other eosinophilic dermatoses. 2) Lesional eosinophils rare or absent, such that, in their presence, the pathologist may question the diagnosis. These include pityriasis lichenoides, graft versus host disease, and connective tissue disorders. 3) Lesional eosinophils variable and, while in some cases expected, are not required for diagnosis. These include drug reactions, atopic dermatitis and allergic contact dermatitis. 4) Lesional eosinophils variable and not expected but may be seen to a limited extent. These include lichen planus and psoriasis.

Eosinophils are surprisingly common in biopsy specimens of cutaneous herpes simplex virus and varicella zoster virus infections: Results of a comprehensive histopathologic and clinical appraisal

BACKGROUND

While usually straightforward, diagnostic features of cutaneous herpes simplex virus and varicella zoster virus infection (HSV/VZV) are not always present in biopsy specimens. Although intuitively the presence of eosinophils may lead the pathologist away from the diagnosis of cutaneous HSV/VZV infection, in our practice we have noted that eosinophils are often encountered in diagnostic specimens.

METHODS

To deduce the frequency with which the inflammatory response accompanying cutaneous HSV/VZV infection includes significant numbers of eosinophils, we performed a retrospective review. We included 159 specimens from our database, diagnosed between 2009 and 2017. We determined the number of eosinophils in 10 high-power fields and noted additional histologic factors including presence of follicular involvement, ulceration, and pseudolymphomatous change.

RESULTS

Of all included cases, 63% had 0-1 eosinophils, 24% had 2-10 eosinophils, and 13% had more than 10 eosinophils. Statistical analysis did not reveal a significant association between any demographic or histologic features examined and the presence of increased eosinophils.

CONCLUSIONS

In this study, more than one-third of biopsy specimens diagnostic of cutaneous HSV/VZV infection had a prominent number of eosinophils. The detection of eosinophils should not be unexpected and should not lessen diagnostic suspicion for cutaneous HSV/VZV infection.

Retrospective chart review in a cohort of patients with urticarial dermatitis

Urticarial dermatitis is a poorly understood skin condition while it seems to be much more common than the paucity of reports suggest. It manifests with severely pruritic papules and plaques that resemble eczematous and urticarial lesions morphologically. The key clues to diagnosis are the urticarial appearance and overlap with an eczematous reaction. Here, we present a series of 19 cases (13 women and six men) with urticarial dermatitis clinically and histologically. The patients' average age was 58 and most of the cases were idiopathic. Trunk and proximal extremities were the most common sites involved followed by the distal extremities. Poor response to potent topical corticosteroids and antihistamines was usual and many patients required oral prednisone or other immunosuppressant agents or phototherapy.