Histopathologic reaction patterns to differentially cross-linked hyaluronic acid fillers: A retrospective case series.

BACKGROUND: Hyaluronic acid filler reactions have been increasingly observed in recent years. Our study investigates whether the increased number of filler reactions observed since 2014 is associated with a specific histopathologic inflammatory pattern and type of filler. METHODS: The institution's dermatopathology electronic database was retrospectively searched for histopathologic reactions to hyaluronic acid from January 2014 to December 2019. The age, sex, type of filler, procedure, location, and histopathologic patterns were recorded. RESULTS: From 2014 to 2019, there were 15 cases of granulomatous reactions to hyaluronic acid filler. In 10 of these cases, there was a characteristic inflammatory pattern characterized by tightly cuffed palisades of histiocytes with varying numbers of eosinophils. Of the 11 cases in which the type of filler was known, all used Vycross technology, a novel manufacturing process in the production of hyaluronic acid filler. CONCLUSION: A characteristic histopathologic pattern of discrete foci of tightly cuffed palisaded granulomas with eosinophils is associated with fillers manufactured using Vycross technology.

The histologic and molecular correlates of COVID-19 vaccine-induced changes in the skin.

A total of 22 patients who had developed an adverse cutaneous reaction to the Moderna or Pfizer vaccine underwent biopsies. Each patient was assessed light microscopically, and, in select biopsies, spike glycoprotein and cytokine assessment were also conducted. The patients developed self-limited cutaneous reactions often described clinically as urticarial or eczematous within 1 day to 4 weeks after receiving the first or second dose of the Pfizer or Moderna vaccine. Classic clinical and morphologic depictions of type IV cutaneous hypersensitivity with features of eczematous dermatitis, interface dermatitis, granulomatous inflammation, and/or lymphocytic vasculitic component were observed. Clinical and/or histologic features of perniosis, pityriasis rosea, pityriasis rubra pilaris, and guttate psoriasis were seen in select cases. In 2 cases the dominant picture was urticarial vasculitis, possibly reflective of an Arthus type III immune complex action. The biopsy specimens of normal skin post vaccine and of skin affected by the post-vaccine eruption showed rare deep microvessels positive for spike glycoprotein with no complement deposition contrasting with greater vascular deposition of spike protein and complement in skin biopsies from patients experiencing severe coronavirus disease 2019 (COVID-19). It is concluded that self-limited hypersensitivity reactions to the vaccine occur possibly owing to a substance found in the vaccine vehicle (eg, polyethylene glycol). An immune response that is directed against human-manufactured spike has to be considered because some of the reactions clinically and or histologically closely resemble mild COVID-19. Finally, vaccine-associated immune enhancement largely attributable to the adjuvant properties of the vaccine may unmask certain inflammatory milieus operational in psoriasis, atopic dermatitis, and subclinical hypersensitivity.