In the diagnostic approach to histiocytic proliferations, immunohistochemistry may be a source of both confusion and clarification. We present a case of a 60-year-old man with a generalized pruritic eruption that demonstrated positive staining for CD1a, but negative staining for langerin and S100 protein. This immunophenotype is neither representative nor characteristic of any recognized dendritic cell tumor but has been previously described in 3 cases of skin-limited histiocytosis. However, our patient also demonstrated pulmonary histiocytic infiltrates that were positive for both CD1a and S100 proteins. This differing expression of S100 protein witnessed in 2 separate organ systems affords us insight into the pathophysiology of these histiocytic proliferations.

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In recent years, the practice of decorative tattooing has seen rising popularity and increased social acceptance. As newer tattoo inks are developed and utilized, it is expected that the rate of reactions will rise. Thus, dermatologists are more likely to encounter tattoo-related complications. An understanding of the most common histopathologic reaction patterns ideally will result in increased clinical detection of situations requiring additional evaluation, whether it is for an underlying infection, systemic involvement of disease, or to rule out a cutaneous malignancy. This review will describe both the clinical and histopathologic features of pathologic reactions to decorative tattoos. The main histopathologic reactions are divided into six distinct categories: allergic hypersensitivity, granulomatous, interface, pseudolymphomatous, oncologic and infectious.

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The dermatologic manifestations of porphyrias result from localized cutaneous formation of reactive oxygen species. The significance of these inflammatory mediators may extend beyond the skin, as increased oxidative stress may play a role in the systemic manifestations of porphyrias. Polypodium leucotomos is a tropical fern that has demonstrated antioxidant, anti-inflammatory and photoprotective properties. Although it has proven effective in the treatment of various photoaggravated dermatoses, we are unaware of any prior reports citing Polypodium leucotomos as a beneficial treatment option in the setting of porphyria cutanea tarda. We describe a patient with refractory porphyria cutanea tarda, who demonstrated dramatic improvement in cutaneous lesions following the initiation of Polypodium leucotomos extract. Due to its low toxicity and demonstrated direct interference in the production of inflammatory mediators are central to cutaneous manifestations of porphyrias, we propose consideration of Polypodium leucotomos as a potential therapeutic option for patients with porphyria cutanea tarda.