Sabra dermatitis: combined features of delayed hypersensitivity and foreign body reaction to implanted glochidia.

A striking dermatitis referred to by its colloquial designation of sabra dermatitis is associated with glochidia inoculation from the Opuntia cactus commonly known as the prickly pear. We report a 45-year-old woman who had an unexpected encounter with a cactus plant during a trip to Texas. She brushed up against the plant and was aware that she had been inoculated with several spines of the plant. Five days later she developed erythematous papules on the digits accompanied by swelling. The biopsy showed a very striking granulomatous reaction pattern within the dermis. There was a linear pattern of necrobiosis, likely representing a tract of inoculation injury palisaded by histiocytes including multinucleated forms. This necrobiotic tract demonstrated retained glochidia, each measuring roughly 40 to 70 microns in diameter. The nature of the inflammatory response is one that combines features of classic delayed hypersensitivity and an innate foreign body response. The glochidia are capable of eliciting a T cell mediated immune response; it is reasonable to assume that a Th1 cytokine signal is responsible for the unique pattern of inflammation including the secondary influx of neutrophils and relative lack of tissue eosinophilia.