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S100-negative, CD1a-positive histiocytosis is a rare histiocytic disorder characterized by proliferation of histiocytic cells possessing a phenotype of epidermal Langerhans cells except for the lack of S100 expression and Birbeck granules. We report the case of a Japanese man suffering from S100-negative, CD1a-positive histiocytosis. The patient showed numerous smooth erythematous 5-10-mm papules/nodules on most of his body. The key histopathological feature was the presence of dermal infiltrates of non-epidermotropic S100-negative CD1a-positive mononuclear cells. No systemic involvement was detected. Initially bath-psoralen plus ultraviolet A therapy was effective, but the lesions became recalcitrant to this treatment. Methylprednisolone pulse therapy followed by low-dose methotrexate (up to 30 mg/week) in combination with prednisolone (15 mg/day) effectively controlled the skin lesions.

Papular elastolytic giant cell granuloma (PEGCG) is a rare variant of annular elastolytic giant cell granuloma (AEGCG). Since Kato et al. [1] reported the first case of PEGCG, only eight additional cases have been reported. Herein, we report a case of PEGCG and review the literature of reported cases.A 75-year-old Japanese man presented with multiple pruritic eruptions on his back that recurred for 2 months. Past medical history included hypertension and hyperlipidemia. Physical examination disclosed [...]

Rationale: Palisaded neutrophilic and granulomatous dermatitis (PNGD) is a benign, inflammatory dermatosis with distinct histopathological features often observed in patients with systemic diseases. There were no reports of PNGD without underlying systemic diseases as an underlying cause of hypercalcemia. Herein, we report a case of a 62-year-old man with hypercalcemia due to PNGD, but with no underlying systemic diseases, including tuberculosis, sarcoidosis, or vasculitis. Patient concerns: Laboratory tests showed an elevated C-reactive protein level, an elevated corrected calcium level, a normal 25-hydroxyvitamin D level, and an elevated 1,25-dihydroxyvitamin D level. There were no other abnormalities to explain the hypercalcemia. Positron emission tomography–computed tomography showed abnormal uptake in his skin. Histopathological examination of the skin showed palisaded granulomatous infiltrate in the dermis. Neutrophils, degenerated collagen, and fibrin were present in the centers of the palisades without prominent mucin. There were no eosinophils, central necrosis, or necrotizing vasculitides. These features were consistent with PNGD. Diagnoses: A diagnosis of PNGD with hypercalcemia was established. Interventions: Oral prednisolone was administered to the patient. Outcomes: After treatment, his symptoms resolved, and his calcium, 1,25-dihydroxyvitamin D and CRP levels returned to normal. Skin specimens before and after treatment were assessed using immunohistochemistry for 1a-hydroxylase. Granuloma and epidermal cells were 1a-hydroxylase-positive before treatment. After treatment, the granuloma diminished in size and the 1ahydroxylase-positive areas of the epidermal cells decreased. Lessons: This case was particularly unique because increased 1a-hydroxylase expression in the granuloma and epidermal cells seemed to result in hypercalcemia due to excessive transformation of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D. Physicians should consider PNGD as an underlying cause of hypercalcemia.