Actinic Granuloma: A Case Report

Introduction Actinic granuloma (AG) is a chronic disorder characterized by the development of elastolytic granulomas on sun-exposed skin. The pathogenesis of AG is unknown. This disease is relatively rare, and only 16 cases were reported on PubMed in the past five years. It is easily misdiagnosed as granuloma annulare or sarcoidosis in clinical practice. We herein report a case of a young man with multiple annular papules diagnosed as AG to enrich the knowledge of clinician. Case report A 24-year-old man presented with a two-month history of small papular eruptions over his neck came to our hospital in August, 2018. The papules gradually enlarged to form ring-like plaques, and similar eruptions developed on his upper limbs. The patient stated that there was no improvement following treatment with topical heparin and tretinoin ointment. He was a construction worker and regularly worked outdoors. The lesions were first found in June. He denied a history of previous trauma or foreign material injection, and he had no associated complaints or comorbidities. Physical examination revealed dome-shaped and fusiform papules ranging from 0.5 cm to 1.0 cm in diameter distributed in isolation or clusters on the back of the neck and upper limbs. Some lesions had annular, elevated, waxy border and slightly atrophic center (Fig. 1).FIGURE 1: Physical examination showed grouped papules. (A) Dome-shaped and fusiform papules on the neck. Some of the lesions had an annular, elevated border and atrophic center. (B) Firm papules distributed in isolation or clusters on the upper limb.Histopathological examination revealed infiltration of epithelioid cells and multinucleated giant cells with a few lymphocytes in the superficial dermis and around the hair follicles. No necrobiosis or mucin deposition was observed. Special elastic fiber staining showed reduced numbers of elastic fibers and the presence of elastorrhexis in the dermis (Fig. 2).FIGURE 2: Histopathologic examination of the lesion on the arm. (A) Infiltration of inflammatory cells in the superficial dermis and around the hair follicles (H&E, ×50). (B and C) The granulomatous component consisted of epithelioid cells and multinucleated giant cells with a few lymphocytes (B: H&E, ×100; C: H&E, ×200). (D) Staining of elastic fibers showed decreased and fragmented elastic fibers (×100).A diagnosis of AG was made based on the clinical and pathological features, and the patient started treatment with prednisone acetate at 10 mg daily and clobetasol ointment twice a day for one month. The lesions gradually faded, and no new rashes developed during a six-month follow-up. Discussion AG was first reported by O’Brien in 1975.1 This disease is considered to be initially caused by solar-damaged elastic fibers, which provide an antigenic trigger for a CD4+ T-helper cell-mediated granulomatous immune reaction.2 The lesions mainly affect sun-exposed areas such as the face, neck, chest, and upper arms, and initially present as red or skin-colored papules and insidiously progress to annular plaques with uplifted edges and atrophic central skin.3 AG is histopathologically characterized by non-palisading granulomatous dermatitis composed of foreign body giant cells, epithelioid cells, and lymphocyte infiltration at the uplifted skin at the lesion edge. Elastic fibers disappear in the area of inflammatory infiltration, and the fiber fragments are phagocytosed by polynuclear giant cells as shown by elastic fiber staining. Acid-fast staining reveals astral bodies in polynuclear giant cells.4 AG and annular elastolytic giant cell granuloma (AEGCG) have long been considered synonymous or overlapping diseases. In 1979, AEGCG was proposed by Hanke et al.5 to describe a clinically and histologically similar cutaneous eruption without limitation to sun exposure and solar elastosis. However, studies have shown that only AEGCG contains mucin, necrobiosis, and palisading histiocytes. Additionally, indirect immunoperoxidase staining shows that the giant cells of AG are intensely positive for lysozyme, while the mononuclear histiocytic infiltrate shows minimal reactivity. In contrast, the histiocytes of AEGCG reveal marked reactivity for lysozyme.6 AG exhibits a female predilection and an age at onset ranging from 40 to 70 years.7 However, the patient in this case was only 24 years old. We speculate that several years of excess solar and high-temperature exposure during his work may have been predisposing factors. AG is easily confused with annular granuloma and sarcoidosis because of the similar clinical manifestations. Histopathological examination is essential in such cases. Annular granuloma most commonly manifests as papules that coalesce into annular plaques, and it favors the extensor aspects of the extremities. The histopathologic findings are characterized by dermal palisading granulomas with central degeneration of collagen and mucin deposition.2 In contrast, the lesions of sarcoidosis are usually symmetrically distributed on face, neck, upper trunk, and extremities, especially within preexisting scars or at sites of prior trauma. It presents clinically as red to red–brown papules and plaques and is occasionally violaceous or annular. The histological hallmark of sarcoidosis is the presence of superficial and deep dermal epithelioid cell granulomas devoid of prominent infiltrates of lymphocytes or plasma cells (naked tubercles). No specific treatment is available for AG. Some patients have spontaneous remission of their skin lesions. Systemic glucocorticoids, hydroxychloroquine, and niacinamide are effective for widespread AG, and topical glucocorticoids or retinoids can be used for localized lesions.8 Pulsed-dye laser therapy and fractionated carbon dioxide laser therapy have also been reported as successful treatments for AG.9 Acknowledgements This work was supported by CAMS Innovation Fund for Medical Sciences (No. CIFMS-2017-I2M-1-017) and Educational and Scientific Research Project of Peking Union Medical College .