Perforating Granuloma Annulare Mimicking Papulonecrotic Tuberculid

Perforating granuloma annulare (PGA), a rare variant of granuloma annulare, is characterized by transepidermal elimination of altered collagen that clinically manifests an umbilicated papule with a central crust. It can be confused with papulonecrotic tuberculid (PNT) because of their similar appearance. Unlike PGA, PNT is usually related to tuberculosis infection with a typical histologic finding of wedgeshaped dermal necrosis. Here, we report the first Korean case of PGA mimicking PNT both clinically and histologically. A 43-year-old Korean woman presented with erythematous papules localized on the extensor surface of her limbs for one year. Some of these papules had a central umbilication or a crust. Regarding comorbidity, she had latent tuberculosis diagnosed with $QuantiFERON^{(R)}-TB$ Gold test about five months ago. She was on antituberculous medication. Initially, a diagnosis of papulonecrotic tuberculid accompanied by latent tuberculosis was considered. However, despite taking the antituberculous medication for five months, her skin lesions were not improved. Biopsy specimen from her arm lesion showed wedge-shaped area of necrosis in the dermis. Additionally, there were multiple focal mucin depositions and palisading granulomatous inflammation throughout the dermis. A diagnosis of PGA was made and she was treated with topical corticosteroid. After two weeks of applying topical corticosteroid, most of her skin lesions disappeared, leaving some hyperpigmented scars.