Generalized papular eruption in a middle-aged woman

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A woman in her 40s presented with multiple asymptomatic papular eruptions over the neck, chin, upper chest, upper back, and bilateral forearms for 1 month. There was no family history of similar dermatological conditions. Cutaneous examination showed multiple, discrete, skin-colored to brownish, smooth, shiny, flat-topped papules 2–5 mm in diameter, distributed over the chin, neck, upper chest, upper back, and bilateral forearms [Figure 1]. The rest of the cutaneous or systemic examination did not reveal any other abnormalities. Systemic evaluation, including complete blood count, serum calcium, serum angiotensin-converting enzyme level, chest radiography, and ophthalmologic examination, did not reveal evidence of systemic sarcoidosis.

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Figure 1: (a) Anterior neck, chin, and upper chest showing multiple, skin colored to brownish, smooth, shiny, flat-topped papules. (b) Upper back showing multiple, skin colored, smooth, shiny, flat-topped papules.

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A 4-mm punch biopsy was obtained from one of the papules on the upper back with the differentials of papular sarcoidosis, papular granuloma annulare, eruptive syringomas, and lichen scrofulosorum. Histopathological examination showed epidermis with orthokeratosis, and upper dermis showed confluent, well-formed, non-necrotizing epithelioid cell granuloma with sparse lymphocytic infiltrate. The granulomas were discrete and not related to adnexal or neural structures. Special stain with Ziehl–Neelsen for acid–fast bacilli was negative for Mycobacterium tuberculosis [Figure 2]. Overall features were suggestive of papular sarcoidosis.

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Figure 2: (a) Dermis showing confluent, well-formed, nonnecrotizing epithelioid cell granulomas with sparse peripheral lymphocytic infiltrate (Hematoxylin and Eosin [H&E], ×10) (black arrow). (b) Higher magnification highlighting compact aggregates of epithelioid histiocytes with occasional Langhans-type giant cells and absence of caseation or involvement of adnexal/neural structures (H&E, ×40) (black arrow). (c) Ziehl–Neelsen (ZN) stain showing no demonstrable acid–fast bacilli (ZN, ×100).

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Sarcoidosis is a multisystem inflammatory disorder that most commonly affects the lungs, lymph nodes, and skin. The disease exhibits a bimodal age distribution, with incidence peaks in the third and fifth decades of life, and demonstrates a higher prevalence among women.^[1] Cutaneous manifestations of sarcoidosis are broadly categorized as specific and non-specific. Specific lesions demonstrate non-caseating granulomas on histopathology and most commonly present as maculopapules, nodules, plaques, infiltrative scars, and lupus pernio. Non-specific lesions, in contrast, represent reactive processes and lack the characteristic granulomatous inflammation.^[2]

Papular sarcoidosis is a distinct cutaneous manifestation of sarcoidosis, an idiopathic multisystem granulomatous disease characterized by non-caseating granulomas.^[2] The pathogenesis is thought to involve an exaggerated Th1-mediated immune response to unidentified antigens, resulting in granuloma formation. Clinically, papular sarcoidosis presents as multiple, discrete, skin-colored to reddish-brown, smooth, shiny, flat-topped papules, most often on the face, neck, and upper trunk. Dermoscopy typically reveals translucent yellow-orange structureless areas corresponding to dermal granulomas, along with linear or branching vessels, which help differentiate it from mimickers such as eruptive syringomas.^[3] Histopathology typically reveals well-formed, non-caseating epithelioid granulomas, usually surrounded by a sparse to mild lymphocytic infiltrate, giving the typical “naked” appearance. Schaumann and asteroid bodies may be seen within giant cells in sarcoidosis, but they are non-specific and present in only about one-third of cases.^[4] Treatment depends on the extent and severity of cutaneous involvement, ranging from topical or intralesional corticosteroids for localized disease to systemic therapies such as hydroxychloroquine, methotrexate, or systemic corticosteroids in refractory or widespread cases. Prognosis is generally favorable in isolated cutaneous disease, with many lesions resolving spontaneously or responding to therapy, although recurrence and chronicity are not uncommon, particularly in patients with systemic involvement.^[5]

The common differential diagnosis of papular sarcoidosis includes papular granuloma annulare, eruptive syringomas, and lichen scrofulosorum [Table 1]. Papular granuloma annulare presents as multiple small, firm, skin-colored to erythematous papules, with histology showing focal collagen degeneration, interstitial histiocytic infiltrates, and mucin deposition, either in a palisading pattern surrounding necrobiotic collagen or an interstitial pattern with histiocytes scattered among dermal collagen bundles. Eruptive syringomas appear as multiple brownish to erythematous, smooth, shiny, flat-topped papules on the trunk, neck, or periorbital area, and histology reveals dermal nests and ductules of basaloid cells in a fibrotic stroma, with some exhibiting the classic comma- or tadpole-shaped appearance. Lichen scrofulosorum presents as tiny, grouped, perifollicular papules on the trunk, with histopathology demonstrating perifollicular and periappendageal tuberculoid granulomas, typically without caseation necrosis.