Asian Journal of Medical Research and Case Reports

Background and Aims: Sarcoidosis is a multisystem granulomatous disease that may initially present with cutaneous lesions. Notalgia paresthetica is a chronic localized neuropathic condition of the upper back, commonly associated with pruritus, dysesthesia, and hyperpigmentation.  To report, to our knowledge, the first observed case of cutaneous sarcoidosis arising within an area of long-standing notalgia paresthetica, and to highlight how this presentation unmasked previously unrecognised systemic sarcoidosis.

Presentation of Case: A 48-year-old man with notalgia paresthetica present for more than 10 years presented with the progressive appearance of multiple asymptomatic orange-to-salmon papules, 2 to 5 mm in diameter, arising over the hyperpigmented area affected by notalgia paresthetica, as well as on the neck, upper trunk, and axillary folds. Dermoscopy showed orange-yellow structureless areas with a few linear and arborising vessels. Serum angiotensin-converting enzyme and calcium levels were within normal limits. A skin biopsy revealed non-caseating epithelioid cell granulomas with multinucleated giant cells; periodic acid-Schiff and Ziehl-Neelsen stains were negative. Systemic evaluation disclosed interstitial pulmonary involvement with mediastinal lymphadenopathy, establishing a diagnosis of systemic sarcoidosis.

Discussion: Cutaneous sarcoidosis may localise to sites of prior cutaneous injury through Koebner-like or isotopic mechanisms. Chronic neuropathic itch, repetitive scratching, and neurogenic inflammation associated with notalgia paresthetica may have contributed to lesion localisation, although a causal relationship cannot be established. Histopathology remained central to the diagnosis and appropriately prompted the systemic evaluation that revealed occult disease.

Conclusion: New or changing lesions arising within a notalgia paresthetica field warrant biopsy and systemic evaluation, as they may unmask occult systemic sarcoidosis.