Round or “coin shaped” dermatitis or eczema is an inflammatory skin condition characterized by the presence of well-demarcated round-to-oval erythematous plaques.
Clinical features
Characterized by chronic or relapsing itchy coin-sized ovoid-shaped red plaques.
Sites: Upper (75.8%) and lower (64.5%) limbs, followed by trunk, dorsum of the hands, and face and neck
Lesions of nummular dermatitits on outer thigh. | Ifnord – CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=76031643
Diagnosis
Patch test:
Contact allergy is common with nummular eczema, patch testing is strongly advisable in every patient with persistent nummular dermatitis.
(A) Allergic contact dermatitis from a chemical in hair dye. (B) Patch testing in the same patient. The positive TRUE Test result for No. 20 (p-Phenylenediamine), an ingredient in hair dye, was crucial in identifying the patient’s allergy. See Table 3 for names of each allergen in the panels. | Usatine, R. P., & Riojas, M. (2010). Diagnosis and management of contact dermatitis. American family physician, 82(3), 249–255.
