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You are seeing a 12-year-old girl with a 5 week history of discoloration on her anterior neck. There are brown, slightly raised plaques that appear like dirt. She has tried scrubbing with various soaps without any improvement. A clinic doctor gave her steroid creams but these did not help. She is not overweight and recently had a normal screening Hemoglobin A1C. She has no history of prior rash of any kind.
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November 10, 2024 at 1:17 pm
E) Wipe the area with 70% isopropyl alcohol pads
Terra Firme Forme Dermatosis is a skin disorder with brown-black plaques that appear like dirt but do not wash off. The plaques have a papillomatous surface. The anterior neck is a common location, but it can occur elsewhere, eg thorax, thighs. Pathophysiology is unclear, but it is thought to be a disorder of keratinization. Wiping the affected areas with 70% isopropyl alcohol removes the lesions and is diagnostic and therapeutic. These lesions are not dirt, and the patient and parents should be reassured of this fact. Differential diagnosis includes acanthosis nigricans (seen particularly in obese patients), “atopic dirty neck,” seen predominantly in young adults (especially Asian) with a history of atopic dermatitis, and postinflammatory hyperpigmentation. See photos here: https://pemsource.org/wp-content/uploads/2024/05/Miscellaneous-Rashes.pdf