Acanthosis nigricans of the ears or terra firma-forme dermatosis?

To the editor,

I read with great interest the case report by Lee et al.1 describing an obese young man with brown, dirt-like plaques on the sulci of the ears. The lesions were biopsied and diagnosed as acanthosis nigricans, which he also had on the neck, axillae, and groin. I would like to suggest a different diagnosis - terra firma-forme dermatosis. I wonder if slightly more aggressive rubbing with an alcohol swab might have significantly cleared the patient's lesions. I have often observed comparable dirt-like papules or plaques in this location in my patients who are obese and have darker skin types (Fig. 1). While these lesions may show overlapping features of (or occur in conjunction with) acanthosis nigricans, confluent and reticulated papillomatosis, and terra firma-forme dermatosis, they frequently demonstrate rapid and significant response or clearing with alcohol swabbing (Fig. 2). Finally, the lack of acanthosis in the biopsy of the patient of Lee et al.1 further puts the diagnosis of acanthosis nigricans in question. Because terra firma-forme dermatosis is rarely biopsied, the literature is lacking in histological descriptions for comparison.

Fig. 1

(A, B) A 32-year-old African-American man with a many year history of bothersome, progressive, dirt-like, brown papules and plaques in the preauricular area, sulci of ear, cheeks, chest, neck, and folds on back, despite normal hygiene and many attempts by the patient to scrub off the lesions with soaps.

Fig. 2

Most of the patient's lesions, including around and involving the ear, markedly improved or cleared with gentle rubbing with an alcohol swab.