To the editor: Unilateral nevoid hyperkeratosis of the nipple and areola: excellent response to cryotherapy.

Hyperkeratosis of the nipple and areola (HNA) is a rare condition that is characterized by verrucous thickening and brownish discoloration of the nipple and areola.1 Different therapeutic options, such as topical keratolytics, retinoid acid, cryotherapy, surgical excision, and carbon dioxide laser, have been used, with varying results.1–4 We describe a patient with unilateral nevoid HNA who responded very well to cryotherapy. A 39-year-old woman presented with a 5-year history of progressive, hyperpigmented, hyperkeratotic lesions over the right nipple and areola. Three years before being admitted to our department, she had undergone skin biopsy at the primary clinic and was told that her skin lesions were benign. On presentation, dermatologic examination revealed hyperpigmented, verrucous plaques on the right nipple and areola, which consisted mainly of two plaques: a large plaque around the nipple and a separate small plaque on the areola (Figure 1). She denied a personal or familial history of other cutaneous problems, including epidermal nevi, ichthyosis, Darier’s disease, and acanthosis nigricans. She reported no history of any use of medications. Routine laboratory tests were within normal limits. Histopathologic examination showed orthokeratotic hyperkeratosis, acanthosis, and papillomatosis. Based on clinical and histopathologic findings, she was diagnosed with nevoid HNA. Although HNA is a benign cutaneous disease, we thought that the extent of hyperkeratotic thickening of our patient is moderate to severe. Moreover, our patient wanted rapid improvement. Thus, we performed cryotherapy with double freeze-thaw cycles of 15 seconds to obtain the maximal cryosurgical effect. After 4 weeks, hyperkeratotic plaques had almost disappeared and completely healed, and an excellent cosmetic result was obtained (Figure 2). There was no recurrence in the subsequent 6 months. In 1938, Levy-Frankel described three distinct types of HNA.5 Type 1 hyperkeratosis is an extension of an epidermal nevus. Type 2 hyperkeratosis is associated with other dermatoses, such as acanthosis nigricans, ichthyosis, lymphoma, chronic eczema, seborrheic keratoses, or Darier’s disease. Type 3 is idiopathic or nevoid hyperkeratosis, with no association with epidermal nevi or other dermatoses. Nevoid HNA occurs more often in women of childbearing age and usually shows bilateral involvement.1 Among the histopathologic features that characterize nevoid HNA are prominent orthokeratotic hyperkeratosis, mild acanthosis, and filiform papillomatosis, features that closely mimic those of epidermal nevus or acanthosis nigricans.1 Various therapeutic agents, such as 6% salicylic acid gel, 12% lactic acid lotion, and topical steroids, have been used with varying success in the treatment of HNA.1 It has been reported that satisfactory cosmetic results have been achieved within 1 to 2 months of continuous or intermittent application of topical tretinoin.2 Calcipotriol has also been shown to be effective in a single report.6 Carbon dioxide laser and surgical excision can be considered if the patient is greatly disturbed by the cosmetic appearance and expects an immediate result.3 Among the various treatment modalities of HNA, we chose cryotherapy because it is simple to perform and effective for hyperkeratotic cutaneous diseases such as wart and epidermal nevus.7 Cryotherapy produces selec-