Hyperkeratosis of the nipple and areola (HNA), formerly known as nevoid hyperkeratosis of the nipple and areola, is a rare benign skin condition that presents with verrucous thickening and hyperpigmentation of the nipple and/or areola. HNA can be unilateral or bilateral. Some patients may experience associated pruritus. The skin lesions are painless and without discharge; they are not associated with any lymphadenopathy.

HNA may be primary or occur secondary to the presence of a seborrheic keratosis or epidermal nevus, or as part of an underlying dermatosis such as Darier disease, acanthosis nigricans, atopic dermatitis, inherited ichthyoses (eg, ichthyosis vulgaris), or confluent and reticulated papillomatosis of Gougerot and Carteaud (CARP). Some cases have been ascribed to medications (estrogens, spironolactone, and vemurafenib).

HNA is seen in both sexes, but the majority of cases have been reported in postpubescent females, mainly those in their second to third decade of life. To date, there have been approximately 150 cases reported in the literature, but it is highly likely that this condition is underreported. A single case has been reported in a prepubescent girl.

Pathophysiology of primary HNA is unclear, although the occurrence of HNA mostly in female patients after puberty, its worsening in pregnancy with improvement post-delivery, and its occurrence in patients on estrogen therapy suggest an underlying hormonal pathogenesis.