Reflectance mode confocal microscopy and digital image analysis in naevus of Hori and pathogenetic evaluation

MADAM, Acquired bilateral naevus of Ota-like macules (ABNOM) or naevus of Hori is a circumscribed dermal melanocytosis characterized by blue-brown mottled hyperpigmentation occurring bilaterally on the forehead, temples, eyelids and nose, with a predilection for malar areas; multiple sites may be involved (Fig. 1a). Clinically it may be hard to distinguish from the congenital bilateral naevus of Ota (type IV naevus of Ota). We report seven cases of ABNOM, periodically evaluated at the Dermatological Department of the University of Palermo from April 2004 to June 2010. The purpose of the present study is to define the in vivo histological features of ABNOM and to elucidate its pathogenesis. A detailed history was taken for each patient with particular reference to the age at onset of pigmented macules, triggering factors, hormonal medication, sunlight exposure, pregnancy, menstruation, stress, trauma, and any family history of similar conditions. All patients were Italian with skin types III–IV. All were female, age range 21–46 years, and the estimated age at onset was 19–40 years. Bilateral involvement was present in six patients and unilateral involvement in one patient. Involvement of more than one site contemporaneously was the commonest clinical manifestation, with no ocular or mucosal membrane involvement. No patient had pigmentation at birth. In our cohort, the two most common individual triggering factors reported were sun exposure (4 ⁄7) and pregnancy (4 ⁄7). In each patient we performed reflectance mode confocal microscopy on the impaired skin, site of the dermal melanocytoses, and in the nearby undamaged skin, using the Vivascope 1500 (Lucid, Rochester, NY, U.S.A.). The results of confocal microscopy revealed a significantly increased number and intensity of ‘bright’ melanocytes in lesional skin (Figs 1b and 2) compared with normal adjacent skin. All of the pigmented lesions were distinct from surrounding normal skin by the presence of strikingly bright cells, particularly in the hair bulb. This was caused by increased production of melanin or abnormal distribution of the melanin pigment. Confocal microscopy images obtained from our patients on the impaired skin showed basilar hyperpigmentation with multiple isolated refractive cells, scattered, bipolar, stellate with no specific pattern, or irregular and increased melano-