Nevus of Ota: Clinical Aspects and Management

Henry H.L. Chan, MB, FRCPG, FRCPE, Taro Kono, MD

In This Article

Epidemiology of Nevus of Ota

Nevus of Ota is a dermal melanocytic hamartoma that was considered to be very common in Asians but rare in Caucasians. One study[2] that examined 27,082 consecutive dermatologic patients in Japan found 110 with nevus of Ota, an incidence rate of 0.4%.[2] A similar clinic-based study in Japan[3] indicated an incidence rate of 1.1%; however, community-based studies, which more accurately assess the dimension of the issue, have demonstrated a much lower rate of occurrence. An examination of 6915 black patients in Canada, found an incidence rate of nevus of Ota of 0.014%.[4] Investigators also found that none of the 5251 Caucasian patients who were examined had the condition. More recently, investigators[5] examined 3914 Chinese children who attended an Asian clinic in Canada for the presence of scleral melanocytosis and nevus of Ota. Results in that study revealed that while scleral melanocytosis was common and affected over 40% of the children, nevus of Ota occurred less frequently and was only seen in one patient, which was an incidence rate of 0.034%.[5]

Although there have been reports of nevus of Ota in three successive generations, most patients have no family history.[6] The age of onset is another interesting aspect; it is not uncommon for nevus of Ota to appear in the perinatal period or around puberty. Among 240 patients examined with nevus of Ota, it was found that 48% developed the nevus at or soon after birth, 11% developed it between 1 and 10 years of age, and the remaining 36% developed it between 11 and 20 years of age.[7] Such findings indicate that in many cases the nevus consists of amelanotic nevoid cells which only become pigmented after stimulation by triggering factors. The findings also indicate a significant predominance among women, with the male to female ratio being 1:4.8. Based on these observations, together with an increase in onset during puberty, female sex hormones have been suggested as potent stimuli. Indeed, female sex hormones have an important role in the development of other melanocytic conditions such as melasma; however, given the fact that women are alleged to be more concerned about their cosmetic appearance, observation bias is at least a contributing factor. Other stimuli, such as infection, trauma, or ultraviolet light exposure have also been reported to trigger the onset of the nevus.[7,8] As with sex hormones, these factors have been proposed to stimulate the production of melanin from amelanotic melanocytes, which leads to the development of clinically apparent nevus.


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