“…107 Four possible theories have been proposed about ADM's pathogenesis: migration of melanocytes from hair bulb to dermis, descendance of melanocytes from epidermis, reactivation of pre-existing dormant dermal melanocytes or secondary development of DM caused by dermal inflammation. 92 It is assumed that dermal melanocytes which are present since birth 108 are either activated by various triggering factors such as pregnancy, 92 trauma, 97 previous inflammatory dermatoses, 98,109 hormonal treatment 104 and PUVA therapy 107 or Table 4 Epidemiological, clinical and histological features of main patchy dermal melanocytoses 2,13,[51][52][53][54][55][56][57][58] Mongolian spot 13,[52][53][54][55][56] Naevus of Ota 2,51,54,57,58 Naevus of Ito 2,54 Epidemiology Asian, African American and Native American population Benign dermal dendritic melanocytic proliferations show a gradual increase in melanin synthesis by increasing age without a known aetiology. 108 Large plaque-type blue naevus with subcutaneous cellular nodules (LPTBN-SN)…”