Background Congenital melanocytic naevi (CMN) are present at birth. Some naevi, tardive congenital naevi (TCN), become clinically apparent only after birth, during the first years of life. The number of naevi continues to increase due to the appearance of acquired melanocytic naevi (AMN). When AMN begin to appear has not been well defined. Objectives To investigate the clinical and dermoscopic features of the melanocytic naevi present in 2-year-old children and to search for and highlight any differences between CMN present at birth (BPN) and naevi appearing after birth during the first 2 years of life (FLN). Methods A nonrandomized observational study was performed. A total of 133 melanocytic naevi in 103 children aged 21-26 months were analysed by clinical and dermoscopic examination. Results Of the subjects, 76% of children had one naevus, 20% had two naevi, 3% had three naevi and 1% had four naevi. Of the naevi, 76 were BPN and 57 were FLN. The naevi with the largest diameters were significantly associated with BPN (P = 0·025). Polycyclic edges (P = 0·0378) were observed with a higher frequency in BPN than in FLN. The predominant dermoscopic patterns were globular (BPN 51%; FLN 58%) and reticular (BPN 28%; FLN 14%). Conclusions The number of naevi present in the first 2 years of life is small, and over half have already appeared at birth. They are distributed widely over the skin. BPN are larger than FLN, but most naevi are small. There was no significant difference in the dermoscopic features between the 133 BPN and FLN. The predominant patterns were globular and reticular. We could not identify defined criteria that allowed us to diagnose CMN with certainty and distinguish them from TCN and AMN.
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