Smith-Lemli-Opitz syndrome is an autosomal recessive disorder caused by mutations of 3β-hydroxysterol -Δ7reductase gene (DHCR7) which maps to 11q12-13 and was the first discovered defect in cholesterol biosynthesis resulting in a congenital dysmorphology syndrome. We present the case of a 46,XY newborn with ambiguous genitalia and multiple congenital anomalies (atrial septal defect, ventricular septal defect, syndactyly of the second and third toe, cleft palate, webbed neck, small fontanels, mesomelia, simian palmar crease, micrognathia, wide nasal bridge with anteverted nostrils, low set ears). Hormonal assessment performed at twelve days revealed a decreased testosterone level (0.03 ng/mL), a high estradiol level (448.8 pg/mL), normal LH (2.8UI/mL), DHEAS (86.61ìg/dL), progesterone (1.34ng/mL) and 17 hydroxyprogesterone (1.08ng/mL) levels. Cholesterol was low (44mg/dL) confirming the diagnostic of Smith-Lemli-Opitz syndrome. [ABSTRACT FROM AUTHOR]