Mondo Description Trisomy 12p is an extremely rare chromosomal disorder (over 30 cases reported worldwide) characterized by craniofacial malformations (round face, prominent cheeks, high bulging forehead, broad and flat nasal bridge, short nose with anteverted nostrils, long philtrum, prominent and everted lower lip, low-set ears, abnormally folded helix, protuberant antihelix), postnatal growth retardation, mental and psychomotor retardation, generalized hypotonia, abnormally short wide hands and/or other abnormalities.