The Lujan-Fryns syndrome or X-linked mental retardation (XLMR) with marfanoid habitus syndrome is a syndromic X-linked form of intellectual disability, associated with tall, marfanoid stature, distinct facial dysmorphism and behavioral problems.

Distance between nasal base and midline upper lip vermilion border more than 2 SD below the mean. Alternatively, an apparently decreased distance between nasal base and midline upper lip vermilion border.