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.

Digits that appear disproportionately short compared to the hand/foot. The word brachydactyly is used here to describe a series distinct patterns of shortened digits (brachydactyly types A-E). This is the sense used here.