Delineation of a characteristic phenotype in distal trisomy 2q.

A recombinant chromosome change with dup(2)(q34----qter) secondary to a paternal inv(2) (pter----q34) was found in a 19-year-old boy and his 12-year-old sister. Both were born at term with normal birth weight and head circumference. Hypertelorism, irregular nystagmus, broad flat nasal bridge, and short beaked nose with anteverted nostrils were noted neonatally. Both developed microcephaly and brachycephaly. Cardiac, urogenital, retinal, and optic disc anomalies and onset of progressive kyphosis in adolescence were detected. Their facial appearance, with birdlike "Muppet Gonzo" features, was increasingly accentuated with age. Both had mild mental retardation with IQ's around 70. The clinical findings in these siblings were compared with those described in 23 cases with various 2q partial trisomies. The results of the present study and previous studies indicate a characteristic clinical presentation in children and adults. The reluctance to define the specific phenotype for distal 2q trisomy might be due to the fact that the clinical features tend to be considerably more pronounced towards adolescence than neonatally.