Russell-Silver syndrome (RSS) is a pattern of malformation characteriz
ed by intrauterine and postnatal growth retardation, limb asymmetry, t
riangular face, and hypospadias. We report on a patient, from a triple
t pregnancy, who was one of identical male twins discordant for RSS. R
.B. was a 710-g male born at 33 weeks of gestation, with hypospadias,
chordee, and undescended testes. He had a normal 46,XY karyotype and n
o renal abnormalities. Female triplet A weighed 1,843 g, and male trip
let B weighed 1,920 g. Both had normal physical findings and neonatal
period. R.B. was first seen by us at age 6 7/12 years with short statu
re, triangular and asymmetric face, lower limb length discrepancy, and
surgically repaired genital anomalies. Growth hormone testing results
were normal. At age 8 7/12 years the brothers appeared physically ide
ntical ex cept for size, with a height differential of 114.25 vs. 121.
5 cm. Testing to establish biological zygosity was performed using VNT
R (variable number tandem repeat) DNA probes YNH24 (D2S44), CMM101 (D1
4S13), EFD52 (D17S26), TBQ7 (D10S28), and 3'HVR (D16S85), PCR loci MCT
118 (D1S80), and HLA-DQ alpha. These data indicate a >99.99% probabili
ty of triplets B and C being monozygotic twins. While most occurrences
of RSS are sporadic, familial cases suggesting autosomal dominance ha
ve been reported. Three other cases of probable monozygotic twins with
RSS have been described. The significance of this confirmation of dis
cordance in determining the cause of RSS is discussed. (C) 1995 Wiley-
Liss, Inc.