Severe hemihypotrophy in a female infant with mosaic Turner syndrome: a variant of Russell–Silver syndrome?

Russell–Silver syndrome is a genetically heterogeneous condition. For most affected individuals, it represents a phenotype rather than a specific disorder. Although chromosomal anomalies, imprinting disorder, maternal uniparental disomy 7 as well as familial autosomal dominant and X-linked forms have been reported, the diagnosis remains determined on clinical grounds. Russell–Silver syndrome is characterized by asymmetric intrauterine growth retardation, postnatal failure to thrive, distinct facial features, limb asymmetry, excessive sweating and minor skin lesions. We report here a female infant who had a karyotype of 45,X on prenatal amniocytes. After delivery she was noted to have features not explainable on the basis of Turner syndrome. Her phenotype actually was quite consistent with Russell–Silver syndrome. She had a triangular face with prominent forehead, large eyes, a thin nose, malar hypoplasia, thin upper lip with down-turned corner of the mouth and a pointed chin. Marked body asymmetry was evident at birth, with the left side significantly smaller than the right side. She has a diphalangeal left fifth finger. Skin fibroblast culture and analysis showed a karyotype of 45,X on the right side and 45,X/46,XX on the left side. The case is another illustration of the genetic heterogeneity of Russell–Silver phenotype.