Silver-Russell syndrome.
Silver-Russell syndrome (SRS) is characterised by intrauterine growth restriction, poor postnatal growth, relative macrocephaly, triangular face, asymmetry and feeding difficulties. As many of these features are non-specific, clinical diagnosis of SRS remains difficult. Hypomethylation of the imprinting control region (ICR) 1 on chromosome 11p15 and maternal uniparental disomy (mUPD) for chromosome 7 are found in up to 60% and around 5-10% of patients with SRS, respectively. Patients with ICR1 hypomethylation are more likely to have classical features of SRS, including asymmetry; patients with mUPD7 are more likely to have learning difficulties, particularly speech problems, although these are usually mild. As features vary widely in severity, clinicians should have a low threshold for genetic investigation of patients with features suggestive of SRS.