Russell silver syndrome
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Russell Silver syndrome clinical features child triangular face
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Russell-Silver Syndrome (RSS / SRS)
Russell-Silver syndrome (RSS, also written Silver-Russell syndrome/SRS) is a clinically and genetically heterogeneous congenital growth disorder first described independently by Silver (1953) and Russell (1954).
Clinical Features
Cardinal Features
| Feature | Detail |
|---|---|
| Intrauterine growth restriction (IUGR) | Low birth weight despite normal gestational age |
| Postnatal growth retardation | Short stature persisting after birth |
| Triangular face / small face | Broad forehead tapering to small, pointed chin; micrognathia |
| Relative macrocephaly | Head circumference relatively preserved → "pseudohydrocephalic" appearance |
| Body asymmetry / hemihypoplasia | One side of body (limbs, trunk) smaller than the other |
| Clinodactyly of the 5th finger | Radial curvature of both little fingers |
Additional Features
- Café-au-lait macules (CALMs) — 1–2 spots in up to 20% of patients
- Feeding difficulties, hypoglycemia (especially neonatal)
- Blue sclera (rare association)
- Precocious puberty (listed as a cause of isosexual precocity)
- ART (assisted reproductive technology) increases risk of RSS
Clinical Photos
Classic SRS phenotype: triangular face, hemihypoplasia of the right hand, limb length discrepancy, and foot size asymmetry.
Molecular Genetics & Pathogenesis
RSS is a paradigm of genomic imprinting disorders, involving chromosome 11p15.5 and chromosome 7.
Chromosome 11p15.5 (most common — 35–65% of cases)
The 11p15 locus contains two independently regulated imprinted domains (DMR1 and DMR2):
- DMR1 (ICR1) controls IGF2 and H19
- Normally: IGF2 is expressed only from the paternal allele; H19 from the maternal allele
- In RSS: Hypomethylation of H19/ICR1 → loss of IGF2 expression from both alleles → reduced IGF2 → growth retardation
- Contrast with Beckwith-Wiedemann syndrome (BWS): hypermethylation of DMR1 → upregulated IGF2 → overgrowth
- DMR2 (ICR2): No altered methylation has been found in RSS (unlike BWS)
Fig: Imprinted domains at 11p15.5. ICR1 controls IGF2/H19; ICR2 controls KCNQ1/CDKN1C. In RSS, hypomethylation of ICR1 silences IGF2 expression, causing growth restriction.
Chromosome 7 (~10% of cases)
- Maternal uniparental disomy of chromosome 7 (UPD7mat) — patient inherits both chromosomes 7 from the mother
- Candidate regions: 7p11.2–p13, 7q31–qter, 7q21
Maternally derived duplications of 11p15
- Paternally derived duplications of 11p15 → BWS (overgrowth)
- Maternally derived duplications of 11p15 → RSS (growth retardation)
Other causes
- Mutations on chromosome 17q and other loci (minority of cases)
- Many cases remain genetically unexplained
RSS vs. Beckwith-Wiedemann Syndrome — Epigenetic Mirror Images
| Feature | RSS | BWS |
|---|---|---|
| 11p15.5 ICR1 methylation | Hypomethylated (loss) | Hypermethylated (gain) |
| IGF2 expression | Decreased | Increased |
| Growth | Retarded (pre- and postnatal) | Overgrowth |
| Chromosomal mechanism | Mat UPD7 or hypo-ICR1 | Pat UPD11 or hyper-ICR1 |
Diagnosis
RSS is a clinical diagnosis supported by molecular testing. The Netchine-Harbison Clinical Scoring System (NH-CSS) is widely used (≥4/6 criteria suggests RSS; molecular testing warranted if ≥3):
- SGA (small for gestational age) — birth weight and/or length ≤ −2 SD
- Postnatal growth retardation — height ≤ −2 SD at ≥24 months
- Relative macrocephaly at birth — head circumference ≥ 1.5 SD above birth weight/length SD
- Body asymmetry (limb length discrepancy ≥0.5 cm or facial asymmetry)
- Feeding difficulties or BMI ≤ −2 SD at 24 months
- Prominent forehead / frontal bossing
Molecular workup:
- Methylation testing of 11p15.5 (ICR1 hypomethylation)
- UPD7 testing (microsatellite analysis or SNP array)
- Chromosomal microarray
- If negative but high clinical suspicion: exome sequencing
Management
- Growth hormone (GH) therapy: Approved for SRS with short stature — improves adult height; should be started early (typically 2–4 years of age)
- Nutritional support: High-risk for neonatal hypoglycemia; nasogastric feeding may be required in infants
- Orthopedic management: Limb length discrepancy may require shoe lifts or leg-lengthening procedures
- Dental/orthodontic care: Due to micrognathia and crowded dentition
- Monitoring for precocious puberty: Can limit final height gain
- Multidisciplinary team: Pediatric endocrinology, genetics, dietetics, developmental pediatrics, physiotherapy
Inheritance & Recurrence
- Most cases are sporadic
- Familial cases exist with variable inheritance (AD, AR, and imprinting-related mechanisms described)
- ART-conceived children have higher rates of RSS and other imprinting disorders (Angelman, Prader-Willi) — likely due to epigenetic errors during early embryonic development
Key Sources
- Emery's Elements of Medical Genetics and Genomics — Genomic Imprinting chapter
- Fitzpatrick's Dermatology — Silver-Russell Syndrome, p. 1391
- Kurup U et al. "Approach to the Patient With Suspected Silver-Russell Syndrome." J Clin Endocrinol Metab, 2024 [PMID: 38888172]
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