A rare genetic disorder characterized by a severe form of asymmetric dwarfism with growth retardation, peculiar facies, and frequent hypoglycemia.
Silver-Russell Dwarfism; Silver Syndrome; Silver-Russell Syndrome.
Rare; estimated 1:30,000-1:100,000.
Most cases are sporadic. No established Mendelian or chromosomal basis.
An underlying molecular cause can be identified in around 60% of patients clinically diagnosed with Russell-Silver Syndrome. The most common underlying mechanisms are loss of methylation on chromosome 11p15 (in 30-60% of patients) and maternal uniparental disomy for chromosome 7p11.2 (in 5–10%). However, the molecular etiology remains unknown in a substantial proportion of patients.
The Netchine–Harbison clinical scoring system is used for diagnosis of Russell-Silver Syndrome (at least 4 out of 6 criteria including prominent forehead and relative macrocephaly):
Small for Gestational Age (birth weight and/or birth length): ≤−2 standard deviations (SDS) for gestational age
Postnatal growth failure: Height at 24 ± 1 months ≤−2 SDS or height ≤−2 SDS below mid-parental target height
Relative macrocephaly at birth: Head circumference at birth ≥1.5 SDS above birth weight and/or length SDS
Protruding forehead: Forehead projecting beyond the facial plane on a side view as a toddler (1-3 years)
Body asymmetry: Leg length discrepancy (LLD) of ≥0.5 cm or arm asymmetry or LLD <0.5 cm with at least two other asymmetrical body parts (one non-face)
Feeding difficulties and/or low BMI: BMI ≤−2 SDS at 24 months or current use of a feeding tube or cyproheptadine for appetite stimulation
The first feature is extreme intrauterine growth retardation with normal head circumference, sometimes referred as pseudohydrocephalus. The characteristic facial features are craniofacial disproportion, delayed fontanel closure, triangular facies, turned-down mouth corners, and micrognathia. Asymmetry of arms and/or legs causes hemihypertrophy and lateral asymmetry. Fifth finger clinodactyly and syndactyly of toes are observed. The radiology findings are usually fifth finger middle or distal phalangeal hypoplasia, ivory epiphyses, second metacarpal pseudoepiphysis, vertebral abnormalities, absent sacrum, and absent coccyx. Hypoglycemia at birth and even after is common. Café-au-lait spots, precocious sexual development, and cryptorchism are frequent. Cardiac defects can be observed. Gastrointestinal manifestations are now known to be a part of the disease (gastroesophageal reflux, esophagitis, food aversion, and failure to thrive). Susceptibility to malignancies is higher. Normal intelligence is the rule with some delay in the early motor milestones because of the decreased muscle bulk and relatively large head. The children remain thin with a lack of subcutaneous fat. Therapeutic trials with growth hormone have not corrected the growth pattern.
Precautions before anesthesia
The airway must be carefully assessed. Search for cardiac defect (clinical, echocardiography). Evaluate hypoglycemic risk (clinical, history, glucose level). Anticipate gastroesophageal reflux.