Russell Silver Syndrome · What Is It, Causes, Diagnosis, and More

Russell Silver syndrome is primarily caused by genetic mutations. Approximately 35% to 50% of individuals with the syndrome have a specific defect in the methylation process, which regulates gene activation and inactivation. This defect typically occurs in the H19/IGF2 gene on chromosome 11p15.5. The H19 gene serves as a tumor suppressor and controls body growth and development. Hypomethylation of the H19 gene can lead to reduced expression, resulting in improper growth and development, a defining characteristic of Russell Silver syndrome. The IGF2 gene is vital for fetal growth. Normally, its expression is higher on the paternal chromosome. Changes in DNA methylation within the H19/IGF2 region can disrupt the regulation of these genes, leading to decreased growth, development, and other clinical features of Russell Silver syndrome. It's important to note that not all patients with the syndrome have this specific genetic alteration, indicating the involvement of other genetic and epigenetic factors in its development.

Russell Silver syndrome is diagnosed during childhood based on physical and developmental characteristics. A special scoring system called the Netchine-Harbison Clinical Scoring System (NH-CSS) has been created to help clinicians identify the condition accurately and sensitively. To receive a clinical diagnosis, an individual must have other disorders ruled out and meet at least four of the NH-CSS criteria, two of which must be relative macrocephaly at birth and frontal bossing. The criteria for diagnosis include the following six criteria: 

• Small for gestational age (SGA) (birth weight and/or length ≥ 2 standard deviations below the mean for gestational age)

• Postnatal growth failure (length/height ≥ standard deviation below the mean at 24 months)

• Relative macrocephaly at birth (head circumference > 1.5 standard deviations above birth weight and/or length) 

• Frontal bossing or prominent forehead (forehead projecting beyond the facial plane on a side view as a toddler) 

• Body asymmetry (limb length discrepancy ≥ 0.5 cm, or < 0.5 cm with ≥ 2 other asymmetric body parts)

• Feeding difficulties or body mass index ≤ 2 standard deviations at 24 months  or current use of a feeding tube or cyproheptadine for appetite stimulation

Treatment of Russell Silver syndrome involves addressing the symptoms and providing early childhood intervention to meet their specific needs. One common approach is growth hormone treatment, which helps promote growth and development in affected children. However, nutritional interventions are also important to manage feeding difficulties and ensure proper nutrition, which may include supplements and medication for gastroesophageal reflux. Physical therapy may be beneficial for addressing musculoskeletal issues, such as limb asymmetry. Various therapies, including physical, occupational, speech, and language therapy, are used to address developmental delays. Psychological counseling can provide support for psychosocial and body image concerns. Multidisciplinary care involving specialists (e.g. pediatricians, geneticists, gastroenterologists, and endocrinologists) is essential for managing specific medical issues, such as craniofacial abnormalities or genitourinary anomalies. 

Regular medical check-ups and early intervention help improve health outcomes and overall quality of life. Although life expectancy can vary depending on factors such as the severity of the condition and associated medical problems, most individuals with Russell Silver syndrome have a life expectancy similar to the general population. With proper management and support, individuals with Russell Silver syndrome can lead healthy and fulfilling lives.