E78.72 Smith-Lemli-Opitz syndrome

Name of the Condition

• Smith-Lemli-Opitz syndrome

Summary

Smith-Lemli-Opitz syndrome is a rare genetic disorder affecting cholesterol metabolism, characterized by intellectual disability, physical abnormalities, and developmental delays. It results from a deficiency in the enzyme 7-dehydrocholesterol reductase, leading to low cholesterol levels and elevated 7-dehydrocholesterol. The condition impacts multiple organ systems, with symptoms ranging from mild to severe.

Causes

Smith-Lemli-Opitz syndrome is caused by mutations in the DHCR7 gene, which encodes the enzyme 7-dehydrocholesterol reductase. This enzyme is essential for converting 7-dehydrocholesterol to cholesterol. Mutations disrupt cholesterol synthesis, leading to the accumulation of 7-dehydrocholesterol and reduced cholesterol availability. The condition is inherited in an autosomal recessive pattern, requiring two copies of the mutated gene for expression.

Risk Factors

• Consanguinity (parents who are blood relatives).
• Family history of Smith-Lemli-Opitz syndrome or related metabolic disorders.
• Carrier status of DHCR7 gene mutations.

Symptoms

Symptoms may include intellectual disability, developmental delays, microcephaly, cleft palate, syndactyly (fused fingers or toes), genital abnormalities, and growth retardation. Additional features can include feeding difficulties, behavioral issues, and congenital heart defects. Severity varies widely among affected individuals.

Diagnosis

Diagnosis is typically confirmed through biochemical testing, which measures elevated 7-dehydrocholesterol levels in blood or tissue samples. Genetic testing for DHCR7 mutations may also be performed. Prenatal diagnosis is possible via chorionic villus sampling or amniocentesis. Clinical evaluation, including physical examination and developmental assessment, supports the diagnosis.

Treatment Options

Treatment focuses on managing symptoms and complications. Cholesterol supplementation may be considered, though its efficacy varies. Multidisciplinary care involving specialists in genetics, cardiology, neurology, and developmental pediatrics is often required. Supportive therapies, such as physical therapy, speech therapy, and educational interventions, address developmental delays.

Prognosis and Follow-Up

Prognosis depends on the severity of symptoms and associated complications. Some individuals have mild impairment, while others experience significant disability or early mortality due to congenital heart defects or other issues. Regular follow-up with a healthcare team is essential to monitor growth, development, and organ function. Early intervention improves outcomes.

Complications

Complications may include congenital heart defects, respiratory issues, gastrointestinal problems, and increased risk of infections. Behavioral challenges, such as autism spectrum disorder, and endocrine abnormalities can also occur. Severe cases may involve life-threatening cardiac or respiratory conditions.

Lifestyle & Prevention

While the condition is genetic, prenatal counseling and genetic testing for at-risk families can aid in family planning. Early intervention services, including developmental support and nutritional guidance, may help manage symptoms. Avoiding environmental triggers that exacerbate complications (e.g., infections) is recommended.

When to Seek Professional Help

Seek medical attention if a child exhibits developmental delays, physical abnormalities, or feeding difficulties. Prompt evaluation is crucial for early diagnosis and intervention. Genetic counseling is recommended for families with a history of the syndrome or unexplained developmental issues.

Tips for Medical Coders

Document the presence of characteristic features (e.g., physical abnormalities, developmental delays) and confirmatory testing (e.g., biochemical or genetic results) to support coding. Ensure documentation aligns with the clinical diagnosis and includes details on severity or associated complications, as these may impact coding specificity.