Tuberous Sclerosis Epidemiology

Tuberous sclerosis can present in individuals of all ages, ethnicity and gender and is estimated to affect 2,000,000 people worldwide.

Overall Prevalence

It has traditionally been regarded as a very rare disease with the prevalence in 1956 to be approximately 1 in 150,000. However, this has steadily been rising and a study from 1998 estimated the prevalence of disease for all live births to be between 7 and 12 cases per 100,000 although more than half of these cases do not cause symptoms and are not detected at birth.

A notable explanation for the recent rise in prevalence may be the use of imaging techniques, such as computed tomography (CT) and ultrasound scans that can diagnose individuals that do not notice characteristic symptoms of the condition.

Although it continues to be regarded as a rare disease, it is relatively common in comparison to many similar genetic diseases.

Demographics

Tuberous sclerosis is an autosomal dominant disease, which leads to the assumption that it occurs equally in both females and males. Although affected equally, female patients tend to experience more severe mortality and morbidity rate, which is likely due to the high incidence of lung involvement in females.

Some population groups and countries, such as Korea and China, have been identified with a prevalence of tuberous sclerosis possibly lower than other areas of the world, such as America and the United Kingdom. However, this has not been confirmed and the complex is currently considered to occur with equal frequency in different races.

The age at diagnosis can range from infancy to adulthood, although it is a congenital disorder that is present from birth. In some cases, diagnosis is only made when the condition is suspected because another family member has it, despite relatively mild symptoms.

Mortality

Most individuals with tuberous sclerosis live a relatively normal life in regards to length, however some of the symptoms related to the complex may be fatal in some cases.

The most common cause of death is status epilepticus, which presents as a result of benign tumors in the brain or bronchopneumonia. Following this, renal failure is the next most common cause, resulting from tumors that inhibit the function of the kidney.

Lymphangioleiomyomatosis is not present in the majority of cases of tuberous sclerosis, however is often lethal when it occurs. Individuals with this type of lesion are more likely to die as a result of this than any other cause.

Morbidity

Quality of life of individuals with tuberous sclerosis is largely dependent on which area of the body is affected by the benign tumors that characterize the disease.

Tumors affecting the brain may result in seizures, hydrocephalus and development disorders. Seizures affect the majority of all patients and infantile spasms are often one of the first signs to be noted in babies with the disease. Developmental delays affect approximately three quarters of children with the severity depending greatly on the size, number and location of the tumors. Various behavioral disorders, including attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD) may also affect quality of life.

Cysts or angiomyolipoma in the kidney can lead to complications such as renal failure or bleeding. In mild cases, the cysts will not noticeably affect renal function but many patients require specialized care.

Cardiac rhabdomyoma in the heart may cause valve dysfunction or obstruct the outflow of ventricles. This is usually only fatal in the neonatal period and after this time is more likely to cause morbidity such as cardiac arrhythmias.

Various different lesions may affect the skin and nails of patients, which is extremely common in nearly all patients with tuberous sclerosis noticing some form of abnormality. Facial angiofibromas that present as red spots on the face are known to cause significant morbidity due to aesthetic effects.

References

• http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(05)78872-3/abstract
• http://emedicine.medscape.com/article/951002-overview#a0199
• http://www.ncbi.nlm.nih.gov/pubmed/23691114
• http://onlinelibrary.wiley.com/doi/10.1111/j.1749-6632.1991.tb37754.x/abstract

Further Reading

• All Tuberous Sclerosis Content
• What is Tuberous Sclerosis?
• Tuberous Sclerosis Symptoms
• Tuberous Sclerosis Diagnosis
• Tuberous Sclerosis Genetics

Written by

Yolanda Smith

Yolanda graduated with a Bachelor of Pharmacy at the University of South Australia and has experience working in both Australia and Italy. She is passionate about how medicine, diet and lifestyle affect our health and enjoys helping people understand this. In her spare time she loves to explore the world and learn about new cultures and languages.