Septo-Optic Dysplasia (SOD)

Description

Septo-Optic Dysplasia (SOD), also known as de Morsier syndrome, is a rare congenital disorder affecting the development of the brain, eyes, and pituitary gland. This complex condition can manifest in a wide range of symptoms, varying in severity from person to person. Understanding SOD is crucial for early diagnosis, appropriate management, and supporting individuals and families impacted by this condition.

Genes Involved

Genes Involved in SOD:

SOD is a complex condition, and the exact genes involved are not fully understood. However, several genes have been linked to SOD, including:

SOX2: This gene plays a critical role in brain development.
SHH: This gene is involved in the formation of the forebrain.
ZIC2: This gene is associated with the development of the midline structures of the brain.
SIX3: This gene is involved in eye development.
PAX6: This gene is crucial for both eye and brain development.

Research is ongoing to identify other genes and understand the complex interplay between genetics and environmental factors contributing to SOD.

Recognizing the Signs and Symptoms

Recognizing the Signs and Symptoms of SOD:

Eye Abnormalities: This is the most common feature of SOD. Affected individuals may have:
- Anophthalmia or Microphthalmia: Absence or small size of one or both eyes
- Coloboma: A gap or opening in the iris, retina, or optic nerve
- Optic nerve hypoplasia: Underdevelopment of the optic nerve leading to vision loss
- Strabismus (crossed eyes): Misalignment of the eyes
- Nystagmus (involuntary eye movements): Rapid, uncontrolled eye movements
Brain Abnormalities:
- Septo-optic dysplasia: A defect in the septum pellucidum, a thin membrane in the brain
- Hypothalamic-pituitary dysfunction: Issues with the hypothalamus and pituitary gland, impacting hormone production and regulation
- Hydrocephalus: Accumulation of cerebrospinal fluid in the brain
- Seizures: Uncontrolled electrical activity in the brain
- Learning difficulties: Challenges with cognitive development
Other Symptoms:
- Delayed development: Slower progress in physical, cognitive, or language skills
- Growth hormone deficiency: Short stature
- Diabetes insipidus: Excessive thirst and urination due to inadequate antidiuretic hormone (ADH) production
- Hearing loss: Less common but can occur in some individuals

It‘s important to note that the severity of symptoms can vary significantly. Some individuals may only have mild visual impairments, while others may have more severe brain and pituitary gland abnormalities.

Causes

Causes of Septo-Optic Dysplasia:

The exact cause of SOD is unknown, but it‘s believed to be caused by a combination of genetic and environmental factors.

Genetic Predisposition: Mutations in certain genes, as mentioned above, can increase the risk of SOD.
Environmental Factors: Exposure to certain toxins or infections during pregnancy may also contribute to SOD.
Spontaneous mutations: These mutations can occur during the development of the fetus and are not inherited from parents.

While SOD can occur in families with a history of the condition, often it appears to be a random event.

Inheritance/recurrence risk

Inheritance or Recurrence Risk of SOD:

The inheritance pattern of SOD is complex and varies depending on the underlying genetic mutation.

Autosomal dominant inheritance: In some cases, a single copy of a mutated gene is sufficient to cause SOD. The risk of passing on the mutation to children is 50%.
Autosomal recessive inheritance: In other cases, two copies of a mutated gene are required for SOD to develop. If both parents carry the mutated gene, there is a 25% chance for each child to inherit SOD.
De novo mutations: Many cases of SOD are caused by spontaneous mutations that occur in the embryo and are not inherited. The risk of recurrence in subsequent pregnancies is low in these cases.

Genetic counseling is recommended for families with a history of SOD to understand their individual risk factors and discuss testing options.

WES Whole Exome Sequencing