Sedaghatian Type Spondylometaphyseal Dysplasia
Description
Sedaghatian Type Spondylometaphyseal Dysplasia (SMD-SED) is a rare genetic disorder characterized by skeletal abnormalities affecting mainly the spine and long bones. It is a type of spondylometaphyseal dysplasia, a group of conditions affecting the development of the spine and the ends of long bones (metaphyses). This blog post delves into the specifics of SMD-SED, covering its signs, causes, inheritance, diagnosis, management, and ways to thrive with the condition.
Genes Involved
SMD-SED is caused by mutations in the COL2A1 gene. This gene provides instructions for making type II collagen, a protein crucial for the development of cartilage, which is the flexible tissue found in joints and other parts of the body. Mutations in COL2A1 disrupt the normal production of type II collagen, leading to the skeletal abnormalities observed in SMD-SED.
Recognizing the Signs and Symptoms
Individuals with SMD-SED typically exhibit a range of symptoms, including:
- Short stature: This is a prominent feature, with individuals often significantly shorter than average.
- Short limbs: The arms and legs may be disproportionately shorter, particularly in the forearms and lower legs.
- Spine abnormalities: Scoliosis (curvature of the spine), kyphosis (rounding of the upper back), and lordosis (inward curve of the lower back) can occur.
- Joint stiffness: Limitations in joint movement are common, particularly in the hips and knees.
- Facial features: A flat nasal bridge, a prominent forehead, and a small jaw are often present.
- Dental abnormalities: Delayed tooth eruption and malocclusion (misalignment of teeth) are possible.
- Delayed development: Motor milestones, such as walking, may be delayed.
Causes
SMD-SED is a genetic disorder, meaning it is caused by alterations in the individual‘s genes. Specifically, it is caused by mutations in the COL2A1 gene. These mutations disrupt the production of type II collagen, a protein essential for cartilage development. This disruption leads to the characteristic skeletal abnormalities associated with the condition.
Inheritance/recurrence risk
SMD-SED is typically inherited in an autosomal dominant pattern. This means that one copy of the altered gene from either parent is sufficient to cause the condition. Individuals with SMD-SED have a 50% chance of passing the altered gene to each of their children.
