Hereditary Diseases Flashcards
Name five growth disorders of bone and cartilage
- Achondroplasia
- Cleidocranial dysplasia
- Marfan syndrome
- Osteogenesis imperfecta
- Osteopetrosis
What is NORD?
National Organization for Rare Disorders
What are some general considerations for hereditary bone and cartilage diseases?
- Autosomal dominant or recessive
- Spontaneous mutation
- Genetic/tissue component involved
- Life expectancy
- Clinical significance
What is achondroplasia?
Congenital dwarfism (4’10” or less); the most common short limbed dwarfism
Which chromosome is affected by achondroplasia?
Chromosome 4 (autosomal dominant mutation)
How will a spontaneous mutation of chromosome 4 lead to achondroplasia?
- Defective fibroblast growth factor receptor 3 (FGFR3)
- Increased signaling suppresses proliferation and maturation of chondrocytes at growth plates
- Deficit in endochondral ossification
- Rhizomelic dwarfism (disproportionate length of proximal limb)
What is the etiology of achondroplasia?
80% spontaneous mutations (but can be hereditary)
What is the mentation and life span of someone with achondroplasia?
- Normal mentation
- Normal lifespan
What is the average height of someone with achondroplasia?
Short stature averaging 50 inches (4’ 2”)
If a patient presents with the following, what is the diagnosis?
- Normal length torso, shortened limbs
- Head to face ratio is altered with smaller foramen magnum
- Depressed nasal ridge
- Thoracic or thoracolumbar hyperhyphosis
- Lumbar hyperlordosis
Achondroplasia
If a patient has the following radiographic features of the spine, what is the diagnosis?
- Posterior vertebral scalloping
- Bullet vertebrae
- Hyperlordosis with horizontal sacrum
- Congenital central stenosis
Achondroplasia
What are the radiographic features of the spine in someone with achondroplasia?
- Posterior vertebral scalloping
- Bullet vertebrae
- Hyperlordosis with horizontal sacrum
- Congenital central stenosis
If a patient has the following radiographic findings in the pelvis and extremities, what is the diagnosis?
- Short, broad metaphyses creating a waddling gait
- Champagne glass pelvis
- Flat ilia
- Horizontal sacrum
Achondroplasia
What are the radiographic features of the pelvis and extremities in someone with achondroplasia?
- Short, broad metaphyses (creating waddling gate)
- Champagne glass pelvis
- Flat ilia
- Horizontal sacrum
What are some treatments for achondroplasia?
- Orthopedic interventions
- Experimental treatment: FGFR3 gene modulation
How does Rx growth hormone affect achondroplasia?
No effect
Which chromosome is affected by cleidocranial dysplasia?
Chromosome 6 (autosomal dominant)
How common is achondroplasia?
1/40,000 live births
How common is cleidocranial dysplasia?
5 in 1 million births
RARE spontaneous mutation
What deficit of ossification is involved in achondroplasia?
Endochondral
What deficit of ossification is involved in cleidocranial dysplasia?
Intramembranous ossification
Which gene is the etiology of cleidocranial dysplasia? What is it meant to do?
RUNX2 gene which helps encode osteoblasts
What is the result of a spontaneous mutation of chromosome 6 affecting the RUNX2 gene?
Deficiency of intramembranous ossification
Which bones are affected by cleidocranial dysplasia?
Flat bones: skull, clavicles
If a patient presents with the following, what is the diagnosis?
- Skull and clavicular anomalies
- Reduced height (but not dwarfism)
- Narrow cone-shaped thorax
- Hearing loss
Cleidocranial dysplasia
What are the skull and clavicular anomalies of cleidocranial achondroplasia that are externally visible?
- Large head and small face
- Hypermobile shoulders
What is the lifespan of someone with cleidocranial dysplasia?
Normal life span
If a patient’s radiographs of the thorax present the following, what is the diagnosis?
- Absent (10%) or hypoplastic clavicles
- Pseudoarthrosis (mid portion missing from clavicle)
- Small, winged, elevated scapulae
- Narrow, cone-shaped chest
Cleidocranial dysplasia
What are the imaging features of the thorax found in someone with cleidocranial dysplasia?
- Absent (10%) or hypoplastic clavicles
- Pseudoarthrosis (mid portion missing from clavicle)
- Small, winged, elevated scapulae
- Narrow, cone-shaped chest
Marfan syndrome involves the failure to produce normal…
fibrillin-1 (FBN1 gene), an elastic component of connective tissue