1. Regarding achondroplasia:
a) Achondroplasia is the most common type of short limb skeletal dysplasia which shortens stature
b) Achondroplasia is an autosomal recessive defect.
c) The short pedicles of achondroplasia lead to spinal stenosis and paraplegia more than 15% of patients
d) Hydrocephalus is an uncommon complication in patients with achondroplasia
e) About 90% of the cases of achondroplasia occur from a spontaneous mutation in patients with normal parents
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2. Which is the most severe form of short-limbed dwarfism? Please pick the BEST answer.
a) Hypochondroplasia
b) Achondroplasia
c) Thanatophoric dwarfism
d) Homozygous achondroplasia
Answers:
1. a, c, e
Achondroplasia is the most common type of short limb skeletal dysplasia which shortens stature. It is an autosomal dominant defect in endochondral bone formation (osteochondrodysplasia) which causes skeletal growth derived from cartilage to be shortened. The most significant shortening occurs in long tubular bones, cranial base, and spinal pedicles. The short pedicles of achondroplasia lead to spinal stenosis and paraplegia more than 15% of patients. Hydrocephalus is a concern in 60% of patients with achondroplasia. About 90% of the cases of achondroplasia occur from a spontaneous mutation in patients with normal parents. However, it's mode of inheritance is autosomal dominant.
2. c
Thanatophoric dwarfism is the most common cause of fatal neonatal dwarfism. Features include cloverleaf skull, short ribs with small thoracic volume, small pedicles, and square iliac bones
