True statement regarding Achondroplasia is :
Ans: D Ref: Apley's System of Orthopaedics and Fractures, 9th edition Explanation: "Achondroplasia typically manifests at birth with short limbs, a long narrow trunk, and a large head with midfacial hypoplasia and prominent forehead and skeletal radiographs confirm the diagnosis. "Ref: Nelson Textbook of Pediatrics. 19th ed. Achondroplasia Causes 'disproportionate' dwarfism. Most common cause of; short-limb' dwarfism. The trunk is disproportionately long in comparison to the limbs. The proximal segments of limbs are disproportionately short - rhizomelic shortening. Other Features o Large skull with prominent forehead, o Saddle-shaped nose, o Frontal bossing, o Mid-face hypoplasia, o Stubby, splayed fingers {trident hands), o Mental development is normal. o During adulthood, short vertebral pedicles may lead to lumbar spinal stenosis. Incidence: 1 in 30,000 births. Inheritance: Autosomal dominant transmission. 80 per cent of cases are sporadic. Occurs due to a mutation in the fibroblast growth factor receptor 3 (FGFR-3) gene on chromosome 4 causing a diminution in endochondral bone growth. Average adult height is usually around 122 cm (48 inches). Disproportionate shortening of the limb bones is detectable in utero by ultrasound scan. X-Rays All bones that are formed by endochondral ossification are affected Tubular bones are short but thick. Metaphyses is flared. Pelvic cavity is small and the iliac wings are flared, producing an almost horizontal acetabular roof. The vertebral interpedicular distance diminishes from L1 to L5. The spinal canal is reduced in size. Vertebral features are best defined on CT or MRI. Also Note: Spinal shortening is not a prominent feature of achondroplasia. Instead, achondroplasia is characterized by a trunk which is disproportionately long in relation to the limbs. Other Similar Conditions: Multiple Epiphyseal Dysplasia (MED): Widespread involvement of the epiphyses. Vertebrae are usually spared. Shortening is lesser than in achondroplasia. Face, skull, and spine are normal. Usually, involve only one or two pairs of joints. Spondyloepiphyseal Dysplasia (SED): Multiple epiphyseal dysplasias along with well-marked vertebral changes. Vertebral changes include, o Delayed ossification. o Flattening of the vertebral bodies (platyspondyly). o Irregular ossification of the ring epiphyses. o Indentations of the end-plates (Schmorl's nodes).
AR inheritance
Shortened spine
Increased risk of pathological fracture
Diagnosed at birth by X-ray