achondroplasia

Deformierte
Wirbelkörper thorakolumbaler Übergang bei Achondroplasie. Die Vorderkante ist ausgerundet, die Hinterkante zeigt ein Scalopping.
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Hochgradige
Stenose des Foramen magnum bei Chondroplasie mit Ausbildung eines Hydrocephalus. Kinking der Medulla oblongata, jedoch noch keine Myelopathie.
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Fig. 259.—
Chondrodystrophia. Adult case. Wide sudden expanding of ends of bones. Short stubby shafts. No bowing in the bones affected. (Original.)Identifier: americanpractice01brya (find matches)Title: American practice of surgery : a complete system of the science and art of surgeryYear: 1906 (1900s)Authors: Bryant, Joseph D. (Joseph Decatur), 1845-1914 Buck, Albert H. (Albert Henry), 1842-1922Subjects: Publisher: New York : W. Wood and companyContributing Library: University of California LibrariesDigitizing Sponsor: Internet ArchiveView Book Page: Book ViewerAbout This Book: Catalog EntryView All Images: All Images From Book Click here to view book online to see this illustration in context in a browseable online version of this book.Note About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.
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Preschooler
with short stature. AP radiograph of the upper extremity shows proximal (rhizomelic) shortening of the humerus along with flaring of the distal metaphysis of the radius and ulna.The diagnosis was achondroplasia.
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Preschooler
with short stature. AP radiograph of the lower extremities shows bilateral rhizomelic shortening of the femora and flaring of the distal femora and proximal and distal tibiae and fibulae.The diagnosis was achondroplasia.
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Preschooler
with short stature. Lateral radiograph of the spine shows kyphosis of the thoracolumbar spine and shortened pedicles, posterior scalloping of vertebral bodies and anterior beaking of vertebral bodies.The diagnosis was achondroplasia.
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Preschooler
with short stature and genu varum. AP radiograph of the lower extremities shows a genu varum deformity and bilateral shortening of the femora and flaring of the proximal tibiae and fibulae.The diagnosis was achondroplasia.
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Identifier:
diseasesofchildr00grah (find matches)Title: Diseases of childrenYear: 1916 (1910s)Authors: Graham, Edwin Eldon, b. 1864Subjects: Children DiseasePublisher: Philadelphia and New York, Lea & FebigerContributing Library: Columbia University LibrariesDigitizing Sponsor: Open Knowledge CommonsView Book Page: Book ViewerAbout This Book: Catalog EntryView All Images: All Images From Book Click here to view book online to see this illustration in context in a browseable online version of this book.Text Appearing Before Image:normal. As a rule, however, they develop slowly, are late in talking,and behind the normal child in acquiring knowledge. The deformityin the sacral region and pelvis caused by defective ossification of theinnominate bones may make normal labor difficult and necessitate theuse of forceps, or, possibly, the performance of Cesarean section. Diagnosis.—The condition has been confounded with hydrocephalus,rickets, and cretinism; but careful examination will invariably resultin a correct diagnosis. X-ray plates will show the short and curvedbones of the arms and legs, and will aid in the recognition of the disease. Prognosis.—The general nutrition of the infant is affected, as isevident from the poor ligamentous and muscular development. Manyof the, children die during birth, or, owing to poor development, soonafterward; others, as has been stated, may live to extreme old age.They marry and have children, and their offspring may either showachondroplasia or be absolutely normal. PLATE IText Appearing After Image:Achondroplasia. ^r^slTf?^r.f^^^^^^l ^f^ ^^ epiphyses with ^.ery short shafts. TheTZs Ina the th h ° proportion than the trunk. The upper feg^ below ;het?eel proportionately shorter than the forearn^s an/lhe CHAPTER VIII.INFANT FEEDING. Cows Milk.—The infant may be fed on cows, goats or asss milk,but as the milk of the cow is almost always obtainable, and that ofthe ass and goat is often difficult to procure, cows milk is, for practicalpurposes, the one which is universally adopted in the United States. Our first thoughts in regard to cows milk should be of the cowsand the farm. The herd should be healthy and free from any taintof tuberculosis. They should be properly fed both in and outside ofthe barn, and care should be taken to see that the pasture fields do notcontain weeds and rank growths. The cows should be carefullygroomed, given an abundance of fresh air and fresh water, and themanure should be removed from the barn as frequently as possible. The milkers should be clean, anNote About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.
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Preschooler
with short stature. AP radiograph of the pelvis shows squaring of the iliac bones, flattening of the acetabulae, and small sacroiliac notches bilaterally, leading to a champagne glass appearance to the pelvic inlet.The diagnosis was achondroplasia.
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Preschooler
with short stature. AP radiograph of the lumbar spine (left) shows progressive narrowing of the distance between the pedicles descending through the lumbar spine (interpedicular narrowing). The lateral radiograph of the lumbar spine (right) shows shortened pedicles leading to narrowing of the anterior-posterior diameter of the spinal canal (spinal stenosis) and that the vertebral bodies have some anterior wedging and posterior scalloping.The diagnosis was achondroplasia.
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Preschooler
with short stature. AP radiograph of the hand shows diffuse shortening of the phalanges and metacarpals, giving the hand the appearance of a trident. There is also metaphyseal flaring of the distal radius and ulna.The diagnosis was achondroplasia.
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X-ray 10y old
male with Achondroplasia
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Preschooler
with short stature and a large skull. Lateral radiograph of the skull shows small facial bones and a relatively large cranium.The diagnosis was achondroplasia.
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nicht verwechseln mit: Achondrogenesie
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Achondroplasia is a congenital genetic disorder resulting in rhizomelic dwarfism and is the most common skeletal dysplasia. It has numerous distinctive radiographic features.

Epidemiology

It occurs due to sporadic mutations in the majority of cases but can be inherited as an autosomal dominant condition. Homozygous achondroplasia is lethal.

There is a prevalence of approximately 1 in 25,000-50,000 births with males affected more frequently than females .

Clinical presentation

Achondroplasia is the most common cause of short-limb dwarfism. Patients are of normal intelligence with normal motor function. However, they may have specific neurologic deficits.

Pathology

The disease results from a mutation in the fibroblast growth factor gene 3 (FGFR3) located on chromosome 4p16.3 which causes abnormal cartilage formation. These are cell surface receptors comprised of an extracellular domain with three immunoglobulin-like regions, a transmembrane domain and an intracellular tyrosine kinase .

The mutation to the FGFR3 gene in achondroplasia is a gain of function mutation with constitutive activation of an inhibitory signal .  All bones that form by endochondral ossification are affected. Bones that form by membranous ossification are not affected, thus allowing the skull vault to develop normally.

Associations
  • SADDAN syndrome: severe achondroplasia with developmental delay and acanthosis nigricans

Radiographic features

Almost all the bones of the skeleton are affected, and hence all parts of the body have bony changes with secondary soft tissue changes. Antenatally it is difficult to diagnose achondroplastic features until the 3 trimester .

Antenatal ultrasound 

Antenatally detectable sonographic features include:

  • short femur length measurement: often well below the 5th centile
    • the femur length (FL) to biparietal diameter (BPD) is taken as a useful measurement
  • trident hand : 2nd, 3rd and 4th fingers appearing separated and similar in length
  • separation of 1st, 2nd, 3rd and 4th fingers
  • protruding forehead: frontal bossing
  • depressed nasal bridge
Plain radiograph / CT / MRI 

Features on radiographs, CT, and MRI are similar and discussed together here.

Cranial
  • relatively large cranial vault with small skull base
  • frontal bossing with the depressed nasal bridge (midfacial retrusion)
  • narrowed foramen magnum
  • cervico-medullary kink
  • relative elevation of the brainstem resulting in a large suprasellar cistern and vertically-oriented straight sinus
  • communicating hydrocephalus (due to venous obstruction at sigmoid sinus)
  • large anterior fontanelle in infancy; may persist to 5 or 6 years of age

Also, see the achondroplastic base of skull abnormalities for further discussion.

Spinal 
  • posterior vertebral scalloping
  • progressive decrease in the interpedicular distance in the lumbar spine
  • gibbus: thoracolumbar kyphosis with bullet-shaped/hypoplastic vertebra (not to be confused with Hurler syndrome)
  • short pedicle canal stenosis
  • laminar thickening
  • widening of intervertebral discs
  • an increased angle between the sacrum and lumbar spine
Chest
  • anterior flaring of the ribs 
  • anteroposterior narrowing of the ribs
Pelvis and hips
Limbs
  • metaphyseal flaring: can give a trumpet bone type appearance
  • the femora and humeri are particularly shortened (rhizomelic shortening)
  • long fibula: the fibular head is at the level of the tibial plateau (case 3)
  • bowing to mesial segment of legs
  • the limbs may also appear thickened but are in fact normal in absolute terms; thickening is perceived due to reduced length
  • trident hand
  • chevron sign 
  • the metacarpal and metatarsal bones, and in some cases the proximal phalanges, are short and of similar length

Treatment and prognosis

There is often a danger of cervical cord compression due to narrowing of the foramen magnum.

Treatment varies and is usually orthopedic, particularly to correct kyphoscolioses, as well as neurosurgical, to decompress the foramen magnum or shunt hydrocephalus .

Overall prognosis is good, with near-normal life expectancy in heterozygous individuals. When homozygous, the condition is fatal due to respiratory failure .

History and etymology

Achondroplasia literally means "without cartilage formation", although the pathology is impaired endochondral ossification (see Pathology above).

Differential diagnosis

The differential diagnosis is that of other less common skeletal dysplasias, including :

See also

Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu Achondroplasie:
Ellis-van-Creveld-Syndrom
 
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Skelettdysplasie
 
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Verbiegung
der langen Röhrenknochen
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chondroectodermal
dysplasia
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camptomelic
dysplasia
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short limb
skeletal dysplasias
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Hypochondroplasie
 
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Knorpel-Haar-Hypoplasie
 
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Foramen
magnum Stenose bei Achondroplasie
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Achondroplasie
Wirbelsäule
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