achondroplasia, pseudoachondroplasia, hypochondroplasia

1. Achondroplasia,
Pseudoachondroplasia &
Hypochondroplasia
Dr. Nikhil Murkey

2.  Autosomal dominant disturbance in
epiphyseal chondroblastic growth and
maturation
 The major abnormality is failure of normal
enchondral cartilage growth at the
physis. Periosteal and membranous
ossification are normal. Some enchondral
ossification centers are affected more
than others, particularly those at the base
of the skull and at the ends of long bones.

3. 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 11: 2,3 and 4 fingers appearing
separated and similar in length
 separation of 1st and 2nd, 3rd and 4th fingers
 protruding forehead : frontal bossing

4. Radiologic features: skull
 Narrowing of the spinal canal is the pathologic hallmark of
achondroplasia.
 The base of the skull (which is formed by enchondral
ossification) is small, often with a stenotic foramen magnum.
 Basilar impression is frequent.
 The cranium is large, though short in its anteroposterior (AP)
dimension (brachycephaly).
 The frontal bones are prominent and the nasal bones are
small.
 The mandible forms normally and, therefore, gives the
impression of prognathism.
 Cervico medullary kink
 relative elevation of the brainstem resulting in a large
suprasellar cistern and vertically-oriented straight sinus
 communicating hydrocephalus

5. Relatively large
cranial vault
with small skull
base.
Prominent
forehead with
depressed
nasal bridge
narrowed
foramen
magnum

6.  There is a relatively large
cranial vault with small
skull base.
 There is a prominent
forehead with
depressed nasal bridge.
 The foramen magnum is
narrowed , and there is
a cervicomedullary kink.
 Relative elevation of the
brainstem gives rise to a
large suprasellar cistern
and a vertically-oriented
straight sinus.

7. The clivus is short such that the tip of
the odontoid is elevated to
the level of the posterior lip of foramen
magnum. At this point, the
AP diameter of the bony
craniocervical junction measures only
7 mm.
The cord fills the available
subarachnoid space at this level, and
there is impingement on the cord by
the posterior lip of foramen
magnum. Subtle T2 hyperintensity is
shown in the medulla and in the
upper cord down to the level of
junction of odontoid with body of C2.
Some T2 hyperintensity within or below
the cruciform ligament raises a
possibility of a little fluid but no
evidence of ligamentous disruption
is shown.

8. Limbs
 There is symmetric shortening of all long bones. The
femora and humeri are particularly shortened
(rhizomelic shortening)
 metaphyseal flaring : can give a trumpet bone type
appearance
 The bone ends are often splayed, with metaphyseal
cupping.
V shaped growth plates are seen.
 Because periosteal ossification proceeds normally,
there is relative widening of the shafts.
 The ulna and tibia are often shorter than the radius and
fibula.
 The tubular bones of the hands and feet are short and
thick.
 The fingers are all the same length, with separation of
the middle and ring fingers (trident hand).

9. rhizomelic shortening of the humerus
with posterior bowing and an
incomplete glenoid fossa.

10. Image shows
inverted femoral
physes (inverted V
configuration),
which contributes to
a waddling gait.

11.  Genu varum.
Image shows
rhizomelic
shortening of the
bilateral femurs
with metaphyseal
flaring. The bones
are wide because
of unaffected
appositional
growth.

12.  thesplayed and
cupped metaphyses as
well as the shortening of
the leg

13.  the
short, thick
tubular bones.

14.  characteristictrident hand, with separation of the
third and fourth digits. The fingers are all the same
length.

15. Spinal
 Posterior vertebral scalloping
 Progressive decrease in interpedicular
distance in 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
 Increased angle between sacrum and
lumbar spine
 The lumbar lordosis is often exaggerated,
complicated by a horizontally oriented
sacrum

16.  Note the posterior
scalloping of the
vertebral bodies.
The pedicles are
short and thick and
contribute to the
development of
lumbar spinal
stenosis. COMMENT:
These individuals are
usually
hyperlordotic.

17.  Notethe increased disc
height and bullet-nosed
vertebrae.

18.  19 year old achondroplastic patient.
 Findings include: short pedicles, posterior vertebral
scalloping, thoracolumbar kyphosis, tombstone iliac wings

19. Pelvis and hips
 The entire pelvis is small(trident pelvis)
 The ilia are shortened caudally and flattened,
with small sciatic notches.
 The acetabula are horizontally oriented
(decreased acetabular angle), and there is
excessive thickening of the Y cartilage.
 The pelvis assumes a characteristic
champagne glass appearance.
(champagne glass type pelvic inlet)
 Small squared (tombstone) iliac wings
 Short sacroiliac notches

20.  The
characteristic
champagne
glass pelvis. The
ilii are short and
flat. Also observe
that the
acetabular roofs
are horizontally
oriented. Of
incidental
notation is
retention of
barium in two
colonic
diverticula
(arrows).

21. Chest
 anterior flaring
of ribs
 anteroposterior
narrowing of
ribs
 Shortened ribs

22. Differential diagnosis
 Achondrogenesis
 Camptomelic dysplasia
 Thanatophoric dysplasia
 Ellis-van Creveld syndrome -
chondroectodermal dysplasia

23. Pseudoachondroplasia
 Pseudoachondroplasia (PSACH) is a rare
form of short-limbed dwarfism with a
reported prevalence of approximately
four per million individuals. Autosomal
dominant inheritance has been reported
in most cases.
 Usually children at 2–3 years of age
presents with delay in walking or waddling
gait.

24. Physical examination
 reveals normal facies and intelligence.
The adult height usually ranges between
82–130 cm with marked shortening of
limbs.
 Associated deformities include genu
valgum/varus, genu reccurvatum, limited
elbow extension, kyphoscoliosis or
increased lumbar lordosis, and joint laxity
with secondary osteoarthritic changes.

25. The radiographic features
 include dramatically rhizomelic type of dwarfism, with flared
and irregular metaphysis.
 Epiphyses are small, irregular, and often fragmented with
delayed appearance, and the femoral capital and humeral
epiphysis are most affected. Medial beaking of the femoral
neck is one of the characteristic features.
 The hand and foot bones (metacarpals, metatarsals and
phalanges) are broad and shortened with small and
rudimentary epiphysis. Madelung deformity can be seen.
 Pelvis appears squared with broad iliac wings and narrow
sacrosciatic notches.
 The acetabulum is poorly formed with horizontal roofs.
 The skull and facial bones are normal.
 Platyspondyly, anterior “beaking,” persistent oval shape,
odontoid dysplasia, and disc space widening may also be
present. Interpedicular distance is characteristically normal.

26. 8 year old.
 (a) Radiograph (AP view)
of pelvis reveals squared
ilium, narrow sacrosciatic
notches, dysplastic
acetabuli, and a
characteristic medial beak
at femoral neck.
 (b) Radiograph (AP view)
of upper limb showing
markedly flared and
irregular metaphysis with
deformed, irregular, and
fragmented epiphyses.
 (c) Lateral radiograph of
Lumbosacral spine
showing platyspondyly
with central beaking.
 (d) Radiograph (AP view)
of hand shows
underdeveloped carpals
with short and broad
metacarpals and
phalanges

27. 2 year old.
(a) Radiograph (AP view) of pelvis showing
milder changes compared to previous case.
(b) Radiograph (Lateral view) of Lumbosacral
spine (in younger child) showing
platyspondyly

28.  in spine platyspondyly, flame-
shaped vertebrae with anterior
projections. The interpedicular
distance does not progressively
decrease in the lumbar spine. At
CV junction odontoid hypoplasia.

29.  Exaggerated thoracolumbar kyphosis, mild to moderate scoliosis.

30. Flaring of the metaphyses. angulations.

31. In hip,
shallow
acetabulum
with hip
dysplasia
and
secondary
degenerativ
e changes.
Marked
dysplasia of
the femoral
head, short
neck of
femur.
Flattend
femoral
head may
show
fragmention.

32.  In knee Genu varum deformity.

33.  Normal skull radiograph.

34.  Short stubby metacarpals

35. Differential diagnoses
 Achondroplasia
 Morquio syndrome
 Hypothyroidism
 Multiple epiphyseal dysplasia (MED)
 Spondyloepiphyseal dysplasia (SED)
congenita

36.  Achondroplasia patients have a large head
with prominent frontal bones and a narrow
base. The interpedicular distance decreases
caudally in lumbar region but with normal
vertebral height. The pelvis is square with small
sciatic notches and shows classic
champagne glass appearance. PSACH
patients, on the other hand, have a normal
skull and interpedicular distance with marked
platyspondyly.

37.  In MED, epiphyses are abnormal, but
there are near normal metaphysis, pelvis,
and spine unlike in PSACH, where
metaphyseal and spinal changes are
more marked.
 In SED, congenital epiphyseal changes
mimic PSACH; however, spinal changes
are more pronounced with marked
kyphoscoliosis. Hip joints are affected
disproportionately in relation to nearly
normal distal limbs.

38.  In Morquio syndrome, the spinal changes are
prominent with flat vertebrae, central
beaking, and marked kyphosis. Metacarpals
show proximal tapering with short, wide
tubular bones. Epiphysis may be affected, but
metaphyseal widening and irregularity as
seen in PSACH is absent.
 In hypothyroidism, epiphyseal changes may
simulate PSACH, but the dwarfism is
symmetrical involving all long bones with
slender shafts and endosteal scalloping.
Metaphyses are normal. The skull shows
wormian bones, J-shaped sella in young
children, and cherry sella in older children.
Bullet-shaped lumbar vertebra with kyphosis is
seen, but general platyspondyly is lacking.
Classical pelvis changes of PSACH are also
lacking

39. Hypochondroplasia
 Hypochondroplasia, a chondrodystrophy
with autosomal dominant inheritance, is a
form of short stature.
 FGFR3 gene mutation is known to be
associated with hypochondroplasia.
 Infants are usually born of low-normal
weight and length, but in early childhood
fall far below the average for their age. 10-
12% have mental retardation.

40. Physical features
 The most common clinical features of hypochondroplasia:
 Short stature (adult height 128 - 165 cm; 2-3 SD below the mean in
children)
 Stocky build
 Shortening of the proximal (rhizomelia) or middle (mesomelia)
segments of the extremities
 Limitation of elbow extension
 Broad, short hands and feet (brachydactyly)
 Generalized, mild joint laxity
 Large head (macrocephaly) with relatively normal facies
 Less common but significant clinical features:
 Scoliosis
 Bow legs (genu varum) (usually mild)
 Lumbar lordosis with protruding abdomen
 Mild to moderate intellectual disability
 Learning disabilities
 Adult-onset osteoarthritis

41. .
Radiologic features
 Shortening of long bones with mild metaphyseal flare
(especially femora and tibiae)
 Narrowing of or failure to widen in the inferior lumbar
interpedicular distances
 Mild to moderate brachydactyly
 Short, broad femoral neck
 Squared, shortened ilia
Less common but significant radiologic features:
 Elongation of the distal fibula
 Shortening (anterior-posterior) of the lumbar pedicles
 Dorsal concavity of the lumbar vertebral bodies
 Shortening of the distal ulna
 Long ulnar styloid (seen only in adults)
 Prominence of muscle insertions on long bones
 Shallow "chevron" deformity of distal femur metaphysis
 Low articulation of sacrum on pelvis with a horizontal
orientation
 Flattened acetabular roof

42.  Short
and broad femoral neck. Squared
and shortened iliium and acetabular roof.

43.  Lumbar stenosis.
Intrapedicular
distance narrowerat
L4 than L3.

44.  Spinal
stenosis.
Lateral radiograph
lumbar spine shows
narrow A-P
diameter of the
lumbar spine.

45. Differential diagnosis
 Mild achondroplasia
 Mild forms of metaphyseal chondrodysplasias
 Mild forms of mesomelic dwarfism
 Mild forms of spondylo-epiphyseal-metaphyseal
dysplasias
 Leri-Weill dyschondrosteosis
 Pseudohypoparathyroidism and
pseudopseudohypoparathyroidism
 Short stature caused by disturbances in the growth
hormone axis
 Constitutive short stature