Abstract: 3-year-old girl came to the radiology department from the
genetics clinic, where she was referred because of widening of the
bonesin her legs. There was concern that other bones were involved.
The patient was delivered by spontaneous vaginal delivery at term,
after an uneventful pregnancy and weighed 6 pounds, 12 ounces.
She had a history of genu valgum, which was noticed at 13 months
of age. Her prior medical and surgical histories were not
significant. There was no history of bony fractures, hip
dislocation or mental retardation.
She had a maternal half-sister who was 12 years old and healthy
and the patient also had a younger 2-year-old full sister who had
started to show the same signs of widening of the leg bones and
There was no history of consanguinity. Her developmental history
was also within normal limits.
Physical examination revealed her weight to be slightly beneath
the 50th percentile and her height was just above the 50th
She had no facial dysmorphism, with no obvious clinodactyly,
polydactyly or syndactyly. No dental caries were noted. There was
noevidence of scoliosis or platyspondyly.
Pyle-type metaphyseal dysplasia (or Pyle's disease)
Differential diagnosis: Chronic anemia (e.g. Sickle-cell
disease), osteopetrosis, Gaucher disease and Niemann-Pick
Skeletal survey revealed a mildly hyperostotic skull, with mild
frontal bossing. There was metaphyseal widening of the long bones.
Lateral bowing of the tibiae produced an S-shaped configuration
(Figures 1C and 1D). However, the spine was normal (Figure 5).
Pyle-type metaphyseal dysplasia is an extremely uncommon and
rare genetic skeletal disorder inherited in an autosomal-recessive
pattern (Gorlin et al. 1970.1 This means that both
parents are unaffected, but there is a 25% chance the affected
alleles will pass to a developing embryo and produce the widened
biones. The actual gene or genetic defect is unknown, and cannot,
therefore, be tested. The striking radiographic manifestations
contrast with the relatively normal clinical features. Genu valgum
is the only consistent abnormality.
Pyle first described the skeletal anomaly in 1931. Less than 35
genuine cases have since been reported.
Pyle-type metaphyseal dysplasia is clinically, radiographically
and genetically distinct from craniometaphyseal dysplasia, a
relatively common condition with which it has been confused.
Pyle-type metaphyseal dysplasia must be distinguished and separated
from craniometaphyseal dysplasia, for prognostication, since
deafness, facial paralysis and occasional impairment of vision may
result from cranial nerve compression in the latter, whereas, they
are unusual in the former.1,2
Bone fragility and spinal malalignment or scoliosis is
infrequent but are well-documented complications.3,4
Carious and misplaced teeth,4 and patchy sclerosis of
the cranial vault with associated moderate supraorbital prominence
and prognathism are features that have been reported in Pyle-type
Genetic considerations are also relevant, as craniometaphyseal
dysplasia is transmitted as an autosomal dominant, whereas,
inheritance in Pyle-type metaphyseal dysplasia is autosomal
In Pyle-type metaphyseal dysplasia there are gross abnormalities
of the tubular bone modeling, with associated mild sclerosis of
the cranium. Prominent radiographic features in the long tubular
bones consist of splaying of the metaphyses with relative
constriction of the diaphyses. The changes are most obvious in the
distal femora, where the appearance has been likened to an
"Erlenmeyer flask." Failure of modeling may also be seen in the
short tubular bones, with widening of the medial ends of the
clavicles, sternal ends of the ribs and pubic bones.
In spite of the striking radiographic manifestations, there are
a few clinical stigmata and the condition has a benign course.
- Gorlin RJ, Koszalka MF, Spranger J. Pyle's disease (familial
metaphyseal dysplasia. A presentation of two cases and argument for
its separation from craniometaphysealdyslasia. J Bone Joint
Surg Am. 1970;52(2):347-354.
- Mabille JP, Benoit JP, Castera D. Dysplasie metaphysaire de
Pyle. Ann of Radiol (Paris). 1973;16:723-730.
- Pyle, E. A case of unusual bone development. J Bone Joint
Surg Am. 1931;13:874-876.
- Bawkin, H, Krida, A. Familial metaphyseal dysplasia.
American Journal of Diseases of Children.
- Raad MS, Beighton, P.Autosomal recessive inheritance of
metaphyseal dysplasia (Pyle disease). Clin Genet. 1978;14: