CASE SUMMARYA 3-year-old girl came to the radiol-

ogy department from the genetics clinic,where she was referred because ofwidening of the bones in her legs. Therewas concern that other bones wereinvolved.

The patient was delivered by sponta-neous 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 histo-ries were not significant. There was nohistory of bony fractures, hip disloca-tion or mental retardation.

She had a maternal half-sister whowas 12 years old and healthy and thepatient also had a younger 2-year-oldfull sister who had started to show thesame signs of widening of the leg bonesand genu valgum.

There was no history of consanguin-ity. Her developmental history was alsowithin normal limits.

Physical examination revealed herweight to be slightly beneath the 50thpercentile and her height was just abovethe 50th percentile.

She had no facial dysmorphism,with no obvious clinodactyly, poly-dactyly or syndactyly. No dental carieswere noted. There was no evidence ofscoliosis or platyspondyly.

IMAGING FINDINGSSkeletal survey revealed a mildly

hyperostotic skull, with mild frontalbossing. There was metaphyseal widen-ing of the long bones. Lateral bowing ofthe tibiae produced an S-shaped config-uration (Figures 1C and 1D). However,the spine was normal (Figure 5).

DIAGNOSISPyle-type metaphyseal dysplasia (or

Pyle’s disease)

Differential diagnosis: Chronic ane-mia (e.g. Sickle-cell disease), osteopetro-sis, Gaucher disease and Niemann-Pick disease.

DISCUSSIONPyle-type metaphyseal dysplasia is

an extremely uncommon and raregenetic skeletal disorder inherited in anautosomal-recessive pattern (Gorlin etal. 1970.1 This means that both parentsare unaffected, but there is a 25%

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Adejimi O. Adeniji, MD

Pyle-type metaphyseal dysplasia

FIGURE 1. “Erlenmeyer flask” femoral deformity in the right (A )and left (B) femurs with lat-eral S-shaped bowing of the right (C) and left (D) tibiae.

A B C D

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chance the affected alleles will pass to adeveloping embryo and produce thewidened biones. The actual gene orgenetic defect is unknown, and cannottherefore be tested. The striking radi-ographic manifestations contrast withthe relatively normal clinical features.Genu valgum is the only consistentabnormality.

Pyle first described the skeletalanomaly in 1931. Less than 35 genuinecases have since been reported.

Pyle-type metaphyseal dysplasia isclinically, radiographically and geneti-cally distinct from craniometaphysealdysplasia, a relatively common condi-tion with which it has been confused.Pyle-type metaphyseal dysplasia must

be distinguished and separated fromcraniometaphyseal dysplasia, for prog-nostication, since deafness, facialparalysis and occasional impairment ofvision may result from cranial nervecompression in the latter, whereas,they are unusual in the former.1,2

Bone fragility and spinal malalign-ment or scoliosis is infrequent but are

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FIGURE 2. Undertubulation of both humeri in their proximal two-thirds.

FIGURE 3. Undertubulation of the distaltwo-thirds of the radius and ulna. Inciden-tally noted, is lucency in the left wrist (rightarrow), which could be either due to a vac-uum phenomenon or artifactual.

A B

A B A B

FIGURE 4. Skull radiographs, AP and lateral views. There is mild sclerosis of the skull basewith prominence of the frontal bones

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well-documented complications.3,4

Carious and misplaced teeth,4 andpatchy sclerosis of the cranial vaultwith associated moderate supraorbitalprominence and prognathism are fea-tures that have been reported in Pyle-type metaphyseal dysplasia.3

Genetic considerations are also rel-evant, as craniometaphyseal dysplasiais transmitted as an autosomal domi-nant, whereas, inheritance in Pyle-typemetaphyseal dysplasia is autosomalrecessive.5

In Pyle-type metaphyseal dysplasiathere are gross abnormalities of thetubular bone modeling, with associatedmild sclerosis of the cranium. Promi-nent radiographic features in the longtubular bones consist of splaying of themetaphyses with relative constrictionof the diaphyses. The changes are mostobvious in the distal femora, where theappearance has been likened to an“Erlenmeyer flask.” Failure of model-ing may also be seen in the short tubu-lar bones, with widening of the medialends of the clavicles, sternal ends ofthe ribs and pubic bones.

CONCLUSION:In spite of the striking radiographic

manifestations, there are a few clinicalstigmata and the condition has abenign course.

REFERENCES1.Gorlin RJ, Koszalka MF, Spranger J. Pyle’s dis-ease (familial metaphyseal dysplasia. A presenta-tion of two cases and argument for its separationfrom craniometaphyseal dyslasia. J Bone JointSurg Am. 1970;52(2):347-354.2. Mabille JP, Benoit JP, Castera D. Dysplasiemetaphysaire de Pyle. Ann of Radiol (Paris).1973;16:723-730.3.Pyle, E. A case of unusual bone development. JBone Joint Surg Am. 1931;13:874-876.4.Bawkin, H, Krida, A. Familial metaphyseal dys-plasia. American Journal of Diseases of Children.1937;53:1521-1527.5. Raad MS, Beighton, P. Autosomal recessiveinheritance of metaphyseal dysplasia (Pyle dis-ease). Clin Genet. 1978;14: 251-256.

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FIGURE 5. Normal lateral view of the spine.

Prepared by Adejimi O. Adeniji,MD, Divisional Chairman, Pedi-atric Radiology, John Stroger Hos-pital of Cook County, Chicago, IL.