Age / Sex : 8 / F

Chief complaint : incidentally found bone mass


What is your diagnosis?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).


Courtesy : 이민희 (Lee Min Hee), 울산의대 서울아산병원 (Asan Medical Center, University of Ulsan College of Medicine)

Ischiopubic synchondrosis (asymmetrically enlarged, or asymmetric closure), left

Discussion

Findings:

Plain radiograph- A focal, expansile, radiolucent bone lesion in left pelvic bone, ischiopubic junction; the distinct, tumor-like appearance

MRI

- signal alteration and contrast enhancement of the bone marrow (hyperintense on FST2WI and STIR, hypointense on T1WI)

- band-like hypointense area on all sequences in the center with fusiform swelling of ischiopubic synchondrosis

Differential Diagnosis: It should not be misinterpreted as an infection, traumatic, or neoplastic process.

Discussion:

• Enlarged ischiopubic synchondrosis; atypical but physiologic ossification patterns. May be regarded as “Temporary joint”.


• Causes; not well explained.

A physiologic reaction to mechanical strain, causing delayed ossification.

In cases of asymmetric enlargement, left enlargement was more common and all with right-footed (in the study by Herneth AM).   

References:

Herneth AM, Philipp MO, Pretterklieber ML, et al. Asymmetric closure of ischiopubic synchondrosis in pediatric patients: correlation with foot dominance. AJR 2004;182:361-365