Imaging of McCune-Albright syndrome using bone single photon emission computed tomography.

ABSTRACT

UNLABELLED McCune-Albright syndrome is a rare disorder caused by a somatic, constitutively activating mutation in the gene (GNAS1) encoding the subunit of the signal transducing guanine nucleotide binding protein (G protein). The condition is characterized by polyostotic fibrous dysplasia, cafe-au-lait pigmentation and multiple endocrine hyperfunction, most commonly gonadotropin-independent precocious puberty in girls. Our patient, a 16-year-old male, with radiologically confirmed polyostotic fibrous dysplasia in cranium, thoracic and pelvic girdles, spine and extremities was studied using planar 99mTc-hydroxymethyldiphosphonate bone scintigraphy and single photon emission computed tomography. Using bone scintigraphy, an unusually extensive and asymmetric fibrous dysplasia was observed in the cranium, face, ribs, femur, humerus, ulna, tibia and the vertebral column, all on the left side. The whole body scan revealed only a few foci on the right side. Single photon emission computed tomography demonstrated extensive unilateral involvement in the base of the skull, facial bones, maxilla and mandible. All the lesions reached only the midline. These findings formed the basis of further treatment, eg. reconstructive surgery of facial asymmetry. CONCLUSION: McCune-Albright syndrome should be considered in the differential diagnosis when interpreting extensive unilateral predominance in paediatric bone scans.