Mutated FGF-23 prevents proteolysis by PHEX.
Imaging features by modalities
Radiographs
In adults:
.
Osteomalacia,
.
Looser’s zones or pseudofractures,
.
Insufficiency fractures ,
.
Vertebral compression deformities
In pediatric patients with features of rickets:
.
Metaphyseal cupping
.
Bowing lower extremities
.
Knock-knee deformity
CT & MR
-Ability to detect phosphaturic tumors by their contrast-enhancing features and MR characteristics (low to isointense T1-weighted signal and bright T2-weighted intensity).
-Limitations for small phosphaturic tumors with regards to CT radiation exposure and large amount of CT and MR “search and destroy” generated images.
Technetium-99m MDP Bone Scintigraphy
-Whole body bone scan shows features corresponding to radiographic findings mentioned above: insufficiency fractures involving the osseous pelvic girdle,
multiple vertebral compression injuries and bilateral rib fractures.
-Bone scintigraphy rarely detects the osseous culprit phosphaturic tumor,
which is difficult to distinguish from coexisting diffuse osteomalacia-related bone injuries
Technetium-99m sestamibi has been used in the evaluation of phosphaturic tumors based on their hypervascularity. Accumulation of sestamibi in this lesion may be also related to the increased concentration of mitochondria.
Somatostatin receptor scintigraphy,
with indium-111 octreotide,
allows visualization of phosphaturic neoplasms with subtype-2 mRNA and to a lesser extent subtype-5 mRNA receptor expression.
False negative findings may be related to a small size of the lesion,
lack of somatostatin receptors or adjacent location of bone fracture.
F-18 FDG PET/CT combines the functional detection of lesions based on their high glucose metabolism with anatomic three-dimensional cross-sectional imaging. This modality provides an exquisite pre-operative mapping of phosphaturic tumors at unanticipated sites thus facilitating their resection and the cure of oncogenic osteomalacia.
Ga-68 DOTATATE PET/CT detects lesions based on their expression of Somatostatin Receptor 2 with anatomic three-dimensional cross-sectional imaging and combines that functional imaging with anatomic three-dimensional cross-sectional imaging of computed tomography.
As with F-18 FDG PET/CT,
it provides exquisite pre-operative mapping,
but is unique as the uptake is specific to neuroendocrine tumors.
With PET/CT high resolution imaging,
Ga-68 DOTATATE is replacing the SPECT/CT imaging with In-111 Octreotide in the clinical practice.