Mechanism: uncertain but there is vitamin D resistance. Some patients have a low serum phosphorus, raising the possibility of oncogenic osteomalacia or a renal tubular defect.
Clinical findings:
(1) bowing of long bones
(2) pathologic fracture
(3) nonunion in fractures, which can result in a pseudoarthrosis (false joint)
(4) lack of response to regular supplemental doses of vitamin D, but there is a good response after massive doses of vitamin D
Imaging findings:
(1) generalized rarefaction of bone with thinning of the cortex
(2) presence of fractures and pseudofractures
Differential diagnosis in NF1:
(1) periosteal erosion by neurofibroma
(2) cystic change within bone
(3) nutritional osteomalacia
(4) senile osteoporosis (in an older patient)
