The lateral skull radiograph shows a large radiolucent lesion with
"geographic" margins that involves a large portion of the
frontoparietal and temporal skull calvarium (Figure 2). This
appearance is known as "osteoporosis circumscripta" and is
consistent with Paget's disease. It is seen in the early or lytic
phase, when osteoclastic resorption overwhelms bone production. The
initial spine study demonstrates another characteristic finding of
Paget's disease, the "picture-frame" vertebral body, which is
secondary to severe osteoporosis centrally and a thickened,
sclerotic cortex (Figure 1). As part of the work-up, skeletal
scintigraphy was performed subsequently, showing diffuse, intense
uptake at the frontal calvarium (Figure 3), corresponding to the
lytic lesion on the skull radiograph. This scintigraphic finding is
consistent with increasing osteoblastic activity, suggesting that
the disease has progressed to a more advanced phase.
Paget's disease is a condition of uncertain pathogenesis that is
characterized by disorderly organization of bone and osseous
overgrowth. Predominantly affecting the Caucasian or Northern
European population, Paget's is characterized by three phases of
marrow cellular activity.1,2
The lytic or early phase is
marked by high levels of osteoclastic activity that overwhelm the
activity of osteoblasts, resulting in the appearance of increasing
radiolucent osseous lesions. Disease during this phase is
responsible for the "flame" appearance or the "blade-of-grass"
sign. The geographic, lytic skull lesion depicted in this patient
is a manifestation of the lytic phase of Paget's disease. The lytic
phase is followed by the mixed blastic-lytic phase, in which
increasing levels of osteoblastic activity (evidenced by increasing
sclerosis) coexist with the ongoing osteoclastic activity,
resulting in a mixed sclerotic and lytic appearance to the affected
bone. It is during this particular phase that trabecular
coarsening, cortical thickening, and generalized osseous
en-largement occur. The third or late phase is char-acterized by
gradual diminishment of both osteoclastic and osteoblastic
activity, with residual smoldering osteoblastic activity. The
affected long bones are weak and can bow during this phase. At any
point in time, different involved bones may be in different
cellular stages. Most patients are asymptomatic at
Laboratory markers of disease activity are
serum alkaline phosphatase and urinary hydroxy-proline, which are
usually elevated when bone destruction is occurring. The major
complications of Paget's disease include full-thickness long bone
fractures, insufficiency fractures, and development of bone
The goal of treatment is to reverse negative
bone balance, using agents that inhibit bone resorption and
stimulate growth, such as calcitonin or the bisphosphonates.
Paget's disease of bone is a chronic osseous disease
characterized by bony enlargement or deformity and bone fragility.
It may involve one or more regions of the skeleton and commonly
presents as pain. Various imaging appearances are possible and
often suggest the phase of cellular activity at the time of
imaging. Most cases are diagnosed by conventional radiography.
Prepared by Justin Q. Ly, MD at the
Department of Radiology, Wilford Hall Medical Center, San Antonio,
1. Dalinka MK, Aronchick JM, Haddad JG Jr. Paget's disease.
Orthop Clin North Am.
2. Mirra JM, Brien EW, Tehranzadeh J. Paget's disease of bone:
Review with emphasis on radiologic features, part I. Skeletal
3. Boutin RD, Spitz DJ, Newman JS, et al. Complication in
Paget's disease at MR imaging. Radiology.
4. Kaufman GA, Sandarac M, McDonald DJ. Magnetic resonance
imaging in symptomatic Paget's disease. Skeletal Radiol.