A 68-year-old white man presented with worsening lower-back pain. An abnormality on the thoracolumbar spine radiographic study prompted further imaging evaluation, which included a skull radiograph.
A 68-year-old white man presented with worsening lower-back
pain. An abnormality on the thoracolumbar spine radiographic study
(Figure 1) prompted further imaging evaluation, which included a
skull radiograph (Figure 2). Upon further questioning, the patient
reported occasional throbbing left-sided headaches, which he said
were relieved temporarily with over-the-counter analgesics. He
denied any recent head trauma or known malignancy and had been in
relatively good health recently. Physical examination of the head,
neck, and back was unremarkable.
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.
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 sarcomas.
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.
Justin Q. Ly, MD
at the Department of Radiology, Wilford Hall Medical Center, San