A middle aged man with abdominal bloating was investigated for possible malignancy.Laboratory tests showed an abnormal high level of alkaline phosphatase of 769 iu/l (normal values are between 30 and 120 iu/l). Abdominal ultrasound examination showed a fatty liver.
On the initial planar 99m Tc bone scan, there was diffuse intense tracer uptake throughout the skull with sparing of left parietal and left frontal area. Hence, the patient proceeded to have a hybrid SPECT-CT bone scan (part of our routine practice). SPECT-CT skull showed diffuse, intense activity in the skull associated with ground glass changes in the right parietal and right frontal bones, bones looked expanded with intact cortex. No other significant abnormality was identified elsewhere in the body.
Osteitis deformans was first described by an English surgeon, (sir) James Paget (1814-1899) and later known as Paget's disease. It is a condition of unknown etiology characterized by excessive and abnormal bone re-modelling. This condition is seen in elderly population. Clinical manifestations are varying, pain being the common clinical presentation. Other symptoms include- diminished mobility, unsteady gait, sense of warmth in the area affected, lethargy. If affecting the skull, patients can present with headache, hearing impairment, visual disturbance, ill-fitting dentures etc. Patients can also present with complications arising from Paget's such as fractures and osteosarcoma. High output cardiac failure is also a recognised complication due to increased blood flow through the Pagetoid bone. Often, Paget's is an incidental diagnosis with no obvious clinical symptoms. There are characteristic radiographic features of early Paget's such as "candle flame" or "blade of grass" pattern of lysis with V-shaped lucency in diaphysis of long bone, often in the tibia. In the skull, appearance is called osteoporosis circumscripta which is well-defined lysis, most commonly in frontal bone producing well-defined geographic lytic lesion
Our patient had no localising symptoms to the skull bone involved. His alkaline phosphatase
(ALP) was high; he was investigated for possible malignancy. All other blood tests including calcium and prostate specific antigen were normal. As a work up towards high ALP, a bone scan was requested by clinicians.
The imaging features of the initial osteolytic phase are most noticeable in the skull (also termed osteoporosis circumscripta) and long bones, with a subsequent osteosclerotic phase, particularly evident in the axial skeleton. 99m Tc MDP bone scan is valuable in the diagnosis of Paget's disease, as areas of skeletal involvement show increased uptake and can also document the extent of the initial lytic phase of Paget's disease, and serial bone scans may provide help in determining the effectiveness of various therapeutic agents. SPECT-CT is routinely used in our practice for further assessment of an abnormal bone scan. In comparison to the conventional planar bone scan, SPECT-CT offers three-dimensional perception and better understanding of the precise extent of involvement. Biochemical markers for Paget’s- Raised Alkaline phosphatase (marker of bone formation), raised urine deoxypyridinoline (bone absorption marker), product of collagen molecule found in bone excreted in during bone degradation. In our patient urine DDP was elevated at 11.6 (normal 2.3 – 5.4 mmol/mmol creat).
Bisphosphonates are the first line of treatment for this condition.
Paget's disease of the skull, lytic phase.
Based on the provided whole-body bone scan (99m Tc MDP) and SPECT-CT images, there is a marked uptake of the radiotracer in a localized area of the skull with an irregular shape, aligning with the early osteolytic changes characteristic of cranial Paget’s disease (“osteoporosis circumscripta”). No obvious similar multifocal lesions are observed in other skeletal structures throughout the body; the long bones of the limbs and the pelvic region may also show increased metabolic activity, but the most prominent findings on the images are concentrated in the skull region.
The patient’s laboratory results indicate a significant elevation of alkaline phosphatase (ALP), whereas other indices such as serum calcium and prostate-specific antigen remain relatively normal. Along with the increased urinary deoxypyridinoline (urine DDP), these findings suggest increased bone turnover and accelerated bone resorption.
Considering the patient’s age, clinical presentation (mainly abdominal distension without significant bone pain or cranial symptoms), markedly elevated alkaline phosphatase, and the typical cranial imaging findings on bone scan and SPECT-CT, the most likely diagnosis is Paget’s Disease (Osteitis Deformans). This case does not currently support the diagnosis of malignant bone tumors or other metabolic bone diseases. If there is any further uncertainty, additional pathology or more imaging follow-up could be used to rule out other rare conditions.
During treatment and rehabilitation, an exercise regimen should be tailored to the patient’s condition, with a gradual increase in intensity and careful avoidance of excessive load on affected bones.
Disclaimer: This report is based only on the provided medical history and imaging for reference purposes and does not replace in-person consultation or the opinion of a specialist. If there is any change in condition or additional concerns, please seek advice from professional healthcare providers or a specialist promptly.
Paget's disease of the skull, lytic phase.
