King Edward Memorial Hospital - Departments: Radiology

Radiology

Case of the Month

Case No. :	03
Month :	March
Year :	1999
Contributor :	Dr. Joban Babhulkar

Other Cases

Presenting Radiograph

Differential Diagnosis

Laboratory Investigations

Clinical Profile:

Fig.1

A 28 year old man presented with swelling of the upper third of the right tibia and low backache since 3 years. There was no history of trauma or of tuberculosis or contact with tuberculosis.
A plain films of the right leg was obtained.

Presenting Radiograph:

Radiographs of the left leg shows generalised osteopenia with multiple, well defined, osteolytic, expansile lesions eccentrically located in the shafts of tibia and fibula. All lesions have narrow zones of transition. Similar lesions are also noted in the metaphyseal region of the upper end of the tibia. There was no fracture seen.

Differential diagnosis:

The narrow zones of transition is suggestive of a benign lesion. A single lesion in the middle third of tibia should raise the possibility of an adamantinoma. However, the multiplicity of lesions mitigates against this diagnosis. For the same reason, other benign primary osteolytic lesions (tumors) are also unlikely. Therefore, a systemic disease or metastasis should be considered. The latter can be discounted on the basis of the narrow zones of transition. Of the systemic diseases, histiocytosis, fibrous dysplasia and hyperparathroidism (HPT) are most likely. The lesions of histiocytosis classically have bevelled edges, which none of these lesions have and are seldom as expansile as these. Lesions of fibrous dysplasia are associated with sclerosis and not pure osteolysis as seen here - the latter is classical of brown tumors in HPT and this is the most likely diagnosis.

Thus a skeletal survey is indicated.

Fig.2

A radiographs of both hands with wrist joints show subperiosteal resorption of bone especially along the radial aspect of the proximal and middle phalanges of the index and middle fingers. There are associated intracortical lucencies in the second metacarpals and in the 2nd and 3rd proximal phalanges.

Fig.3

The radiograph of the skull showed osteopenia with a speckled appearance - the so called "pepper pot skull". The mandible also showed absence of lamina dura around the teeth

Fig. 4

Fig.5

The film of the pelvis with both hip joints showed severe osteopenia. The pelvis is also deformed. Brown tumors are seen in the pubic rami.

Laboratory investigations:

Serum calcium= 12 mg% ( N= 9-10 mg%)

Serum phosphorus=10.6 mg%

Alkaline phosphatase was raised

Serum parathormone was raised = 848 ng/L

USG and CT of the neck revealed a left parathyroid adenoma.

A diagnosis of primary hyperparathyroidism due to a paratyroid adenoma was thus made.

Case Discussion:

Parathormone (PTH) secreted by the 4 parathyroid glands has the following effects on calcium metabolism:
1. It increases bone resorption of calcium and thus increases the serum calcium.
2. It increases the renal reabsorption of calcium.
3. It promotes the change of vitamin D3 from its inactive to active form.
4. It increases the phosphate excretion from kidneys thus decreasing the serum phosphorus.

Primary hyperparathyroidism occurs as a result of abnormality in one or more parathyroid glands.

Causes of autonomous hyperfunction:
1.Diffuse hyperplasia 10-40%
2.Single adenoma 50-80%
3.Multiple adenomas 10%

Serum PTH levels are high along with hypercalcemia and hypophosphatemia as against secondary hyperparathyroidism.

PTH influences all 3 types of bone cells- osteoclasts , osteoblasts and osteocytes.There is mobilisation of calcium from the bone and extensive bone remodelling.

Bone resorption is characterised as follows:

Subperiosteal:
Virtually diagnostic of hyperparathyroidism. Seen most frequently along the radial aspects of the middle phalanges of the index and middle fingers. Additional sites include the phalangeal tufts, medial aspect of proximal portion of the tibia, humerus and femur, superior and inferior margins of the ribs and the lamin dura.
DD: focal areas of subperiosteal resorption seen adjacent to a variety of soft tissue processes.

Intracortical:
Osteoclactic resorption within cortical Haversian canals produce intracortical linear striations , best seen in the cortex of the second metacarpal. It is almost always associated with subperiosteal resorption.
DD: acromagaly.

Endosteal:
Pocket like or scalloped defects along the inner margin of the cortex, particularly in the hands.
DD: multiple myeloma.

Subchondral:
Seen in the sacroiliac, sternoclavicular and acromioclavicular joints, symphysis pubis and discovertebral junctions. Osseous erosion and reactive new bone formation produce a " pseudo widening of the sacroiliac joint space.
DD: similar lesions are seen in osteoporosis, septic arthritis, AVN, crystal induced arthropathy.

Trabecular:
In the skull, the diploe is replaced by connective tissue containing newly formed trabeculae and definition between the diploic portion of the skull and the inner and outer tables is lost. An osteopenic and speckeld appearance of the skull is termed " pepper pot" or a "salt and pepper" skull.

Subligamentous:
Osseus resoption occurs at sites of tendon and ligament attachment to bone.
DD: ankylosing spondylitis and related disorders.

Brown tumors:
They represent localised accumulations of fibrous tissue and giant cells, which can replace bone and may produce osseous expansion. They appear as single or multiple, well defined lesions, commonly affecting the facial bones, pelvis, ribs and femora. With treatment. Brown tumours may demonstrate healing with increased radiodensity.
DD: Giant cell tumour, Fibrous dysplasia.

Bone Sclerosis:
Usually occurs in patients with renal osteodystrophy and secondary hyperparathyroidism. In primary hyperparathyroidism, bone sclerosis may be localised or patchy in distribution, in the mataphyseal regions of long bones , the skull or vertebral endplates.

Rheumatic Manifetations of Hyperparathyroidism:

Subchondral resorption leading to collapse and fragmentation of bone.

Subperiosteal resoption leading to periarticular erosions.

Conclusion:

In any suspected case of hyperparathyroidism , it is essential to find out whether it is primary or secondary hyperparathyroidism, since primary hyperparathyridism is totally cured by removal of the hyperfunctioning gland. Thus in case of any doubt, it is essential that the patient undergoes the entire array of investigations, to prove or disprove an abnormally functionig parathyroid gland.