Teaching Case

A 54-year-old man with chronic renal failure was admitted to a district general hospital with a three week history of left hip pain and reduced mobility of the joint. He had also noticed a bony lump growing over the sternal notch over the course of several months.

1) Plain radiograph pelvis: Revealed a large (10cm x 6.5cm) area of calcification adjacent to the left greater trochanter [Fig. A].
2) CT Pelvis: Demonstrates peri-articular multilobulated calcification anterolateral to the left greater trochanter. Multiple fluid calcium levels, demonstrating the sedimentation sign may be seen [Fig. B].
3) CT Thorax:  Revealed a 3cm x 3cm calcification adjacent to the sternum. [Fig. C].
4) Nuclear medicine scan:  demonstrated a focus of retained radiotracer in the region of the lower pole of right lobe of the thyroid gland suggestive of a parathyroid adenoma. [Fig. D].

Background:
Secondary tumoral calcinosis involves extensive calcification of periarticular tissues and is often associated with chronic renal failure, presenting as a palpable cutaneous mass that is usually found in the extensor aspects of the periarticular regions of hips, knees, elbows, shoulder, and more rarely the feet, hands and spine. [1, 2, 3] This is most frequently attributed to hyperparathyroidism and disturbances of calcium-phosphate metabolism. [2]
Primary tumoral calcinosis is a radiologically and histologically indistinguishable condition seen in patients without chronic renal failure, affecting a younger subgroup of patients, and is a hereditary condition [3]. In this condition, biochemical tests of calcium-phosphate metabolism and parathyroid hormones are often normal [4]
Clinical Perspective:
A 54-year-old male patient was admitted with a three week history of left-sided hip pain, which resulted in reduced mobility and the patient had an antalgic gait. In addition, he described hard prominence over the sternal notch. He had a coronary artery bypass procedure a year back. There was no known history of trauma to either the hip or the sternum. The sternal mass was recently biopsied at another hospital , having produced a few millilitres of a creamy aspirate.

Imaging Perspective:
Plain radiography of hip demonstrated a large area of calcification. Subsequent CT Pelvis demonstrated periarticular multilobulated calcification anterolateral to the greater trochanter. A previous CT Chest was reviewed and calcification was noted juxtaposed to the sternum (X-ray Chest was not available). The case was discussed in the multidisciplinary team meeting and as the Chest CT did not show any parathyroid mass. A nuclear medicine scan was performed which demonstrated a focus of retained radiotracer in the region of the lower pole of the right lobe of the thyroid gland suggestive of a parathyroid adenoma.

Outcome:
The patient subsequently underwent a total parathyroidectomy. An Ultrasound-guided steroidal injection into the left trochanteric region  was performed and subsequent CT demonstrated complete resolution of calcification. The blood calcium levels also improved.

Teaching points:
•    Soft-tissue calcification should be considered as a cause of joint pain or bony prominence in patients with renal failure together with a broad range of differential diagnoses that have similar radiological appearances. [5, 6, 7]  
•    Tumoral calcinosis is a rare condition present in only 0.5% - 1.2% of patients with renal failure and therefore may be misdiagnosed. [5]
•    It is important to correlate radiological appearances with biochemical findings in patients who are known to have conditions causing metabolic abnormalities.

Written informed patient consent for the publication has been obtained.