Renal Transplant Unit and
1Department of Orthopaedic Surgery, Hospital Clinic, University of Barcelona, Barcelona, Spain
SIR, Tumoral calcinosis is an unusual benign condition characterized by the presence of slow-growing calcified periarticular soft tissue masses composed of calcium salts and usually located around the large joints. There is a primary form (idiopathic or hereditary), but it can also be found in a wide variety of conditions, such as primary hyperparathyroidism, vitamin D intoxication, scleroderma and uraemic tumoral calcinosis [1]. It is usually asymptomatic and nerve compression is rare.
We describe an unusual case of a patient on long-term haemodialysis for chronic renal failure who presented carpal tunnel syndrome (CTS) secondary to extensive uraemic tumoral calcinosis that affected her wrist and hand.
A 25-yr-old woman with chronic renal failure due to systemic lupus erythematosus, who had been receiving chronic haemodialysis since 1989, required medical attention for pain, loss of strength and paraesthesia in the territory of the median nerve of the right hand. Physical examination disclosed several tumours on the right wrist and the proximal part of the palmar surface, of firm consistency and painless when touched. Phalens test and Tinel's sign in the right wrist were positive.
Conventional radiographs revealed a lobulated, homogeneous, densely calcified mass on the carpus and the metacarpus of the right hand. Computed tomography (CT) showed a large calcified mass extending through the carpal tunnel to the proximal region of the second, third and fourth metacarpals (Fig. 1). Magnetic resonance imaging (MRI) disclosed a mass of 4x3.5 cm occupying the carpal tunnel and the thenar eminence with a low signal density area on T1-weighted sequences and with a well-defined wall.
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Calcifications in the wrist and thenar region of the right hand were removed by surgery. Microscopy showed numerous calcified masses surrounded by granulation tissue with histiocytes and some multinucleated cells, and tumoral calcinosis was diagnosed. The duration of dialysis was increased, hyperphosphataemia was corrected and calcitriol was suspended, thereby obtaining a reduction in calciumphosphorus product. Parathyroidectomy was performed. The paraesthesia disappeared in the early period after surgery and electrophysiological data 3 months later were normal. No recurrence of tumoral calcinosis was documented after a 14-month follow-up.
The pathogenesis of uraemic tumoral calcinosis is not well understood. Precipitation of calcium phosphate salts occurs when the solubility of calciumphosphorus product reaches a critical value (usually CaxP >70). In the past, the most frequent cause of this increase was severe uncontrolled hyperparathyroidism. Nowadays, this increase in calciumphosphorus product is caused mainly by iatrogenic hypercalcaemia and/or severe hyperphosphataemia of multifactorial aetiology: excessive administration of calcitriol or calcium carbonate, inadequate phosphorus-chelating therapy and insufficient dialysis [2].
The lesion consists of encapsulated, multilobulated masses of variable size, containing a creamy toothpaste-like material. The clinical manifestations are round, progressively growing, periarticular tumours with a firm consistency, usually located around the large joints [3]. Radiographs reveal lobulated, homogeneous, densely calcified periarticular masses with normal joint spaces. CT can disclose the presence of fluid-calcium levels (sedimentation sign) and MRI shows low-signal density on T1-weighted sequences. The radiological characteristics allow tumoral calcinosis to be distinguished from other diseases that produce soft tissue calcification [1]. Treatment of uraemic tumoral calcinosis consists in correction of the factors responsible for the increased calciumphosphorus product. Surgery is advised when the masses cause symptoms. Renal transplantation or an increase in dialysis may lead to reduction of masses by inducing a negative calcium balance [2].
Nerve compression due to uraemic tumoral calcinosis is uncommon in dialysis patients. We recently described a patient with ulnar nerve compression caused by uraemic tumoral calcinosis in Guyon's canal [4] and another with a giant uraemic tumoral calcinosis in the left elbow with compression of the cubital nerve [5]. In patients undergoing long-term dialysis, the development of CTS is well recognized and, less frequently, cubital nerve compression due to dialysis-related amyloidosis (ß2-microglobulin deposition) occurs [6, 7]. Nevertheless, the development of CTS secondary to tumoral calcinosis is very uncommon. To date, CTS due to idiopathic tumoral calcinosis has been described only in patients without renal disease [8, 9] and no cases have been described in dialysis patients.
In conclusion, uraemic tumoral calcinosis is an uncommon aetiology of secondary CTS that has not been reported in a dialysis patient until now.
Notes
Correspondence to: F. Cofan, Renal Transplant Unit, Hospital Clinic, Villarroel 170, 08036 Barcelona, Spain.
References
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