Nephrocalcinosis in a patient with Sjögren's syndrome/systemic lupus erythematosus.

Figure 1 – Abdominal X-ray of the patient showing clustered calcifications in projection of the kidneys, more evident at the right side (upper arrow identifies one of these clusters). An 8-mm right distal ureteral stone is present (lower arrow). A 46-year-old white woman has been followed in this nephrology clinic since 1995 due to recurrent nephroli-thiasis and medullary nephrocalcinosis resulting from renal tubular acidosis (urinary pH of 8 in the context of systemic normal anion gap acidosis; serum potassium at lower limit, and 24-hour urine with normocalciuria but no detectable citrate) due to Sjögren's syndrome (SS). During follow-up, her adherence to alkali therapy had been suboptimal due to gastric intolerance to Shohl's solution, potassium citrate, and sodium bicarbonate. As consequence, she had progression in her nephrocal-cinosis and passed several urinary calculi (biochemical analysis showed them to be composed of calcium phosphate and calcium oxalate). Currently, she presents normal estimated GFR (MDRD, 82 mL/min/1.73 m 2) and no significant proteinuria, despite having presented, ten years after the diagnosis of SS, onset of systemic lupus er-ythematosus (SLE) with severe diffuse proliferative class IV lupus nephritis, treated successfully with corticoste-roids and intravenous ciclophosphamide. Figure 1 shows the radiological appearance and Figure 2 depicts the ul-trasonographic aspect of the patient's nephrocalcinosis. Nephrocalcinosis is characterized by the presence of calcium deposits in the renal parenchyma; nephrolithia-sis represents calcification within the lumen of the collecting system, ureter, and bladder 1. Recent observation suggests that nephrocalcinosis and calcium nephrolithi-asis are to be considered independent pathologies, and that nephrocalcinosis may cause calcium nephrolithiasis only in certain conditions 2. Both types of renal calcifica-tion may be present in patients with SS. Nephrocalcinosis may be classified as cortical or medullary, according to the anatomic area involved 3. When associated with SS, it is typically medullary and secondary to distal renal tubular acidosis (RTA). It is believed that the renal acidifica-tion problem seen in patients with SS is due to immune-mediated loss of proton regulation 4. In addition to RTA, other disorders such as hyperparathyroidism, medullary sponge kidney, renal papillary necrosis, renal tuberculosis , hyperoxaluria, milk-alkali syndrome, sarcoidosis, immobilization, and other conditions associated with hypercalcemia and hypercalciuria, may cause medullary nephrocalcinosis. Nephrocalcinosis is usually identifiable by X-ray, but both ultrasonography (US) and computed tomogra-phy (CT) can detect it earlier than ordinary abdominal X-ray 1. US is considered to be an excellent diagnostic method for detection and monitoring of nephrocalci-nosis 3. The …