ULTRASOUND DIAGNOSIS OF NEPHROCALCINOSIS DURING TREATMENT OF HEREDITARY RICKETS

Abstract

Patients with autosomal recessive vitamin D dependency, type I (ARVDD) are treated with vitamin D (Vit. D); those with X-linked hypophosphatemia (XLH) also receive oral phosphate. Since episodic hypercalcemia and hypercalciuria are complications of therapy, we performed renal ultrasounds to detect nephrocalcinosis (NC). Ten patients with ARVDD were treated from infancy with Vit. D or its analogs for a mean of 12 years (range 3-20). Two patients (treated 4.5 and 9 years) had NC (echodense renal pyramids). Mean serum calcium (9.2, 9.7 mg/dl) and UCa/creat ratios (0.15, 0.17) did not differ from patients without NC. Among 17 patients with XLH, 8 had NC. Duration of treatment in affected and unaffected patients was not significantly different (p=0.09). Therapy began before age 3 in all affected XLH patients, whereas in unaffected patients treatment began after 4 years (mean 18 years of age, p=0.001). Hypercalciuria during treatment was more frequent in XLH than ARVVD. NC was not found in untreated XLH patients despite longstanding severe disease. Estimated creatinine clearance was normal in all patients except one with XLH and severe 2° hyperparathyroidism. Water deprivation tests suggested a modest deficit of concentrating ability in many patients with XLH. Vit. D treatment of inherited rickets is associated with NC, especially in patients with hypophosphatemia treated from infancy.