Calcium and phosphate are present in serum at concentrations that should encourage precipitation, but ectopic mineral deposition outside of osseous tissue is rarely seen in children outside disease states. However, in ageing and some pathologies e.g. chronic kidney disease, chronic inflammatory disease and in diabetes, extra-osseous mineral deposition is common. For many years a high serum phosphate level has been considered one of the prime drivers to this event, yet evidence that modifying phosphate levels affects calcification is lacking.

Calciprotein particles ( CPP ) are a novel marker of mineral stress. High levels of CPP are found in patients with calciphylaxis, a condition associated with marked vascular calcification and a poor prognosis. We report substantial reductions in CPP levels in a dialysis patient having combined haemodialysis ( HD ) and plasma exchange ( PEx ) prior to an ABO ‐incompatible kidney transplant. We also report the effects of the same treatments combined with sodium thiosulphate ( STS ) in a patient newly diagnosed with calciphylaxis. Combining HD with intra‐dialytic STS and PEx we achieved a significant reduction in CCP with the least rebound between treatment sessions. After 6 weeks of treatment, the CPP reduction was paralleled by clinical improvement. Measurement of CPP may be an attractive marker for monitoring the effectiveness of calciphylaxis therapy.

ObjectiveWe recently showed that a urine albumin/total protein ratio (uAPR) < 0.4 identifies tubular pathology in proteinuric patients. In tubular disorders, proteinuria is usually of low molecular weight and contains relatively little albumin. We tested the hypothesis that uAPR is useful in identifying tubular pathology related to antiretroviral use in HIV‐infected patients.MethodsWe retrospectively identified urine protein/creatinine ratios (uPCRs) in HIV‐infected patients. A subset of samples had uPCR and urine albumin/creatinie ratio (uACR) measured simultaneously. We classified proteinuric patients (uPCR > 30 mg/mmol) into two groups: those with predominantly ‘tubular’ proteinuria (TP) (uAPR < 0.4) and those with predominantly ‘glomerular’ proteinuria (GP) (uAPR ≥ 0.4).ResultsA total of 618 of 5244 samples from 1378 patients had uPCR ≥ 30 mg/mmol. uAPRs were available in 144 patients: 46 patients (32%) had TP and 21 (15%) GP; the remainder had uPCR < 30 mg/mmol. The TP group had a higher fractional excretion of phosphate compared with the GP group (mean 27% vs. 16%, respectively; P < 0.01). Patients with TP were more likely to be on tenofovir and/or a boosted protease inhibitor compared with those with GP. In 18 patients with heavy proteinuria (uPCR > 100 mg/mmol), a renal assessment was made; eight had a kidney biopsy. In all cases, the uAPR results correlated with the nephrological diagnosis.ConclusionsIn HIV‐infected patients, measuring uAPR may help to identify patients in whom a renal biopsy is indicated, and those in whom tubular dysfunction might be an important cause of proteinuria and which may be related to antiretroviral toxicity. We suggest that this would be useful as a routine screening procedure in patients with proteinuria.