Oxalate nephropathy in systemic sclerosis: Case series and review of the literature.

OBJECTIVE: To increase awareness of oxalate nephropathy as a cause of acute kidney injury (AKI) among systemic sclerosis patients with small intestinal dysmotility and malabsorption, and to prompt consideration of dietary modification and early treatment of predisposing causes of oxalate nephropathy in this population. METHODS: Two cases of biopsy-proven oxalate nephropathy were identified among systemic sclerosis patients in the course of direct clinical care. Subsequently, a retrospective search of the Johns Hopkins Pathology databases identified a third patient with systemic sclerosis who developed oxalate nephropathy. RESULTS: Among the three patients with qualifying biopsies, all three had systemic sclerosis with lower gastrointestinal involvement. All three presented with diarrhea, malabsorption, and AKI. In two of the three patients, diarrhea was present for at least 2 years before the development of AKI; in the third, incidental oxalate nephropathy was noted 3 years before she developed AKI and extensive oxalate nephropathy in the setting of a prolonged mycobacterium avium-intracellulare enteritis. In the first case, oxalate crystals were present by urinalysis months before diagnosis by biopsy; in the second, hyperoxaluria was diagnosed by urine collection immediately after; and in the third, oxalate crystals had been noted incidentally on post-transplant renal biopsy 3 years before the development of fulminant oxalate nephropathy. All three patients died within a year after diagnosis. CONCLUSIONS: Patients with systemic sclerosis and bowel dysmotility associated with chronic diarrhea and malabsorption may be at risk for an associated oxalate nephropathy. Regular screening of systemic sclerosis patients with small bowel malabsorption syndromes through routine urinalysis or 24-h urine oxalate collection, should be considered. Further studies defining the prevalence of this complication in systemic sclerosis, the benefit of dietary modification on hyperoxaluria, the effect of treating small intestinal bowel overgrowth with antibiotics, and the effectiveness of probiotics, calcium supplements, or magnesium supplements to prevent hyperoxaluria-associated renal disease in these patients, are warranted.

Dietary intake of micronutrient antioxidants in relation to blood levels in patients with systemic sclerosis.

OBJECTIVE: To document habitual intakes of micronutrient antioxidants in patients with systemic sclerosis (SSc) in light of studies reporting subnormal levels of ascorbate and selenium in this patient group. METHODS: Dietary intakes of vitamin C, selenium, alpha-tocopherol, beta-carotene, and sulfur amino acid precursors of glutathione were assessed using the 7 day weighed record in 12 patients with SSc and in 12 healthy control subjects. The intakes of the first 4 substances were examined in relation to plasma/serum levels, while intakes of sulfur amino acids were examined in relation to urinary inorganic sulfate. RESULTS: Antioxidant and sulfur amino acid intakes were similar in patients and controls, although the patients had lower levels of selenium (median 74 compared to 87 milligrams in controls; p = 0.014) and of vitamin C in plasma (median 6.0 compared to 11.1 milligrams/l in controls; p = 0.08). Inorganic sulfate concentration in urine was similar in patients and controls. CONCLUSION: Our results suggest that reduced blood levels of the water soluble antioxidants selenium and ascorbic acid in patients with SSc are not due to dietary deficiency. Other explanations must therefore be sought.

Effect of warfarin sodium therapy on excretion of 4-carboxy-L-glutamic acid in scleroderma, dermatomyositis, and myositis ossificans progressiva.

The effect of warfarin sodium on excretion of calcium, phosphorus, and 4-carboxy-L-glutamic acid (Gla) was studied in 5 patients with ectopic calcification (2 with scleroderma, 1 with dermatomyositis, and 2 with myositis ossificans progressiva). Warfarin reduced urinary excretion of Gla in all patients, but no changes in calcium and phosphorus excretion or in objective parameters of calcinosis were observed during 6-36 months of treatment. Two patients experienced hemorrhagic complications during therapy, emphasizing a hazard of long-term anticoagulation treatment. Since ectopic calcium deposits contain Gla-rich protein, suppression of Gla synthesis by warfarin sodium over a longer period may prevent deposition and allow removal of existing calcinosis deposits.