High frequency of iron bone deposits in a Mexican population with renal osteodystrophy.

Renal osteodystrophy (ROD) is a multifactorial disease. Aluminium deposits have been implicated in its physiopathology but iron deposits have seldom been described. The purpose of this study was to investigate the presence of iron on the mineralization front, in 70 patients with ROD. Their mean age was 48 ± 16 years, 36 were female, 34 male, 55 were admitted on peritoneal dialysis (78.5%) and 15 to haemodialysis (21.5%), for a period of 28 ± 22 months. A bone biopsy was obtained from each patient after double tetracycline labelling. Blood samples were also obtained at the time of bone biopsy. The histomophometric analysis was performed following the criteria of Sherrard et al., with slight modifications; beside the usual stains, aluminium, iron and amyloid stainings were done on all bone specimens. Biochemical findings were: Ca 8.8 ± 0.9 mg/dl, P 6.1 ± 1.5 mg/dl; total alkaline phosphatase 197 ± 258; PTHm 4.9 ± 4.05 ng/ml (normal 0.4-0.7 ng/ml), calcitonin 11 ± 6 pg/ml (normal 1-26 pg/ml). Osteitis fibrosa was found in 31 patients (44.28%), mixed bone disease in two patients (2.28%); mild bone disease in 20 subjects (28.57%), adynamic bone lesion in 15 cases (21.42%) and osteomalacia in two patients (2.28%). Iron deposits were found on the mineralization front in 43 patients (61.4%); in 17, the percentage was 25%. The iron deposits in the osteitis fibrosa group were highly significant (25/31). The aluminium deposit at the mineralization front was observed in eight patients (11.4%); in all but one, the percentage of this metal was < 10%. Amyloid deposits were negative in all cases. The results show: (i) a Mexican population with ROD, present a highly significant incidence of siderosis on the bone mineralization front; (ii) in contrast, the aluminium deposits in this group of patients is lower than that reported in other series, and (iii) the spectrum of RO in this Mexican population is similar to that reported in other studies.