Epidemiology of primary glomerulonephritis in the elderly. Report from the Italian Registry of Renal Biopsy

BACKGROUND

In the pre-biopsy era, primary glomerulonephritis (GN) was thought to pertain to children and adults. On the contrary, as renal biopsy came into clinical practice, this disease was recognized to affect the elderly too, even if the rate of such an occurrence still had to be defined. Recently, the Italian Registry of Renal Biopsy provided the opportunity to ascertain the diffusion of elderly GN in epidemiological terms.

METHODS

Eighty-eight per cent of the Italian Renal Units known to routinely perform renal biopsy reported the records of patients who underwent biopsy investigation in 1996. Thus, 2,511 cases were ranked according to patient's age, histological diagnosis and clinical manifestation. The age-related incidence of each clinicopathological picture was calculated as the ratio between the number of patients found to be affected during the year and the number of subjects at risk, namely all age-matched people living in Italy in the same year.

RESULTS

A diagnosis of primary GN was found in 1,474 records. Elderly patients accounted for 19% of those biopsy-proven primary GN, though elderly people were only 16% of the Italian population. This disproportion indicated that the incidence of primary GN in the elderly was higher than expected: actually, when compared to the incidence in the adult, it was 30.8 vs. 28.3 cases per million of population (PMP). Four histological pictures were found to be more frequent in the elderly than in the adult: membranous GN (13.4 vs. 4.2 PMP), crescentic GN (3.1 vs. 0.9 PMP), membranoproliferative GN (2.9 vs. 0.4 PMP), acute post-streptococcal GN (0.9 vs. 0.4 PMP). As for clinical manifestations, all GN-related symptoms were more frequent in the elderly than in the adult, except one: urinary abnormalities (4.5 vs.14.1 PMP).

CONCLUSION

Through the Italian Registry of Renal Biopsy, primary GN was found to occur more frequently in the elderly than in the adult. Such a high incidence would be even higher if aged patients showing urinary abnormalities regularly underwent renal biopsy. As this result reverses all previous views, many issues about elderly GN should be reconsidered.

Heterogeneity of carnitine-palmitoyltransferase deficiency

Episodes with muscle ache, rhabdomyolysis and myoglobinuria with or without associated renal insufficiency are characteristic of muscle carnitinepalmitoyltransferase (CPT) deficiency. However, patients differ from each other in many aspects, such as the kind of stimulus that triggers rhabdomyolysis, the ability to produce ketone bodies when fasting, whether the enzyme defect is localized in skeletal muscle or is general, and the nature of the enzyme defect, which may be in CPT I or CPT II or both. Studies of muscle, liver and fibroblasts from a patient with recurrent rhabdomyolysis spontaneously occurring or triggered by exercise or fever, revealed a CPT deficiency in the muscle and liver biopsy samples but normal CPT activity in cultured cells, differing from previously reported patients. The enzyme defect in muscle was evidenced by two different methods, but not when determined with a method that measures the formation of palmitoylcarnitine. The enzyme abnormality in the patient's liver was associated with a delayed ketone body production and with a dramatic increase in long-chain acylcarnitines in the serum when fasting. Moreover the patient was unable to build up ketones when fed long-chain triglycerides (LCT) but showed prompt ketogenic response when fed medium-chain triglycerides (MCT). The heterogeneity of clinical presentations and of the biochemical findings in patients with CPT deficiency are discussed.