Tsuchida S, Hiraoka M, Hori C, Suzuki T, Gejyo F, Ichikawa I
Defective renin-angiotensin system in a subset of type 4 RTA
with prominent medial hypertrophy of renal vasculature and
interstitial changes in infancy
Am Soc Nephrol
J Am Soc Nephrol (abstract)
(Sep) 7:1344 1996
In normal newborn infants, all components of the RAS have been found to be
activated. The exact reason for this is still unclear. Some investigators
believe that this activation is important in regulating the changes that
occur in intrarenal bloodflow during development and the transition from
uterine to extrauterine life, while other investigators believe that this
is primarily designed to maintain a positive sodium balance during fetal
growth and development. Inhibition of the RAS in fetuses or newborn infants
may therefore have untoward effects, as is seen in the case of ACE
fetopathy.
The authors of this paper present a case of an infant with type IV RTA with
interesting morphologic changes on renal biopsy. The patient presented with
severe failure to thrive at the age of 11 months. Work-up revealed a
hyperkalemic metabolic acidosis with hypoaldosteronism. Further studies
revealed the presence of concomitant hyporeninism, and the infant's
metabolic acidosis was corrected by the administration of
mineralocorticoid.
A renal biopsy was also done as part of the infant's work-up, and this
revealed medial hypertrophy of renal arterioles, tubular dilatation and
interstitial fibrosis. These changes were felt to be similar to those seen
in angiotensinogen-gene deficient, RAS inhibited newborn mice. The authors
then postulate that there is a subtype of type IV RTA that is characterized
by a defective RAS system with characteristic arterial and interstitial
lesions.
Comment: This paper adds further data to our knowledge of the
effects of the RAS on the developing kidney. Morphologic examination of
kidneys from newborns afflicted with ACE fetopathy have revealed tubular
dysplasia with tubular dilatation, lack of differentiation of tubular
structures, and tubular necrosis (Pryde et al, AJKD 9:1575, 1993), thus
illustrating the importance of angiotensin during renal development; this
paper demonstrates that deficiency of other components of the RAS may also
have important adverse effects.
(Joseph Flynn, M.D., University of Michigan, Ann Arbor)
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Am Soc Nephrol
Acidosis/alkalosis :
Metabolic acidosis