Abstract
Ever since the demonstration of the “swan-neck” lesion (shortening and narrowing of the neck of the proximal renal tubule) in cystinosis by nephron microdissection, it has been a source of speculation. The prenatal or postnatal onset of the lesion and its role in the pathogenesis of cystine storage have been debated. To study this problem, renal function tests, kidney biopsies, and renal tissue amino acid analyses were performed on two cystinotic infants at six and 12 months of age. At six months, the infants showed a generalized aminoaciduria, proteinuria and glucosuria but not hypophosphatemia, hypokalemia or polyuria; and they were pitressin responsive. Renal biopsies did not show the “swan-neck” lesion by light microscopy or nephron microdissection. However, electron microscopy revealed vacuolization and previously undescribed ultramicroscopic crystals in the epithelial cells of the neck region of the proximal tubule. The unbound cystine concentration in the kidney biopsies was threefold greater than in controls. At 12 months of age the infants exhibited hypokalemia, hypophosphatemia, polyuria and subnormal pitressin responses. Typical “swan-neck” lesions were demonstrated by nephron microdissection. The unbound cystine concentration was ten times normal levels. These studies indicate the “swan-neck” lesion in cystinosis is an acquired rather than congenital defect and it follows rather than precedes cystine storage.
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Mahoney, C., Striker, G., Fetterman, G. et al. The “swan-neck” lesion in childhood cystinosis. Pediatr Res 5, 385–386 (1971). https://doi.org/10.1203/00006450-197108000-00063
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DOI: https://doi.org/10.1203/00006450-197108000-00063