The use of a cystine binding protein assay to establish the diagnosis of cystinosis was investigated. The assay has a lower limit of detection of 0.03μmol/l, is linear to a concentration of 1.5μmol/l and has a coefficient of variation of 1.7 and 15.0% between 0.05 and 0.6μmol/l. In 32 patients the mean ± SD pre-treatment leucocyte cystine concentration was 5.78 ± 2.49 nmol 1/2 cystine per mg protein (controls 0.10 ± 0.05). The median polymorphonuclear leucocyte cystine concentration in a group of 24 obligate heterozygotes was 0.55 (range 0.23 - 1.79) nmol 1/2 cystine per mg protein (controls 0.10, range 0.04 - 0.38). The effects of single doses of phosphocysteamine solution, rectal cysteamine gel, intravenous cysteamine and a cysteamine capsule were studied in 10 patients with cystinosis. No significant diurnal variation in leucocyte cystine was found. Compared with the intravenous dose, cysteamine was poorly absorbed from rectal gel (21% bioavailability) but well absorbed after administration of either oral phosphocysteamine solution (73% bioavailability) or a cysteamine capsule (50% bioavailability). Oral phosphocysteamine (10mg/kg cysteamine base), intravenous cysteamine (5mg/kg) and cysteamine capsule (15mg/kg) significantly reduced the mean leucocyte cystine with maximal depletion 1-3 hours after the dose. At 12 hours the mean leucocyte cystine was significantly lower than the pre-treatment level in each of these studies. Rectal cysteamine did not significantly reduce the mean leucocyte cystine concentration. In conclusion, phosphocysteamine suspension may be administered 12 hourly. Rectal cysteamine administration is feasible but higher doses are required before efficacy can be judged. A cysteamine capsule may prove to be a viable alternative to oral phosphocysteamine. 59 patients have received cysteamine and/or phosphocysteamine in the UK up to May 1990. In the 44 pre-transplant patients, cysteamine did not prevent a decline in glomerular renal function but a normal growth rate was maintained.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:504870 |
| Date | January 1994 |
| Creators | Van't Hoff, W. G. |
| Publisher | King's College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://kclpure.kcl.ac.uk/portal/en/theses/cystinosis--the-diagnosis-and-treatment(99b73f67-2549-469e-acaf-23707eefa96b).html |
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