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Cysteamine (2-aminoethanethiol) has been given orally to 19 patients with néphropathie cystinosis for periods of 8-24 months in doses ranging from 50 to 70 mg base/kg/day. Adverse reactions were noted in 3 patients early in the study when a rapidly increasing dosage schedule was followed. The reactions included hyperthermia, lethargy and rash. These reactions were not seen when patients were started on a very low dosage which was increased gradually at 3-week intervals to a level which depleted leukocytes of about 90% of their free cystine. All three reactions resolved within 24 h of cessation of therapy and in these cases successful readministration of drug was achieved. Chronic cysteamine administration to pediatric patients with cystinosis is feasable. The efficacy of this therapy is still being evaluated.

The transport and intracellular fate of cysteine-35 S was studied in leukocytes from nine children with cystinosis and nine control subjects of similar age in an attempt to explain the presence of 80 times the normal quantity of free cystine in cystinotic leukocytes. Two differences were observed: the cystin- SpeculationThe increased uptake of cysteine-35 S shown by cystinotic leukocytes could be taken as valid conventional evidence for a primary defect in the transport of cysteine in cystinosis. The prompt appearance of the extra 35 S transported as intracellular cystine-3S S suggests, however, that this rapid conversion may be the primary defect and that the increased uptake of cysteine-35 S is but a compensatory mechanism for maintaining the physiological concentration of intracellular cysteine.

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