Levelling up or levelling down?

Cystinosis is a lysosomal storage disorder usually with onset in infancy. Intracellular accumulation of cystine occurs in all organs. In the kidney it results in excessive loss of electrolytes and water. Treatment involves replacement of fluid and electrolytes and cysteamine, which reduces intracellular cystine, limiting tissue damage. We present the case of a 22 year old female with nephropathic cystinosis and renal Fanconi syndrome treated with lifelong cysteamine. She presented to hospital with dehydration secondary to infective colitis. She was admitted to intensive care for rehydration and electrolytes were cautiously replaced. Three days after admission, when metabolically stable, she acutely deteriorated with tremor, confusion and agitation. On examination she was encephalopathic and had a spastic quadriparesis with spontaneous and sustained clonus. An MRI brain scan, EEG and CSF analysis didn’t reveal a cause, however her white cell cystine levels were very low, suggestive of cysteamine toxicity. Copper levels were low which can theoretically precipitate toxicity. Her cysteamine dose was reduced and copper replaced. After four days she showed neurological improvement, after two weeks she was fully recovered. Cysteamine toxicity alongside hypocupraemia can present with acute neurological deterioration but recovery can be full if this is recognised and managed promptly.