UCSD Cystine Determination Laboratory

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Cystinosis: Types/Phenotypic Range

(information and text from: "Update on nephropathic cystinosis", Pediatric Nephrology, JA Schneider, B Katz, RB Melles, (1990) 4: 645-653)

NephropathicNon-nephropathic
Infantile
(onset 6-18 months)
Late-onset
   child (4-5 yrs)
   adolescent (12-13 yrs)
   adult-onset (25 yrs)
Benign (formerly "adult")
Infantile Nephropathic Cystinosis
Children with infantile nephropathic cystinosis generally appear normal at birth and during the first 6-8 months of life. As a proximal renal tubular defect in sodium and water resabsorption develops, leading to polyuria and polydipsia, affected children become especially vulnerable to dehydration. This, and a defect in sweat production, often leads to recurrent fevers as a presenting symptom. By 1 year of age children usually show growth retardation, rickets, metabolic acidosis, and other chemical evidence or renal tubular abnormalities, such as increased renal excretion of glucose, amino acids, phosphate and potassium. Less overt clinical and biochemical evidence of the disease can be found at a much earlier age by careful examination of children known to be at risk because of an affected older sibling or other relative. As the children age, failure to thrive is prominent. Without specific therapy children remain below the third percetile in both height and weight throughout life. The typical patient with infantile nephropathic cystinosis has short stature, retinopathy, photophobia, and onset of renal Fanconi syndrome in the 1st year of life. By 1-2 years of age corneal cystine crystals and rickets are apparent. Glomerular failure progresses slowly with end-stage renal disease by an average age of 9 years.
Late-onset Nephropathic Cystinosis
The age of presentation ranges from 2 to 26 years. When more than one sibling has this condition, their age of onset and symptoms are similar. The most usual age of presentation has been 12-13 years. These patients have crystalline deposits in the cornea and conjunctiva, and have cystine crystals within bone marrow aspirates. Patients with late-onset cystinosis often do not develop the complete Fanconi syndrome, but their renal failure progresses to require renal transplantation, as in infantile nephropathic cystinosis. They are usually in end-stage renal failure within a few years of diagnosis.
Benign Non-Nephropathic Cystinosis
Other patients have this form of cystinosis (formerly referred to as "adult cystinosis") that is usually discovered by serendipity when an ophthalmologic examination reveals crystalline opacities within the cornea and conjunctiva. These patients may suffer from photophobia similar in character to that of patients with the nephropathic forms of cystinosis, but their photophobia may not begin until middle age, and is usually not as debilitating. Since the only patients found to have this condition are those who have slit-lamp examination, it is possible that many such patients have no eye symptomatology and are never diagnosed. Benign cystinosis patients have crystalline deposits in their bone marrow and leukocytes, but do not develop renal dysfunction or retinopathy.


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