Cystinosis is an in-born error in cystine metabolism characterized by tissue deposition of cystine in multiple organs with associated renal tubular pathology with Fanconi syndrome, nephropathic diabetes insipidus, and chronic renal insufficiency; primary hypothyroidism and pituitary resistance to T4 also may occur. Affected children may be severely growth retarded. We report our experience with GH in 3 such patients. None was hypothyroid (Pt 1 Rx'd w/L-T4); each had data suggestive of GH insensitivity.TABLE 1 TABLE 2 While all patients eventually received GH at a dose of 0.375 mg/kg/wk, Patients 1 & 2 initially received 0.18 mg/kg/wk for 3 mos and 1 yr, respectively. Follow up GHBP concentrations in Patients 1 & 2 remain low (335 and 341 pmol/L, respectively). Conclusions: The growth retardation associated with cystinosis is multi-factorial and GH insensitivity may play an important role; these patients may demonstrate end-organ insensitivity to other hormones. Pharmacologic doses of GH may lead to a normalization of growth rate and stabilized/increased height Z scores, if GH therapy is given early in the course. Such therapy may accelerate progression to end-stage renal disease.

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