Growth hormone therapy for a patient with idiopathic Fanconi syndrome and growth hormone deficiency

Idiopathic Fanconi syndrome (FS) is characterized by a generalized dysfunction of the renal proximal tubules. Patients with FS often exhibit growth retardation due to complex factors, such as hypophosphatemia, metabolic acidosis, disturbed vitamin D metabolism and hypokalemia. To date, one FS patient has been reported to exhibit growth failure due to growth hormone deficiency (GHD), but the long-term clinical course of recombinant human GH (rhGH) therapy has not been reported. At 10 months of age, the patient was admitted to our hospital due to growth failure. Blood and urinary biochemical abnormalities, such as hypophosphatemia, metabolic acidosis, glycosuria and low-molecular-weight proteinuria, indicated a generalized dysfunction of the renal proximal tubules. The presence of cystinosis, collagen diseases, toxic agents and metabolic diseases were excluded. These features are compatible with idiopathic FS. Treatment with high-dose alkali, potassium citrate, phosphate buffer, hydrochlorothiazide and vitamin D supplement was initiated. The biochemical abnormalities achieved nearly normal values, and the patient’s height was within −2.5 SD at the age of 2 years. However, his height did not continue to increase at the same rate and gradually declined to −2.9 SD at 4 years of age. GH stimulation test demonstrated GHD. After initiation of rhGH therapy, his height improved to −2.0 SD at the age of 9 years with no adverse effects. In conclusion, we report the case of a patient with FS and GHD who continued rhGH therapy for 5 years. The differential diagnosis of GHD should also be considered for FS patients with short stature.