Approach to renal tubular disorders

The renal tubule plays an important role in fluid and electrolyte homeostasis. Renal tubular disorders may affect multiple (e.g., Fanconi syndrome) or specific (e.g., nephrogenic diabetes insipidus, renal glucosuria) tubular functions. Most conditions are primary and monogenic but occasionally are secondary to other disorders (focal segmentai glomerulosclerosis, cystinosis, Lowe syndrome). Tubular dysfunction should be considered in all children with failure to thrive, polyuria, refractory rickets, hypokalemia and metabolic acidosis. Careful clinical and laboratory evaluation is essential for appropriate diagnosis and specific management of these conditions.     

Nephrogenic diabetes insipidus presenting with developmental delay and intracranial calcification

A one-year-boy presented with constipation, fever, failure to thrive and developmental delay from the neonatal period. Investigations revealed persistent hypernatremia and deranged renal functions. Diagnostic work-up was suggestive of nephrogenic diabetes insipidus (NDI). Computerized tomography of head revealed calcification in the frontal, thalamic and basal ganglia region. The rare association of NDI and intracranial calcification is discussed     

Pseudohypoparathyroidism presenting with bony deformities resembling rickets

Pseudohypoparathyroidism (PHP), characterized by hypocalcemia, hyperphosphatemia and elevated parathormone level, may rarely be associated with bony deformities resembling rickets. The authors report two siblings with clinical and radiological features suggestive of rickets unresponsive to treatment with vitamin D. Low serum calcium, elevated serum phosphate, normal renal functions, raised tubular maximum of phosphate and high serum parathormone were suggestive of PHP. Treatment with 1-hydroxyvitamin D and calcium carbonate led to decrease in bone pain, increase in height and weight and resolution of radiological features. PHP should be suspected in patients with bony deformities, hypocalcemia, elevated blood phosphate levels and normal renal functions.     

Long-acting GnRH analogue triptorelin therapy in central isosexual precocious puberty

OBJECTIVE: To evaluate the efficacy of long acting GnRH analogue in improving the auxological outcome of patients with central isosexual precocious puberty (CIPP) and to determine the factors influencing the response. METHODS: Thirty-five patients (30 girls, 5 boys) with CIPP were treated with a long acting GnRH analogue, triptorelin. Final height outcomes and factors affecting treatment were analyzed. RESULTS: Treatment was started at the chronological age (CA) of 6.5 1.8 years in girls and 4.4 1.5 years in boys and continued for a period of 3.7 1.8 years in girls and 6 1.8 years in boys. Follow-up period after discontinuation of treatment was 2.2 0.5 years in girls and 2.6 0.3 years in boys. Treatment led to regression of precocious puberty and reversal of secondary sexual characteristics. There was decline in growth rate reflected by a fall in heightSD of 0.8 0.8 in girls and 2.3 0.9 in boys (p = 0.014), an even greater retardation in bone age (BA) advancement with a decrease in BA-CA of 1.7 1 years in girls and 2.7 1 years in boys and a fall in heightSDBA of 1.5 1.1 in girls and 2.1 1.6 in boys. Final height (149.8 6.9 cm in girls and 161.9 3.9 cm in boys) exceeded projected height at the onset of treatment (143.4 8.3 cm in girls and 154.3 2.7 cm in boys) by 6.4 2.4 cm in girls and 7.6 1.5 cm in boys ( p < 0.001 in both the groups). Factors influencing height gain included age at start of therapy (r = 0.715), BA-CA at the time of initiation of treatment (r = 0.734), heightSDBA at the onset of treatment ( r = 0.566) and the duration of treatment (r = 0.711). Girls treated at an age of less than 6 years (n = 9) had a greater height gain (8.7 1.6 cm versus 5.3 1.9 cm, p < 0.001) and achieved similar final height (148.7 8 cm versus 150.2 6.6 cm) in those treated after this age (n = 21). No side effects of GnRH therapy were observed in the study. CONCLUSION: Long acting GnRH therapy is effective in improving the auxological outcome of patients with CIPP. Maximum benefit is observed in girls with greater bone age advancement treated at a younger age and for a longer duration of treatment. These girls had lower bone age advance at discontinuation of treatment.