C. Suhitha, B. Vivekanand, A. Mythili, K. A. V. Subrahmanyam
Department of Endocrinology, Andhra Medical College, Visakhapatnam, Andhra Pradesh, India
Corresponding Author: Dr. C. Suhitha, Flat No. 7, Sarojini Court Apartments, Street No. 21, CBM Compound, Visakhapatnam - 530 001, Andhra Pradesh, India. E-mail: drsuhitha36@gmail.com
Introduction: Pineal masses are not uncommon in the pediatric age group. They may be associated with central diabetes insipidus (DI) due to concomitant involvement of the pituitary stalk especially seen in germ cell type. However, pineal incidentalomas are also common and found in 5-10% of autopsy series.
Case Report: A 6-year-old female child was referred in view of polyuria and polydipsia since 6 m of age. In view of difficulty in performing biochemical evaluation, outside she had undergone magnetic resonance imaging (MRI) brain and a pineal mass was detected with no evidence of posterior pituitary bright spot. Patient had no response to inhaled desmopressin. With this history, she was referred here. There was no H/S/O hypothyroidism, hypocortisolism, raised ICT, polyphagia, behavioral or sleep disturbances, recurrent urinary tract infections, hemoglobinopathies or any drug intake. O/E – weight and height were appropriate for age with normal general and systemic examination. On evaluation, urine output was around 7000 ml, euthyroid, normal glucose levels, calcium and potassium. Water deprivation test was suggestive of complete nephrogenic DI. Renal evaluation failed to reveal an acquired cause of nephrogenic DI. Contrast enhanced MRI did not show any increase in the size of the pineal mass. Patient responded to thiazides with a decrease in urine output to 2500 ml and is under follow-up.
Discussion: Despite the presence of an obvious radiological lesion (pinealoma) biochemical evaluation for polyuria and polydipsia should be performed. In this case, biochemical evaluation was suggestive of nephrogenic DI. Most of the cases of nephrogenic DI are acquired. However, presence of symptoms as early as 6 m of age suggests the possibility of hereditary cause. Among the hereditary causes 90% are due to arginine vasopressin receptor defects.
Conclusion: This case reiterates the concept that initial biochemical evaluation should be performed prior to radiological investigations.
Key words: Nephrogenic diabetes insipidus, pineal mass, thiazides