Diabetes insipidus secondary to Langerhans' cell histiocytosis: is radiation therapy indicated?

Langerhans' cell histiocytosis (LCH) is a proliferative disease of Langerhans' cells that has multiple clinical manifestations including diabetes insipidus (DI). This study reviews the effectiveness of hypothalamic-pituitary radiation therapy (HPRT) as a treatment of LCH-induced DI in the modern era. A retrospective review was done of 116 pediatric patients with LCH seen from 1975 to 1992. Seventeen of the 116 patients (15%) were diagnosed with complete or partial diabetes insipidus. Diagnosis was made either by water deprivation test or on clinical grounds. Fourteen patients received hypothalamic-pituitary irradiation as treatment for DI. The median interval from the onset of DI symptoms (polyuria and polydipsia) to treatment was 30 days. The median interval from the onset of diagnosis to treatment was 4 days. With a mean follow-up of 7.3 years (range, 2.4-14.3), only two patients had a complete response to therapy, as defined as no need for antidiuretic hormone (ADH) replacement therapy. No patient had a partial response, defined as a decrease in the dose of ADH replacement. Of the two responders, neither had a complete ADH deficiency, suggesting "early" disease. In addition, both received RT within 3 days. We feel that the standard treatment of RT to all patients with LCH-induced DI is no longer justified. Our series has shown no benefit in treating patients with a long history of DI. Rather, an improved rationale would be rapid initiation of hypothalamic-pituitary irradiation in patients with new symptoms of DI and an abnormal water deprivation test.