ESPE Abstracts

Background: Langerhans cell histiocytosis (LCH) is a rare disease with an incidence of less than 10 per million, and characterized by the clonal proliferation of pathogenic Langerhans cells. The clinical courses are diverse, ranging from spontaneously remitting single organ disease to life-threatening multisystem involvement. One of the serious complications of LCH is diabetes insipidus (DI), and patients with CNS-risk lesions had higher cumulative incidence of DI. On the other hand, the risk of DI has been reported to be extremely low in LCH with non-CNS-risk single-system single site lesion.

Case presentation: a 6 years old boy: A six-year-old boy was referred with one and a half months history of polyuria and polydispia. At the age of two years, he had a single lytic lesion in his femoral head, which was curettage surgically and diagnosed as LCH at the other hospital. As any other affected organs were not detected, he was not followed up thereafter. He was diagnosed as DI by confirming hypernatraemia (Na: 148 mEq/l) with hyperosmolar serum (s-Osm 298 mOSM/kg) and inappropriately diluted urine (u-Osm 205 mOSM/kg). His polyuria and polydispia improved dramatically by perioral diuretic hormone. Anterior pituitary functions were not impaired. MRI imaging study revealed enlarged pituitary stalk and placental alkaline phosphatase and b-hCG in the spinal fluid were not detected, suggesting relapse of LCH.

Discussion: At the onset, the type of LCH in the patient was compatible with non-CNS single organ affected, and systematic follow in collaborating with pediatrician was not carried out, that would have led to delayed diagnosis of DI. Several literatures suggested that DI is not commonly present at initial diagnosis of LCH, and DI develops with various time lags, even more than five years in some cases. We recommend to systematically follow up the patients with a history of LCH, even non CNS-risk single-system single site affected type.