We describe the case of a 32 year-old woman who presented six weeks post partum with headache, polydipsia and polyuria (6L/day) in the context of vulval lesions present for four years. Her serum sodium was 145mmol/L, serum osmolality 298mosm/kg, urine osmolality 121mmol/L, urine sodium 29mmol/L consistent with diabetes insipidus (DI). Other pituitary function tests included LH 0.6IU/L, FSH 6.3IU/L oestradiol 22pmol/L, prolactin 1004mIU/L in setting of breastfeeding, GH 0.6ug/L, IGF-1 26.6nmol/L, early morning cortisol 450nmol/L with a normal synacthen test. TSH 1.86mIU/L, T4 12.2pmol/L and T3 3.7pmol/L. MRI brain revealed a mildly enlarged pituitary and loss of the normal bright spot consistent with an infiltrative process in the posterior pituitary. Biopsy of vulval lesion demonstrated histology consistent with Langerhan’s Cell Histiocytosis (LCH). Extensive staging investigations did not demonstrate other disease sites. Pituitary stalk biopsy was not performed due to potential of compromising anterior pituitary function, however both Haematology and Endocrinology units were satisfied the clinical presentation and imaging findings were in keeping with LCH. She was commenced on desmopressin and treated with vinblastine and prednisolone for LCH.
LCH is a rare neoplastic disorder of immature myeloid dendritic cells affecting 1-2 people per million yearly, with 30% of adults affected having DI. Treatment for single site vulval LCH consists of well tolerated local therapies whilst treatment guidelines for multi-system LCH involving the CNS suggest treating with corticosteroids and vinblastine. These have significant side effects, however failure to treat CNS lesions could risk dissemination and irreversible neurological events. Typically once DI is established in LCH, it is irreversible despite treatment. Classification of single system LCH vs multi-system LCH has significant therapeutic implications, thus it may be important to investigate for pituitary involvement.