Deficiência de arginina-vasopressina (diabetes insipidus central) como primeira manifestação de histiocitose de células de Langerhans: relato de caso

Abstract

Introduction: Langerhans cell histiocytosis (LCH) is a rare clonal neoplasm of the mononuclear phagocyte system characterized by proliferation of CD1a⁺/Langerin⁺ myeloid dendritic cells and activating mutations in the MAPK/ERK pathway (such as BRAF V600E and MAP2K1). Involvement of the hypothalamic–pituitary axis occurs in up to 30% of cases, presenting as arginine-vasopressin (AVP) deficiency—classically known as central diabetes insipidus (CDI)—often with panhypopituitarism. In adults, isolated pituitary disease is uncommon and frequently mimics sellar tumors. Methodology: This study is a clinical case report developed during the Medical Residency in Endocrinology and Metabolism at the HUPES/UFBA. Data were obtained retrospectively from clinical records and complementary tests, ensuring patient anonymity and confidentiality in accordance with Resolution No. 510/2016 of the Brazilian National Health Council. Case report: A 24-year-old white female with no prior comorbidities initially presented with polyuria estimated at 8 L/day and polydipsia. After 5 months, she developed amenorrhea associated with a moderate, band-like, frontal headache without radiation, progressing to bitemporal hemianopsia at 9 months. Laboratory work-up showed panhypopituitarism with 8 a.m. serum cortisol levels of 1.1 μg/dL and 1.9 μg/dL on different days; TSH 1.1 μIU/mL (reference 0.38–5.33); free T4 0.43 ng/dL (reference 0.54–1.24); FSH 1.56 mIU/mL; LH < 0.20 mIU/mL; estradiol < 15 pg/mL; IGF-1 43 ng/mL (reference 98–289); and hyperprolactinemia with PRL 83.23 ng/mL. Pituitary MRI revealed a 1.7 × 2.2 × 2.1 cm suprasellar lesion abutting the optic chiasm, suggestive of craniopharyngioma. She was admitted for endocrine evaluation and surgery, with documented polyuria of 10 L/day, water intake of 6 L/day, serum sodium of 147 mEq/L, and urine specific gravity < 1.005. Hydrocortisone, levothyroxine, and desmopressin were initiated. Endoscopic transsphenoidal surgery was performed; the macroscopic appearance suggested an optic nerve glioma. Initial histopathology was inconclusive, but subsequent immunohistochemistry was consistent with LCH, positive for CD1a, Langerin, and S100. Postoperative chest CT and abdominal MRI showed no extrasellar disease. Discussion: Infiltration of the hypothalamic–pituitary axis by Langerhans cells leads to loss of AVP-producing neurons and anterior pituitary damage, accounting for polyuria, polydipsia, and multiple trophic hormone deficiencies. The clinical response to desmopressin confirmed central origin. Concomitant hyperprolactinemia indicates disruption of hypothalamic dopaminergic control (tuberoinfundibular pathway). The suprasellar mass mimicking craniopharyngioma highlights the need for histological confirmation using specific immunomarkers. The absence of extrasellar involvement makes this case atypical; in isolated pituitary disease, management is primarily supportive with hormone replacement and long-term surveillance, as functional pituitary recovery is uncommon. Conclusion: LCH should be included in the differential diagnosis of sellar and suprasellar masses in patients with polyuria, polydipsia, and hypophyseal dysfunction. AVP deficiency may be the initial manifestation. Definitive diagnosis requires biopsy with specific immunohistochemistry, and multidisciplinary follow-up is crucial to minimize complications and preserve quality of life.