Syndrome of inappropriate antidiuretic hormone secretion associated with an ovarian immature teratoma: A case report and review of the literature

Immature ovarian teratoma with gliomatosis peritonei, paraneoplastic hyponatremia and growing teratoma syndrome: a case report and literature review

Introduction and relevance

Paraneoplastic hyponatremia is often secondary to syndrome of inappropriate antidiuretic hormone secretion (SIADH) by tumour cells. Immature ovarian teratomas (IOT) are uncommon and may present with SIADH.

Case report

A 26-year-old female presented with a 3-month history of abdominal pain and constipation. Imaging identified a mixed solid-cystic right ovarian mass containing fat and peritoneal deposits. Biochemistry showed severe, refractory hyponatremia (117 mmol/l). She underwent diagnostic fertility-preserving right salpingo-oophorectomy and resection of peritoneal nodules with the aim to achieve symptom control and hyponatraemia resolution. Pathology revealed a FIGO Stage 2 Grade 2 IOT with extensive benign peritoneal gliomatosis. Initial management was conservative. After 6 months of active follow-up, a rise in AFP, and recurrent hyponatremia supported the decision to administer three cycles of Bleomycin-Etoposide-Cisplatin chemotherapy. One month later, given radiological disease progression despite satisfactory biomarker response, cytoreductive surgery with complete macroscopic resection was performed. Pathology consisted solely of peritoneal mature glial elements: a growing teratoma syndrome (GTS). The patient remains disease-free after 2 years of surveillance.

Clinical discussion

Specimen histological assessment from the patient's initial surgery showed immature neuroectodermal tubules, which are thought to be the source of vasopressin secretion. The authors hypothesise that recurrent hyponatremia and rising AFP levels represented postoperative disease relapse. Biochemical response despite radiological disease progression was pathognomonic of a GTS.

Conclusion

Paraneoplastic SIADH secondary to an IOT must be considered in female patients presenting with abdominal symptoms and hyponatremia. Management requires a multidisciplinary approach. Serum electrolytes are useful surveillance biomarkers supplementary to tumour markers.

Case report: Twice-daily tolvaptan dosing regimen in a challenging case of hyponatremia due to SIAD

Background

Syndrome of inappropriate antidiuresis (SIAD) is one of the most frequent causes of euvolemic hyponatremia (serum sodium levels < 135 mEq/L) and it represents more than 35% of hyponatremia cases in hospitalized patients. It is characterized by an inappropriate vasopressin (AVP)/antidiuretic hormone (ADH) secretion, which occurs independently from effective serum osmolality or circulating volume, leading to water retention via its action on type 2 vasopressin receptor in the distal renal tubules. Corpus callosum agenesis (CCA) is one of the most common congenital brain defects, which can be associated to alterations in serum sodium levels. This report presents a rare case of chronic hyponatremia associated with SIAD in a woman with CCA, whose correction of serum sodium levels only occurred following twice-daily tolvaptan administration.

Case presentation

A 30-year-old female was admitted to our hospital for non-acute hyponatremia with dizziness, headache, distal tremors, and concentration deficits. She had profound hyponatremia (Na 121 mmol/L) with measured plasma hypo-osmolality (259 mOsm/Kg) and urinary osmolality greater than 100 mOsm/Kg (517 mOsm/Kg). She presented clinically as normovolemic. After the exclusion of other causes of normovolemic hyponatremia, such as hypothyroidism and adrenal insufficiency, a diagnosis of SIAD was established. We have ruled out paraneoplastic, inflammatory, and infectious causes, as well as ischemic events. Her medical history showed a CCA and frontal teratoma. We administered tolvaptan initially at a low dosage (15 mg once a day) with persistence of hyponatremia. Therefore, the dosage was first doubled (30 mg once a day) and then increased to 45 mg once a day with an initial improvement in serum sodium levels, although not long-lasting. We therefore tried dividing the 45 mg tolvaptan administration into two doses of 30 mg and 15 mg respectively, using an off-label treatment schedule, thus achieving long-lasting serum sodium levels in the low-normal range associated with a general clinical improvement.

Conclusions

This report underlines the importance of the correct diagnosis, management and treatment of SIAD, as well as the need for further studies about the pharmacokinetics and pharmacodynamics of vasopressin receptor antagonists.