Posterior reversible encephalopathy syndrome in drug-induced syndrome of inappropriate ADH secretion: a case report.

BACKGROUND: The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a condition with multiple possible causes, leading to hypotonic overhydration and reduced serum osmolality. Complications include seizures, headaches and cerebral edema resulting from rapid and severe hyponatremia. Posterior reversible encephalopathy syndrome (PRES) is a largely reversible, neurological condition typically associated with arterial hypertension, autoimmune diseases or infections. Complications include visual disturbances, seizures and increased intracranial pressure. While concurrent occurrence of both entities has been documented, such cases are often confounded by malignancies or antineoplastic treatment. Co-occurrence in an otherwise relatively healthy individual is rare and offers new insights into pathophysiology.

CASE PRESENTATION: We report on a case of concurrent SIADH and PRES in a 54-year-old Ukrainian woman with minimal confounding factors (pre-existing medical conditions or recent medical interventions). The patient developed acute-onset SIADH following high-dose antihypertensive drug intake and subsequently presented with PRES, characterized by typical clinical findings and characteristic imaging results. She required intensive care treatment, fully recovered within days and showed no long-term deficits.

CONCLUSIONS: The concurrent presentation of SIADH and PRES has rarely been described in the absence of clinical confounders. This report supports a direct, pathophysiological link between vasopressin/SIADH activity and the pathogenesis of PRES. Furthermore, it reinforces the role of cerebral hyperperfusion as a risk factor.