The Lennox-Gastaut Syndrome (LGS) is a childhood epileptic encephalopathy. Incidence: 1/1.000.000/year, prevalence: 15/100.000. LGS covers 5-10% of epileptic patients and 1-2% of childhood epilepsies. Also referred to as cryptogenic or symptomatic generalized epilepsy. LGS is characterized by: multiple seizures (atypical absences, axial tonic seizures and sudden atonic or myoclonic falls), diffuse slow cryptic EEG waves when awake (<3 Hz), fast rhythmic peaks (10 Hz) during sleep, mental retardation and personality disorders. The LGS is not responding to treatment. Some new drugs have proven to be effective in controlling the disease (Felbamate, Lamotrigine, Topiramate, Levetiracetam). The mortality rate is about 5%; only rarely death is due to epilepsy, which is usually caused by stroke or epileptic episodes. Here we describe the case of a 45-year-old female patient with LGS, severe hypokalemia, mental retardation and focal seizures. Normal renal function: creatinine 0.9 mg/dl, urea 26 mg/dl, creatinine clearance 96 ml/min, serum potassium levels to the minimum: 3.5 mEq/L. This level of potassium, however, had been achieved with the assumption of 8 oral tablets/day of potassium chloride. Osmotic diuresis, use of diuretics, Bartter, Gitelman (normal urinary calcium and magnesium) and pseudo-Bartter syndromes were all excluded whereas aldosteronism was found. Our findings lead to hypokalemia related to assumption of topiramate and hyperaldosteronism. Reduction in drug intake was not effective due to the increased seizures, so the drug was maintained, along with potassium supplementation. In conclusion, the patient has been diagnosed with hypokalemia and iatrogenic hyperaldosteronism, rare in our outpatient practice.