The goal of this observational study is to learn about the clinical and nutritional effectiveness of ketogenic diet (KD) in pediatric patients with genetic, neurological or metabolic conditions requiring KD.

The main question[s] it aims to answer are:

• does KD support adequate growth?
• does KD improve clinical symptoms?
• how does KD impact quality of life? Participants will be followed up as per clinical practice

Scientific and clinical interest in KD is growing with a progressive increase in its therapeutic indications, ie recent studies show beneficial effects of KD in other diseases like migraine, autism spectrum disorder and brain tumors.

However, so far, the majority of results on KD effects have been collected in patients with drug-resistant epilepsy proving its effectiveness on clinical outcome (e.g. reducing epileptic seizures), frequently leaving out the nutritional assessment and the impact on quality of life. Nonetheless, these factors are indeed essential to ensure safety and efficacy of KD treatment, especially when dealing with children and in perspective of the progressive expansion of the target population that can benefit from this nutritional therapy.

The present multicenter study aims to analyse these poorly explored areas, by evaluating, in a cohort of pediatrics patient with indication to KD therapy, not only the KD effectiveness on the course of the underlying disease, but also the impact on nutritional parameters (e.g. growth, lipid profile, vitamin intake, bone mineral density, ..) and on quality of life.

Inclusion Criteria:

• Pediatric patients (aged < 18 years) with drug-resistant epilepsy (fail to achieve (and maintain) seizure freedom with adequate trials of two or more antiseizure medications) or genetic, metabolic, neurological (congenital and acquired) diseases treated with ketogenic diet
• Pediatric patients (aged < 18 years) with metabolic, genetic or neurological (congenital and acquired) diseases (not necessarily associated with drug-resistant epilepsy) treated with ketogenic diet; this includes the new KD indications or the administration of KD in the ICU for status epilepticus.

Exclusion Criteria:

• Patients affected by beta-oxidation cycle disorders, systemic primary carnitine deficiency, primary dyslipidemia, pyruvate carboxylase deficiency, porphyria, mitochondrial disease, defects in ketone body metabolism (ketogenesis or ketolysis), defect in gluconeogenesis.
• Children with type 1 diabetes
• Parents (or caregivers) unable to guarantee adherence to the

Pediatri patients (0-18 years) affected by any disease which require a ketogenic diet (KD), i.e. metabolic or genetic disorder or neurological (congenital and acquired) diseases