Drugs evaluated here are used in routine care in children and will be prescribed according to department practices concerning treated disease. Medical checks will be done during usual follow-up. Several features will be collected: reason of treatment, drug chosen and prescription modalities, observance, concomitant treatments, side effects, clinical examination, photography, score… Blood samples will be performed at different interval during usual biological follow-up. Three samples per patient will be required for pharmacokinetic and pharmacogenetic.