Congenital and adult-onset hyperinsulinism (CHI) must be taken under considerationinthedifferentialdiagnosisofhypoglycaemiasymptomswithendogenous hyperinsulinism,especiallyincasesinwhichtherewasfailuretofindaninsulinoma. Histologicalexaminationisnecessaryforadefinitivediagnosis.CHIisadisorder withthreehistopathologicalvariants:focalCHI,diffuseCHI,andatypicalCHI. These variants are clinically indistinguishable. According to published statistics, 0.5to5%ofnesidioblastosiscasesoccurinadults.Clinicalmanifestationranges from mildly symptomatic up to life-threatening hypoglycaemia. Early diagnosis andtreatmentareimportantinyoungandveryyoungpatientsbecauseearlytreatmentaccountsforfavourablementaloutcomes.