La tirosinemia de tipo I es un error innato del metabolismo de aminoácidos, ocasionada por la deficiencia o ausencia de la actividad enzimática de la hidrolasa del fumarilacetoacetato del catabolismo de tirosina; con un cuadro clínico variable, se puede manifestar desde una forma neonatal grave hasta una presentación asintomática tardía. El diagnóstico rápido y el manejo nutricional son importantes para la evolución. Se presentan cuatro casos, dos confirmados como tirosinemia I y dos con diagnósticos equivocados, y se resaltan los criterios diagnósticos y el manejo terapéutico. Tyrosinemia type I is an inborn error of metabolism of the amino acids, caused by a deficiency or absence of the enzyme activity of fumaril-acetoacetate hydrolase in the catabolism of tyrosine. It has a variable clinical presentation, from an acute severe neonatal form until a virtually asymptomatic form with late presentation. The rapid diagnosis and nutritional management is essential for a good outcome. Four clinical cases are presented, two of which were confirmed as tyrosinemia type I and two that were initially misdiagnosed. Diagnostic criteria and therapeutic management are emphasized.