Background: There is a growing number of inborn errors of metabolism (IEM) with late onset but nevertheless life threatening course.
Patients: Patients with late onset variants of urea cycle defects, fatty acid oxidation defects and organic acidurias are demonstrated.
Methods: Biochemical, enzymatic, molecular methods and especially tandem mass spectrometry (TMS) are used for diagnostic purposes.
Results: IEM variants with late onset are difficult to be detected. TMS has some advantages as the simple sampling of dried blood on filter paper cards and the simultaneous detection of a broad spectrum of disturbances in amino acids and acylcarnitines. This may facilitate a prompt diagnosis. Asymptomatic persons not only carry an unrecognized risk for severe metabolic decompensation but also pass on their mutation of IEM and the associated disease risk to the next generation (Non-disease).
Conclusion: TMS, which is used in newborn screening centers is very convenient to establish a prompt diagnosis in some unexpected late onset metabolic crisis following surgeries, infections or other catabolic stress. Furthermore TMS may be a suitable and rapid adjunct method to improve transplantation management.