Challenges in Biochemical Diagnosis of Krabbe and Gaucher Disease

Background/Purpose: Krabbe and Gaucher diseases (KD, GD) are rare, inherited disorders caused by the deficiency of a specific lysosomal enzyme. Biochemical verification through enzyme assays remains crucial to guide downstream diagnostic pathway. Although assays with artificial substrates (AS) are preferred due to their less laborious technique, their sensitivity and specificity, however, might not be equal to assays using natural substrates. Based on case examples, we describe potential pitfalls when using AS.

Methods/Results: Eight individuals had been tested for KD elsewhere using AS (5 diagnosed as KD, 3 with normal enzyme activity) and were referred to us for re-evaluation because of a mismatch between clinical/genetic and biochemical findings. Using the natural, radioactively-labelled substrate galactocerebroside [Stearoyl-1-¹⁴C], we found normal enzyme activity in the five children initially diagnosed as KD, and pathological enzyme activity in the three patients clinically suspected as KD.

Two adult patients were enzymatically tested for GD. While ß-glucocerebrosidase activity was not clearly pathological using AS, testing with natural substrate showed pathologically reduced activity indicating GD, in line with clinical findings.

Conclusion: Due to the different chemical properties of AS, unspecific activity or lower enzyme affinity may lead to false-negative or false-positive results. This has been reported previously for KD and GD. Here, we illustrate that the use of natural substrates in biochemical diagnosis should be considered, especially when there is a mismatch between clinical, genetic, and biochemical findings. It thus seems important to critically analyze these aspects in combination to the diagnostic process of sphingolipidoses.

Publikationsverlauf

Artikel online veröffentlicht:
28. Oktober 2021