Is genotype determination useful in predicting the clinical phenotype in lysosomal storage diseases?

Understanding the relationship between genotype and clinical phenotype will clearly aid in the prognosis, treatment and counselling of patients with l ysosomal storage diseases (LSDs). This, however, will require the establish ment of widely accepted indices with which to score the severity of LSDs, a s these diseases are characterized by their marked clinical heterogeneity. Even in the complete absence of a functional enzyme, presentation may be va riable, depending on the patient's genetic background and on a range of epi genetic and environmental factors. Further difficulties in predicting disea se severity and progression from the genotype arise from the rarity of thes e disorders, the low enzyme levels required for a normal phenotype and the relative lack of understanding of the pathophysiology of LSDs.