The difference between lysosomal storage diseases and other classic metabolic diseases is the fact that you can be born normally and then you can develop the disease later on, that the disease progresses slowly and you don’t have these acute metabolic derangements that we call metabolic crises, that we see with a small molecule metabolic diseases - the patients have to be in the ICU, there are electrolyte derangements.  This does not happen in the LSDs. Common laboratory tests are often normal, like urine organic acidurias for example or plasma amino acidopathies where you have electrolyte imbalance, acidosis, kidney dysfunction, heart problems, elevated CK lactic acidosis.  This does not happen when you have an LSD, most labs are normal. Then there are the dysmorphic features which are not always obvious at birth, and they tend to change with age.