Lysosomal storage disorders are genetic disorders that manifest due to
the absence of an enzyme
. As a result, some substances that are normally broken down in the
body by the enzyme escape degradation and accumulate, causing a variety of
health problems. These diseases are progressive and cause complications that
could affect the heart, brain, muscles and the kidneys. They are estimated to
affect 1 in 7700 live births in the white population.
Neonatal screening tests are
tests carried out in newborns to detect any diseases before the appearance of
symptoms. Early detection is useful to start treatment early or to take
precautions to prevent complications. In order to be cost-effective, screening
tests under National Programs are done for conditions which affect a large
number of people.
Researchers in Austria conducted a study to test the practicality and
usefulness of using neonatal screening for four lysosomal storage disorders-
Gaucher's disease, Pompe's disease, Fabry's disease, and Niemann-Pick disease
The study was conducted in
34,736 newborn babies between the period of January and July, 2010 in Austria.
Enzyme activity was measured on dried blood samples. The enzymes whose activity
were measured included acid β-glucocerebrosidase (which is deficient in
Gaucher's disease), α-galactosidase (which is deficient in Fabry's disease),
α-glucosidase (which is deficient in Pompe's disease), and acid
sphingomyelinase (which is deficient in Niemann-Pick disease types A and B).
The positive cases were rechecked on a second blood sample. Genetic testing on
the blood samples with low enzyme activity was also carried out.
The study identified 124 cases with low enzyme activity. When tests
were carried out on second blood samples, 38 babies were found to have low
enzyme activity. Genetic testing confirmed the disease in 15 of the 38 babies.
Among these, Fabry's disease was found to be most common with an incidence of 1
per 3859 births.
This study thus concluded that lysosomal storage disorders may not be
as rare as they are thought to be - the incidence found in this study was 1 in
Enzyme replacement therapy is available for Fabry's disease. Thus, early
diagnosis of this condition can help in initiating early treatment. Also, since
these diseases are genetically transmitted, early diagnosis can help the
parents understand the risk of the similar disease occurring in other children.
Neonatal screening for these
diseases also has its disadvantages - it detects disease in babies who may not
suffer from any symptoms later in life or may have a very mild disease. Many
patients who are likely to suffer from late-onset disease may well be screened
later at early maturity rather than in the neonatal period.
Larger studies will be
required to establish the usefulness of screening for lysosomal storage
disorders in different ethnic groups.
1. Neonatal screening for lysosomal storage disorders: feasibility and
incidence from a nationwide study in Austria; Thomas P Mechtler et al; The
Lancet, Early Online Publication, 30 November 2011.