We would recommend the following as a starting point, but would always advise caution over some of the quoted figures:
Genetics Home Reference, published by the National Institutes of Health (NIH)
Pompe disease is classified as a Lysosomal Disorder (LD), it currently treated by Myozyme (Lumizyme in the USA) an Enzyme Replacement Therapy (ERT) developed and commercialised by Sanofi-Genzyme. Kevin O’Donnell and Allan Muir were both closely involved with the development through their positions in the International Pompe Association. Kevin is author of the online blog, “Pompe Disease – The Real Story”
In the UK, treatment by Myozyme can only be prescribed in one of eight Highly Specialised Centres in NHS-England, through the Scottish Metabolic Network, or at the Welsh LD centre in Cardiff. There are very few diagnosed cases in Northern Ireland and they are managed at Belfast City Hospital. Please contact Allan Muir if you would like to understand the referral process.
There are a number of ways to classify Pompe disease, but none of them are totally satisfactory. Generally they are referred to as:
- Infantile Onset Pompe Disease – IOPD
- Classical (severe muscular weakness with cardiomyopathy)
- Non-classical (severe muscular weakness with no heart involvement)
- Late Onset Pompe Disease – LOPD
Within IOPD there are children who produce virtually no enzyme of their own; they are classed as CRIM-(CRIM negative). These are almost universally Classical IOPD and require a course of immunosuppressants with their initial infusions of ERT. Other children are classed as CRIM+ and they produce sufficient enzyme of their own to allow ERT to be administered safely, without the need for drugs to suppress an immune response.
There was once a “Juvenile Pompe Disease” classification which was abandoned after ERT became available. The classification does have some merit, however, as young children go through very difficult times as they approach puberty. When they experience growth spurts, their body imposes increased demands on their metabolism, they may suffer from rapid disease progression and skeletal deformities, such as scoliosis. That is because their muscles are unable to adequately support their spine as it grows. That is particularly true of untreated children, but is becoming evident in many children receiving the standard dose of ERT.
LOPD can experience the first symptoms at any age from birth to 100, although they will have been subject to the enzyme deficiency since birth. Because the condition is so rare, they will struggle for many years before receiving a correct diagnosis. Raising awareness of the condition among healthcare professionals is extremely difficult and the long-term diagnostic odyssey will not be resolved until the universal adoption of new-born screening.