In late-onset Pompe disease, unlike the infantile-onset form, there is a low level of GAA enzyme. It can be diagnosed from age one but is also known to present much later in life.
Interpreting results
There are two genetic testing services for late-onset Pompe disease in the UK. One is in Manchester Children’s Hospital and the other at Great Ormond Street Children’s Hospital. They will look for mutation of the acid alpha-glucosidase gene, mapped to chromosome 17 (location 17q25.2-q25.3).
A results letter is sent from the genetic service and if help is needed to understand the contents contact the Clinical Nurse Specialist in the team that requested the tests in the first place. Very often the medical team helping you will ask you to come to discuss the diagnosis and letter but sometimes the letter is sent to the home and this can feel quite a shock.
Late-onset Pompe disease is an autosomal recessive disorder. This means that when two parents each carrying one mutated gene have a child, there is a one in four chance that child will have Pompe disease.
Coming to terms with a diagnosis
The time during and immediately after diagnosis can be hard and causes a wide variety of mixed emotions. Some express great relief to have a final answer after years of uncertainty. Others find the process of absorbing this new information emotionally complicated and challenging. There are implications for siblings, who might be offered testing. There are wide effects on the whole family and sometimes it is not easy to break the news to siblings that they might need to be tested.
Remember to distinguish between late-onset Pompe disease and infantile-onset Pompe disease because the two are quite different from one another.
Staying well informed
Drug treatment for late-onset Pompe disease only started in 2006. When reading and researching about this condition much of the research and information will come from a time before treatment started and was widely available. It is important to check when the information was written and whether it refers to patients who had access to treatment or not. Quite a lot of the research done since 2006 includes patients who were diagnosed in the 1990s and before, so they had the condition for many years without access to any drug treatment. Late-onset Pompe disease is so rare that there are hardly enough people to provide good numbers for large scale research.
While many find help in speaking with other people who have Pompe disease, some prefer to wait until they know more. If you or a loved one has been diagnosed remember you are not alone. There is a large amount of information to absorb and decisions to be made. There is a friendly and willing group of people with Pompe disease ready to offer a chance to listen and share their experiences. Get in touch if you would like to speak with someone who understands.
Keeping track of your care
If not before then soon after diagnosis patients will visit their Highly Specialist Medical Treatment Centre.
The team is likely to include a Metabolic Consultant, Neurologist, Physiotherapist, Pharmacist, Dietitian, Psychologist and Clinical Nurse Specialist. There is a team coordinator organising appointments and clinics.
Usually the Clinical Nurse Specialist is the first point of contact for medical matters or queries on a day to day basis. Patients routinely attend this multi-disciplinary team clinic (MDT) every six months.
Patients require close management and monitoring. They will also see a respiratory consultant and cardiologist. It can be quite a challenge to manage and monitor all the appointments and letters.
However, it is very important to keep a record, update diaries and know when tests are overdue or results are coming through. The Clinical Nurse Specialist can help enormously with this.
Helping to gather knowledge about a rare disease
The Pompe Centre at the Erasmus University Medical Centre in Rotterdam maintains a catalogue of all the GAA mutations. There are around 500 identified GAA mutations to date and the number is increasing all the time. It is important to remember that everyone with late-onset Pompe disease varies greatly and the large number of different mutations recorded underlines this.
Many people in the UK who have Pompe disease are part of the Erasmus programme which records symptoms and how they have changed every year. This is a long set of questions completed by the patient themselves.