Prevalence of Pompe's Disease in Respiratory Clinics

Study Overview
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Brief Summary
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Pompe's disease is a very rare condition which causes weakness of the respiratory muscles and may therefore cause symptoms of breathlessness or even respiratory failure, requiring the use of a ventilator at night. Recently a treatment for this condition has become available as well as a simple diagnostic test. However, we believe it is possible that there are patients with this condition who are presently undiagnosed attending respiratory clinics. We would like to complete an observational study of patients with respiratory muscle weakness of an unknown cause, who are attending respiratory clinics at two London centres, to determine whether patients attending these services have undiagnosed Pompe's disease.

Detailed Description
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Participation in the study will involve taking measurements of respiratory muscle strength, lower limb strength and collecting blood samples to test for enzymes which relate to Pompe's disease. These measures will be completed during a routine clinic visit. Participation will also involve the study coordinator accessing medical notes to gain information about disease history. The study aims to collect information about the number of patients attending respiratory clinics with undiagnosed Pompe's disease and the characteristics of these patients so that other specialist services could use these criteria to identify patients who may benefit from investigations and treatment. If any participants are diagnosed with Pompe's disease and could benefit from treatment medical staff would refer them for treatment at local UK centres.

Official Title
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Prevalence of Pompe's Disease Amongst Patients With Unexplained Respiratory Muscle Weakness or Respiratory Failure

Conditions
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Pompe's Disease

Intervention / Treatment
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* Other: Prospective observational study


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients presenting to home mechanical ventilation or other respiratory clinics: who are over 18 years old with unexplained respiratory muscle weakness with breathlessness and/or type II respiratory failure which may be treated by a ventilator which is: unexplained by a known pulmonary disease, radiological abnormality or distortion of body hiatus (e.g scoliosis or massive obesity defined as BMI > 50 kg/m2), associated with a restrictive ventilatory defect or associated with unexplained muscle weakness. Exclusion Criteria: respiratory muscle weakness confirmed to be due to another cause known to have Pompe's disease at time of referral

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Other: Prospective observational study|Prospective observational study collecting data during a clinic vist including measurement of respiratory muscle strength, respiratory failure, lung function, physical performance and blood testing for enzymes related to Pompe's disease and muscle function.|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The prevalence of undiagnosed adult onset Pompes disease. This will be assessed through dry blood spot testing measuring α-glucosidase (GAA) deficiency and the Activity Ratio +/Acarbose. | dry blood spot testing | 12 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| CK levels | blood tests | 12 months | 
| Respiratory muscle strength | Using sniff nasal inspiratory pressure, spirometry in lying and sitting, maximal inspiratory and expiratory mouth pressure | 12 months | 
| Respiratory failure | Blood gases | 12 months | 
| Muscle weakness | performance on the short physical performance battery | 12 months | 
| Disease history | review of notes to establish duration of symptoms, time interval between presentation and referral to secondary care and any signs of respiratory failure or respiratory muscle weakness at presentation. | 12 months |