Respiration and its correlation with motoric function in non-classic Pompe disease

Aims: Pompe disease is a lysosomal storage disorder with a broad clinical spectrum. Leading symptom in patients with non-classic disease is progressive muscle weakness.

This study describes respiratory dysfunction in non-classic Pompe disease as well as its correlation with motoric disability.

Methods: In 35 patients with non-classic Pompe disease we retrospectively analysed muscle force according to MRC, results of the 6-minute walk test, mobility according to Walton & Gardner-Medwin, forced vital capacities (FVC) as well as use of respiratory support before start of enzyme replacement therapy by frequencies, boxplots as well as rank correlations.

Results: Eight patients (22%) used non-invasive ventilation while lying. It was started at the median age of 46 years (Quartiles: 21, 48, range 1–63). One patient needed continuous invasive ventilation since the age of 27 years.

Median FVC in sitting position was 71% (Quartiles: 50, 92, range 28–124), in supine position 60% (Quartiles: 33, 88, range 18–119). Quotient of FVC in the sitting and supine position had a median of 84% (Quartiles 69, 94, range 37–104).

FVC in sitting and supine position correlated with the sum of MRC scores (r_s=0.608, p=0.000 and r_s=0.638, p=0.000), the age-normalised distance reached in the six minute walk test (r_s=0.637, p=0.000 and r_s=0.630, p=0.000) as well as with the mobility according to Walton & Gardner-Medwin (r_s=0.534, p=0.001 and r_s=0.563, p=0.001).

Conclusion: Respiratory dysfunction has a broad variation.

Mostly FVC does not decrease more than 20% while going from sitting to supine position indicating an involvement of respiratory system as a whole rather than an isolated diaphragm weakness. Yet, there are also some patients with a moderate to severe decrease showing predominant diaphragm dysfunction.

Respiratory dysfunction correlates with the disability of the locomotive system. In individual cases however, no bidirectional conclusions are possible.

Respiratory function should be evaluated independently of motoric symptoms in sitting and supine position in every patient.

Glycogen storage disease type II - Pompe disease - Lysosomal storage disease