Abstract
BackgroundDue partly to physicians’ unawareness, many adults with Pompe disease are diagnosed with great delay. Besides, it is not well known which factors influence the rate of disease progression, and thus disease outcome. We delineated the specific clinical features of Pompe disease in adults, and mapped out the distribution and severity of muscle weakness, and the sequence of involvement of the individual muscle groups. Furthermore, we defined the natural disease course and identified prognostic factors for disease progression.MethodsWe conducted a single-center, prospective, observational study. Muscle strength (manual muscle testing, and hand-held dynamometry), muscle function (quick motor function test), and pulmonary function (forced vital capacity in sitting and supine positions) were assessed every 3–6 months and analyzed using repeated-measures ANOVA.ResultsBetween October 2004 and August 2009, 94 patients aged between 25 and 75 years were included in the study. Although skeletal muscle weakness was typically distributed in a limb-girdle pattern, many patients had unfamiliar features such as ptosis (23%), bulbar weakness (28%), and scapular winging (33%). During follow-up (average 1.6 years, range 0.5-4.2 years), skeletal muscle strength deteriorated significantly (mean declines of −1.3% point/year for manual muscle testing and of −2.6% points/year for hand-held dynamometry; both p<0.001). Longer disease duration (>15 years) and pulmonary involvement (forced vital capacity in sitting position <80%) at study entry predicted faster decline. On average, forced vital capacity in supine position deteriorated by 1.3% points per year (p=0.02). Decline in pulmonary function was consistent across subgroups. Ten percent of patients declined unexpectedly fast.ConclusionsRecognizing patterns of common and less familiar characteristics in adults with Pompe disease facilitates timely diagnosis. Longer disease duration and reduced pulmonary function stand out as predictors of rapid disease progression, and aid in deciding whether to initiate enzyme replacement therapy, or when.
Highlights
Due partly to physicians’ unawareness, many adults with Pompe disease are diagnosed with great delay
The pattern of muscle weakness was symmetrical in 95% of patients, and the distribution of weakness did not differ between males and females
Our findings about the distribution of muscle weakness, based on clinical examinations, match those of CT and MRI studies. [24,25,26] We found weakness of the quadriceps muscle in 55% of patients only. This may have been due to our method of measuring muscle strength: whereas the advantage of the Medical Research Council (MRC) score and Hand-held dynamometry (HHD) lie in the fact that they are easy for the clinician to use, quantitative muscle testing using Quantitative Muscle Testing (QMT) [13,27] may be more reliable in patients with only minor loss of strength
Summary
Due partly to physicians’ unawareness, many adults with Pompe disease are diagnosed with great delay It is not well known which factors influence the rate of disease progression, and disease outcome. [2,3] Many adults with Pompe disease are diagnosed late in life, when they are already in an advanced stage of the disease While this may be due to clinicians’ unawareness, it may be explained by similarities in clinical presentation with other ‘limbgirdle’ diseases such as the limb-girdle muscular dystrophies (LGMD), Becker muscular dystrophy, or metabolic myopathies. We prospectively studied the natural disease course, and aimed to identify prognostic factors for faster disease progression and poor outcome in a large cohort of adult Pompe patients
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