P.213 - Identification of patients with late-onset Pompe disease (LOPD) based on muscle biopsy and clinical correlates: experience of a reference centre

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To review clinical and pathological findings in patients without specific diagnosis which finally were Pompe Disease (PD). A systematic review of clinical data and muscle biopsy reports were conducted. Cases without a specific biopsy diagnosis and with clinical criteria suggestive of PD were re-evaluated studying GAA activity in blood on filter paper, lymphocytes, muscle, and molecular studies, while cases with a PD diagnosis were reassessed. Between 1995 and 2013, 5409 muscle biopsies were performed. From 2000 to 2013, 4249 cases were included, and 3396 cases have currently been reviewed for this study; 378 biopsies of patients meeting PD clinical criteria were found. Of the latter, 76 patients were contacted. Eleven fulfilled criteria for GAA measurement. One patient was identified. Additionally, PD was confirmed in a 24-y-old patient biopsied at 3y8mo of age, whose biopsy was compatible with PD. Three other adults were identified in this context. Three other patients (previously published) in whom the biopsy did not confirm PD were diagnosed using blood spots. In one of them a second biopsy performed several years after the first was positive. Therefore, from the registry of biopsied patients, 18 with PD were identified: 11 were diagnosed by biopsy (two with infantile PD) and six had a negative biopsy. Diagnostic biopsies were 62.5% in LOPD. Based on the index cases (6), 11 positive siblings were identified using GAA assay. Furthermore, among patients meeting clinical criteria and with a negative biopsy, 58 in whom blood spots were not performed were contacted, for 23 others no contact data were available, and 290 are being studied. In conclusion, as previously reported, a diagnostic muscle biopsy can confirm the presence of PD; however, a negative biopsy does not rule out the diagnosis. Much remains to be elucidated regarding clinical and pathological findings in correlation with the differential diagnoses.