T.P.23: Search for Pompe patients in patients with undetermined myopathies in South-West Sweden

Abstract

In Pompe disease glycogen accumulates in lysosomes which in a muscle biopsy is seen as a vacuolar myopathy in most but not all cases. In a Danish study of unclassified LGMD patients 3/39 were found to have Pompe disease. We therefore asked if we also had un-diagnosed Pompe patients in Vastra Gotaland Region (VGR) of Sweden. We searched the muscle biopsy registry during the time period of 1986 until 2006 including 3665 biopsies. We also included patients at our Neuromuscular Center (NMC) who in 2011 did not have a definite diagnosis (either limb-girdle muscular dystrophy or myopathy of undetermined type). Patients who accepted to participate were examined personally. A dry blood spot (DBS) test was taken according to instructions from the lab (Centre for metabolic and mitochondrial diseases, CMMS at Karolinska, Stockholm, Sweden). Of the 193 patients identified by the muscle biopsy registry, 44 were deceased, 24 were in 2011 not living in the VGR and 65 had already a definite diagnosis. Thus 60 fulfilled the inclusion criteria and were invited, 46 accepted while 14 declined to come. We also identified and tested 36 patients at the NMC. Based on the laboratory test in 82 patients we did not find any patient with Pompe disease. The DBS test was low in 3 cases (11, 16 and 18% of normal) but a second blood sample showed a normal result based on GAA enzyme activity in lymphocytes. By further analyses we could diagnose 2 patients with Becker MD, 3 patients with FSHD, 2 patients with LGMD2A and one with 2I, one was shown to have OPMD, one sIBM and in 2 patients Welander distal myopathy. We did not find any Pompe patients in our survey; Thus, the prevalence of Pompe disease in adults in the VGR remains low – 3 in 1.6 million. We conclude that it is not fruitful to investigate patients with “unspecific myopathies” by DBS. However, reevaluation of the patients may reveal diagnosis of other myopathies, a finding that is important for the patients and their families.