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Pompe disease is caused by the accumulation of glycogen in the lysosomes due to a deficiency of the lysosomal acid-α-glucosidase (GAA) enzyme. Depending on residual enzyme activity, the disease manifests two distinct phenotypes. In this study, we assess an enzymatic and genetic analysis of Hungarian patients with Pompe disease. Twenty-four patients diagnosed with Pompe disease were included. Enzyme activity of acid-α-glucosidase was measured by mass spectrometry. Sanger sequencing and an MLPA of the GAA gene were performed in all patients. Twenty (83.33%) patients were classified as having late-onset Pompe disease and four (16.66%) had infantile-onset Pompe disease. Fifteen different pathogenic GAA variants were detected. The most common finding was the c.-32-13 T &gt, G splice site alteration. Comparing the α-glucosidase enzyme activity of homozygous cases to the compound heterozygous cases of the c.-32-13 T &gt, G disease-causing variant, the mean GAA activity in homozygous cases was significantly higher. The lowest enzyme activity was found in cases where the c.-32-13 T &gt, G variant was not present. The localization of the identified sequence variations in regions encoding the crucial protein domains of GAA correlates with severe effects on enzyme activity. A better understanding of the impact of pathogenic gene variations may help earlier initiation of enzyme replacement therapy (ERT) if subtle symptoms occur. Further information on the effect of GAA gene variation on the efficacy of treatment and the extent of immune response to ERT would be of importance for optimal disease management and designing effective treatment plans.

Pompe disease (PD) is a rare lysosomal disease caused by the deficient activity of acid alpha-glucosidase (GAA) enzyme due to mutations in the GAA gene. The enzymatic deficiency leads to the accumulation of glycogen within the lysosomes. Clinically, the disease has been classically classified in infantile and childhood/adult forms. Presently cc. close to 600 mutations distributed throughout the whole gene have been reported. The c.-32-13TG splice mutation that is very common in patients of Caucasian origin affected by the childhood/adult form of the disease, with an allelic frequency close to 70%. Enzyme replacement treatment (ERT) is available for the patients with Pompe disease (Myozyme). In this paper, we are presenting the long term follow up of 13 adult onset cases treated more than 5 years. The longest follow up was 15 years. To evaluate the treatment efficacy, the 6 minutes walking test (6MWT) and the respiratory functions were monitored annually. The analysis revealed that at the beginning of ERT for 3-4 years the 6MWT had been generally increasing, then it declined, and after 10 years it was lower in 77% of the cases than it had been at the start of the treatment. In 23% of the cases the 6MWT increased during the follow up time. Only one of the patients become wheelchair dependent during the follow-up period. The respiratory function showed similar results especially in supine position. A high degree of variability was observed among patients in their responses to the treatment, which only partially associated with the antibody titer against the therapeutic protein. The efficacy of the ERT was associated with the type of the disease causing mutation, the baseline status of the disease, the lifestyle and the diet of the patient. The long-term follow up of the patients with innovative orphan drugs is necessary to really understand the value of the treatment and the need of the patients.A Pompe-kór (PD) egy ritka lizoszomális tárolási betegség, amit a GAA gén mutációja következtében kialakuló α-glü­kozidáz (GAA) enzim elégtelen mûködése okoz. Az enzim­deficientia a glikogén lizoszomális felszaporodásához vezet. A betegségnek két klinikai formája ismert, az újszülöttkori, valamint a késôi forma. Jelenleg a betegség hátterében a GAA génnek közel 600 mutációja ismert. A kaukázusi populációban a késôi forma hátterében a c.-32-13TG mutáció a leggyakoribb, az allélfrekvencia közel 70%. A Pompe-kórt enzimpótló terápiával (ERT) tudjuk kezelni, kéthetente Myozyme infúzió adásával. Közleményünkben 13, több mint öt éve kezelt, késôi kezdetû formában szen­vedô beteg hosszú távú követését mutatjuk be. A leg­hosszabb követési idô 15 év volt. A kezelés eredmé­nyességének megítélésére évente mértük a 6 perces járó­távolságot és a légzésfunkciót. Az adatok alapján a 6 per­ces járótávolság az enzimpótló kezelés indítása után körülbelül 3-4 évig javult, ezt követôen az esetek többségében a megtett távolság csökkent. A több mint 10 éves követés után a kezdeti 6 perces járótávolsághoz képest romlást tapasztaltunk az esetek 77%-ában, javulást az esetek 23%-ában. A követés ideje alatt mindössze egyetlen beteg került kerekesszékbe. A légzésfunkció, különösen fekvô helyzetben hasonlóan alakult. A betegek terápiára adott válaszában nagy variabilitást figyeltünk meg, ami csak részben mutatott összefüggést a terápiás fehérje ellen termelôdô antitestszinttel. Az ERT eredményessége jelentôsen függött a betegséget okozó mutáció típusától, a betegség státuszától a kezelés kezdetekor, a beteg fizikai aktivitásától és táplálkozási szokásaitól. Az innovatív orphan gyógyszerekkel kezelt betegek hosszú távú követése kiemelkedôen fontos ahhoz, hogy megismerjük a kezelés valós hasznát és a betegek igényeit.

Pompe's disease is an autosomal recessive disease caused by deficiency of acid-alpha-glucosidase.Authors analyzed the phenotype of 11 Hungarian patients with Pompe's disease and evaluated clinical parameters and response to enzyme replacement therapy during a long-term follow-up in 8 patients.One patient with atypical infantile form presented with cardiomyopathy and a very slow progression of motor deficits; after 2 years of enzyme replacement therapy no disability was present at the age 6 years. Another patient was asymptomatic at the age of 2.5 years. The adult onset form was characterized by slight to prominent limb-girdle myopathy with an age of onset between 20 and 50 years. In 3 of such cases respiratory insufficiency was also present.Hungarian patients with Pompe's disease presented with a wide phenotypic variability ranging from atypical early childhood form with slowly progressive course to late-onset limb-girdle myopathy with variable courses. Enzyme replacement therapy resulted in significant improvement in motor and respiratory functions in most of the patients.