G.P.113 What lies beneath: Progressive scoliosis unravelling a late onset Pompe disease presentation

Abstract

Abstract Pompe disease (PD) or acid maltase deficiency (glycogen storage disease type II) is a rare autosomal recessive lysosomal glycogen storage disease particularly affecting the myocardium, skeletal muscle and liver. Late-onset Pompe disease (LOPD) is not an uncommon presentation of PD and has a wide clinical variability. To report a case of a patient referred for evaluation of progressive scoliosis whose clinical investigation pointed out to LOPD. Case A female patient, 15 years old, born to non-consanguineous and heatlhy parents, was referred to our neurogenetics clinics because of progressive scoliosis of unknown cause. There was no complaint regarding skeletal muscle weakness, but the patient described morning headache and some breathing difficulties. Evaluation for genetic causes of progressive scoliosis (such as late-onset spinal muscular atrophy, connective tissue disorders and limb-girdle myopathies) was performed. Enzyme assays for alpha-glucosidase (acid maltase) on filter paper showed decreased activity, later confirmed in leukocytes and fibroblasts; mild elevation of Hex4 was seen in urine. Molecular studies showed that the patient harbored a mutation associated with a late-onset form of Pompe disease (c.-32-13T>G). LOPD comprises a continuum of phenotypes ranging from typical progressive limb-girdle myopathy to more severe diaphragmatic weakness as first presentation. Probably because of this wide range of clinical manifestations, many patients are misdiagnosed with more common diseases. Scoliosis is a very common feature of LOPD, although it was never reported before as the main manifestation in a patient with subclinical muscle weakness. Our report reinforces the importance looking for atypical presentation of LOPD and the practical aspects of using dried-blood spots in the investigation of patients with progressive scoliosis of unknown cause.