529P Paucisymptomatic late onset Pompe disease: lessons from the clinical, radiological and histopathological long-term follow-up of an untreated patient.

To describe the natural history of a Late-onset Pompe disease (LOPD) asymptomatic and untreated patient in order to gain insight to guide evidence-based patient care and therapeutic decisions. Clinical, radiological, and histopathological reevaluation of a LOPD asymptomatic and untreated patient 32 years after the initial diagnosis. A presymptomatic diagnosis of LOPD was made in a 2-year-old male patient with isolated elevation of CK levels, based on widespread left deltoid muscle glycogen deposits on biopsy and an enzymatic and genetic confirmation. The patient remains asymptomatic at 34 years old, despite not introducing enzyme replacement therapy (ERT). The clinical examination is normal, with stable functional outcomes (6-minutes' walk test > 600 m, 4 stairs climb test < 2 sec, MFM=100%) and normal supine vital capacity, despite moderate but steady progression of fatty degeneration of teres major, abdominal and adductor magnus muscles on MRI in the last 14 years. Interestingly, a new biopsy of the same muscle shows now an almost normal histological picture. Int the advent of neonatal screening, this case report advises against the systematic introduction of ERT in asymptomatic LOPD patients. Furthermore, muscle MRI seems to be the most sensitive method to detect the earliest signs of disease progression. The normality (or normalization) of the muscle biopsy performed in the same muscle years after the diagnosis advises against the prospective analysis of muscle glycogen accumulation in clinical trials. Finally, whether muscle glycogen deposits may spontaneously improve over time in mild cases needs further study. [ABSTRACT FROM AUTHOR]