Adult acid maltase deficiency: an open trial with albuterol and branched- chain aminoacids

We studied natural history and morphological features in 10 adult onset Acid Maltase Deficient (AMD) patients who were ambulant (age range 23-69 yrs), and 1 juvenile-onset AMD patient, who was wheelchair-bound and respirator-dependent (disease duration 36 yrs). Morphological features in muscle biopsy showed a vacuolar myopathy, there was Golgi apparatus proliferation within fibers, the autophagic vacuoles were positive at their periphery for caveolin-3 and dystrophin, documenting extensive protein turnover. We first clinically followed the patients periodically during the baseline period of the trial, by evaluating 5 limb-girdle muscles with the Medical Research Council Scale and monitored the performance of 4 functional tests (walking, climbing stairs, Gowers’ manoeuvre and rising from a chair). We then performed in 5 patients (4 adult-onset and 1 juvenile-onset) an open prospective clinical trial with a β2 agonist (albuterol) and pulsed branched-chain aminoacids (dose 500 ml 4% intravenous for 10 days subsequently every month) for six months. During this period, treated patients improved in functional score. In the 4 adultonset patients no side effects were found, while the only respirator-dependent juvenileonset patient, following an initial intravenous infusion of albuterol, presented signs of pulmonary oedema. He then well tolerated oral albuterol. The 5 treated patients continued oral albuterol treatment after the initial 6 months, for over 3 years. Our data suggest that in adult-onset AMD, the use of oral β2-agonist drug might be efficacious to antagonize muscle wasting and might be used as symptomatic therapy until enzyme replacement or aminoacid (leucine) therapy will be available.