Adult Pompe disease: Report of a case as a differential diagnosis of inflammatory myopathy / Enfermedad de Pompe del adulto: reporte de un caso como diagnóstico diferencial de una miopatía inflamatoria

ABSTRACT Pompe disease, or glycogen storage disease type II, is an autosomal recessive disorder due to the deficiency of lysosomal acid α-glucosidase, the enzyme responsible for degrading glycogen to glucose. The adult-onset form is rare and is characterized, primarily by accumulation of glycogen in striated, cardiac, and smooth muscle tissue. It causes muscle weakness of proximal predominance, so it can be confused with an inflammatory myopathy. The case is presented of a 60 year-old adult with a previous diagnosis of polymyositis in whom Pompe disease was confirmed with a demonstration of the enzymatic deficit in a biological substrate and a genetic identification was obtained.

RESUMEN La enfermedad de Pompe o glucogenosis tipo n es un trastorno autosómico recesivo, debido a la deficiencia de la enzima lisosomal α-glucosidasa ácida encargada de degradar glucógeno a glucosa. La forma de inicio en el adulto es rara y se caracteriza fundamentalmente por acumulación de glucógeno en tejido muscular estriado, cardiaco y liso. Causa debilidad muscular de predominio proximal, por lo que se puede confundir con una miopatía inflamatoria. Se presenta el caso de un adulto de 60 arios con diagnóstico previo de polimiositis, en quien se confirmó una enfermedad de Pompe con demostración del déficit enzimático en sustrato biológico y se logró realizar una identificación genética.

First clinical and genetic description of a family diagnosed with late-onset Pompe disease from Costa Rica.

Glycogen storage disease type II, also known as Pompe disease, is an autosomal recessive disorder caused by deficiency of enzymatic activity of acid alpha-glucosidase. The wide phenotypical variation of this disease relates to the amount of residual enzymatic activity depending on the combination of mutations on each allele. We confirmed Pompe disease in a patient that presented with progressive weakness, recurrent episodes of respiratory failure associated with pneumonia, a predominantly demyelinating mixed sensorimotor polyneuropathy and paraspinal complex repetitive discharges. Genetic analysis of the GAA gene from this patient revealed two pathogenic compound heterozygous mutations: c.-32-13T>G (rs386834236, intronic), c.2560C>T (rs121907943, p.Arg854Ter); and one variant of unknown significance: c.1551+42G>A (rs115427918, intronic). We found expected mutations in two siblings and two nieces. Genetic variants reported in this family reflect on the European and African ancestry that we carry in our Costa Rican population.

Blunted Hypercapnic Respiratory Drive Response in Subjects With Late-Onset Pompe Disease.

BACKGROUND: Patients with late-onset Pompe disease develop progressive hypercapnic respiratory failure that can be disproportionate to the respiratory muscle compromise and/or thoracic restriction. Although recent studies have reported the presence of a blunted hypercapnic respiratory response in some subjects with neuromuscular disorders and chronic hypercapnia, no study has evaluated the integrity of the respiratory drive in subjects with late-onset Pompe disease. Thus, we endeavor to determine the CO2 rebreathing response in subjects with late-onset Pompe disease. METHODS: Respiratory muscle strength was assessed by measuring the maximum inspiratory pressure, and the maximum expiratory pressure. The maximum inspiratory pressure reflects the strength of the diaphragm and other inspiratory muscles, whereas the maximum expiratory pressure reflects the strength of the abdominal muscles and other expiratory muscles. We studied the hypercapnic drive response (measured as the ratio of the change in airway-occlusion pressure 0.1 s after the start of inspiration and end-tidal PCO2 in 13 subjects with late-onset Pompe disease and 51 healthy controls. RESULTS: Overall inspiratory muscle strength was within normal limits or slightly diminished in the late-onset Pompe disease group. Five subjects (38.5%) were chronically hypercapnic, and 9 (69.2%) had an increased breath-holding time. Compared with controls, the change in airway-occlusion pressure 0.1 s/change in end-tidal CO2 pressure slope (hypercapnic respiratory drive) was lower in the late-onset Pompe disease group (median 0.050 [interquartile range 0.027-0.118] vs 0.183 [0.153-0.233], P < .001). Nine subjects (69.2%) had a blunted change in airway-occlusion pressure 0.1 s/change in end-tidal carbon dioxide pressure slope. CONCLUSIONS: Subjects with late-onset Pompe disease had an impaired hypercapnic respiratory drive response. The clinical impact of this phenomenon in this subject subset deserves further investigation.