Prominent Respiratory Involvement Featured in High-Risk Screening for Late-Onset Pompe Disease in China

Abstract

Backgroud: Pompe disease is a rare metabolic disorder with available enzymatic replacement therapy. Contrasting with the classic infantile form, the others subtypes have a heterogeneous presentation that makes an early and accurate diagnosis difficulty. A multicenter observational study was aimed to assess the prevalence of late-onset Pompe disease (LOPD) in high-risk population, using dried blood spot (DBS) as a main screening tool.Methods: 20 Chinese neuromuscular centers were involved in the early LOPD screening study. Inclusion criteria were: (1) age ≥1 years, (2) either one of a) persistent hyperCKemia; or b) muscle weakness of axial and/or limb-girdle muscles; or c) unexplained restrictive respiratory insufficiency. Enzymatic activity of acid α-glucosidase (GAA) was measured on DBS by tandem mass spectrometry (MS/MS) assay. For the final diagnosis genotype was assessed by next-generation sequencing.Result: In a 9-month period, we studied 492 cases: 26 positive samples (5.3%) were detected by DBS screening. Molecular studies finally confirmed LOPD diagnosis in 8 cases (1.6%). The GAA activities in individuals bearing pseudodeficiency alleles were well separated from those in LOPD patients by MS/MS assay. The median interval from the onset of symptoms to diagnosis was 5 years. Besides axial/proximal muscle weakness, all patients showed respiratory insufficiency with a mean forced vital capacity of predicted of 48%. The level of creatine kinase ranged from normal to no more than 5-fold of upper normal limit. LOPD with isolated hyperCKemia was not identified.Conclusions: This study confirms that DBS test is a reliable method for screening for LOPD. Respiratory insufficiency is earlier and more severe among Chinese LOPD patients. LOPD presented with paucisymptomatic hyperCKemia. Therefore, a prompt diagnosis is critical to prognosis.