Dried Blood Spots Allow Targeted Screening to Diagnose Mucopolysaccharidosis and Mucolipidosis

Abstract

Background: As patients with different types of mucopolysaccharidosis (MPS) and mucolipidosis (ML) may present with overlapping clinical features -including coarse face, hepatosplenomegaly, bone dysplasia and claw-hand deformities, collectively also called 'MPS-like phenotype', enzymatic and/or molecular genetic analyses are indispensable for accurate diagnosis and applying specific therapy. In this prospective study, we screened patients with symptoms compatible with MPS for MPS I, II (males) and VI.Methods: Dried blood spots/specimens (DBS) were collected from 200 patients with an MPS-like phenotype and analysed for activities of a-iduronidase (IDUA), iduronate-2-sulphatase (IDS), and arylsulphatase B (ARSB), the enzymes deficient in mucopolysaccharidosis (MPS) type I, II and VI, respectively. For the samples with pathologic enzyme activity, mutational analysis was carried out using the same DBS.Results: Based on enzymatic analysis of 200 DBS samples, a total of 45 (22.5%) showed low activity; 17 for MPS I (8.5%), 11 for MPS II (5.5%) and 9 for MPS VI (4.5%). Enzyme activities were suggestive for ML II/III in 8 (4.0%) cases. For 41 (91.1%) samples, DNA could be extracted from the filter paper. Mutations were identified in 11 (64.7%), 11 (100%), 9 (100%) and 5 (62.5%) patients putatively diagnosed biochemically with MPS I, II, VI, and ML II/III, respectively.Conclusions: DBS enzymatic analysis can be used to diagnose MPS/ML. Initial results should be confirmed by a second enzyme assay and/or by molecular genetic testing. Given the advantages of DBS over other sample types in terms of ease of collection, storage and transportation, DBS are particularly useful for screening patients with an MPS-like phenotype in regions lacking specialised laboratories. In order to ascertain the diagnosis in a large number of cases, patients should be assessed in parallel for at least MPS I, II and VI.

Analysis of Mucolipidosis II/III GNPTAB Missense Mutations Identifies Domains of UDP-GlcNAc:lysosomal Enzyme GlcNAc-1-phosphotransferase Involved in Catalytic Function and Lysosomal Enzyme Recognition

“…H956R was not analyzed in this study, as it likely has the same consequence as H956Y. The patient with C523R was homozygous for this mutation, but the clinical phenotype was not specified (23). Antisense Morpholino Injection and mRNA Rescue-Expression of GlcNAc-1-phosphotransferase (␣␤ subunit, gnptab) was inhibited by injection of morpholino oligonucleotides (17).…”

Prevalence of Mucopolysaccharidosis Types I, II, and VI in the Pediatric and Adult Population with Carpal Tunnel Syndrome (CTS). Retrospective and Prospective Analysis of Patients Treated for CTS

“…All patients who consented were included and had a filter paper blood spot sample taken. The tests were sent by courier post at room temperature to the Metabolic Laboratory at Hamburg University Medical Center and analyzed enzymatically for activities of a-iduronidase (IDUA), iduronate-2-sulfatase (IDS), and arylsulfatase B (ARSB), the enzymes deficient in mucopolysaccharidosis (MPS) type I, II, and VI, respectively (Cobos et al 2014).…”

Combined in vitro and in silico analyses of missense mutations in GNPTAB provide new insights into the molecular bases of mucolipidosis II and III alpha/beta

“…Whereas the Trp 357 , Leu 358 , Leu 380 , Ile 392 , Ile 395 , Leu 398 , and Phe 420 residues in the CR2 domain may be crucial for intermolecular and/or intramolecular hydrophobic interactions of GlcNAc‐1‐phosphotransferase, the conformation of Pro 355 and Pro 381 may stabilize the molecular structure of the enzyme and, in particular, of the CR2 domain (Dill, ). Most importantly, among conserved residues within the stealth domains, missense mutations leading to amino acid substitutions of Glu 389 , Asp 408 , His 956 , and Arg 986 have been identified in individuals affected by MLII and MLIII alpha/beta, that is, p.Glu389Lys (Velho et al, ), p.Asp408Asn (Wang et al, ), p.His956Tyr (Otomo et al, ), p.His956Arg (Cathey et al, ), p.Arg986Cys (Cobos, Steglich, Santer, Lukacs, & Gal, ; Coutinho et al, ), p.Arg986Gly (Velho et al, ), and p.Arg986His (Mistri et al, ). The clinical description and the molecular analysis of the patient with severe MLII harboring the homozygous mutation p.Glu389Lys (Velho et al, ) have become available and are presented here for the first time (Supporting Information).…”