GM1 gangliosidosis and Morquio B syndrome, both arising from beta-galactosidase (GLB1) deficiency, are very rare lysosomal storage diseases with an incidence of about 1:100,000– 1:200,000 live births worldwide. Here we report the beta-galactosidase gene (GLB1) mutation analysis of 21 unrelated GM1 gangliosidosis patients, and of 4 Morquio B patients, of whom two are brothers. Clinical features of the patients were collected and compared with those in literature. In silico analyses were performed by standard alignments tools and by an improved version of GLB1 three-dimensional models. The analysed cohort includes remarkable cases. One patient with GM1 gangliosidosis had a triple X syndrome. One patient with juvenile GM1 gangliosidosis was homozygous for a mutation previously identified in Morquio type B. A patient with infantile GM1 gangliosidosis carried a complex GLB1 allele harbouring two genetic variants leading to p.R68W and p.R109W amino acid changes, in trans with the known p.R148C mutation. Molecular analysis showed 27 mutations, 9 of which are new: 5 missense, 3 microdeletions and a nonsense mutation. We also identified four new genetic variants with a predicted polymorphic nature that was further investigated by in silico analyses. Three-dimensional structural analysis of GLB1 homology models including the new missense mutations and the p.R68W and p.R109W amino acid changes, showed that all the amino acids replacements affected the resulting protein structures in different ways, from changes in polarity to folding alterations. Genetic and clinical associations led us to undertake a critical review of the classifications of late-onset GM1 gangliosidosis and Morquio B disease.

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Aim: To investigate the presence of inflammatory bowel disease (IBD) and to evaluate the progression of bowel involvement after two years’follow‐up in seven patients affected by glycogen storage disease type Ib (GSDIb). Methods: Seven patients (5F, 2M, aged 4.5–20.6 y) entered the study. Bowel involvement was evaluated by ileocolonoscopy and specific IBD serologic markers. To evaluate disease activity, Paediatric Crohn's Disease Activity Index (PCDAI), terminal ileum wall thickness detected at ultrasonography (US), 99mTechnetium labelled autologous White Cell Scan (Tc‐WCS) and barium meal with follow‐through were investigated. Results: Ileocolonoscopy and histology examination revealed variable degrees of bowel involvement in all patients. The results of serologic markers were indicative of a Crohn's‐like ileocolitis. US and Tc‐WCS, could clearly define patients with severe inflammatory involvement, but failed to identify all patients with mild to moderate disease. For the most severely affected patients, anti‐inflammatory agents and steroids were prescribed, whereas nutritional therapy with polymeric formula and antibiotics were assumed by two other patients and antibiotics only by one patient. Granulocyte colony‐stimulating factor (G‐CSF) was prescribed to all patients. Ileocolonoscopy and histology data improved in all patients. The assumption of G‐CSF and/or gastric drip feeding (g.d.f.) was inversely associated with the PCDAI results (p < 0.05). Conclusion: IBD is common in patients affected by GSDIb independently of the severity of gastrointestinal signs and symptoms. Different therapeutic approaches can be used according to the severity of IBD. G‐CSF treatment and g.d.f. can be protective factors for IBD.

Type 1 Gaucher's disease (GD1) is traditionally regarded as "non-neurological". Spatiotemporal and kinematic analysis of gait was carried on thirteen GD1 patients and thirteen healthy controls. We identified a previously unknown subclinical reduction of amplitude of movements in GD1. Articular excursion of ankle, knee and hip was reduced during the swing phase of gait (p < 0.0001). Furthermore, the excursion of the knee appeared also significantly more asymmetric in GD1 patients (p = 0.02). Correction for age, BMI and basal walking speed did not modify the significance. Accordingly to the recent observations that GD1 predisposes to Parkinson's disease, the impaired and asymmetric gait kinematics that we observed might be interpreted as a form of extrapyramidal involvement.

Mucolipidosis type III (MLIII) is an autosomal recessive disorder affecting lysosomal hydrolase trafficking. In a study of 10 patients from seven families with a clinical phenotype and enzymatic diagnosis of MLIII, six novel GNPTG gene mutations were identified. These included missense (p.T286M) and nonsense (p.W111X) mutations and a transition in the obligate AG-dinucleotide of the intron 8 acceptor splice site (c.610-2A>G). Three microdeletions were also identified, two of which (c.611delG and c.640_667del28) were located within the coding region whereas one (c.609+28_610-16del) was located entirely within intron 8. RT-PCR analysis of the c.610-2A>G transition demonstrated that the change altered splicing, leading to the production of two distinct aberrantly spliced forms, viz. the skipping of exon 9 (p.G204_K247del) or the retention of introns 8 and 9 (p.G204VfsX28). RT-PCR analysis, performed on a patient homozygous for the intronic deletion (c.609+28_610-16del), failed to detect any GNPTG RNA transcripts. To determine whether c.609+28_610-16del allele-derived transcripts were subject to nonsense-mediated mRNA decay (NMD), patient fibroblasts were incubated with the protein synthesis inhibitor anisomycin. An RT-PCR fragment retaining 43 bp of intron 8 was consistently detected suggesting that the 33-bp genomic deletion had elicited NMD. Quantitative real-time PCR and GNPTG western blot analysis confirmed that the homozygous microdeletion p.G204VfsX17 had elicited NMD resulting in failure to synthesize GNPTG protein. Analysis of the sequences surrounding the microdeletion breakpoints revealed either intrinsic repetitivity of the deleted region or short direct repeats adjacent to the breakpoint junctions. This is consistent with these repeats having mediated the microdeletions via replication slippage and supports the view that the mutational spectrum of the GNPTG gene is strongly influenced by the properties of the local DNA sequence environment.

MPS VI (mucopolysaccharidosis type VI) is a lysosomal storage disease in which deficient activity of the enzyme N-acetylgalactosamine 4-sulfatase [ASB (arylsulfatase B)] impairs the stepwise degradation of the GAG (glycosaminoglycan) dermatan sulfate. Clinical studies of ERT (enzyme replacement therapy) by using rhASB (recombinant human ASB) have been reported with promising results. The release of GAG into the urine is currently used as a biomarker of disease, reflecting in some cases disease severity and in all cases therapeutic responsiveness. Using RNA studies in four Italian patients undergoing ERT, we observed that TNFalpha (tumour necrosis factor alpha) might be a biomarker for MPS VI responsive to therapy. In addition to its role as a potential biomarker, TNFalpha expression could provide insights into the possible pathophysiological mechanisms underlying the mucopolysaccharidoses.

Hyperphenylalaninemia (Online Mendelian Inheritance in Man ®database: 261600) is an autosomal recessive disorder mainly due to mutations in the gene for phenylalanine hydroxylase; the most severe form of hyperphenylalaninemia is classic phenylketonuria. We sequenced the entire gene for phenylalanine hydroxylase in 51 unrelated hyperphenylalaninemia patients from Southern Italy. The entire locus was genotyped in 46 out of 51 hyperphenylalaninemia patients, and 32 different disease‐causing mutations were identified. The pathologic nature of two novel gene variants, namely, c.707‐2delA and p.Q301P, was demonstrated by in vitro studies. c.707‐2delA is a splicing mutation that involves the accepting site of exon 7; it causes the complete skipping of exon 7 and results in the truncated p.T236MfsX60 protein. The second gene variant, p.Q301P, has very low residual enzymatic activity (∼ 4.4%), which may be ascribed, in part, to a low expression level (8–10%). Both the decreased enzyme activity and the low expression level are supported by analysis of the 3D structure of the molecule. The putative structural alterations induced by p.Q301P are compatible with protein instability and perturbance of monomer interactions within dimers and tetramers, although they do not affect the catalytic site. In vivo studies showed tetrahydrobiopterin responsiveness in the p.Q301P carrier but not in the c.707‐2delA carrier. We next investigated genotype–phenotype correlations and found that genotype was a good predictor of phenotype in 76% of patients. However, genotype–phenotype discordance occurred in approximately 25% of our patients, mainly those bearing mutations p.L48S, p.R158Q, p.R261Q and p.P281L.