Maria Alice Donati

North Star Ambulatory Assessment, 6-minute walk test and timed items in ambulant boys with Duchenne muscular dystrophy

The North Star Ambulatory Assessment is a functional scale specifically designed for ambulant boys affected by Duchenne muscular dystrophy (DMD). Recently the 6-minute walk test has also been used as an outcome measure in trials in DMD. The aim of our study was to assess a large cohort of ambulant boys affected by DMD using both North Star Assessment and 6-minute walk test. More specifically, we wished to establish the spectrum of findings for each measure and their correlation. This is a prospective multicentric study involving 10 centers. The cohort included 112 ambulant DMD boys of age ranging between 4.10 and 17 years (mean 8.18±2.3 DS). Ninety-one of the 112 were on steroids: 37/91 on intermittent and 54/91 on daily regimen. The scores on the North Star assessment ranged from 6/34 to 34/34. The distance on the 6-minute walk test ranged from 127 to 560.6 m. The time to walk 10 m was between 3 and 15 s. The time to rise from the floor ranged from 1 to 27.5 s. Some patients were unable to rise from the floor. As expected the results changed with age and were overall better in children treated with daily steroids. The North Star assessment had a moderate to good correlation with 6-minute walk test and with timed rising from floor but less with 10 m timed walk/run test. The 6-minute walk test in contrast had better correlation with 10 m timed walk/run test than with timed rising from floor. These findings suggest that a combination of these outcome measures can be effectively used in ambulant DMD boys and will provide information on different aspects of motor function, that may not be captured using a single measure.

Reliability of the North Star Ambulatory Assessment in a multicentric setting

The aim of this study was to investigate the suitability of the North Star Ambulatory Assessment as a possible outcome measure in multicentric clinical trials. More specifically we wished to investigate the level of training needed for achieving a good interobserver reliability in a multicentric setting. The scale was specifically designed for ambulant children with Duchenne Muscular Dystrophy and includes 17 items that are relevant for this cohort. Thirteen Italian centers participated in the study. In the first phase of the study we provided two training videos and an example of the scale performed on a child. After the first session of training, all the 13 examiners were asked to send a video with an assessment performed in their centre and to score all the videos collected. There were no difficulties in performing the items and in obtaining adequate videos with a hand held camera but the results showed a poor interobserver reliability (<.5). After a second training session with review and discussion of the videos previously scored, the same examiners were asked to score three new videos. The results of this session had an excellent interobserver reliability (.995). The level of agreement was maintained even when the same videos were rescored after a month, showing a significant intra-observer reliability (.95). Our results suggest that the NSAA is a test that can be easily performed, completed in 10 min and can be used in a multicentric setting, providing that adequate training is administered.

Long Term Natural History Data in Ambulant Boys with Duchenne Muscular Dystrophy: 36-Month Changes

The 6 minute walk test has been recently chosen as the primary outcome measure in international multicenter clinical trials in Duchenne muscular dystrophy ambulant patients. The aim of the study was to assess the spectrum of changes at 3 years in the individual measures, their correlation with steroid treatment, age and 6 minute walk test values at baseline. Ninety-six patients from 11 centers were assessed at baseline and 12, 24 and 36 months after baseline using the 6 minute walk test and the North Star Ambulatory Assessment. Three boys (3%) lost the ability to perform the 6 minute walk test within 12 months, another 13 between 12 and 24 months (14%) and 11 between 24 and 36 months (12%). The 6 minute walk test showed an average overall decline of −15.8 (SD 77.3) m at 12 months, of −58.9 (SD 125.7) m at 24 months and −104.22 (SD 146.2) m at 36 months. The changes were significantly different in the two baseline age groups and according to the baseline 6 minute walk test values (below and above 350 m) (p<0.001). The changes were also significantly different according to steroid treatment (p = 0.01). Similar findings were found for the North Star Ambulatory Assessment. These are the first 36 month longitudinal data using the 6 minute walk test and North Star Ambulatory Assessment in Duchenne muscular dystrophy. Our findings will help not only to have a better idea of the progression of the disorder but also provide reference data that can be used to compare with the results of the long term extension studies that are becoming available.

Clinical and genetic heterogeneity of branching enzyme deficiency (glycogenosis type IV)

Background: Glycogen storage disease type IV (GSD-IV) is a clinically heterogeneous autosomal recessive disorder due to glycogen branching enzyme (GBE) deficiency and resulting in the accumulation of an amylopectin-like polysaccharide. The typical presentation is liver disease of childhood, progressing to lethal cirrhosis. The neuromuscular form of GSD-IV varies in onset (perinatal, congenital, juvenile, or adult) and severity. Objective: To identify the molecular bases of different neuromuscular forms of GSD-IV and to establish possible genotype/phenotype correlations. Methods: Eight patients with GBE deficiency had different neuromuscular presentations: three had fetal akinesia deformation sequence (FADS), three had congenital myopathy, one had juvenile myopathy, and one had combined myopathic and hepatic features. In all patients, the promoter and the entire coding region of the GBE gene at the RNA and genomic level were sequenced. Results: Nine novel mutations were identified, including nonsense, missense, deletion, insertion, and splice-junction mutations. The three cases with FADS were homozygous, whereas all other cases were compound heterozygotes. Conclusions: This study expands the spectrum of mutations in the GBE gene and confirms that the neuromuscular presentation of GSD-IV is clinically and genetically heterogeneous.

NPHP1 gene deletion is a rare cause of Joubert syndrome related disorders

Joubert syndrome (JS) is an autosomal recessive disorder presenting with congenital hypotonia evolving into ataxia, developmental delay, and either oculomotor apraxia or abnormalities of respiratory pattern or both. JS is characterised, using magnetic resonance imaging (MRI), by cerebellar vermian hypoplasia and a complex brain stem malformation called the “molar tooth sign” (MTS), consisting of thickened, elongated, and reoriented superior cerebellar peduncles and a deep interpeduncular fossa.1 JS has been classified into two groups, A and B, the latter being characterised by the occurrence of retinal and/or renal involvement.2 Key associated features of JS are retinal dystrophy and nephronophthisis, but other manifestations include ocular colobomas, liver fibrosis, and polydactyly. The variable involvement of other organs identifies a large spectrum of syndromes sharing the MTS (such as Arima, COACH, and Senior-Loken syndromes) which, together with JS, are termed Joubert syndrome related disorders (JSRD) or MTS related syndromes.3–5 To date, three genetic loci associated with JSRD have been mapped to chromosome 9q34.3 (JBTS1), 11p11.2–q12.3 (JBTS2), and 6q23 (JBTS3).6–9 Recently, mutations in the AHI1 gene have been identified in three JBTS3 linked families presenting with a pure cerebellar phenotype.10 Isolated nephronophthisis (NPH) is an autosomal recessive tubulointerstitial medullary kidney disease and is one of the most frequent monogenic causes of chronic renal failure in childhood. Four genes causing infantile or juvenile NPH have been cloned so far (NPHP1 to 4).11–14 Of these, NPHP1 is the most commonly mutated gene, being responsible for at least 50% of cases with juvenile NPH.15,16 A large homozygous deletion of the NPHP1 gene is found in more than 80% of patients, while less than 5% are compound heterozygote for the gene deletion and a point mutation on the other allele.16 Most patients with the NPHP1 deletion demonstrate …

Biochemical evaluation of a patient with a familial form of leucine-sensitive hypoglycemia and concomitant hyperammonemia

A case of a child with recurrent episodes of severe hypoglycemia since the age of 6 months is reported. Biochemical evaluation extended to the first-degree relatives is consistent with a familial form of hypoglycemia due to a leucine-sensitive hyperinsulinism. In addition, this patient has a persistent elevation of serum ammonia levels of uncertain etiology that is more pronounced after meals. Urea cycle defects, organic acidurias, and beta-oxidation defects have been ruled out, as well as a possible excessive deamination of glucogenetic amino acids. This unexpected hyperammonemia, which was also detected in the mother, might be related to leucine hypersensitivity.

Diagnosis of glycogenosis type II

The diagnosis of glycogenosis type II is often complicated by the rarity of the condition and the heterogeneity of the clinical manifestations of the disease. It is a progressive, debilitating, and often fatal neuromuscular disorder that manifests as a continuum of clinical phenotypes, which vary with respect to organ involvement, age at onset, and severity. Early diagnosis requires both increased awareness among physicians regarding the clinical characteristics of the disease and fast and reliable acid alpha-glucosidase (GAA) enzyme activity assays to confirm the GAA deficiency. The clinical diagnosis of glycogenosis type II is confirmed by virtual absence (found in infants) and marked reduced activity (found in juveniles and adults) of GAA enzyme in blood samples, cultured fibroblasts, and muscle biopsies. This article specifically highlights the need for early recognition of the clinical manifestation of the disease in infants, juveniles, and adults. Descriptions of the main clinical features of the condition, as well as differential diagnosis are included. In addition, the tests required for a confirmed diagnosis are described, and use of muscle imaging to evaluate muscle pathology is reviewed.

24 Month Longitudinal Data in Ambulant Boys with Duchenne Muscular Dystrophy

Objectives The aim of the study was i) to assess the spectrum of changes over 24 months in ambulant boys affected by Duchenne muscular dystrophy, ii) to establish the difference between the first and the second year results and iii) to identify possible early markers of loss of ambulation. Methods One hundred and thirteen patients (age range 4.1–17, mean 8.2) fulfilled the inclusion criteria, 67 of the 113 were on daily and 40 on intermittent steroids, while 6 were not on steroids. All were assessed using the 6 Minute Walk Test (6MWT), the North Star Ambulatory Assessment (NSAA) and timed test. Results On the 6MWT there was an average overall decline of −22.7 (SD 81.0) in the first year and of −64.7 (SD 123.1) in the second year. On the NSAA the average overall decline was of −1.86 (SD 4.21) in the first year and of −2.98 (SD 5.19) in the second year. Fourteen children lost ambulation, one in the first year and the other 13 in the second year of the study. A distance of at least 330 meters on the 6MWT, or a NSAA score of 18 at baseline reduced significantly the risk of losing ambulation within 2 years. Conclusions These results can be of help at the time of using inclusion criteria for a study in ambulant patients in order to minimize the risk of patients who may lose ambulation within the time of the trial.

GM1 gangliosidosis and Morquio B disease: an update on genetic alterations and clinical findings

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 acid 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.

Management and treatment of glycogenosis type II

Glycogenosis type II is a multisystem disorder that requires management by a multidisciplinary team. The team should include several specialists, such as a metabolic disease specialist or biochemical geneticist, cardiologist, pulmonologist, neurologist, neuromuscular specialist, intensivist, orthopedist, respiratory therapist, physical therapist, occupational therapist, otolaryngologist speech therapist, audiologist, genetic counselor, and a metabolic dietician, who, as a team, will be capable of addressing the different manifestations of the condition. Aspects of functional assessment, rehabilitation, nutritional management, care coordination, nursing, genetic counseling, prenatal diagnosis, and screening are discussed in this article. In addition, treatment of glycogenosis type II is reviewed with attention to emerging therapeutic options.