Eugénia Pinto

Prevalence of lysosomal storage diseases in Portugal

Lysosomal storage diseases (LSDs) are a group of inherited metabolic disorders individually considered as rare, and few data on its prevalence has been reported in the literature. The overall birth prevalence of the 29 different LSDs studied in the Portuguese population was calculated to be 25/100 000 live births, twice the prevalence previously described in Australia and in The Netherlands. The comparison of the prevalence profile of the LSDs presenting a prevalence higher than 0.5/100 000 in the Portuguese, Dutch and Australian populations showed, in the Portuguese, the existence of a higher prevalence of GM2 gangliosidoses (B variant), mucolipidoses (II and III), Niemman-Pick type C and metachromatic leukodystrophy (MLD), and a lower prevalence of Pompe and Fabry. The highest prevalence value for a single LSD is the one of GM2 gangliosidoses (B variant), corresponding to 3/100 000, a value which is significantly higher than the prevalence of the most frequent LSD in Dutch, Pompe disease (2/100 000) and Australians, Gauchers disease (GD) (1.8/100 000). It is worth noting that the highest prevalence of GM2 gangliosidoses found in the Portuguese is mainly due to the existence of a unique subtype, the rare juvenile B1 variant.

Clinicopathological and molecular characterization of neuronal ceroid lipofuscinosis in the Portuguese population

Abstract. A series of 53 Portuguese patients (derived from 43 families) born in the period 1963–1999 have been diagnosed with neuronal ceroid lipofuscinosis (NCL) based on clinicopathological findings. Plotting the cumulative number of new cases per year against the year of birth resulted in a slightly S-shaped curve, with a nearly straight central segment over a period of 14 years (1977–1990) indicating a continuous registration of new cases born during the corresponding time period. In this period the prevalence of overall NCL in the Portuguese population was calculated to be 1.55 per 100.000 live births.Twenty-six patients from 20 unrelated families were further evaluated by combining clinicopathological with biochemical and genetic data. No intra-familial heterogeneity was observed. Four sub-types of childhood NCL were identified: infantile NCL (INCL) with granular osmiophilic inclusions (GROD) and PPT1 deficiency (1/26), classical LINCL with curvilinear (CV) inclusions and tripeptidyl peptidase (TPP1) deficiency (3/26), variant late infantile NCL (LINCL) with fingerprint/curvilinear (FP/CV) inclusions and normal TPP1 enzyme activity (11/26) and juvenile NCL (JNCL) with a mix of FP/CV (11/26). Eight of 11 JNCL patients were homozygous for the 1.02-kb deletion in the CLN3 gene, and 3 were heterozygous with an unidentified mutation in the second allele. The 1.02-kb deletion in the CLN3 gene accounted for 86.3 % (19/22) of CLN3-causing alleles and 36.5 % (19/52) of childhood NCL defects. The causal mutations for CLN1 and CLN2 were V181M (2/2) and R208X (4/6), respectively. CLN1, CLN2 and CLN3 affected 3.8 %, 11.5 % and 42.3 % of NCL Portuguese patients, respectively. In 42.3 % of patients affected by the vLINCL form, CLN3, CLN5 and CLN8 gene defects were excluded by direct sequencing of cDNA. Genetic variants such as CLN6 might therefore cause a significant portion of childhood NCL in the Portuguese population.The relative frequency of classical childhood forms of NCL in the Portuguese population is reported and contributes to the knowledge of genetic epidemiology of these world-widely distributed disorders.

Homozygosity for two mild glucocerebrosidase mutations of probable Iberian origin.

To the Editor: Gaucher disease (GD) (McKusick 230800) is characterised by the accumulation of glucosylceramide, usually due to the defective activity of lysosomal glucocerebrosidase (EC 3.2.1.45). Most patients are compound heterozygotes for different mutations. Common exceptions are homozygosity for N370S, which results in type 1 GD, and for L444P usually giving rise to neuronopathic forms (1). Mutations G377S and N396T were first described in type 1 compound heterozygotes with L444P and N370S, respectively (2, 3). However, in the Portuguese they have also appeared in homozygosity. Six homozygous patients are presented in this report. Patient characteristics are summarised in Table 1 and, with the exception of patient 6, at least the last three generations originated from the same region of central Portugal. Standard methods were used in the protein studies (4–6) and genotype characterisation (3). G377S and N396T are easily detected by PCRSSCA of exon 9, and confirmed by restriction analysis with Pvu II and Rsa I, respectively. Three G377S homozygotes were identified (one of whom has Sephardic Jewish background). All of them originate from a region of central Portugal, suggesting the origins of this mutation to that particular region. G377S seems to be common in Iberian patients (representing 7 and 5% of the alleles in Portuguese (7) and in Spanish (8) patients, respectively). Only a few cases with other origins have been reported (3, 9). The finding of two N396T homozygotes from central Portugal and another one in the Azores islands suggests that N396T has spread to different regions. Nevertheless, it has only been found in the Portuguese. As in the case of N370S, homozygotes for N396T might remain sub-clinical and escape diagnosis until late in life. In GD patients of Iberian (Spanish or Portuguese) ancestry, both of these mutations should be assessed. The stability and processing of the G377S and N396T mutated enzymes from fibroblasts, as observed by Western blot (not shown, antibodies used were a gift from Dr Aerts, Amsterdam, The Netherlands), was similar to the N370S and to the control glucocerebrosidases, presenting as molecular forms of 66, 63 and 59 kDa. The residual activity of mutant enzymes, isolated by immunobinding, showed that in the absence of effectors, the G377S glucocerebrosidase presented with the lowest activity (close to 0). Significant activation was observed in the presence of phosphatidylserine and saposin C. Under those conditions, N396T presented the highest residual activity ( 18% of control) followed by N370S and G377S (10 and 5%, respectively). According to these findings, phenotypic heterogeneity could result from altered interaction with physiological effectors. As depicted in Table 1, N396T homozygotes were generally milder than G377S homozygotes, although clinical heterogeneity was found.

ARSA-PD associated alleles in the Portuguese population: frequency determination and haplotype analysis

Arylsulfatase A pseudodeficiency (ARSA-PD) may be related to increased susceptibility to neuro-psychiatric disorders. An association of allele 2417G/3352A with schizophrenia was found in a group of Portuguese patients. In the Portuguese population, at least one PD associated alteration exists in 18.3% of the ARSA alleles. Allele 2417G/3352G was invariably associated with a conserved haplotype, while 2417G/3352A and the rare 2417A/3352G alleles appeared on different haplotypes.

Lack of Cystatin B Protein as a Cause Of Myoclonic Epilepsy

Publicado em: Molecular Genetics and Metabolism 105 (2012) S15–S69. Disponivel em: http://www.sciencedirect.com/science/article/pii/S1096719211004343

Unverricht–lundborg disease: report of a new mutation

Purpose: Patients with localized refractory temporal lobe epilepsy (TLE) enrolled in the presurgical workout protocol at Ghent University Hospital undergo, among many investigations, extensive neuropsychological assessment including auditory and visual naming tests. We developed dutch adaptations of these tests to presurgically asses visual object naming and auditory description naming in surgical candidates with lateralized refractory TLE. Both tests will eventually be adapted to be incorporated in the presurgical neurostimulation mapping protocol. Method: Auditory and visual naming target words were matched controlling for word frequency and word length, resulting in two equally difficult naming tasks. Stimuli were based on Snodgrass and Vanderwart pictures and dictionary definitions. Both naming tasks were administered to left and right lateralized TLE patients and the performance of both groups in both tasks was compared. Results: Patients with left lateralized focal TLE performed significantly worse on the auditory version of the naming task compared to the visual alternative. This pattern was also seen in the right lateralized group, but less pronounced. Also, the left lateralized group performed worse on the auditory naming test compared to the right lateralized group, while their results on the visual naming task were less differentiated. Conclusion: The inclusion of auditory and visual naming tasks in presurgical neuropsychological assessment of refractory epilepsy patients is a valuable tool in the prediction of possible naming decline after surgical intervention. Particularly, the inclusion of an auditory naming task proves to be a valuable addition because of its unique capability to capture subtle naming deficits in patients with left TLE. Auditory naming characterizes and lateralizes left TLE-associated language dysfunction better, compared to the visual alternative.