In 1999, based on a single family, spondyloepimetaphyseal dysplasia (SEMD) with mental retardation (MR) was described as a novel syndrome with probably X‐linked recessive inheritance and unknown ...molecular defect (MIM 300232). Our purpose was to search for the causative defect in the originally described family and in an independently ascertained second family. All patients had slowly progressive neurodegeneration with central and peripheral involvement and identical skeletal dysplasia. Whole exome sequencing performed in two subjects showed a single plausible candidate – the p.Asp237Gly variant in AIFM1 (chr. Xq26.1). The p.Asp237Gly segregated with disease as indicated by linkage analysis maximum logarithm of odds score (LOD) score at theta 0 for the two families was 3.359. This variant had not been previously reported and it was predicted to be pathogenic by Polyphen2, SIFT, MutationTaster and Mutation Assessor. AIFM1 encodes mitochondria associated apoptosis‐inducing factor. The AIFM1 gene has been linked with COXPD6 encephalomyopathy (MIM 300816), Cowchock syndrome (MIM 310490) and X‐linked deafness with neuropathy (DFNX5, MIM 300614), none of which are similar to SEMD‐MR. Our results place SEMD as the third instance of a skeletal phenotype associated with a mitochondrial disease (the others being EVEN‐PLUS syndrome caused by mutations of HSPA9 and CODAS syndrome due to LONP1 mutations).
A case of late onset GM2 gangliosidodis with spinal muscular atrophy phenotype followed by cerebellar and extrapyramidal symptoms is presented. Genetic analysis revealed compound heterozygous ...mutation in exon 10 of the HEXA gene. Patient has normal intelligence and emotional reactivity. Neuroimaging tests of the brain showed only cerebellar atrophy consistent with MR spectroscopy (MRS) abnormalities. (18)F-fluorodeoxyglucose positron emission tomography (18)F-FDG PET/CT of the brain revealed glucose hypometabolism in cerebellum and in temporal and occipital lobes bilaterally.
•Late onset GM2 with spinal SMA phenotype followed by cerebellar symptoms and dystonia.•Compound heterozygous mutation in exon 10 of the HEXA gene.•MRI of the brain showed cerebellar atrophy consistent with MRS abnormalities.•FDG PET/CT showed hypometabolism in cerebellum and in temporal and occipital cortex.
Gaucher disease is generally caused by a deficiency of the lysosomal enzyme glucocerebrosidase. The degradation of glycosphingolipids requires also the participation of sphingolipid activator ...proteins. The prosaposin PSAP gene codes for a single protein which undergoes post‐translational cleavage to yield four proteins named saposins A, B, C and D. Saposin (SAP‐) C is required for glucosylceramide degradation, and its deficiency results in a variant form of Gaucher disease. In this report, we present clinical, biochemical, and molecular findings in a 36‐year‐old man and his 30‐year‐old sister with non‐neuronopathic Gaucher disease due to SAP‐C deficiency. Very high levels of chitotriosidase activity, chemokine CCL18, and increased concentration of glucosylceramide in plasma and normal β‐glucosidase activity in skin fibroblasts were observed in the patients. A molecular genetics study of the PSAP gene enabled the identification of one missense mutation, p.L349P, located in the SAP‐C domain and another mutation, p.M1L, located in the initiation codon of the prosaposin precursor protein. The presented findings describe the first cases where the non‐neuronopathic Gaucher disease has been definitely demonstrated to be a consequence of SAP‐C deficiency. Three previously described cases in the literature displayed a Gaucher type 3 phenotype.
Acid sphingomyelinase deficiency (ASMd, Niemann-Pick disease A/B) and Niemann-Pick type C disease (NPC) share core clinical symptoms. Initial diagnostic discrimination of these two rare lysosomal ...storage diseases is thus difficult. As sphingomyelin accumulates in ASMd as well as NPC, lysosphingomyelin (sphingosylphosphorylcholine) and its m/z 509 analog were suggested as biomarkers for both diseases.
Herein we present results of simultaneous LC-ESI-MS/MS measurements of lysosphingomyelin and lysosphingomyelin 509 in plasma and dried blood spots (DBS) collected from ASMd and NPC patients and suggest that the plasma but not DBS levels of the two analytes allow differential biochemical screening of ASMd and NPC.
Metachromatic leukodystrophy (MLD), a severe neurodegenerative metabolic disorder, is caused by deficient activity of arylsulfatase A (ARSA; EC 3.1.6.8), which leads to a progressive demyelinating ...process in central and peripheral nervous systems. In this study, a DNA sequence analysis was performed on six Polish patients with different types of MLD. Six novel mutations were identified: one nonsense (p.R114X), three missense (p.G122C, p.G293C, p.C493F) and two frameshift mutations (g.445_446dupG and g.2590_2591dupC). Substitutions p.G293C and p.C493F and duplication g.445_446dupG caused a severe reduction of enzyme activity in transient transfection experiments on mammalian cells (less than 1% of wild‐type (WT) ARSA activity). Duplication 2590_2591dupC preserved low‐residual ARSA activity (10% of WT ARSA). In summary, the novel MLD‐causing mutations in the exons 2, 5 and even in 8 of the ARSA gene described here can be classified as severe type 0, leading in homozygosity to the late infantile form MLD. Growth retardation, delayed motor development, gait disturbances, tonic–clonic seizures and non‐epileptic muscle spasms were the first onset symptoms in patients with late infantile form of MLD. In individual with juvenile type MLD gait disturbances evidenced the onset of the disease, while in a patient with late juvenile MLD, difficulties at school were displayed.
The occurrence and genotype–phenotype correlations of the eight most common mutations in the arylsulfatase A (ARSA) gene were studied in 43 unrelated Polish patients suffering from different types of ...metachromatic leukodystrophy (MLD). Screening for mutations p.R84Q, p.S96F, c.459+1G>A, p.I179S, p.A212V, c.1204+1G>A, p.P426L, and c.1401–1411del allowed the identification of 53.5% of the mutant alleles. In the whole investigated group of patients, mutations c.459+1G>A and p.P426L were the most frequent, 19 and 17%, respectively. The prevalence of the third most frequent mutation, i.e. p.I179S (13%), seems to be higher than that in other populations. The incidence of c.1204+1G>A was 5%, which is higher than reported earlier (2%). It seems that p.I179S and c.1204+1G>A are more prevalent in MLD patients from Poland than from other countries. In the group examined by us, mutations p.R84Q, p.S96F, p.A212V, and c.1401–1411del were not detected; thus, 46.5% of MLD alleles remained unidentified. This indicates that other, novel or already described, but rare, mutations exist in Polish population. In late infantile homozygotes for c.459+1G>A and one homozygote for c.1204+1G>A, first clinical symptom was motor deterioration. In adult homozygotes for p.P426L, the disease onset manifested as gait disturbances, followed by choreoathetotic movements, difficulties in swallowing, dysarthria, tremor, and nystagmus. In the carriers of the p.I179S mutation, the hallmark of the clinical picture was psychotic disturbances.
Pompe disease is an autosomal recessive disorder of glycogen metabolism caused by a deficiency of the lysosomal enzyme acid α-glucosidase (GAA). It presents at any age, with variable rates of ...progression ranging from a rapidly progressive course, often fatal by one-year of age, to a more slowly, but nevertheless relentlessly progressive course, resulting in significant morbidity and premature mortality. In infants, early initiation of enzyme replacement therapy is needed to gain the maximum therapeutic benefit, underscoring the need for early diagnosis. Several new methods for measuring GAA activity have been developed. The Pompe Disease Diagnostic Working Group met to review data generated using the new methods, and to establish a consensus regarding the application of the methods for the laboratory diagnosis of Pompe disease. Skin fibroblasts and muscle biopsy have traditionally been the samples of choice for measuring GAA activity. However, new methods using blood samples are rapidly becoming adopted because of their speed and convenience. Measuring GAA activity in blood samples should be performed under acidic conditions (pH 3.8–4.0), using up to 2
mM of the synthetic substrate 4-methylumbelliferyl-α-
d-glucoside or glycogen (50
mg/mL), in the presence of acarbose (3–9
μM) to inhibit the isoenzyme maltase–glucoamylase. The activity of a reference enzyme should also be measured to confirm the quality of the sample. A second test should be done to support the diagnosis of Pompe disease until a program for external quality assurance and proficiency testing of the enzymatic diagnosis in blood is established.
