Clinical and neuroimaging features of the m.10197G>A mtDNA mutation: New case reports and expansion of the phenotype variability.

Complex I (CI) is the largest component of the mitochondrial respiratory chain (MRC) and it is made up of 7 mitochondrial DNA (mtDNA)-encoded and at least 38 nuclear DNA-encoded subunits. Isolated CI deficiency is the most common single enzyme deficiency in the heterogeneous group of MRC disorders and it is a relatively common etiology of Leigh-like syndrome (LS). With a few exceptions, descriptions of the clinical spectrum of specific mutations in CI are scarce. We here present three unrelated Italian children who harbored the homoplasmic m.10197G>A mutation in MT-ND3 associated with reduced enzyme activity of CI in muscle. Compared with the spectrum of phenotypes seen in 13 previously described families with the same mutation, these children showed some novel clinical features. Two of the boys presented with subacute onset of dystonia, which showed a remitting-relapsing clinical course in one of them. The third boy presented acute symptoms consisting of speech impairment, progressive left-sided hemiparesis, and also vertebral and arterial malformations. In all the children, molecular studies identified a similar mutation load in tissues, and neuroimaging findings were consistent with the features seen in LS. Functional investigations in cultured skin fibroblasts suggested low ATP production in homoplasmic cells. Our results confirm that the m.10197G>A mutation is relevant to these patients' clinical and biochemical phenotypes, which thus expand the array of phenotypes associated with this variant.

MYH7-related myopathies: clinical, histopathological and imaging findings in a cohort of Italian patients.

BACKGROUND: Myosin heavy chain 7 (MYH7)-related myopathies are emerging as an important group of muscle diseases of childhood and adulthood, with variable clinical and histopathological expression depending on the type and location of the mutation. Mutations in the head and neck domains are a well-established cause of hypertrophic cardiomyopathy whereas mutation in the distal regions have been associated with a range of skeletal myopathies with or without cardiac involvement, including Laing distal myopathy and Myosin storage myopathy. Recently the spectrum of clinical phenotypes associated with mutations in MYH7 has increased, blurring this scheme and adding further phenotypes to the list. A broader disease spectrum could lead to misdiagnosis of different congenital myopathies, neurogenic atrophy and other neuromuscular conditions. RESULTS: As a result of a multicenter Italian study we collected clinical, histopathological and imaging data from a population of 21 cases from 15 families, carrying reported or novel mutations in MYH7. Patients displayed a variable phenotype including atypical pictures, as dropped head and bent spine, which cannot be classified in previously described groups. Half of the patients showed congenital or early infantile weakness with predominant distal weakness. Conversely, patients with later onset present prevalent proximal weakness. Seven patients were also affected by cardiomyopathy mostly in the form of non-compacted left ventricle. Muscle biopsy was consistent with minicores myopathy in numerous cases. Muscle MRI was meaningful in delineating a shared pattern of selective involvement of tibialis anterior muscles, with relative sparing of quadriceps. CONCLUSION: This work adds to the genotype-phenotype correlation of MYH7-relatedmyopathies confirming the complexity of the disorder.

Allelic and phenotypic heterogeneity in 49 Italian patients with the muscle form of CPT-II deficiency.

As genotype-phenotype correlations require the study of large patient populations, we investigated 49 Italian patients (33 unreported) with the muscle form of carnitine-palmitoyl-transferase-II (CPT-II) deficiency and CPT2 gene mutations. CPT enzyme activity below 25% of controls would lead to the development of muscle symptoms, and CPT activity below 15% would cause a relatively severe phenotype of the muscle form. Of the 15 different mutations found, 6 are novel (40%). A functional significance of mutations could be derived only for the two homozygous missense mutations found: both the p.S113L and the p.R631C (recurring in four unrelated patients from a genetic isolate) alleles caused a severe CPT enzyme defect (15% and 7%, respectively) and a relatively severe clinical phenotype of the muscle form. We identified three genotypes (homozygous p.R631C, homozygous p.S113L, and heterozygous null mutations) usually associated with a relatively severe and often life-threatening condition, which should be considered both in the clinical management of newly diagnosed patients (to prevent symptoms) and in their possible inclusion in therapeutic trials. We confirmed the existence of symptomatic heterozygous patient(s), through a family study, providing an important issue when offering genetic counseling and suggesting the crucial role of polymorphisms or environmental factors in determining the phenotype.

Pontocerebellar hypoplasia: clinical, pathologic, and genetic studies.

BACKGROUND: Mutations in genes encoding subunits of the tRNA-splicing endonuclease (TSEN) complex were identified in patients with pontocerebellar hypoplasia 2 (PCH2) and pontocerebellar hypoplasia 4 (PCH4). OBJECTIVE: We report molecular genetic findings in 12 Italian patients with clinical and MRI findings compatible with PCH2 and PCH4. METHODS: We retrospectively selected a cohort of 12 children from 9 Italian families with MRI of hypoplastic pontocerebellar structures and clinical manifestations suggesting either PCH2 or PCH4 and submitted them to direct sequencing of the genes encoding the 4 subunits of the TSEN complex, namely TSEN54, TSEN34, TSEN15, and TSEN2. RESULTS: In a cohort of 12 children, we detected the common p.A307S mutation in TSEN54 in 9/12 available patients from nine unrelated families. We also detected a novel c.1170_1183del (p. V390fs39X) in compound heterozygosity with the common p.A307S in a child with a severe PCH4 phenotype. In another severely affected patient, the second mutant allele was not identified. Two sibs without mutations in the TSEN complex were unlinked to the PCH3 locus. In addition to typical clinical and neuroradiologic features of PCH2, both children were affected by a tubulopathy resembling Bartter syndrome. CONCLUSIONS: We confirm that the common p.A307S mutation in TSEN54 is responsible for most of the patients with a PCH2 phenotype. The presence of a heterozygous in/del variant correlates with a more severe phenotype as PCH4. In addition, we describe a new clinical form of PCH in 2 sibs with clinical and MRI features of PCH2.

Congenital muscular dystrophies with cognitive impairment. A population study.

BACKGROUND: Cognitive impairment has been reported in a significant proportion of patients with congenital muscular dystrophies (CMD), generally associated with brain changes. OBJECTIVES: The aim of this study was to establish 1) the overall prevalence of CMD and cognitive impairment in the Italian population; 2) the frequency of individual genetically defined forms; and 3) the presence of distinct phenotypes not associated with mutations in the known genes. METHODS: We included all patients with CMD and cognitive impairment followed in all the Italian tertiary neuromuscular centers. Clinical, brain MRI, and morphologic data were collected. Genetic screening of the known genes was performed according to clinical and muscle biopsy findings. RESULTS: Ninety-two of the 160 (58%) patients with CMD followed in our centers had cognitive impairment. alpha-Dystroglycan (alpha-DG) reduction on muscle biopsy was found in 73/92 (79%), with 42/73 carrying mutations in the known genes. Another 6/92 (7%) showed a laminin alpha2 deficiency on muscle biopsy and 5 of the 6 carried mutations in LAMA2. The remaining 13/92 (14%) patients had normal alpha-DG and laminin alpha2 expression on muscle. CONCLUSIONS: This is the first population study establishing the prevalence of CMD and cognitive impairment and providing a classification on the basis of clinical, MRI, and genetic findings. We also showed that cognitive impairment was not always associated with alpha-DG or laminin alpha2 reduction or with structural brain changes.

McArdle disease: a clinical review.

METHODS: The clinical phenotype of 45 genetically confirmed McArdle patients is described. RESULTS: In the majority of patients (84%), the onset of symptoms was from early childhood but diagnosis was frequently delayed until after 30 years of age. Not all patients could recognise a second wind although it was always seen with exercise assessment. A history of myoglobinuria was not universal and episodes of acute renal failure had occurred in a minority (11%). The condition does not appear to adversely affect pregnancy and childbirth. Clinical examination was normal in most patients, muscle hypertrophy was present in 24% and mild muscle wasting and weakness were seen only in patients over 40 years of age and was limited to shoulder girdle and axial muscles. The serum creatine kinase was elevated in all but one pregnant patient. Screening for the mutations pArg50X (R50X) and pGly205Ser (G205S) showed at least one mutated allele in 96% of Caucasian British patients, with an allele frequency of 77% for pArg50X in this population. A 12 min walking test to evaluate patients is described. CONCLUSION: The results demonstrated a wide spectrum of severity with the range of distance walked (195-1980 m); the mean distance walked was 512 m, suggesting significant functional impairment in most patients.

Congenital muscular dystrophies with defective glycosylation of dystroglycan: a population study.

BACKGROUND: Congenital muscular dystrophies (CMD) with reduced glycosylation of alpha-dystroglycan (alpha-DG) are a heterogeneous group of conditions associated with mutations in six genes encoding proven or putative glycosyltransferases. OBJECTIVES: The aim of the study was to establish the prevalence of mutations in the six genes in the Italian population and the spectrum of clinical and brain MRI findings. METHODS: As part of a multicentric study involving all the tertiary neuromuscular centers in Italy, FKRP, POMT1, POMT2, POMGnT1, fukutin, and LARGE were screened in 81 patients with CMD and alpha-DG reduction on muscle biopsy (n = 76) or with a phenotype suggestive of alpha-dystroglycanopathy but in whom a muscle biopsy was not available for alpha-DG immunostaining (n = 5). RESULTS: Homozygous and compound heterozygous mutations were detected in a total of 43/81 patients (53%), and included seven novel variants. Mutations in POMT1 were the most prevalent in our cohort (21%), followed by POMT2 (11%), POMGnT1 (10%), and FKRP (9%). One patient carried two heterozygous mutations in fukutin and one case harbored a new homozygous variant in LARGE. No clear-cut genotype-phenotype correlation could be observed with each gene, resulting in a wide spectrum of clinical phenotypes. The more severe phenotypes, however, appeared to be consistently associated with mutations predicted to result in a severe disruption of the respective genes. CONCLUSIONS: Our data broaden the clinical spectrum associated with mutations in glycosyltransferases and provide data on their prevalence in the Italian population.

McArdle disease: molecular genetic update.

McArdle disease or Glycogenosis type V is an autosomal recessive metabolic disorder caused by a deficiency of the muscle isoform of glycogen phosphorylase (myophosphorylase, PYGM), the specific skeletal muscle enzyme that initiates glycogen breakdown. Since the first clinical description by Brian McArdle in 1951, several patients have been identified worldwide and significant advances have been made in the study of molecular genetics of the disease. Molecular heterogeneity has been demonstrated by the identification to date of more than 65 mutations in the PYGM gene.

Neuromuscular forms of glycogen branching enzyme deficiency.

Deficiency of glycogen branching enzyme is causative of Glycogen Storage Disease type IV (GSD-IV), a rare autosomal recessive disorder of the glycogen synthesis, characterized by the accumulation of amylopectin-like polysaccharide, also known as polyglucosan, in almost all tissues. Its clinical presentation is variable and involves the liver or the neuromuscular system and different mutations in the GBE1 gene, located on chromosome 3, have been identified in both phenotypes. This review will addresses the neuromuscular clinical variants, focusing on the molecular genetics aspects of this disorder.

Revelation of a novel CLN5 mutation in early juvenile neuronal ceroid lipofuscinosis.

Neuronal ceroid lipofuscinoses (NCLs) are relatively common storage diseases of childhood and early adolescence. Ultrastructural shape of storage cytosomes, type of disease gene, and age of onset serve to classify the different NCLs, some of which appear to cluster in Scandinavian countries. The CLN5 form usually presents as a classical epileptiform encephalopathy of late infancy but a more aggressive cognitive impairment has been described in a single family. We report two sibs harbouring a novel mutation (p.Tyr258Asp) in the CLN5 gene and displaying behaviour disturbances and mental deterioration, rather than epilepsy, as the dominant disease manifestation at onset.

Lipoid proteinosis: case report and review of the literature.

Lipoid proteinosis is a rare autosomal recessive disorder, characterized histologically by infiltration of periodic acid Schiff-positive hyaline material into the skin, upper aerodigestive tract, and internal organs. Classical clinical features include skin scarring, beaded eyelid papules, and laryngeal infiltration leading to hoarseness. Moreover, the infiltrates in the tongue and its frenulum limit lingual movements and cause speech difficulties. Usually, the hoarse voice is present at birth or in early infancy, as the first manifestation. In more severe cases, diffuse infiltration of the pharynx and larynx might cause respiratory distress, at times requiring tracheostomy. The disorder has recently been shown to result from loss-of-function mutations in the extracellular matrix protein 1 gene on chromosome 1q21. The function of the protein extracellular matrix protein 1 gene is still unclear, although an important role in skin physiology and homeostasis has been hypothesized. In this report, the case is described of a 6-year-old girl with lipoid proteinosis. Histopathological examination of a laryngeal biopsy specimen showed massive deposits of eosinophilic, periodic acid Schiff-positive, and diastase resistant material in the lamina propria corroborating the clinical diagnosis of lipoid proteinosis. Molecular analyses in this patient also confirmed the clinical diagnosis. The proposita was a compound heterozygote for a new small rearrangement (543de1TG/ins15) in exon 6, and a nonsense mutation (Arg243Stop) in exon 7. Together with previously documented mutations in the extracellular matrix protein 1 gene, this study supports the hypothesis that exons 6 and 7 are the most common sites for extracellular matrix protein 1 gene mutations in lipoid proteinosis.

Phenotypic heterogeneity in two unrelated Danon patients associated with the same LAMP-2 gene mutation.

Danon disease, an X-linked cardioskeletal myopathy caused by primary deficiency of lysosome-associated membrane protein-2 (LAMP-2), is clinically characterized by cardiomyopathy, myopathy, and variable mental retardation. The pathological hallmark of the disease is the absence of LAMP-2 immunohistochemical staining in muscle. The LAMP-2 gene mutations reported thus far are generally private mutations. We describe two cases of Danon disease with different clinical presentation, in whom we identified the same exon skipping mutation c.928G>A in the LAMP-2 gene. The first patient was affected by an early onset myopathy and hypertrophic cardiomyopathy (HCM) that partially improved with drug treatment. A first muscle biopsy at age 4 months showed markedly increased glycogen, and acid maltase deficiency was ruled out biochemically. A second muscle biopsy, performed at age 3(1/2) years, showed very mild abnormalities. The second child at age 15 years had mild, diffuse muscle weakness and wasting, moderate mental deficiency, and HCM. Two serial biopsies performed at age 8 and 15 years showed similar findings of multiple esterase-positive vacuoles in type I myofibers. In both patients the immunohistochemical study demonstrated the absence of LAMP-2 in skeletal muscle.

A novel mutation of GDAP1 associated with Charcot-Marie-Tooth disease in three Italian families: evidence for a founder effect.

BACKGROUND: Mutations in a gene encoding a novel protein of unknown function-the ganglioside-induced differentiation-associated protein 1 gene (GDAP1)-are associated with the autosomal recessive Charcot-Marie-Tooth disease type 4A (CMT4A). OBJECTIVE: To investigate the role of GDAP1 mutations in causing autosomal recessive neuropathies in an Italian population. METHODS AND RESULTS: 76 patients with severe early onset polyneuropathy and possible autosomal recessive inheritance were screened for mutations. A T>G transversion (c.347 T>G) at codon 116 (M116R) was detected in four affected subjects from three apparently unrelated families. All patients had early onset of disease with pronounced foot deformities and impaired walking. Neurophysiological studies showed an extremely variable expression. Sural nerve biopsies revealed signs of both de-remyelination and axonal impairment, the most prominent feature being a severe loss of larger fibres. Haplotype analysis of the GDAP1 locus demonstrated a common disease haplotype. CONCLUSIONS: The association of the mutation with a common haplotype suggested a common ancestor.

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.

A novel mutation of myelin protein zero associated with an axonal form of Charcot-Marie-Tooth disease.

OBJECTIVE: To report a new mutation in the MPZ gene which encodes myelin protein zero (P0), associated with an axonal form of Charcot-Marie-Tooth disease (CMT). METHODS: Three patients from an Italian family with a mild, late onset axonal peripheral neuropathy are described clinically and electrophysiologically. To detect point mutation in MPZ gene the whole coding sequence was examined. The structure of the mutated protein was investigated using the three dimensional model of P0. RESULTS: All patients showed a relatively mild CMT phenotype characterised by late onset and heterogeneity of the clinical and electrophysiological features. Molecular analysis demonstrated a novel heterozygous T/A transversion in the exon 3 of MPZ gene that predicts an Asp109Glu amino acid substitution in the extracellular domain of the P0. Asp109 is found at the protein surface, on beta strand E, in the interior of the P0 tetramer. CONCLUSIONS: The identification of Asp109Glu mutation confirms the pivotal role of P0 in axonal neuropathies and stresses the phenotypic heterogeneity associated with MPZ mutations. This study suggests the value of screening for MPZ mutations in CMT family members with minor clinical and electrophysiological signs of peripheral neuropathy.

Clinical and molecular findings in patients with giant axonal neuropathy (GAN).

Giant axonal neuropathy (GAN) is a rare autosomal recessive neurodegenerative disorder of early onset, clinically characterized by a progressive involvement of both peripheral and CNS. The diagnosis is based on the presence of characteristic giant axons, filled with neurofilaments, on nerve biopsy. Recently, the defective protein, gigaxonin, has been identified and different pathogenic mutations in the gigaxonin gene have been reported as the underlying genetic defect. Gigaxonin, a member of the BTB/kelch superfamily proteins, seems to play a crucial role in the cross talk between the intermediate filaments and the membrane network. The authors report clinical and molecular findings in five Italian patients with GAN. This study shows the allelic heterogeneity of GAN and expands the spectrum of mutations in the GAN gene. The frequent occurrence of private mutations stresses the importance of a complete gene analysis.