Dementia, delusions and seizures: storage disease or genetic AD?

We describe a case of a young patient suffering from a rapidly progressive cognitive decline, associated with delusions, myoclonus and seizures and with no family history for dementia. Clinical features, along with skin biopsy findings were overlapping storage disease; the genetic analysis, however, demonstrated a de novo presenilin 1 mutation. The present report suggests the usefulness of genetic determinations in early-onset cases of dementia, even without an autosomal dominant trait of inheritance; for these cases and their relatives an extensive genetic counselling should be recommended.

Neuropathology of mitochondrial diseases

The term "mitochondrial diseases" (MD) refers to a group of disorders related to respiratory chain dysfunction. Clinical features are usually extremely heterogeneous because MD may involve several tissues with different degrees of severity. Muscle and brain are mostly affected, probably because of their high dependence on oxidative metabolism. Muscle can be the only affected tissue or involved as a part of a multi-system disease; ragged red fibers, accumulation of structurally altered mitochondria and cytochrome-c-oxidase (COX) negative fibers are the main pathological features. In mitochondrial encephalopathies, central nervous system (CNS) structures are affected according to different patterns of distribution and severity. Characteristic lesions are neuronal loss, vasculo-necrotic changes, gliosis, demyelination and spongy degeneration. In accordance with either grey matter or white matter involvement two main groups of diseases may be distinguished. Neuronal loss and vasculo-necrotic multifocal lesions are the common features of grey matter involvement; demyelination and spongy degeneration occur when white matter is affected, often associated with less severe lesions of the grey structures. Grey matter lesions are prevalent in MERRF, MELAS, Alpers and Leigh syndromes. White matter involvement is always seen in Kearns-Sayre syndrome and was recently described in mtDNA depletion syndrome linked to dGK mutations and in the rare conditions associated with complex I and II deficiency. In this review we describe the main histopathological features of muscle and CNS lesions in mitochondrial diseases.

The role of muscle biopsy in investigating isolated muscle pain

OBJECTIVE

To evaluate the muscle biopsy findings from 240 patients who had isolated muscle pain.

METHODS

Histopathology, immunohistochemistry for dystrophin, dystrophin-related proteins, major histocompatibility complex type I, and biochemical analysis of glycolytic and mitochondrial respiratory chain enzymes were performed on muscle biopsies. An attempt was made to correlate pathologic data and clinical findings (sex, age, quality and distribution of symptoms, serum CK levels, and EMG recording).

RESULTS

We have described five groups of patients based on muscle biopsy findings: 51.6% had heterogeneous myopathic abnormalities; only 19% of them had a specific myopathic picture, i.e., central nuclei myopathy, central core disease, myopathy with tubular aggregates or with trabecular fibers or abnormalities of fiber typing; 20% had signs of respiratory chain dysfunction but only one patient had a probable mitochondrial disease; 7% had a neurogenic pattern; 2.4% had a metabolic myopathy (phosphorylase or phosphofructokinase deficiency); and 19% had normal muscle biopsy. No clear-cut correlation between muscle biopsy and clinical data was observed except for those patients with a metabolic myopathy.

CONCLUSIONS

The probability that a patient complaining only of muscle pain and with a normal neurologic examination has a definite muscle pathology is 2%. Only patients with sole exercise-related muscle pain and sCK seven times higher than the normal value are strongly suspected of having a metabolic myopathy. A rigorous selection of patients is needed before performing a muscle biopsy.

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.

Clinical and electrophysiological features of epilepsy in Italian patients with CLN8 mutations

Neuronal ceroid lipofuscinoses (NCLs) are characterized by epilepsy, visual failure, psychomotor deterioration, and accumulation of autofluorescent lipopigment. CLN8 mutations result in Northern epilepsy and Turkish variant late infantile NCL. We describe the clinical and neurophysiological findings of three patients with CLN8 mutations from Italy. In these patients, the onset of epilepsy occurred between 3 and 6 years of age, with myoclonic, tonic-clonic, and atypical absence seizures. Electroencephalograms revealed focal and/or generalized abnormalities. In all cases, blindness and progressive attenuation of the electroretinogram were observed. Magnetic resonance imaging revealed cerebral and cerebellar atrophy, thinning of the corpus callosum, deep white matter hyperintensity, and hyperintensity of the posterior limb of internal capsules. Skin biopsy revealed lysosomal storage in the cytoplasm of fibroblasts. The clinical picture of our cases resembles that of the Turkish patients and clearly differs from that of Northern epilepsy, which is marked by a prolonged course without myoclonus and visual loss. Definition of the clinical spectrum of this condition will aid in its recognition and have implications for diagnosis and genetic counseling.

PLA2G6, encoding a phospholipase A2, is mutated in neurodegenerative disorders with high brain iron

Neurodegenerative disorders with high brain iron include Parkinson disease, Alzheimer disease and several childhood genetic disorders categorized as neuroaxonal dystrophies. We mapped a locus for infantile neuroaxonal dystrophy (INAD) and neurodegeneration with brain iron accumulation (NBIA) to chromosome 22q12-q13 and identified mutations in PLA2G6, encoding a calcium-independent group VI phospholipase A2, in NBIA, INAD and the related Karak syndrome. This discovery implicates phospholipases in the pathogenesis of neurodegenerative disorders with iron dyshomeostasis.

Neuronal-specific roles of the survival motor neuron protein: evidence from survival motor neuron expression patterns in the developing human central nervous system

Despite recent data on the cellular function of the survival motor neuron (SMN) gene, the spinal muscular atrophy (SMA) disease gene, the role of the SMN protein in motor neurons and hence in the pathogenesis of SMA is still unclear. The spatial and temporal expression of SMN in neurons, particularly during development, could help in verifying the hypotheses on the SMN protein functions so far proposed. We have therefore investigated the expression and subcellular localization of the SMN protein in the human central nervous system (CNS) during ontogenesis with immunocytochemical, confocal immunofluorescence, and Western blot experiments using a panel of anti-SMN antibodies recognizing the full-length SMN protein. The experiments not only revealed the early SMN expression in all neurons, but also demonstrated the progressive shift in SMN subcellular localization from mainly nuclear to cytoplasmic and then to axons during CNS maturation. This finding was present in selected neuronal cell populations and it was particularly conspicuous in motor neurons. Our data support the idea of a specific role for SMN in axons, which becomes predominant in the ontogenetic period encompassing axonogenesis and axonal sprouting. In addition, the asymmetric SMN staining demonstrated in the germinative neuroepithelium suggests a possible role for SMN in neuronal migration and/or differentiation.

A novel missense mutation in the L1CAM gene in a boy with L1 disease

A novel missense mutation of the L1CAM gene (Xq28) is described in an adult patient affected with severe mental retardation, spastic paraparesis, adducted thumbs, agenesis of corpus callosum and microcephaly (L1 disease). We detected a transition c2308G-->A in exon 18 that caused an amino acid change in codon 770. The patient's mother and two sisters were heterozygous for the same mutation. This newly described mutation predicts the substitution of an aspartate by asparagine (D770N) in the second fibronectin (Fn2) domain of the extracellular portion of the mature L1 protein. Even if amino acid substitution does not significantly change the physico-chemical properties of the Fn2 domain, it seems clear that the integrity of this domain is required to maintain the biological functions of the protein. The feature peculiar to this patient is the decelerated head growth post-natally, leading to microcephaly. Mutations of L1CAM associated with prolonged survival may hamper post-natal brain and head growth.

Protein glutathionylation in human central nervous system: potential role in redox regulation of neuronal defense against free radicals

Neuronal defense against free radicals is mediated primarily by the glutathione system. A cerebral defect of this system gives rise to the oxidative stress occurring in some neurological diseases. Glutathione provides a means of regulating protein function by glutathionylation, consisting of the formation of mixed disulfides between cysteines and glutathione. The glutathionylation of proteins, during both constitutive metabolism and oxidative stress, represents for the cell a mechanism to link physiological processes, and/or adaptive stress responses, to changes in intracellular redox states. In this study, we analyzed the topographic distribution of the protein glutathionylation normally occurring in human central nervous system. Constitutively glutathionylated proteins appeared uniformly distributed throughout all cortical layers of the cerebral and cerebellar cortex as well as throughout the gray matter of the spinal cord. The degree of immunocytochemical staining was clear in neurons, mild in oligodendrocytes, and weaker in astrocytes. The proteins preferentially glutathionylated were cytoskeletal proteins. Our results suggest a potential role of glutathionylation in the redox regulation of neuronal survival and in the control of axon/dendrite stability.

Novel CLN1 mutation in two Italian sibs with late infantile neuronal ceroid lipofuscinosis

We detected a novel CLN1 mutation (c.125-15t>g) in two Italian siblings. The clinical phenotype is that of a variant late-infantile neuronal ceroid lipofuscinosis and consisted of early-onset visual loss, psychomotor deterioration, and seizures. Ultrastructurally, granular osmiophilic deposits were found in skin biopsy of both patients. The novel mutation occurs in the acceptor sequences for splicing and leads to skipping of multiple exons. This predicts a protein lacking part or all of the active site of the enzyme and the palmitate-binding pocket. Consequently, biochemical activity of the palmitoyl protein thioesterase-1 enzyme was drastically reduced. The new mutation was not identified in a large set of ethnically matched control chromosomes. Our findings support the notion that CLN1 patients are not rare in Southern Europe and facilitate DNA-based mutation and carrier testing in this family.

Novel mutations in CLN8 in Italian variant late infantile neuronal ceroid lipofuscinosis: another genetic hit in the Mediterranean

Neuronal ceroid lipofuscinoses (NCLs) are autosomal recessive neurodegenerative disorders typically characterized by the accumulation of autofluorescent material in tissues. On the basis of clinical features, age at onset, and molecular genetic defects, it is possible to distinguish at least nine forms. The CLN8 form was first described in Finland, where all the patients are homozygous for a p.Arg24Gly mutation in CLN8. More recently, it has been found that a subset of a Turkish variant of late infantile NCL (v-LINCL) is also associated with CLN8 mutations. To identify the molecular defect in Italian patients with v-LINCL, the CLN8 gene was directly sequenced in 10 patients. Controls were screened by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. Five fluorescent-labeled microsatellite markers covering 1 cM around the gene were used for haplotype analysis. In three Italian v-LINCL patients, identified in a small area in southern Italy, we detected four new mutations in CLN8: c.66delG (p.Gly22fs), c.88G>C (p.Ala30Pro), c.473A>G (p.Tyr158Cys), and c.581A>G (p.Gln194Arg). The single-base deletion was found in two unrelated patients. The novel missense mutations were not identified in ethnically matched control chromosomes. Our findings expand the number of CLN8 variants and corroborate the notion that CLN8 patients are not confined to the Finnish population.

Infantile hepatocerebral syndromes associated with mutations in the mitochondrial DNA polymerase- A

We studied nine infant patients with a combination of progressive neurological and hepatic failure. Eight children, including two sibling pairs and four singletons, were affected by Alpers' hepatopathic poliodystrophy. A ninth baby patient suffered of a severe floppy infant syndrome associated with liver failure. Analysis of POLG1, the gene encoding the catalytic subunit of mitochondrial DNA polymerase, revealed that all the patients carried different allelic mutations in this gene. POLG1 is a major disease gene in mitochondrial disorders. Mutations in this gene can be associated with multiple deletions, depletion or point mutations of mitochondrial DNA (mtDNA). In turn, these different molecular phenotypes dictate an extremely heterogeneous spectrum of clinical outcomes, ranging from adult-onset progressive ophthalmoplegia to juvenile ataxic syndromes with epilepsy, to rapidly fatal hepatocerebral presentations, including Alpers' syndrome.

Cerebral cortex three-dimensional profiling in human fetuses by magnetic resonance imaging

Seven human fetuses of crown/rump length corresponding to gestational ages ranging from the 12th to the 16th week were studied using a paradigm based on three-dimensional reconstruction of the brain obtained by magnetic resonance imaging (MRI). The aim of the study was to evaluate brain morphology in situ and to describe developmental dynamics during an important period of fetal morphogenesis. Three-dimensional MRI showed the increasing degree of maturation of the brains; fronto-occipital distance, bitemporal distance and occipital angle were examined in all the fetuses. The data were interpreted by correlation with the internal structure as visualized using high-spatial-resolution MRI, acquired using a 4.7-T field intensity magnet with a gradient power of 20 G cm(-1). The spatial resolution was sufficient for a detailed detection of five layers, and the contrast was optimized using sequences with different degrees of T1 and T2 weighting. Using the latter, it was possible to visualize the subplate and marginal zones. The cortical thickness was mapped on to the hemispheric surface, describing the thickness gradient from the insular cortex to the periphery of the hemispheres. The study demonstrates the utility of MRI for studying brain development. The method provides a quantitative profiling of the brain, which allows the calculation of important morphological parameters, and it provides informative regarding transient features of the developing brain.

Hepato-cerebral syndrome: genetic and pathological studies in an infant with a dGK mutation

Focal spongy degeneration of the white matter and Purkinje cell loss were the neuropathological hallmarks in an infant with hepato-cerebral syndrome and a 4-bp GATT duplication (nucleotides 763-766) in exon 6 of the dGK gene. Liver disease became manifest in the first months of life and was followed by progressive cirrhosis and death at 31 months. Neurological symptoms appeared later and were mild, in agreement with the limited brain pathology. Molecular analysis of the dGK gene should be performed in infants with cirrhosis even in the absence of CNS involvement.

MELAS: clinical phenotype and morphological brain abnormalities

We describe the clinical and neuropathological findings of three unrelated autopsy cases of MELAS harboring the A3243G transition in the mitochondrial DNA (mtDNA). Using immunohistochemical techniques, we studied the expression of several subunits of the respiratory chain in various brain regions from the same cases. In all three cases there was a reduced immunocytochemical staining for mtDNA-encoded subunits of the respiratory chain, confirming the presence of a defective mitochondrial protein synthesis in this disease. Mitochondrial abnormalities were mostly confined to multiple areas of different size and shape, in agreement with the focal character of the brain pathology in MELAS, and were most prominent in the cerebral cortex, providing a morphological contribution to the explanation of the cognitive regression of the patients. Immunoreactivity for mtDNA-encoded subunits was reduced in the walls of many pial and intracerebral arterioles of different brain regions but there was no clear correlation between territories of affected vessels and distribution of the histological and immunohistochemical lesions. Cerebral focal lesions in MELAS might have a metabolic nature and several pathogenetic mechanisms might be involved in the genesis of stroke-like episodes when there is a local increased ATP demand.

Features of cell death in brain and liver, the target tissues of progressive neuronal degeneration of childhood with liver disease (Alpers-Huttenlocher disease)

Alpers-Huttenlocher disease (AHD) is a rare encephalopathy of infancy and childhood characterized by myoclonic seizures and progressive neurological deterioration, usually associated with signs and symptoms of liver dysfunction. There is no biological marker of the disease, and ultimate diagnosis still relies on pathological examination. Features of clinical progression and pathological findings suggest AHD to be secondary to a genetically determined disorder of mitochondrial function. We report on four AHD patients and focus on their pathological features in brain, liver and muscle. Liver and muscle biopsy specimens were examined using histochemical markers of the oxidative pathways, probes to immunodetect molecules of the apoptotic cascades and electron microscopy. In liver (but not in muscle) biopsy samples, activated caspases were detected by immunohistochemistry: foci of caspase-9-positive cells were seen in a child affected with chronic, progressive fibrosis. In an 18-year-old boy, who suffered from valproic acid-associated acute hepatitis, caspase-3 cells were clustered among the necrotic foci and the foamy cells. In both patients electron microscopy revealed apoptotic nuclei. Normal muscle biopsy specimens were observed in two children, 2 and 8 years-old respectively; in the 18-year-old patient cytochrome oxidase-negative fibers as well as ultrastructural findings of mitochondrial abnormalities were observed. In no patient was there biochemical evidence of impaired oxidative metabolism. Neuropathological examination of the brains of two patients (13 months and 19 years old, respectively) showed focal distribution of the lesions affecting the telencephalic cortex and, to a lesser extent, subcortical gray nuclei. Along with the necrotizing lesions, characterized by neuronal loss, neuropil microcysts and newly formed vessels, we also observed acutely shrunken neurons and features of apoptotic cell death in the cerebral cortex only. Severe neuronal loss without necrotizing features was observed in the cerebellar cortex. The presence of both anoxic and apoptotic nuclei in brain and liver, the target tissues of the disease, is consistent with the hypothesis that abnormal activation of mitochondrion-related cell death pathways might be involved in the pathogenesis of AHD.

Central-peripheral sensory axonopathy in a juvenile case of Alpers-Huttenlocher disease

Peripheral ataxia is reported in a juvenile case of Alpers-Huttenlocher disease (AHD). Neurophysiological and neuropathological investigations revealed a central-peripheral axonopathy, affecting the deep sensation carried by the peripheral nerve fibres and the posterior tracts of the cord, due to neuronal loss of the sensory ganglia. Involvement of the sensory pathways is regarded as a major feature of juvenile AHD.

The K-Cl cotransporter KCC3 is mutant in a severe peripheral neuropathy associated with agenesis of the corpus callosum

Peripheral neuropathy associated with agenesis of the corpus callosum (ACCPN) is a severe sensorimotor neuropathy associated with mental retardation, dysmorphic features and complete or partial agenesis of the corpus callosum. ACCPN is transmitted in an autosomal recessive fashion and is found at a high frequency in the province of Quebec, Canada. ACCPN has been previously mapped to chromosome 15q. The gene SLC12A6 (solute carrier family 12, member 6), which encodes the K+-Cl- transporter KCC3 and maps within the ACCPN candidate region, was screened for mutations in individuals with ACCPN. Four distinct protein-truncating mutations were found: two in the French Canadian population and two in non-French Canadian families. The functional consequence of the predominant French Canadian mutation (2436delG, Thr813fsX813) was examined by heterologous expression of wildtype and mutant KCC3 in Xenopus laevis oocytes; the truncated mutant is appropriately glycosylated and expressed at the cellular membrane, where it is non-functional. Mice generated with a targeted deletion of Slc12a6 have a locomotor deficit, peripheral neuropathy and a sensorimotor gating deficit, similar to the human disease. Our findings identify mutations in SLC12A6 as the genetic lesion underlying ACCPN and suggest a critical role for SLC12A6 in the development and maintenance of the nervous system.

Dejerine-Sottas neuropathy with multiple nerve roots enlargement and hypomyelination associated with a missense mutation of the transmembrane domain of MPZ/P0

In a patient affected with a slowly progressive, severe form of Dejerine-Sottas syndrome, symmetric enlargement of cranial nerves and focal hypertrophy of cervical and caudal roots were detected following MRI. Neuropathological features of the sural nerve disclosed a dramatic loss of myelinated fibres, with skewed-to-the-left, unimodal distribution of the few residual fibres, consistent with the diagnosis of congenital hypomyelination neuropathy. Genetic analysis revealed this condition to be associated with a heterozygous G to A transition at codon 167 in the exon 4 of the MPZ/P0 gene causing a Gly138Arg substitution in the transmembrane domain of the mature MPZ/P0 protein. Focal enlargement of the nerve trunks in demyelinating, hereditary motor and sensory neuropathies (HMSN) was previously reported in both asymptomatic and symptomatic cases with root compression, but peculiar to this case is the diffuse involvement of both cranial and spinal nerves. We believe that the relevance of nerve trunk hypertrophy in HMSN is probably underevaluated: therefore MRI investigation of the head and spine should be included in the diagnostic study of selected HMSN patients. Molecular analysis of peripheral myelin genes will help to rule out misdiagnosed cases.

No mutation in the TRKA (NTRK1) gene encoding a receptor tyrosine kinase for nerve growth factor in a patient with hereditary sensory and autonomic neuropathy type V

Hereditary sensory and autonomic neuropathy type IV (HSAN-IV) and type V (HSAN-V) are autosomal recessive genetic disorders, both characterized by a lack of pain sensation. We report a girl with clinical and neurophysiological findings consistent with a diagnosis of HSAN-V. We sequenced her TRKA gene, encoding a receptor tyrosine kinase for nerve growth factor and responsible for HSAN-IV, but we could not detect any mutation. These data indicate that a gene (or genes) other than TRKA is probably responsible for HSAN-V in some patients.

Genetic mapping of a susceptibility locus for disc herniation and spastic paraplegia on 6q23.3-q24.1

It has been suggested that a genetic factor(s) or a familial predisposition may contribute to the clinical manifestations of disc herniation; moreover, no genetic linkage between spinal disc herniation and spastic paraplegia has ever been described. A family with consanguineous parents and four of eight sibs affected by multiple disc herniations and spastic paraplegia was clinically and genetically analysed. Surgery caused partial improvement in all of them. After the exclusion of type II collagen and vitamin D receptor genes and the recessive loci for HSPs, a genome wide search was performed with about 500 fluorescent markers. Positive lod score values were obtained for chromosome 6q22.31-q24.1, with evidence of three homozygous intervals. The maximum multipoint lod score of 3.28 was obtained in only one interval, between markers D6S1699 and D6S314. On the whole, a susceptibility locus for disc herniation and autosomal recessive spastic paraplegia was found on chromosome 6q23.3-q24.1. This is the first time that disc herniation and the associated neurological syndrome has been linked to a human chromosomal region.

Neuronal ceroid lipofuscinoses: pathological features of bioptic specimens from 28 patients

Clinical findings and pathological features of 28 patients affected with neuronal ceroid lipofuscinoses (NCL) are reviewed. The patient group included 15 children affected with the late-infantile form of NCL (LINCL), 10 patients affected with the juvenile form (JNCL), and 3 adult cases. Ultrastructural examinations of 50 biopsies from 6 tissues were consistent with clinical features in all LINCL and JNCL cases but one. The importance of electron microscopic (EM) examination of blood lymphocytes in these forms is outlined, particularly when combined with molecular analysis of the CLN2 or CLN3 genes, respectively. This approach leads to a definite diagnosis of LINCL and JNCL in a relatively short time. In adult NCL, diagnosis still relies on pathological grounds, and difficulties in interpreting the osmiophilic storage bodies in different tissues are outlined. EM investigation of blood lymphocytes was not helpful in any case of adult NCL. Results of one stereotactic brain biopsy are also reported.