A novel type of hereditary motor and sensory neuropathy characterized by a mild phenotype.

BACKGROUND: Three loci for autosomal dominant hereditary motor and sensory neuropathy type I (HMSN I) or Charcot-Marie-Tooth disease type 1 (CMT1) have been identified on chromosomes 17p11.2 (CMT1A), 1q21-q23 (CMT1B), and 10q21.1-q22.1 (designated here as CMT1D). The genes involved are peripheral myelin protein 22 (PMP22), myelin protein zero (MPZ), and the early growth response element 2 (EGR2), respectively. Probably a fourth locus (CMT1C) exists since some autosomal dominant HMSN I families have been excluded for linkage with the CMT1A and CMT1B loci. Four loci for autosomal dominant hereditary motor and sensory neuropathy type II (HMSN II) or Charcot-Marie-Tooth disease type 2 (CMT2) have been localized on chromosomes 1p35-p36 (CMT2A), 3q13-q22 (CMT2B), 7p14 (CMT2D), and 3p (HMSN-P). OBJECTIVE: To describe the clinical, electrophysiologic, and neuropathological features of a novel type of Charcot-Marie-Tooth disease. PATIENTS AND METHODS: We performed linkage studies with anonymous DNA markers flanking the known CMT1 and CMT2 loci. Patients and their relatives underwent clinical neurologic examination and electrophysiologic testing. In the proband, a sural nerve biopsy specimen was examined. RESULTS: Linkage studies excluded all known CMT1 and CMT2 loci. The clinical phenotype is mild and almost all affected individuals remain asymptomatic. Electrophysiologic and histopathological studies showed signs of a demyelinating neuropathy, but the phenotype is unusual for either autosomal dominant HMSN I or HMSN II. CONCLUSION: Our findings indicate that the HMSN in this family represents a novel clinical and genetic entity.

Early-onset Alzheimer's disease in 2 large Belgian families.

Familial Alzheimer's disease (FAD) is a dominantly inherited condition that may present with an early onset, and myoclonus occurs frequently in the course of the disease. We report clinical and neuropathologic data on 2 large Belgian families with FAD in which we obtained 17 autopsies of the CNS. In family A, each of 11 autopsies had the typical neuropathologic features of Alzheimer's disease (AD), and there were a few cerebellar plaques in the molecular layer. In family B, in addition to the typical characteristics of AD in 6 autopsies, there were numerous amyloid plaques in the cortical cerebellar layers. In both families, we immunostained the amyloid deposits for the A4 protein, and they were negative for prion-associated protein immunoreactivity.

Novel missense mutation in the early growth response 2 gene associated with Dejerine-Sottas syndrome phenotype.

BACKGROUND: Mutations in the early growth response 2 (EGR2) gene have recently been found in patients with congenital hypomyelinating neuropathy and Charcot-Marie-Tooth type 1 (CMT1) disease. OBJECTIVE: To determine the frequency of EGR2 mutations in patients with a diagnosis of CMT1, Dejerine-Sottas syndrome (DSS), or unspecified peripheral neuropathies. METHODS: Fifty patients and 70 normal control subjects were screened. RESULTS: A de novo missense mutation (Arg359Trp) in the alpha-helix of the first zinc-finger domain of the EGR2 transcription factor was identified in a patient diagnosed with a clinical phenotype consistent with DSS. This patient had a motor median nerve conduction velocity of 8 m/s. A sural nerve biopsy showed a severe loss of myelinated and unmyelinated fibers, evidence for demyelination, numerous classic onion bulbs, and focally folded myelin sheaths. DSS is a severe, childhood-onset demyelinating peripheral neuropathy initially thought to be inherited as an autosomal recessive trait. However, several dominant heterozygous mutations in the peripheral myelin protein 22 (PMP22) gene and dominant mutations in the peripheral myelin protein zero (MPZ) gene, both in the heterozygous and homozygous state, have been reported in patients with DSS. CONCLUSIONS: Hereditary peripheral neuropathies represent a spectrum of disorders due to underlying defects in myelin structure or formation.

Mutations in GDAP1: autosomal recessive CMT with demyelination and axonopathy.

BACKGROUND: Mutations in the ganglioside-induced differentiation-associated protein 1 gene (GDAP1) were recently shown to be responsible for autosomal recessive (AR) demyelinating Charcot-Marie-Tooth disease (CMT) type 4A (CMT4A) as well as AR axonal CMT with vocal cord paralysis. METHODS: The coding region of GDAP1 was screened for the presence of mutations in seven families with AR CMT in which the patients were homozygous for markers of the CMT4A locus at chromosome 8q21.1. RESULTS: A nonsense mutation was detected in exon 5 (c.581C>G, S194X), a 1-bp deletion in exon 6 (c.786delG, G262fsX284), and a missense mutation in exon 6 (c.844C>T, R282C). CONCLUSIONS: Mutations in GDAP1 are a frequent cause of AR CMT. They result in an early-onset, severe clinical phenotype. The range of nerve conduction velocities (NCV) is variable. Some patients have normal or near normal NCV, suggesting an axonal neuropathy, whereas others have severely slowed NCV compatible with demyelination. The peripheral nerve biopsy findings are equally variable and show features of demyelination and axonal degeneration.

On a dominantly inherited myopathy with tubular aggregates.

A 19-year-old patient presented with exercise-related myalgia, fatigue and elevated creatine kinase levels. Histology of a muscle biopsy was characterized by the presence of very large amounts of tubular aggregates. Both his father and paternal grandfather had elevated creatine kinase and large amounts of tubular aggregates in their muscle biopsies. The aggregates consisted of closely packed vesicles and tubules filled with electron-dense material or with one to several smaller tubules. Disorders with tubular aggregates in the muscle fibres such as hyperornithinaemia with gyrate atrophy of the retina, hypokalaemic periodic paralysis, hyperkalaemic periodic paralysis, myotonia congenita, alcoholism, osteomalacic myopathy etc. have been excluded. Tubular aggregates can be found in muscle disorders characterized by exercise-induced cramps, pain and stiffness. They also represent the predominant histological feature of some familial myopathies due to a yet unidentified genetic defect. In our family, there was male-to-male transmission, confirming dominant inheritance.

A novel 3'-splice site mutation in peripheral myelin protein 22 causing hereditary neuropathy with liability to pressure palsies.

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant, demyelinating peripheral neuropathy. Clinical hallmarks are recurrent painless focal neuropathies mostly preceded by minor trauma or compression at entrapment sites of peripheral nerves. In the majority of the patients, HNPP is caused by a 1.5 Mb deletion on chromosome 17p11.2-p12 containing the peripheral myelin protein 22 (PMP22) gene. Point mutations within this gene are reported in only a few families. We report a novel mutation in the PMP22 gene in a Spanish family with HNPP. The mutation is a 3' splice-site mutation, preceding coding exon 3 (c.179-1 G>C), causing a mild HNPP phenotype.

Recessive POLG mutations presenting with sensory and ataxic neuropathy in compound heterozygote patients with progressive external ophthalmoplegia.

Autosomal recessive progressive external ophthalmoplegia is a mitochondrial disease characterized by accumulation of multiple large-scale deletions of mitochondrial DNA. We previously reported missense mutations in POLG, the gene encoding the mitochondrial DNA polymerase gamma in two nuclear families compatible with autosomal recessive progressive external ophthalmoplegia. Here, we report a novel POLG missense mutation (R627W) in a sporadic patient and we provide genetic support that all these POLG mutations are actually causal and recessive. The novel patient presented with sensory ataxic neuropathy and has the clinical triad of sensory ataxic neuropathy, dysarthria and ophthalmoparesis (SANDO). This is the first finding of a genetic cause of Sensory Ataxic Neuropathy, Dysarthria and Ophthalmoparesis and it implies that this disorder may actually be a variant of autosomal recessive progressive external ophthalmoplegia. Sensory neuropathy is the initial feature in Belgian compound heterozygote autosomal recessive progressive external ophthalmoplegia patients, all carrying the POLG A467T mutation, which occurs at a frequency of 0.6% in the Belgian population.

Identification and localization of ataxin-7 in brain and retina of a patient with cerebellar ataxia type II using anti-peptide antibody.

Autosomal dominant cerebellar ataxias (ADCAs) are a complex group of neurodegenerative disorders characterized by progressive degeneration of the cerebellum, brain stem and spinal cord. The spinocerebellar ataxia type 7 (SCA7) is associated with pigmentary macular dystrophy and retinal degeneration leading to blindness caused by a CAG/polyglutamine (polyGln) expansion in the coding region of the SCA7 gene/protein. The SCA7 gene codes for ataxin-7, a protein of unknown function. To investigate its cellular and subcellular localization, we have developed a sequence-specific polyclonal antibody against the N-terminal part of the protein. Immunohistochemical analysis indicated that ataxin-7 accumulates as single nuclear inclusion (NI) in the cells of the brain and retina of a SCA7 patient but not of controls. The 1C2 antibody, directed against expanded polyGln, confirmed the aggregation of mutant ataxin-7 in these NIs. Furthermore, ubiquitin was found in these aggregates, suggesting that mutant ataxin-7 is a target for ubiquitin-dependent proteolysis, but resistant to removal. Electron microscopic studies using immunogold labeling showed that ataxin-7 immunoreactive NIs appear as dense aggregates containing a mixture of granular and filamentary structures. Together, these data confirm the presence of NIs in brain and retina of a SCA7 patient, a common characteristic of disorders caused by expanded CAG/polyGln repeats.

Caspr1/Paranodin/Neurexin IV is most likely not a common disease-causing gene for inherited peripheral neuropathies.

Contactin associated protein 1 (Caspr1/Paranodin/Neurexin IV) is an axonal transmembrane molecule mainly localised at the paranodal junction. Since molecular alterations in septate-like junctions at the paranodes might have important consequences for the function of the nerve fiber, we considered that Caspr1 could be involved in the pathogenesis of inherited peripheral neuropathies. In this study, we physically mapped the Caspr1 gene on chromosome 17q21.1 and determined its genomic structure. We performed a mutation analysis of the Caspr1 gene in a cohort of 64 unrelated patients afflicted with distinct inherited peripheral neuropathies. Since no disease causing mutations were found, we suggest that Caspr1 is probably not a common cause of inherited peripheral neuropathies.

Rimmed vacuoles of inclusion body myositis and oculopharyngeal muscular dystrophy contain amyloid precursor protein and lysosomal markers.

Rimmed vacuoles are small areas of focal destruction of muscle fibres, found in inclusion body myositis, oculopharyngeal muscular dystrophy and other muscle disorders. They are known to contain amyloid proteins, probably of beta-amyloid type. We examined rimmed vacuoles immunohistochemically in 12 patients with inclusion body myositis and two patients with oculopharyngeal muscular dystrophy with antibodies to beta-amyloid precursor protein and cathepsin B and D. We found evidence for the presence of all these markers in rimmed vacuoles. These results confirm the presence of beta-amyloid in rimmed vacuoles, and provide additional support for the hypotheses that rimmed vacuoles are of lysosomal origin and that lysosomes are probably important in the metabolism of amyloid precursor protein.

Adrenomyeloneuropathy. A report on two families.

Adrenomyeloneuropathy (AMN) is reported in two kindreds. In the first family, four male patients were affected: two adults with the full clinical picture but with a different chronology of the main symptoms, a third adult with central nervous system involvement and a child who died early with adrenal insufficiency. The second family included two male patients with AMN, one adult with raised ACTH levels and his nephew with normal adrenal function. Two other young males died with adrenoleukodystrophy (ALD), one being subjected to a postmortem study. Clinical, endocrinological, neurophysiological and pathological studies were performed. The following conclusions can be made (1) AMN and ALD are closely related entities; (2) there exists a considerable intrafamilial variability of the clinical picture; (3) AMN is to be included in the differential diagnosis of myelopathies and, conversely, signs of central nervous system damage must be sought in males patients with adrenal insufficiency; (4) electron microscopy of nerve twigs brings supportive diagnostic evidence pending the more widespread determination of the C26/C22 fatty acids ratios in cultured fibroblasts or plasma.

Sporadic early adult-onset distal myopathy with rimmed vacuoles: immunohistochemistry and electron microscopy.

We report the histoenzymology, immunohistochemistry and electron microscopy of the tibialis anterior muscle of a 50-year-old male patient affected by a sporadic distal myopathy with onset during adolescence. There was no family history of muscle disorder and no clinical signs of cardiomyopathy. Extremely large variations in muscle fibre diameter (the size of some fibres exceeding 200-250 microns), rimmed vacuoles, necrotic fibres invaded by macrophages, atrophic fibres and perimysial fibrosis were observed. Using a wide range of antibodies raised against membrane- and cytoskeletal muscle proteins, granular desmin immunoreactivity was observed in muscle fibre lesions. There were no inflammatory parameters. Of special interest was the occurrence of autophagic vacuoles without 18-20 nm thick sarcoplasmic filaments and the presence of small aggregates of intermediate desmin-like filaments among a great diversity of ultrastructural findings. The morphological differential diagnosis is discussed. Our results stress the importance of combined immunohistochemistry and electron microscopy in the delineation of distal myopathies. DNA defects, however, still have to be identified which would improve the present classifications of distal myopathies.

Electron microscopic features of skin in neurometabolic disorders.

Skin biopsy may contribute to the clinical diagnosis of neurometabolic disorders. It is an easy and much less traumatic procedure than brain, rectal, peripheral nerve and skeletal muscle biopsies. The method is informative and not too time-consuming for an experienced examiner. Differential diagnosis is possible in most storage disorders since the ultrastructure of the storage is virtually typical in lysosomal and in nonlysosomal diseases. The storage has a particular distribution with characteristic ultrastructural patterns in the various cell types. Skin biopsy plays a major diagnostic role when clinical features are atypical for a storage disorder, to discover new phenotypic variants of known enzymatic deficiencies or when the biochemical defect has not yet been determined. It can be used as a screening procedure to orientate the investigations, to suggest specific biochemical assays on cultured fibroblasts or other tissues or body fluids. It can be applied to detect "presymptomatic" patients in affected families. Other disorders of the nervous system should be investigated in the future to ascertain whether skin biopsies could possibly be used for diagnostic purposes. Thorough knowledge of the morphological features of these disorders may also improve the understanding of their pathogenesis, shed some light on the underlying basic defects and control the results of therapy.

Diagnostic role of skin or conjunctival biopsies in neurological disorders. An update.

Updated figures from our reports on electron microscopy of skin or conjunctival biopsies include 256 patients, mostly suffering from lysosomal diseases. Significant morphological data supportive of the diagnosis and additional to enzyme assay (when and if an assay is available for the disorder) were discovered in 95% of the cases. Equivocal or negative data amounted to 5%. The present paper deals with some metabolic disorders which had not been fully dealt with in our previous publications and with an extension of the indications of skin biopsies: adult form and atypical variants of ceroid-lipofuscinoses, galactosialidosis, mucolipidosis IV, infantile neuroaxonal dystrophy, Lafora's disease, cardiomyopathy with generalized accumulation of intermediate filaments and congenital hypomyelination neuropathy. A comparison between biopsy and autopsy material in storage diseases shows that the storage of inclusions does not remain limited to one cell type or to one tissue even if no clinical signs are detectable. This ubiquitous character of the storage can be used for diagnostic purposes. On the other hand, the membrane-bound inclusions are not necessarily similar in all cell types and the search for characteristic features can be difficult in adult patients. Finally it is evident that skin biopsies can be used in other conditions than lysosomal disorders. The applicability of this procedure to other diseases needs further exploratory work.

Pathology of peripheral nerves in metachromatic leucodystrophy. A comparative study of ten cases.

Results of qualitative and quantitative studies on 1 to 13 peripheral nerves from 10 cases (6 late infantile, 2 juvenile and 2 adult cases) of metachromatic leucodystrophy (MLD) are reported. Peripheral nerve biopsies are still useful despite the arylsulphatase A assays on leucocytes and cultured fibroblasts, since they provide extremely rapid and reliable diagnostic information. The following points are investigated: (1) are there differences in the severity and characteristics of demyelination according to MLD subtypes; (2) are there major differences in various nerves of one patient; (3) are some inclusions characteristic of a given MLD subtype; (4) is there a direct relationship between demyelination and storage of characteristic inclusions? While question 1 can be answered positively, the three following ones must receive a negative or at best an equivocal answer.

Juvenile dystonic lipidosis (variant of Niemann-Pick disease type C).

In two siblings affected with dementia, epilepsy and vertical supranuclear ophthalmoplegia, foam cells and sea-blue histiocytes were found in the bone marrow. Electron microscopy of skin and neuromuscular biopsies gave presumptive evidence in favour of a storage disorder. Postmortem examination of both cases revealed an intraneuronal polymorphous lysosomal storage in the central nervous system (in the cortex and in many nuclei e.g. the substantia nigra and the reticular formation of the brain stem). In the visceral organs with the spleen most severely affected, the inclusions had a different ultrastructure, being composed of tightly apposed leaflets. The biochemical study revealed accumulation of sphingomyelin and other lipids in liver and spleen, with normal sphingomyelinase activities, which is consistent with the diagnosis of Niemann-Pick disease type C. In the brain, the most striking abnormalities involved the glycolipids. Sphingomyelinase activities were unchanged in cultivated skin fibroblasts. These data compared with those of reported cases, allowed the following conclusions to be made: (1) although the combination of clinical features appears to be unique, none of them, when considered separately, is pathognomonic for juvenile dystonic lipidosis; (2) diagnosis during life can be suggested by careful examination of nerve bundles and fibroblasts with the electron microscope, although the method of choice appears to be the study of bone marrow; but final assessment of the diagnosis, in the absence of demonstrable enzymic deficiency, requires in most cases a study of the lipid profile in a liver biopsy (or better, spleen tissue whenever available); (3) the intralysosomal storage is different, both morphologically and biochemically, in the central nervous system and in the spleen; (4) juvenile dystonic lipidosis represents a juvenile variant of Niemann-Pick disease type C, pending the discovery of the primary defect responsible for this disorder.

Two cases of mucopolysaccharidosis type III (Sanfilippo). A biochemical study.

The mucopolysaccharide and lipid composition of human nervous tissue and viscera from one case of Sanfilippo disease type A and one case of Sanfilippo disease type C, were investigated. In the brain a moderate increase of acid glycosaminoglycans occurred. This phenomenon was much more pronounced in the viscera, especially in the liver. In all tissues this increase was mainly due to an accumulation of heparan sulphate. Changes in lipid composition were noted, but can be regarded as secondary effects. The biochemical results reported also suggest some general conclusions. (a) AGAG and lipid analyses do not permit differentiation between the subtypes of Sanfilippo disease. (b) The differences in lipid composition can probably be considered as consequences of variation in secondary effects. (c) The severe demyelination in brain correlates well with the biochemical lipid analysis. However, in other instances it remains difficult to bridge the gap still existing between some morphological and biochemical data.

Defect in succinate oxidation by isolated muscle mitochondria in a patient with symmetrical lesions in the basal ganglia.

A 3-year-old boy was referred for evaluation of psychomotor retardation. He had a waddling gait with proximal hypotonia and paresis. Computed tomography (CT scan) and magnetic resonance imaging (MRI) of the brain demonstrated symmetrical lesions in the basal ganglia suggesting bilateral necrosis. Lactate and pyruvate levels in blood and cerebrospinal fluid were persistently elevated. A biopsy of the quadriceps muscle showed normal light microscopic findings except for a slightly raised number of lipid droplets. Electron microscopy confirmed this and also showed a rather large number of subsarcolemmal mitochondria without crystalline inclusions. Biochemical studies showed a normal carnitine level and normal mitochondrial enzyme activities in muscle homogenate, including succinate-cytochrome c reductase. However, intact isolated mitochondria failed to oxidize succinate. An explanation for this paradoxical finding is a deficiency in that part of the coenzyme Q (CoQ) that is reduced by the succinate dehydrogenase complex. The differential diagnosis between Leigh's syndrome and infantile bilateral striatal necrosis (IBSN) is discussed. The role of neuroradiology in prompting complementary investigations is stressed.

Linkage analysis of distal hereditary motor neuropathy type II (distal HMN II) in a single pedigree.

We describe a six generation family affected with the autosomal dominant form of distal hereditary motor neuropathy type II (distal HMN II). The distal HMN shows similarities with the hereditary motor and sensory neuropathies type I and II (HMSN I and HMSN II) or Charcot-Marie-Tooth disease type 1 and 2 (CMT 1 and CMT 2) and with some proximal HMN or spinal muscular atrophies (SMA). Gene loci have been assigned to chromosomes 1q, 17p, and 19q for CMT 1 and to chromosome 5q for recessive SMA. In this study we excluded all four regions for the presence of distal HMN II, indicating that this neuropathy is genetically different from CMT 1 and recessive SMA.

Ocular ultrastructural study in a fetus with type II glycogenosis.

The general pathological and ocular studies in an aborted fetus with type II glycogenosis revealed the widespread lysosomal storage of glycogen. Obvious lesions are observed in the viscera, in the skeletal and ocular muscles, and in all ocular tissues except the pigment epithelium of the retina. Brain and heart are relatively spared. Conjunctival and skin biopsies have a diagnostic importance, since specific alterations are evident early in the course of the disease.