Natural history of Tay-Sachs disease in sheep

Tay-Sachs disease (TSD) is a fatal neurodegenerative disease caused by a deficiency of the enzyme β-N-acetylhexosaminidase A (HexA). TSD naturally occurs in Jacob sheep is the only experimental model of TSD. TSD in sheep recapitulates neurologic features similar to juvenile onset and late onset TSD patients. Due to the paucity of human literature on pathology of TSD, a better natural history in the sheep TSD brain, which is on the same order of magnitude as a child's, is necessary for evaluating therapy and characterizing the pathological events that occur. To provide clinicians and researchers with a clearer understanding of longitudinal pathology in patients, we compare spectrum of clinical signs and brain pathology in mildly symptomatic (3-months), moderately symptomatic (6-months), or severely affected TSD sheep (humane endpoint at ~9-months of age). Increased GM2 ganglioside in the CSF of TSD sheep and a TSD specific biomarker on MRS (taurine) correlate with disease severity. Microglial activation and reactive astrocytes were observed globally on histopathology in TSD sheep with a widespread reduction in oligodendrocyte density. Myelination is reduced primarily in the forebrain illustrated by loss of white matter on MRI. GM2 and GM3 ganglioside were increased and distributed differently in various tissues. The study of TSD in the sheep model provides a natural history to shed light on the pathophysiology of TSD, which is of utmost importance due to novel therapeutics being assessed in human patients.

Patent Foramen Ovale and Cryptogenic Strokes in the Stroke in Young Fabry Patients Study

BACKGROUND AND PURPOSE

A patent foramen ovale (PFO) is disproportionately prevalent in patients with cryptogenic stroke. Without alternative explanations, it is frequently considered to be causative. A detailed stratification of these patients may improve the identification of incidental PFO.

METHODS

We investigated the PFO prevalence in 3497 transient ischemic attack and ischemic stroke patients aged 18 to 55 years in the prospective multicenter SIFAP1 study (Stroke in Young Fabry Patients 1) using the ASCO classification. Patients without an obvious cause for transient ischemic attack/stroke (ASCO 0) were divided into subgroups with and without vascular risk factors (ASCO 0+ and 0-). In addition, we looked for PFO-related magnetic resonance imaging lesion patterns.

RESULTS

PFO was identified in 25% of patients. Twenty percent of patients with a definite or probable cause of transient ischemic attack/stroke (≥1 grade 1 or 2 ASCO criterion; n=1769) had a PFO compared with 29% of cryptogenic stroke patients (ASCO 0 and 3; n=1728; P<0,001); subdivision of cryptogenic strokes revealed a PFO in 24% of 978 ASCO 3 patients (n.s. versus ASCO 1 and 2) and a higher prevalence of 36% in 750 ASCO 0 cases (P<0.001 versus ASCO 3 and versus ASCO 1 and 2). PFO was more commonly observed in ASCO 0- (n=271) than in ASCO 0+ patients (n=479; 48 versus 29%; P<0.001). There was no PFO-associated magnetic resonance imaging lesion pattern.

CONCLUSIONS

Cryptogenic stroke patients demonstrate a heterogeneous PFO prevalence. Even in case of less conclusive diseases like nonstenotic arteriosclerosis, patients should preferentially be considered to have a non-PFO-mediated stroke.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00414583.

Family History in Young Patients With Stroke

BACKGROUND AND PURPOSE

Family history of stroke is an established risk factor for stroke. We evaluated whether family history of stroke predisposed to certain stroke subtypes and whether it differed by sex in young patients with stroke.

METHODS

We used data from the Stroke in Fabry Patients study, a large prospective, hospital-based, screening study for Fabry disease in young patients (aged <55 years) with stroke in whom cardiovascular risk factors and family history of stroke were obtained and detailed stroke subtyping was performed.

RESULTS

A family history of stroke was present in 1578 of 4232 transient ischemic attack and ischemic stroke patients (37.3%). Female patients more often had a history of stroke in the maternal lineage (P=0.027) than in the paternal lineage. There was no association with stroke subtype according to Trial of Org 10172 in Acute Stroke Treatment nor with the presence of white matter disease on brain imaging. Patients with dissection less frequently reported a family history of stroke (30.4% versus 36.3%; P=0.018). Patients with a parental history of stroke more commonly had siblings with stroke (3.6% versus 2.6%; P=0.047).

CONCLUSIONS

Although present in about a third of patients, a family history of stroke is not specifically related to stroke pathogenic subtypes in patients with young stroke. Young women with stroke more often report stroke in the maternal lineage.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00414583.

Lessons from everyday stroke care for clinical research and vice versa: comparison of a comprehensive and a research population of young stroke patients

Background

Translating knowledge derived from medical research into the clinical setting is dependent on the representativeness of included patients. Therefore we compared baseline data of patients included in a recent large study addressing young stroke in comparison to a large representative stroke registry.

Methods

We analysed baseline data of 5023 patients (age 18-55 years) with an acute cerebrovascular event included in the sifap1 (Stroke in Young Fabry Patients) study. For comparison 17007 stroke patients (age 18-55 years) documented (2004-2010) in a statutory stroke registry of the Institute of Quality Assurance Hesse of the Federal State of Hesse (GQH), Germany.

Results

Among 17007 juvenile (18-55 years) patients identified in the GQH registry 15997 had an ischaemic stroke or TIA (91%) or an intracranial haemorrhage (9%). In sifap1 5023 subjects were included. Sex distribution was comparable (men: 59% sifap1 versus 60.5% GQH) whereas age differed between the groups: median age was 46 years in sifap1 versus 49 years in GQH. Slightly higher percentages for diabetes mellitus and hypertension in the GQH registry were noted. There were no differences in stroke severity as assessed by NIHSS (median 3) and mRS (median 2). In patients with ischaemic stroke or TIA (n = 4467 sifap1; n = 14522 GQH) higher rates of strokes due to small artery occlusion and atherosclerosis occurred in older age groups; cardioembolism and strokes of other determined cause occurred more frequently in younger patients.

Conclusions

The comparison of baseline characteristics between the sifap1 study and the GQH registry revealed differences mainly determined by age.

Acute Cerebrovascular Disease in the Young

Background and Purpose—

Strokes have especially devastating implications if they occur early in life; however, only limited information exists on the characteristics of acute cerebrovascular disease in young adults. Although risk factors and manifestation of atherosclerosis are commonly associated with stroke in the elderly, recent data suggests different causes for stroke in the young. We initiated the prospective, multinational European study Stroke in Young Fabry Patients (sifap) to characterize a cohort of young stroke patients.

Methods—

Overall, 5023 patients aged 18 to 55 years with the diagnosis of ischemic stroke (3396), hemorrhagic stroke (271), transient ischemic attack (1071) were enrolled in 15 European countries and 47 centers between April 2007 and January 2010 undergoing a detailed, standardized, clinical, laboratory, and radiological protocol.

Results—

Median age in the overall cohort was 46 years. Definite Fabry disease was diagnosed in 0.5% (95% confidence interval, 0.4%–0.8%; n=27) of all patients; and probable Fabry disease in additional 18 patients. Males dominated the study population (2962/59%) whereas females outnumbered men (65.3%) among the youngest patients (18–24 years). About 80.5% of the patients had a first stroke. Silent infarcts on magnetic resonance imaging were seen in 20% of patients with a first-ever stroke, and in 11.4% of patients with transient ischemic attack and no history of a previous cerebrovascular event. The most common causes of ischemic stroke were large artery atherosclerosis (18.6%) and dissection (9.9%).

Conclusions—

Definite Fabry disease occurs in 0.5% and probable Fabry disease in further 0.4% of young stroke patients. Silent infarcts, white matter intensities, and classical risk factors were highly prevalent, emphasizing the need for new early preventive strategies.

Clinical Trial Registration Information—

URL: http://www.clinicaltrials.gov .Unique identifier: NCT00414583

Splice site, frameshift, and chimeric GFAP mutations in Alexander disease

Alexander disease (AxD) is a usually fatal astrogliopathy primarily caused by mutations in the gene encoding glial fibrillary acidic protein (GFAP), an intermediate filament protein expressed in astrocytes. We describe three patients with unique characteristics, and whose mutations have implications for AxD diagnosis and studies of intermediate filaments. Patient 1 is the first reported case with a noncoding mutation. The patient has a splice site change producing an in-frame deletion of exon 4 in about 10% of the transcripts. Patient 2 has an insertion and deletion at the extreme end of the coding region, resulting in a short frameshift. In addition, the mutation was found in buccal DNA but not in blood DNA, making this patient the first reported chimera. Patient 3 has a single-base deletion near the C-terminal end of the protein, producing a short frameshift. These findings recommend inclusion of intronic splice site regions in genetic testing for AxD, indicate that alteration of only a small fraction of GFAP can produce disease, and provide caution against tagging intermediate filaments at their C-terminal end for cell biological investigations.

Hippocampal atrophy as a surrogate of neuronal involvement in Fabry disease

Cerebral micro- and macro-vasculopathy have been described in Fabry disease (FD). Neuronal globotriaosylceramide accumulation in selective cortical and brain stem areas including the hippocampus has been reported by autopsy studies in FD, but clinical surrogates as well as the clinical relevance of these findings have not been investigated so far. We measured the hippocampus volumes in a group of clinically affected patients with FD and correlated the findings with the cognitive performance of the patients. Hippocampal volumes were determined manually on T1-weighted MR-images of 25 FD patients (age 36.5 ± 11.0 years) and 20 age-matched controls. Additionally, individual white matter (WM) and gray matter (GM) volumes were measured using brain segmentation analyses. After controlling for age, white matter lesion (WML) volume, and WM/GM-volumes hippocampal volumes were significantly decreased in FD. These findings were substantially more pronounced in a subgroup of men with FD. WM and WM/GM volumes, and memory function did not significantly differ between patients and controls. In patients with FD hippocampal volumes were neither significantly correlated to WML volume nor to WM or WM/GM volumes. Hippocampus atrophy was not driven by the WML or other brain tissue atrophy and seems to correlate with the neuronal involvement in FD. In this young to middle-aged Fabry cohort the hippocampus degeneration was functionally compensated without memory impairment. Longitudinal studies are needed to determine whether this degenerative component in FD will progress and, in concert with the individual WML-load, predict subsequent cognitive decline.

A mutation in SCARB2 is a modifier in Gaucher disease

Lysosomal integral membrane protein type 2 (LIMP-2) is responsible for proper sorting and lysosomal targeting of glucocerebrosidase, the enzyme deficient in Gaucher disease (GD). Mutations in the gene for LIMP-2, SCARB2, are implicated in inherited forms of myoclonic epilepsy, and myoclonic epilepsy is part of the phenotypic spectrum associated with GD. We investigated whether SCARB2 mutations impact the Gaucher phenotype focusing on patients with myoclonic epilepsy, including a pair of siblings with GD who were discordant for myoclonic seizures. Sequencing of SCARB2 genomic and cDNA identified a heterozygous, maternally inherited novel mutation, c.1412A>G (p.Glu471Gly), in the brother with GD and myoclonic epilepsy, absent from his sibling and controls. Glucocerebrosidase activity, Western blots, real-time PCR, and immunofluorescence studies demonstrated markedly decreased LIMP-2 and glucocerebrosidase in cells from the sibling with (p.Glu471Gly) LIMP-2, and diminished glucocerebrosidase in lysosomes. The cells secreted highly glycosylated enzyme and showed mistrafficking of glucocerebrosidase. Sequencing of SCARB2 in 13 other subjects with GD and myoclonic epilepsy and 40 controls failed to identify additional mutations. The study provides further evidence for the association of LIMP-2 and myoclonic epilepsy, explains the drastically different phenotypes encountered in the siblings, and demonstrates that LIMP-2 can serve as a modifier in GD.

Neuronopathic Gaucher disease: demographic and clinical features of 131 patients enrolled in the International Collaborative Gaucher Group Neurological Outcomes Subregistry

OBJECTIVE

To describe demographic, genetic, and clinical characteristics of patients with neuronopathic Gaucher disease (NGD).

METHODS

All patients enrolled in the Neurological Outcomes Subregistry of the International Collaborative Gaucher Group (ICGG) Gaucher Registry as of June 2007 were identified.

RESULTS

The study cohort comprised 131 patients from 17 countries who were enrolled in the Neurological Outcomes Subregistry. The onset of neurological manifestations had occurred before 2 years of age in 47% (61 out of 131 patients), 2 years of age or older in 41% (54 out of 131), and could not be ascertained in the remaining 12% (16 out of 131). The most common manifestations were inability to look to the extreme up or down (45%, 55 out of 123), abnormally slow object tracking (43%, 53 out of 123), convergent squint (36%, 44 out of 121), and ataxia (15 to 20%, 18-27 out of 117). Seizures were reported in 19 out of 122 patients (16%), and myoclonic seizures were reported in 3 out of 121 patients (2%). The most common genotypes were L444P/L444P (76 out of 108, 70%), L444P/D409H (9 out of 108, 8%), D409H/D409H (8 out of 108, 7%), and L444P/rare allele (6 out of 108, 6%); full sequencing was not performed in all patients.

CONCLUSIONS

Neurological manifestations of GD often begin to appear before the age of 2 years. The most common neurological signs and manifestations are brainstem abnormalities and fine motor dysfunction. The most common genotype is L444P/L444P.

Head trauma can initiate the onset of adreno-leukodystrophy

X-linked adreno-leukodystrophy and its adult variant, adrenomyeloneuropathy, are caused by mutations in ABCD1 that encodes a peroxisomal membrane protein of unknown physiological significance. In spite of identical mutations, they can have markedly divergent neurological and neuropathologic characteristics. Adreno-leukodystrophy classically presents in normal boys with mild neuropsychiatric features, which progress to frank neurological signs, the vegetative state and death in approximately three years. Adrenomyeloneuropathy typically affects young men with spastic paraparesis and sensory ataxia that can progress over decades. The neuropathologic correlate for adreno-leukodystrophy is severe inflammatory demyelination of posterior cerebral white matter, while a chronic distal axonopathy of spinal cord and peripheral nerve occurs in adrenomyeloneuropathy. Consequently, both modifier genes and environmental factors have been implicated in their pathogeneses. We report five cases of adreno-leukodystrophy whose onsets were initiated by moderate to severe head trauma, two of whom were conversions from adrenomyeloneuropathy. Their clinical courses were rapidly incapacitating, short (i.e., weeks to a few years) and fatal due to marked cerebral inflammatory demyelination. These cases, in concert with several previous reports, indicate that head trauma is one environmental factor that can have a profoundly deleterious effect on those genetically at risk for, or with milder clinical phenotypes of, this disease. Avoidance of potential head trauma and a rapid response to episodes of moderate to severe head trauma in this patient population seem prudent.

Management of neuronopathic Gaucher disease: revised recommendations

The original guidelines drawn up for the management of the neuronopathic forms of Gaucher disease were felt to be in need of revision; in particular, the role of high-dose enzyme replacement therapy (120 IU/kg of body weight every 2 weeks) in stabilizing neurological disease. The existing published evidence was analysed; it was concluded that it did not support the role of high-dose ERT, although this might be required to treat severe visceral disease.

Juvenile-onset G(M2)-gangliosidosis in an African-American child with nystagmus

G(M2)-gangliosidosis is a neurodegenerative lysosomal disease with several clinical variants. We describe a 2-year-old black child with juvenile-onset disease, who presented with abnormal eye movements and cherry-red spots of the maculae. Mutation analysis of the HEXA gene revealed the patient to be a compound heterozygote (M1V/Y37N). The M1V mutation was previously described in an African-American child with acute infantile G(M2)-gangliosidosis. The Y37N mutation is novel. This combination of mutations is consistent with juvenile-onset disease, and provides further evidence for the association of the M1V mutation with individuals of black ancestry. The presence of oculomotor abnormalities is an unusual finding in this form of G(M2)-gangliosidosis, and adds to the phenotypic spectrum.

T118M PMP22 mutation causes partial loss of function and HNPP-like neuropathy

OBJECTIVE

To determine the clinical consequences of the PMP22 point mutation, T118M, which has been previously considered to either cause an autosomal recessive form of Charcot-Marie-Tooth (CMT) disease or be a benign polymorphism.

METHODS

We analyzed patients from five separate kindreds and characterized their peripheral nerve function by clinical and electrophysiological methods.

RESULTS

All heterozygous patients had clinical and/or electrophysiological features of a neuropathy similar to hereditary neuropathy with liability to pressure palsies (HNPPs). The homozygous patient had a severe axonal neuropathy without features of demyelination.

INTERPRETATION

These findings suggest that T118M PMP22 retains some normal PMP22 activity, allowing the formation of compact myelin and normal nerve conduction velocities in the homozygous state. Taken together, these findings suggest that T118M is a pathogenic mutation causing a dominantly inherited form of CMT by a partial loss of PMP22 function.

Splice-site contribution in alternative splicing ofPLP1 andDM20: molecular studies in oligodendrocytes

Mutations in the proteolipid protein 1 (PLP1) gene cause the X-linked dysmyelinating diseases Pelizaeus-Merzbacher disease (PMD) and spastic paraplegia 2 (SPG2). We examined the severity of the following mutations that were suspected of affecting levels of PLP1 and DM20 RNA, the alternatively spliced products of PLP1: c.453G>A, c.453G>T, c.453G>C, c.453+2T>C, c.453+4A>G, c.347C>A, and c.453+28_+46del (the old nomenclature did not include the methionine codon: G450A, G450T, G450C, IVS3+2T>C, IVS3+4A>G, C344A, and IVS3+28-+46del). These mutations were evaluated by information theory-based analysis and compared with mRNA expression of the alternatively spliced products. The results are discussed relative to the clinical severity of disease. We conclude that the observed PLP1 and DM20 splicing patterns correlated well with predictions of information theory-based analysis, and that the relative strength of the PLP1 and DM20 donor splice sites plays an important role in PLP1 alternative splicing.

Clinical protocol. Gene therapy of Canavan disease: AAV-2 vector for neurosurgical delivery of aspartoacylase gene (ASPA) to the human brain

This clinical protocol describes virus-based gene transfer for Canavan disease, a childhood leukodystrophy. Canavan disease, also known as Van Bogaert-Bertrand disease, is a monogeneic, autosomal recessive disease in which the gene coding for the enzyme aspartoacylase (ASPA) is defective. The lack of functional enzyme leads to an increase in the central nervous system of the substrate molecule, N-acetyl-aspartate (NAA), which impairs normal myelination and results in spongiform degeneration of the brain. No effective treatment currently exists; however, virus-based gene transfer has the potential to arrest or reverse the course of this otherwise fatal condition. This procedure involves neurosurgical administration of approximately 900 billion genomic particles (approximately 10 billion infectious particles) of recombinant adeno-associated virus (AAV) containing the aspartoacylase gene (ASPA) directly to affected regions of the brain in each of 21 patients with Canavan disease. Pre- and post-delivery assessments include a battery of noninvasive biochemical, radiological, and neurological tests. This gene transfer study represents the first clinical use of AAV in the human brain and the first instance of viral gene transfer for a neurodegenerative disease.

Cognitive functioning after pallidotomy for refractory Parkinson's disease

BACKGROUND

Earlier approaches to pallidotomy for refractory Parkinson's disease had significant complication rates. More recent approaches show fewer complications, but the effect of pallidotomy on cognition is unclear. The current study was conducted to examine the neuropsychological effects of unilateral pallidotomy.

METHODS

Neuropsychological testing was performed on patients with medically refractory, predominantly unilateral Parkinson's disease at baseline and after unilateral ventral pallidotomy (n=28) or after an equivalent period without surgery in control patients (n=10).

RESULTS

Pallidotomy patients showed no significant changes from baseline to retesting relative to the control group for any measure. Across all of the tests administered, only five of the surgery patients showed a significant decline, and of these five none declined on more than one test. Depression did not relate to preoperative or postoperative cognition. The pallidotomy group showed a significant improvement in motor functioning and activities of daily living whereas the control group did not. These measures were not associated with the neuropsychological test scores at baseline or retest.

CONCLUSIONS

Stereotactic unilateral ventral pallidotomy does not seem to produce dramatic cognitive declines in most patients.

Heller syndrome in a pre-school boy. Proposed medical evaluation and hypothesized pathogenesis

The case of a 6-year-old boy who developed childhood disintegrative disorder (Heller syndrome) at the age of 4 years is presented, and specifics of the neurologic evaluation are detailed. A table is provided suggesting the complete neurologic work-up with the potential findings for children presenting with signs and symptoms of deterioration. A hypothesis for the aetiology of Heller syndrome proposes that predisposing genetic factors when combined with an environmental stress result in the deposition of amyloid and the disruption of synaptic transmission during the deterioration period. Speculation that the deterioration may be self-limited by activation of an immune response is based upon earlier findings that interleukin 1 has been shown to be involved in the breakdown of amyloid precursor protein in humans.

Stereotactic ventral pallidotomy for Parkinson's disease

Eighteen patients with medically intractable Parkinson's disease that was characterized by bradykinesia, rigidity, and marked "on-off" fluctuations underwent stereotactic ventral pallidotomy under local anesthesia. Targeting was aided by anatomic coordinates derived from the MRI, intraoperative cell recordings, and electrical stimulation prior to lesioning. A nonsurgically treated group of seven similarly affected individuals was also followed. Assessment of motor function was made at baseline and at 3-month intervals for 1 year. Following the lesioning, patients improved in bradykinesia, rigidity, resting tremor, and balance with resolution of medication-induced contralateral dyskinesia. When compared with preoperative baseline, all quantifiable test scores after surgery improved significantly with the patients off medications for 12 hours: UPDRS by 65%, and CAPIT subtest scores on the contralateral limb by 38.2% and the ipsilateral limb by 24.2%. Walk scores improved by 45%. Medication requirements were unchanged, but the patients who had had surgery were able to tolerate larger doses because of reduced dyskinesia. Ventral pallidotomy produces statistically significant reduction in parkinsonism and contralateral "on" dyskinesia without morbidity or mortality and with a short hospitalization in Parkinson's disease patients for whom medical therapy has failed.

A new Tay-Sachs disease B1 allele in exon 7 in two compound heterozygotes each with a second novel mutation

Three novel Tay--Sachs Disease (TSD) mutations have been identified in two unrelated, non-Jewish compound heterozygous patients. A G772C transversion mutation causing an Asp258His substitution is shared by both patients. The mutant enzyme had been characterized, on the basis of previous kinetic studies (1) as a B1, or alpha-subunit active site mutation. This is the first B1 mutation not found in codon 178 (exon 5). A C508T transition causing an Arg170Trp substitution also occurred in one of the patients. The third mutation is a two base deletion occurring in exon 8 involving the loss of either nts 927-928 or 929-930 in codon 310. The deletion creates an inframe termination codon 35 bases downstream. The Arg170Trp mutation was also detected in a third unrelated TSD patient. In both families this allele was traced to French Canadian ancestors originating in the Estrie region of the province of Quebec. This mutation is the third TSD allele unique to the French Canadian population and the ancestral origins of the carrier parents are distant from the center of diffusion of the more common 7.6 kb deletion mutation which is in the eastern part of the province.

Characterization of 6-hexadecanoylamino-4-methylumbelliferyl-beta-D- galactopyranoside as fluorogenic substrate of galactocerebrosidase for the diagnosis of Krabbe disease

6-Hexadecanoylamino-4-methylumbelliferyl-beta-D-galactopyranoside (HMGal) has been shown to be a specific fluorogenic substrate of galactocerebrosidase and to facilitate the simple enzymatic diagnosis of Krabbe disease in human patients and in twitcher mice. HMGal hydrolysis at pH 4.5 is optimally stimulated by sodium taurocholate (0.25%) and oleic acid (0.05%) with a Km of 0.150, 0.04 and 0.03 mM, respectively for control mouse kidney, human fibroblasts and leukocytes. In control samples, the specific activity (nmol/mg prot./h) for HMGal is higher than for the natural substrate, galactocerebroside, and is severely deficient in the twitcher mouse and in patients with Krabbe disease. Comparative investigation of galactocerebrosidase activity in fibroblasts, leukocytes and brain with radioactive and fluorogenic substrates reveals a good agreement between the results of the two methods. Galactocerebroside (Gal-Cer) is a competitive inhibitor of HMGal hydrolysis in mouse kidney homogenates while GM1-ganglioside has no inhibitory effect in the same assay system. The sensitivity and specificity of this fluorogenic substrate for galactocerebrosidase provides a simple and rapid method for the diagnosis of Krabbe disease, and for the purification of this enzyme from normal tissues.

Recommendations regarding handling of the necropsy in Rett syndrome

In order to maximize biochemical, neurochemical, molecular, and pathologic information from patients with Rett syndrome, a uniform procedure has been developed for the conduct of the postmortem examination. Tissue should be prepared for freezing, for electron microscopy studies, and for standard histologic examination. For the purposes of uniformity, three central repositories for necropsy materials have been established and are available at all times. In the event of the death of a patient with Rett syndrome, parents who consent to necropsy should request that materials be handled according to the protocol and transported under appropriate conditions to the central repository. The National Neurological Research Bank (Los Angeles), the Brain Tissue Bank (Belmont, Mass), and the Department of Neuropathology at Johns Hopkins Hospital (Baltimore) have agreed to serve as repositories for tissues. A committee of the International Rett Syndrome Association medical advisory panel will monitor this process in cooperation with the directors of the respective tissue banks.

Tay-Sachs disease with hexosaminidase A: characterization of the defective enzyme in two patients

Cases of infantile Tay-Sachs disease (TSD) with high residual hexosaminidase A (Hex A) activity have recently been described. The clinical presentation of the disease in these patients is identical to that found among Ashkenazi-Jewish patients. Fibroblasts from two such TSD patients had Hex A activity comprising 16% of total Hex when measured by thermal fractionation and quantitation with 4-methylumbelliferyl-beta-D-N-acetylglucosamine (4MUG). Hydrolysis of 4-methylumbelliferyl-beta-D-N-acetylglucosamine-6-SO4 (4MUGS) by patient fibroblast extracts is catalyzed by an enzyme activity that comprises less than 1% of total Hex. Kinetic analysis of patient Hex A by using 4MUGS revealed Km's similar to that of control Hex A but Vmax's significantly different from that of the control enzyme. The inhibitors N-acetylglucosamine and N-acetylglucosamine-6-PO4 were used to distinguish between active sites associated with the two different subunits of Hex A. A beta-subunit site with little activity toward 4MUGS is sensitive to N-acetylglucosamine but resistant to N-acetylglucosamine-6-PO4. This site accounts for most of the hydrolysis of 4MUG. By contrast, an alpha-subunit site that is sensitive to N-acetylglucosamine-6-PO4 but resistant to N-acetylglucosamine accounts for almost all of the hydrolysis of 4MUGS. In mutant cells, this site retains the ability to bind substrate but is deficient in catalytic activity toward 4MUGS. The pH optima of patients' Hex A is shifted to a more acidic range, and the enzymes are significantly more thermostable than control Hex A. By using the thermal fractionation procedure for serum isozyme discrimination, one parent of each patient is unambiguously classified as heterozygous for the TSD gene whereas the other parent has test values in the grey zone. When parents are tested by use of 4MUGS, however, all four parents are classified as heterozygotes. Comparison of the results of both assay procedures allows the carrier of the atypical TSD allele to be recognized and identifies the probands as compound heterozygotes.

Urinary sediment dolichols in the diagnosis of neuronal ceroid-lipofuscinosis

Long-chain polyisoprenol alcohol (dolichols) levels are significantly increased in the urinary sediment of patients with infantile, late-infantile, and juvenile forms of neuronal ceroid-lipofuscinosis (NCL). The values in obligate heterozygotes for these diseases are similar to those in patients with other neurological diseases and in healthy controls. Antioxidant treatment of patients with juvenile NCL has no effect on dolichol values. The rate of false-negative results is 13.9% in infantile, 7.5% in late-infantile, and 15.0% in juvenile NCL. False-positive results were found in 8.2 to 14.3% of patients with other neurological diseases and in 15.4% of healthy controls. The test is of considerable value in the diagnosis of NCL and in decisions on whether to perform a biopsy. It is not useful in the screening of random samples, however.

Gangliosidoses and the fetal retina

Abnormal membranous cytoplasmic inclusions were found in the retinal ganglion cells of two fetuses with gangliosidosis. One was a documented case of incipient Tay-Sachs disease (Gm2) and the other a case of generalized gangliosidosis (Gm1). Both specimens were obtained iatrogenically in the 20th to 21st week of gestation after amniocentesis had indicated the enzyme deficiency.

Compressive myelopathy in Maroteaux-Lamy syndrome: clinical and pathological findings

A 41-year-old woman with Maroteaux-Lamy syndrome developed spastic tetraparesis due to a compressive cervical myelopathy. There was substantial improvement following laminectomy and excision of the markedly thickened dura. Light and electron microscopic studies showed extensive accumulations of balloon cells in the dura.

M-mode ultrasonic localization and identification of fluid-containing pulmonary cysts

Successful ultrasonic localization of pleural fluid has been well documented in recent reports. The ability of ultrasound to detect and identify fluid within a parenchymal lesion has not been defined. We examined nine patients with cystic lesions and air-fluid levels noted on the chest roentgenogram. In all nine patients, an echo-free space that corresponded anatomically to the level of fluid noted on the x-ray film could be recorded in the M-mode presentation. The combined thickness of the wall of the chest and the overlying lung as judged by ultrasound ranged from 2 to 8 cm, with a mean of 4 cm. The following two characteristics appeared to distinguish parenchymal from pleural fluid: (1) similar characteristics of motion of the proximal and distal interfaces of the sonolucent space; or (2) the ultrasonographic pattern of overlying lung proximal to the loculation of fluid. Ultrasonograms in eight (89 percent) of nine patients demonstrated one or both of these characteristics. These findings indicate that ultrasound can detect fluid within a parenchymal structure and may be used to differentiate intraparenchymal loculations from those in the pleural space.