Phenotype of patients with peroxisomal disorders subdivided into sixteen complementation groups

OBJECTIVE

To use the technique of complementation analysis to help define genotype and classify patients with clinical manifestations consistent with those of the disorders of peroxisome assembly, namely the Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), infantile Refsum disease (IRD), and rhizomelic chondrodysplasia punctata (RCDP).

STUDY DESIGN

Clinical findings, peroxisomal function, and complementation groups were examined in 173 patients with the clinical manifestations of these disorders.

RESULTS

In 37 patients (21%), peroxisome assembly was intact and isolated deficiencies of one of five peroxisomal enzymes involved in the beta-oxidation of fatty acids or plasmalogen biosynthesis were demonstrated. Ten complementation groups were identified among 93 patients (54%) with impaired peroxisome assembly and one of three phenotypes (ZS, NALD, or IRD) without correlation between complementation group and phenotype. Forty-three patients (25%) had impaired peroxisome assembly associated with the RCDP phenotype and belonged to a single complementation group. Of the 173 patients, 10 had unusually mild clinical manifestations, including survival to the fifth decade or deficits limited to congenital cataracts.

CONCLUSIONS

At least 16 complementation groups, and hence genotypes, are associated with clinical manifestations of disorders of peroxisome assembly. The range of phenotype is wide, and some patients have mild involvement.

Diagnoses of neuronal ceroid-lipofuscinosis by immunochemical methods

The neuronal ceroid-lipofuscinoses (NCL), also known as Batten disease, are a not uncommon group of disorders affecting infants, children, and young adults. The abnormal ultrastructural profiles seen in NCL are used for standard diagnosis; however, they can be missed, and are also found in other neurodegenerative conditions. Furthermore, there is an overlap between the types of inclusion profiles among the different forms of NCL. Therefore, a more specific and biochemically-based marker is necessary to confirm the diagnosis of NCL. Antibodies raised against the storage material from the ovine form of NCL (mitochondrial ATP synthase subunit c) were utilized to determine whether NCL could be distinguished from other metabolic-neurodegenerative disorders. By immunoblotting and immunohistochemistry, several brain samples of well-evaluated NCL cases confirmed increased accumulations in all NCL cases except in the brain of an infantile-onset NCL patient. The immunoblot studies of skin fibroblasts and brain were sensitive but not highly specific to NCL, due to the recognition of this material in normal controls as well as in other neurogenetic diseases. Immunocytochemistry of skin fibroblasts clearly distinguished LINCL and JNCL cases from controls, and with further refinement has the potential for becoming a diagnostic tool.

Rett syndrome studies of natural history and search for a genetic marker

The commonly held notion that Rett syndrome (RS) is a neurodegenerative disorder with normal early development was examined by an epidemiological survey and review of medical records and serial neurological and development evaluations. In some subjects, deviance from normal development was evident from the perinatal period, and gradually became more prominent with age. These findings are convincing when seen in conjunction with a reduction in velocity of brain growth, as early as 2-4 months of life, well before the recognition of gross neurological deficits. Neurodevelopmental evaluations provide no indication that there is progressive loss of adaptive behaviors, or communication skills to indicate a neurodegenerative process. Taken together with the known neuropathological and neurochemical changes in RS brain we hypothesize that RS is a neurodevelopmental disorder, which has a genetic basis, and affects subsets of neurons and their connections during a period of vigorous brain growth, when synapse formation and pruning are at a peak. Studies of mitochondrial (mt) DNA in brain to understand the genetic mechanisms underlying matrilineal inheritance in the few familial cases, and mt structural and enzyme deficiencies have been unrevealing to date.

Abnormal expression of microtubule-associated protein 2 (MAP-2) in neocortex in Rett syndrome

Immunocytochemical evaluations of the neocortex of three classical Rett syndrome (RS) individuals revealed a selective abnormality in the expression of microtubule-associated protein 2 (MAP-2). MAP-2 immunoreactivity (ir) was reduced throughout the neocortex of all three RS cases with a reversal of the normal pattern of more intense staining in deep cortical layers. This anomaly was selective for MAP-2 because nonphosphorylated neurofilament (SMI-32) labeling of deep pyramidal neurons and calbindin (CaBP)-stained GABAergic cells remained unchanged. Moreover, MAP-2 ir was virtually undetected in white matter while GABAergic and, particularly, peptidergic (neuropeptide Y: NPY) profiles were easily recognized. These results demonstrate a marked disruption of a major cytoskeletal component in neocortex in RS which seems to affect, predominantly, pyramidal projection and white matter neurons. MAP-2 expression appears early in neuronal maturation of the neocortex, particularly in the subplate region, the future superficial white matter, suggesting that these reported abnormalities in RS represent a developmental disturbance. Considering that MAP-2 expression is regulated by several neurotransmitter systems in adult cerebral cortex, particularly dopaminergic and cholinergic afferents that are deficient in RS, these neurochemical alterations could be related to this anomalous MAP-2 expression.

Studies of X inactivation and isodisomy in twins provide further evidence that the X chromosome is not involved in Rett syndrome

Rett syndrome (RS), a progressive encephalopathy with onset in infancy, has been attributed to an X-linked mutation, mainly on the basis of its occurrence almost exclusively in females and its concordance in female MZ twins. The underlying mechanisms proposed are an X-linked dominant mutation with male lethality, uniparental disomy of the X chromosome, and/or some disturbance in the process of X inactivation leading to unequal distributions of cells expressing maternal or paternal alleles (referred to as a "nonrandom" or "skewed" pattern of X inactivation). To determine if the X chromosome is in fact involved in RS, we studied a group of affected females including three pairs of MZ twins, two concordant for RS and one uniquely discordant for RS. Analysis of X-inactivation patterns confirms the frequent nonrandom X inactivation previously observed in MZ twins but indicates that this is independent of RS. Analysis of 29 RS females reveals not one instance of uniparental X disomy, extending the observations previously reported. Therefore, our findings contribute no support for the hypothesis that RS is an X-linked disorder. Furthermore, the concordant phenotype in most MZ female twins with RS, which has not been observed in female twins with known X-linked mutations, argues against an X mutation.

Abnormalities of thyroid function and glucose control in subjects with Rett syndrome

We have identified subtle abnormalities of thyroid function and glucose control in patients with Rett syndrome. The mean serum total thyroxine (T4) concentration was significantly lower in a group of subjects with Rett syndrome (6.9 +/- 1.5 microgram/dl, n = 34; p < 0.001) than the adult reference range (8.5 +/- 1.75 microgram/dl, n = 200). This differences remained significant even for the 17 subjects not taking anticonvulsants (7.6 +/- 1.5 microgram/dl; p < 0.05 vs. adult reference). The difference was more marked when compared to age-adjusted normals, with 10 subjects having a serum total T4 concentration below normal for age including 3 of 17 of the subjects not taking anticonvulsants. This decrease in serum total T4 concentration was not due to changes in binding proteins as measured by 3,5,3'-triiodothyronine resin uptake, and was associated with a decreased concentration of thyroid-stimulating hormone (1.7 +/- 1.6 mU/l, n = 23 vs. 2.5 +/- 1.0 mU/l, n = 200; p < 0.01). Oral glucose tolerance tests were performed in 10 of the subjects with Rett syndrome. They had a delay in the peak glucose and insulin concentrations. Glucose levels were elevated at 1 and 2 hours (p < 0.05), and insulin levels were elevated at 1, 2, and 3 hours (p < 0.05). Two subjects fulfilled criteria for impaired glucose tolerance.

MR findings in adult-onset adrenoleukodystrophy

PURPOSE

To describe the MR findings of brain and spinal cord in adult-onset adrenoleukodystrophy.

METHODS

One hundred sixty-four adult patients ranging from 19 to 74 years of age (119 men and 45 women) with clinically and biochemically proved adrenoleukodystrophy underwent MR of the brain. In 30 patients the spinal cord also was evaluated with MR.

RESULTS

The brain MR findings were abnormal in 54 of 119 males and in 9 of 45 female heterozygotes and consisted of varying degrees of demyelination of the cerebral white matter in 40 patients, corpus callosum in 25 patients, corticospinal tracts in 46 patients, visual tracts in 31 patients, and auditory tracts in 18 patients. The thoracic spinal cord showed diffuse atrophy in 18 of 20 men and in 8 of 10 women.

CONCLUSION

It is important to recognize the MR findings of adult-onset adrenoleukodystrophy, because not uncommonly the clinical and MR findings of adrenoleukodystrophy are misdiagnosed as multiple sclerosis, olivopontocerebellar or spinocerebellar atrophy, amyotrophic lateral sclerosis, or dementia. Analysis of the MR findings and correlation of the clinical findings has permitted a tentative subdivision of adult-onset adrenoleukodystrophy population into four subtypes that appear to differ in respect to prognosis and possibly pathogenesis. MR evaluation of the brain in adrenoleukodystrophy also is helpful in patient selection for experimental therapy, which is most effective if offered in the early stage of the disease.

Peroxisomal disorders

Disorders of peroxisome function result in severe and progressive neurologic deficits. Knowledge of these disorders and their role in neurodegenerative disorders has been growing rapidly over the last 40 years. Noninvasive diagnostic tests can identify all of the peroxisomal disorders, many of them prenatally. The genetic basis of some of these peroxisomal disorders is being established, which will advance understanding of their pathobiology and provide clues for therapeutic interventions.

Sex- and tissue-specific Bkm(GATA)-binding protein in the germ cells of heterogametic sex

The ZZ male/ZW female system of sex determination (female heterogamety) is found in snakes and birds whereas XY male/XX female system of sex determination (male heterogamety) operates in mammals including humans. The W and Y chromosomes are largely heterochromatic and undergo cycles of condensation and decondensation in the germ cells of ovary and testis, respectively, whereas they remain highly condensed and transcriptionally inactive in all somatic cells. Both chromosomes have enriched stretches of GATA repeats along their entire length (which is identified as banded krait minor satellite DNA and called Bkm) that are highly conserved through widely separated orders of eukaryotes. Here we report the existence of a factor, which specifically binds to Bkm, in the germ cells of the heterogametic sex (ovary in female heterogamety and testis in male heterogamety) where decondensation (activation) of the W and Y chromosomes, respectively, occurs; it has been purified as a polypeptide of 57.5 kDa from the rat snake ovary and designated as Bkm-binding protein (BBP) by virtue of its binding to GATA repeats of Bkm. Such a sex- and tissue-specific BBP is also present in the ovary of other species of snakes and in the testis of mouse and human where the Y chromosome is highly decondensed. We suggest that GATA repeats of Bkm brings about a coordinated decondensation of the W and Y sex chromosomes in the germ cells of the heterogametic sex in response to BBP which may serve as a "switch" for the activation of the genes present on the W and Y chromosomes.

Neurofibromatosis type 1: the evolution of deep gray and white matter MR abnormalities

PURPOSE

To investigate the evolution of deeply located high-signal-intensity abnormalities of the brain on T2-weighted MR images of patients with neurofibromatosis type 1 (NF-1).

METHODS

The study consists of two patient groups: 1) retrospective evaluation of MR scans of 24 symptomatic NF-1 patients, 10 of whom were sequentially studied, and 2) prospective MR evaluations of 20 asymptomatic NF-1 subjects from 14 families; 2 of these families were sequentially studied.

RESULTS

Deeply located, high-signal-intensity abnormalities on T2-weighted images were noted in 34 of 44 NF-1 subjects (77%). If NF-1 patients are grouped according to age, 28 of 30 subjects (93%) younger than 15 years had the lesions, whereas 4 of 7 subjects (57%) between 16 and 30 years, and 2 of 7 subjects (29%) older than 31 years had lesions. High-signal lesions in basal ganglia and brain stem were demonstrated in all decades with relatively high frequency. Lesions in the cerebellar white matter and dentate nuclei were mainly found in the patients younger than 10 years, and never found after the third decade. In 13 sequential studies (mean interval, 24 months), lesions appeared to increase in size in 3, remain unchanged in size in 2, and decrease in size in 7. One subject showed a mixed pattern of lesion size change.

CONCLUSIONS

Deeply located high-signal-intensity lesions on T2-weighted MR images are more evident in young NF-1 patients. The underlying brain abnormality, while pathologically unproved, is probably transient.

Growth plate matrix vesicle biogenesis. The role of intracellular calcium

Isolated bovine growth plate chondrocytes suspended in a synthetic cartilage buffer containing 10(-7) to 10(-3) M concentrations of calcium were treated with 1 microM ionomycin to induce changes in intracellular ionized calcium as measured by Fura-2 fluorescence. An increase in intracellular calcium of 10(-6) to 10(-4) M calcium resulted in the secretion of vesicles that contain alkaline phosphatase. An increase in intracellular calcium above 10(-4) M resulted in nonspecific cell fragmentation because of cell damage. Electron microscopy of the secreted vesicles demonstrated that their structure resembled matrix vesicles. Isolated cells treated with ionomycin (synthetic cartilage buffer with 10(-6) M calcium) demonstrated intact cell membranes, normal intracellular architecture, and numerous plasma membrane processes undergoing vesiculation. The plasma membrane of these isolated cells and the isolated vesicles demonstrated a positive stain for alkaline phosphatase. Fresh growth plate tissue demonstrated plasma membrane staining for alkaline phosphatase at the lower proliferative and upper hypertrophic cell zone, and an increasing number of alkaline phosphatase stained matrix vesicles in the matrix of the lower hypertrophic cell zone. The data indicate that an increase in intracellular calcium in the lower proliferative and hypertrophic cell zones of the growth plate induces the secretion of plasma membrane derived matrix vesicles.

Raynaud's phenomenon and cold stress testing: a new approach

There are a number of methods of evaluating digital blood flow in the vascular laboratory but none fulfills the criteria of providing a quick and reproducible diagnostic test for Raynaud's phenomenon. We present our experience with the use of high frequency ultrasound to provide direct real time imaging of the digital arteries. Using this method and a standardised cold challenge test, consisting of exposure of the hand to a temperature of 10 degrees C for 5 minutes, it is possible to distinguish patients with Raynaud's phenomenon from normal controls on the basis of extent of digital artery closure. The mean fall in digital artery diameter on cold challenge, expressed as a percentage of the original diameter, was 92.4% (S.D. = 16.4, S.E.M. = 2.1) in patients with Raynaud's phenomenon as against 8.7% (S.D. = 11.5, S.E.M. = 2.5) in a group of normal volunteers. Using a 45% fall in digital artery diameter as the diagnostic cut-off point, the test has a specificity of 100% and a sensitivity of 96.6% in differentiating patients with Raynaud's phenomenon from controls. It is suggested that the test could be used as objective confirmation of a clinical diagnosis and to assess the efficacy of therapeutic interventions.

Polysomnographic characteristics of patients with Rett syndrome

During wakefulness, patients with Rett syndrome have disordered breathing. To understand further this ventilatory control disorder, we performed polysomnography in 30 patients with Rett syndrome and 30 control subjects (female subjects with primary snoring). The median age was 7 years (range, 1 to 32 years) for Rett syndrome and 6 years (range, 1 to 17 years) for control subjects. During periods of wakefulness, 67% of patients with Rett syndrome had the characteristic pattern of disordered breathing (i.e., episodes of hyperventilation followed by central apnea and desaturation). No such events occurred during sleep. Sleep efficiency and sleep architecture were similar for both groups. During sleep, there was no difference in duration of periodic breathing, number of episodes of central apnea with desaturation, or number of episodes of obstructive apnea or end-tidal carbon dioxide tension between the two groups. Although arterial oxygen saturation during rapid eye movement (REM) sleep was slightly lower in patients with Rett syndrome (nadir, 94% +/- 2% vs 96% +/- 2%), it remained within the normal range. Parental history reflected the awake respiratory findings in most cases. We conclude that patients with Rett syndrome have normal breathing during non-rapid eye movement (NREM) sleep. We speculate that patients with Rett syndrome have normal brain-stem control of ventilation, and that the disordered breathing seen during wakefulness is due to an abnormality of the cortical influence on ventilation.

Cytosolic compartmentalization of hepatic alanine:glyoxylate aminotransferase in patients with aberrant peroxisomal biogenesis and its effect on oxalate metabolism

Two patients with atypical manifestations of aberrant peroxisomal biogenesis are described. Contrary to previous studies, which had shown that Zellweger syndrome patients usually have normal levels of urinary oxalate excretion, the patients in the present study had evidence of abnormal oxalate metabolism in the form of hyperoxaluria and, in one of the patients, calcium oxalate urolithiasis. Activity of the liver-specific peroxisomal enzyme alanine:-glyoxylate aminotransferase (AGT), which is a major determinant of the level of endogenous oxalate synthesis in humans, was normal in one patient and markedly supranormal in the other. Using the technique of post-embedding protein A-colloidal gold immunoelectron microscopy, AGT was found to be mainly cytosolic in the livers of both patients, with significant amounts also localized in the nuclei. In a small minority of the hepatocytes of one patient, who was homozygous for the more common (major) AGT allele, large numbers of unidentified fibrillar arrays were found in the cytosol, which labelled heavily for immunoreactive AGT. The background cytosolic AGT labelling was markedly reduced in such cells when compared to the majority of cells that did not contain fibrils. In the other patient, who was heterozygous for the major and minor AGT alleles, there appeared to be low levels of mitochondrial AGT labelling. In the light of these data, the possible metabolic function of cytosolic AGT in the livers of panperoxisomal disease patients is discussed.

Neuroanatomy of Rett syndrome: a volumetric imaging study

Rett syndrome is a pediatric neurological disorder of unknown etiology defined by the presence of severe neurodevelopment decline, acquired microcephaly, dementia, abnormalities of movement, autistic behavior, and seizures in young female children. In this study, the neuroanatomy of 11 females with Rett syndrome and 15 age- and gender-matched control subjects was investigated in vivo with quantitative neuroimaging techniques. Compared to control subjects, the patients with Rett syndrome were found to have significantly reduced cerebral volume; evidence of greater loss of gray matter in comparison to white matter; regional variation in cortical gray matter, with the frontal regions showing the largest decrease; and reduced volume of the caudate nucleus and midbrain, even when taking into account general reduction in the size of the brain. In addition, there was no evidence of an ongoing degenerative process in this sample of girls with Rett syndrome. The consistency of these data with results from neuropathological investigations points to the need for continued quantitative neuroimaging studies of children with this condition. In particular, research employing serial longitudinal scans of very young children manifesting early signs of the clinical syndrome holds promise for helping to elucidate the neuropathological pathways leading to the debilitating clinical manifestations of Rett syndrome.

Neurochemical alterations in Rett syndrome

The Rett syndrome (RS) is a neurological disorder associated with severe mental deficiency and neurological manifestations of cortical and extrapyramidal dysfunction. The present report is (1) a postmortem brain study that compares the levels of choline acetyltransferase (ChAT) activity and the binding density of selected neurotransmitter receptors in four cases of RS and five normal controls of similar age and (2) a study of cerebrospinal fluid (CSF) concentrations of the endogenous tridecapeptide neurotensin in 12 RS patients and 8 controls of similar age. The level of ChAT activity was lower in many cortical and subcortical regions in the RS brains as compared to control levels. The number of NMDA, AMPA, mu opioid and neurotensin binding sites, as well as CSF concentrations of neurotensin, did not differ significantly from control levels. The results suggest that changes in specific neurotransmitter systems, particularly cholinergic neurons, in the thalamus, cerebellum and basal ganglia may underlie the progressive deterioration in motor and cognitive function characteristic of this disorder.

Increased very long chain fatty acids in patients on a ketogenic diet: a cause of diagnostic confusion

We found an elevation of very long chain fatty acids in 13 of 22 plasma samples from patients on a ketogenic diet for the treatment of uncontrolled seizures. Because elevated values of very long chain fatty acids are a biochemical manifestation of peroxisomal dysfunction, this phenomenon might lead to diagnostic confusion. Thus the history and clinical status should be considered when plasma levels of very long chain fatty acids are interpreted.

The efficacy of phenytoin in relation to serum levels in severe pre-eclampsia and eclampsia

OBJECTIVES

To investigate the efficacy of phenytoin in relation to total and free serum levels in patients with severe pre-eclampsia and eclampsia.

DESIGN

Prospective descriptive study.

SETTING

Labour Ward, King Edward VIII Hospital, Durban, South Africa. Tertiary referral centre serving an underprivileged community.

SUBJECTS

Eleven patients admitted with a hypertensive crisis. Four patients had eclampsia and 7 had impending eclampsia.

MAIN OUTCOME MEASURES

Free and total phenytoin levels; efficacy of phenytoin as an anticonvulsant and side-effects of therapy.

RESULTS

Although total phenytoin levels were within the therapeutic range, free phenytoin levels were abnormally high in all patients. Three patients (2 with eclampsia and 1 with imminent eclampsia) each had a seizure after phenytoin treatment had been initiated.

CONCLUSION

Neither total nor free phenytoin levels were good predictors of seizure control. It is postulated that the poor performance of phenytoin as an anticonvulsant in severe eclampsia may relate to inadequate distribution of the drug to the brain as a result of cerebral oedema and poor cerebral perfusion rather than paradoxical seizure activity associated with high free phenytoin levels.

Proton NMR spectroscopy of Canavan's disease

Proton Nuclear Magnetic Resonance (NMR) spectroscopy was used to quantitatively determine cerebral N-Acetyl Aspartate (NAA) concentrations in four patients with Canavan's disease and in four age-matched control subjects. Macroscopic NAA concentrations (mumol/gm wet weight) were not found to be significantly different from controls. Reduced levels of choline and creatine were observed in all patients, and increased levels of lactate and inositol in the eldest three patients.

Positron emission tomography in the Rett syndrome: clinical, biochemical and pathological correlates

A consistent constellation of clinical signs and symptoms define the Rett syndrome, the most prominent of which are disorders of movement and tone. Preliminary pathologic and neurochemical data indicate predominant involvement of the nigrostriatal dopaminergic pathways and the cholinergic system of the basal forebrain region. The age of onset differentiates the Rett syndrome from Alzheimer and Parkinson disease with similar lesions. PET scanning makes it possible to relate the chemistry of the brain to function by measuring the number and affinity of neuroreceptors, metabolism in specific brain regions, and provide important determinants of the underlying mechanisms in disease states.

Tokyo symposium on the Rett syndrome: neurobiological approach--concluding remarks and epilogue

Based on data presented at the Tokyo Rett Syndrome Symposium, November 1990, actual neurobiological knowledge and interpretations are compiled. The underlying biological concepts, as well as the potential origin of the condition are particularly discussed.

Altered neurochemical markers in Rett's syndrome

Rett's syndrome (RS) is a neurologic disorder associated with severe mental deficiency and neurologic manifestations of cortical and extrapyramidal origin. The present report is a preliminary postmortem brain study that compares the levels of endogenous biogenic amines and selected neurotransmitter receptors in five cases with RS and six normal controls of similar age. The level of choline acetyltransferase activity was reduced in several cortical and subcortical regions. Endogenous levels of dopamine in the superior frontal and superior temporal gyri, occipital cortex, and putamen were reduced. The changes in specific neurotransmitter markers, particularly those associated with the basal ganglia and cortex, may underlie the progressive deterioration in motor and cognitive function characteristic of this progressive disorder.

Adrenoleukodystrophy

X-linked adrenoleukodystrophy (ALD) is a disorder of very long chain fatty acid (VLCFA) metabolism that can be diagnosed by demonstrating increased levels of VLCFA in plasma and, prenatally, by similar assays in cultured amniocytes or chorionic vilus samples. ALD causes Addison disease frequently in men and occasionally in women. Prompt diagnosis is important for genetic counseling and for the institution of therapies aimed to prevent or ameliorate the progressive neurologic disability that often is associated with this illness.

Quantitative magnetic resonance imaging in Rett syndrome

Rett syndrome (RS) is a progressive neurological disorder of females, characterized by the early onset of autistic behavior, ataxia, and "handwringing" movements. The present magnetic resonance imaging study was undertaken with the purpose of investigating whether structural brain abnormalities of RS patients are similar to those recently reported in autism. The subject population consisted of eight patients and an equal number of age- and sex-matched controls. Area and shape measurements were taken at selected anatomical levels for the following structures: brain hemisphere, corpus callosum, midbrain, pons, lobules I-V and VI-VII of the cerebellum, and head of the caudate. Results revealed significant differences in area for the whole brain hemisphere (p < 0.05) and in both right and left caudate (p < 0.04). These morphological findings are different from those recently reported in autism and emphasize the involvement of the striatal system in RS.

Clinical aspects of adrenoleukodystrophy and adrenomyeloneuropathy

Adrenoleukodystrophy (ALD) is an X-linked recessive disorder that affects mainly the nervous system white matter and the adrenal cortex. It is associated with an abnormal accumulation of saturated very long chain fatty acids and can be diagnosed by demonstrating an excess of these substances in plasma or red cells. Our laboratory has identified more than 900 hemizygotes and 1,000 heterozygotes. Approximately 50% of the hemizygotes have a rapidly progressive childhood or adolescent form of the disease. Twenty-five percent of males have a slowly progressive paraparesis in adulthood, but often are not diagnosed correctly. The illness may also present as Addison disease without apparent neurological involvement. Approximately 15% of heterozygotes develop moderately severe spastic paraparesis. It is important to diagnose ALD promptly because of the urgent need for genetic counseling and the availability of promising therapeutic interventions.

Peroxisomal disorders

Although peroxisomes were once considered a vestige, their importance in cellular metabolism is clearly established by the many inherited diseases that have been described in the past two decades. Unfortunately there is no definitive treatment for the various disorders, but based on the recognition of the biochemical abnormalities, prenatal testing and appropriate genetic counseling can be provided. It is essential for clinicians to be aware of this group of diseases, as diagnosis and further study of these patients are essential in understanding the basic etiologic mechanisms underlying these complex groups of disorders. Clearly, there is much to be learned about the relationship between biochemical abnormalities and the phenotypic variability of the peroxisomal disorders.

Cognitive impairment in adult-onset adrenoleukodystrophy

Adrenoleukodystrophy (ALD) is a progressive X-linked disorder that produces pathological changes, mainly in the adrenal cortex and the white matter of the central nervous system. The main biochemical abnormality is the accumulation of saturated unbranched fatty acids with a chain length of 24 or more, referred to as very-long-chain fatty acids (VLCFA). Affected children develop large zones of demyelination associated with perivascular lymphoctyic infiltrations resembling those seen in multiple sclerosis. Adults show a more chronic form of the disease, referred to as adrenomyeloneuropathy (AMN). AMN mainly involves the spinal cord ad peripheral nerves, although the cerebral hemispheres may also be affected. Approximately 15% of female carriers have nervous-system involvement that resembles AMN. It is well known that ALD may initially appear as a psychiatric disorder. In the present study, we have assessed the prevalence of cognitive impairment in a group of AMN patients and neurologically symptomatic ALD heterozygotes initially presenting primarily physical complaints. Sixty percent of these patients demonstrated significant neuropsychological impairment, most commonly a pattern of spared and impaired functions typical of a subcortical dementia. We suggest that this progressive cognitive impairment may underlie other behavioral deficits, affirming the significance of the psychological features of this genetically determined disorder.

Ipsiversive eye deviation and epileptic nystagmus

We studied an 11-year-old boy with focal seizures in the right temporo-occipital cortex. During the seizure, there was a 1- to 2-second period of ipsiversive (rightward) conjugate eye deviation, followed by 10 to 15 seconds of horizontal jerk nystagmus with slow phases that were directed to the right and appeared linear. The patient was conscious throughout the seizure. These findings fit the description of epileptic nystagmus. We postulate that the eye deviation and slow phases of the nystagmus in this patient were induced by epileptic activation of a cerebral smooth pursuit pathway originating from temporoccipital cortex.

The Rett syndrome: progress report on studies at the Kennedy Institute

Clinical, biochemical and pathological studies in patients with the Rett syndrome (RS) are presented. The neuropathological changes and alterations in neurotransmitter markers are particularly interesting and provide valuable information that may be helpful in understanding the behavior and neurological phenotype of RS.

Further EEG observations in children with the Rett syndrome

In four cases of the Rett syndrome (RS) (age 3 1/2, 6, 11 and 12 years), paroxysmal activity and especially spike discharges over the central region could be blocked or attenuated by passive finger movements. This response, however, is not demonstrable in the majority of children with RS. The blocking or attenuating effect of passive movements is compared with earlier observations of central spike discharges occurring in children with benign Rolandic epilepsy. In some of these children, central spikes could be blocked by active hand movements. It was assumed that such a positive blocking response underscores the "functional" ("dysfunctional") character of the Rolandic spikes and the lack of local structural damage. In children with cerebral palsy, seizures and central spike (and evidence of structural brain damage), such a blocking response was not obtainable. Taking into consideration these earlier observations, there is reason to presume that the central spike activity found in RS is based on dysfunction rather than on structural impairment.

Childhood adrenoleukodystrophy. Failure of intensive immunosuppression to arrest neurologic progression

Cyclophosphamide in a dosage of 350 to 700 mg/m2/d was administered for five to 11 days to four patients with childhood adrenoleukodystrophy (ALD) and to one patient with the adult cerebral form of the disease. The rate of neurologic progression in the four patients with childhood ALD did not differ from that of 167 untreated patients with childhood ALD surveyed previously.

Neonatal seizures and retardation in a girl with biochemical features of X-linked adrenoleukodystrophy: a possible new peroxisomal disease entity

Neonatal hypotonia, seizures beginning at 5 days, and severe retardation were noted in a girl with normal karyotype and biochemical evidence of impaired adrenal function. Postmortem examination at 14 months revealed malformative and destructive lesions of central gray and white matter, atrophy of adrenal cortex with striated adrenocortical cells, hepatic fibrosis, and PAS-positive macrophages in several organs. Pathologically and clinically, this patient most closely approximated neonatal adrenoleukodystrophy (ALD) and differed strikingly from X-linked childhood ALD. In contrast, biochemical changes resembled the abnormalities observed in X-linked ALD and differed from those in the neonatal form. The very-long-chain fatty acid accumulation characteristic of both disorders was demonstrated, but unlike neonatal ALD, the levels or metabolism of plasmalogens, pipecolic acid, phytanic acid, and bile acid intermediates were normal, and peroxisomes in a liver biopsy specimen were present in normal number and appeared enlarged. While the case resembles the recently reported entity of peroxisomal acyl-CoA oxidase deficiency, assignment to this category was excluded by immunoblot studies on postmortem liver, which revealed normal amounts of this enzyme. Correlation of clinical, morphologic, and biochemical data suggests that this case is an example of a so-far undescribed entity, and reinforces the concept that the phenotypic spectrum of peroxisomal disorders is wider than realized.

Auditory brainstem response and audiologic findings in adrenoleukodystrophy: its variant and carrier

Auditory brain stem response, auditory sensitivity, speech discrimination function, acoustic reflex threshold, and reflex decay were studied in seven children with adrenoleukodystrophy (ALD), nine adults with adrenomyeloneuropathy (AMN), one child with neonatal ALD, and two carriers of ALD. Significant auditory dysfunctions were found in only two patients; a retrocochlear type auditory disorder in one child with ALD, and a profound deafness in a child with neonatal ALD. None of the patients showed significant abnormality in acoustic reflex threshold and reflex decay except for one patient with ALD who showed a slightly elevated reflex threshold. All but two ALD patients showed significantly prolonged wave latencies and interwave intervals. The latency values revealed the highest incidence of abnormality in the I to III interval; this was followed by the III to V interval, then by wave I. Significantly, one child with asymptomatic ALD and both heterozygous female relatives showed abnormal ABRs, demonstrating the high sensitivity of ABR in detection of the existence of pathophysiological condition in subclinical or presymptomatic ALD.

Galactosylceramide-beta-galactosidase deficiency in association with cherry red spot

A 13-month-old white girl was the product of a normal pregnancy and delivered by caesarean section for breech presentation. Regression of motor milestones started by 11 months, when delayed language development was also noted. She was normocephalic without major dysmorphic features or organomegaly. Fundus examination disclosed a subtle cherry red spot bilaterally. No startle response was elicited. By 17 months she was extremely irritable and unable to tolerate liquids; there was symmetrical spasticity and florid cherry red spots. She died at 18 months of age. A systematic search for conditions associated with a cherry red spot was unrevealing. The absence of galactosylceramide galactosidase activity was unexpected and was confirmed on three occasions in two laboratories. Lactosylceramide I content, an enzyme thought to be identical to galactosylceramide-beta-galactosidase, was significantly decreased. The presence of a cherry red spot in Krabbe's disease, indicative of neuronal storage, has not been previously recognized. The existence of this variant has implications for genetic and biochemical studies.

The clinical recognition and differential diagnosis of Rett syndrome

Rett syndrome (RS) is characterized by progressive loss of intellectual functioning and fine and gross motor skills as well as development of stereotypic hand movement abnormalities, occurring after 6 to 18 months of normal development. Rett syndrome has been previously reported only in girls, but the possibility of the syndrome existing in male children cannot be currently excluded. Although the syndrome is thought to be relatively common, it was only described in the English literature 5 years ago. There is currently no marker for the syndrome; diagnosis is based on clinical criteria. The newly developed diagnostic criteria for RS are reviewed, with special attention given to the historical aspects of the diagnosis in the prenatal, perinatal, neonatal, and early childhood periods. Rett syndrome is characterized by a predictable, orderly progression of signs and symptoms. Four stages of RS have been described; each stage has special characteristics and offers different diagnostic challenges for the neurologist. Infantile autism is the most common incorrect diagnosis made for children with RS. The simultaneous regression of both motor and language skills, as well as the stereotypic hand movements, hyperventilation, bruxism, and seizures in early childhood are all typical in RS and help distinguish RS from infantile autism.

Research on Rett syndrome: strategy and preliminary results

The research strategy presented here involves four assumptions: (1) Rett syndrome exists; (2) a single cause will eventually be found to account for the majority of cases presently assigned to this disease category; (3) it is genetically determined; and (4) it represents a neurodegenerative disorder that can be defined by quantitative studies of nervous system structure and function. The strategy proposed here involves the comprehensive study of 100 patients with the classic Rett syndrome phenotype. Studies include the (1) search for a diagnostic marker; (2) high-resolution cytogenetic banding techniques, (3) quantitative morphologic studies of postmortem brain tissue as well as neurochemical analyses including autoradiographic techniques, radioimmunoassays, and in situ hybridization; and (4) positron emission tomography studies of cerebral glucose metabolism and neurotransmitters.

Phenotypic and genotypic variability of generalized peroxisomal disorders

This article classifies and describes the various entities that comprise the generalized peroxisomal disorder. The variability in both phenotype and genotype is stressed. A heretofore undescribed generalized peroxisomal disorder is reported.

Selenium treatment in neuronal ceroid-lipofuscinosis

Neuronal ceroid-lipofuscinosis (NCL) refers to a group of disorders with devastating effects on the central nervous system. The accumulation of autofluorescent lipopigments containing lipid peroxides is considered a pathogenetic mechanism of the cell damage seen in NCL. Therapy aimed at preventing further lipid peroxidation, such as the Zeman regimen, did not slow progression of the disease. Therefore, Santavuori and Westermarck [Santavuori and Westermarck 1984] introduced treatment with a combination of selenium and vitamin E and reported favorable results with few side effects. We present information on the rationale for the use of selenium, recommendations on the daily intake, and reported side effects. However, our limited experience with selenium in this disorder does not permit conclusions. Additionally, careful studies are indicated before this treatment is dispensed routinely.