Novel mutation in GLRB in a large family with hereditary hyperekplexia.

Hereditary hyperekplexia (HH) is a disorder of the inhibitory glycinergic neurotransmitter system. Mutations in five genes have been reported to cause the disease. However, only single mutation in GLRB, the gene encoding beta-subunit of the glycine receptor, in a singleton patient with HH has been found to date. In this study, 13 patients with HH were identified through neurology and genetic clinics. Formal clinical examinations, linkage analysis, homozygosity mapping, in-mutation screening of GLRB and in silico functional analyses were carried out. A novel mutation in GLRB among nine patients was identified. This c.596 T>G perturbation results in the change of the highly conserved methionine at position 177 to arginine. Besides the classical HH phenotype, seven patients had esotropia and few of them had behavioral problems. This study presents a large family with HH as a result of homozygous mutation in GLRB and expands the clinical spectrum of HH to include eye misalignment disorder. Moreover, the report of these familial cases supports the previous evidence in a single patient of an autosomal recessive inheritance of HH because of defects in GLRB.

Early neurosurgical intervention in spondyloepiphyseal dysplasias.

GOALS: The aim of this study is to evaluate the benefits of early intervention in two major spondyloepiphyseal dysplasias of Saudi Arabia, namely, multiple sulfatase deficiency (MSD, Austin's disease) and Morquio's disease. The MSD is encountered frequently in the Kingdom and poses significant health risk to the child because of cord compression. The clinics of this hospital have several Austin's patients. RESULTS: This study indicates that early intervention before serious irreversible damage to the cervical cord occurs improves the neurological course of the patient; no patient had a worse outcome. On the other hand, neurosurgical intervention after the neurological symptoms of cord compression occurs was not as rewarding. CONCLUSION: Morquio's disease is more common outside the Kingdom. The results in this study also confirm that early intervention in this disease is beneficial. Other surgeons make a similar recommendation for Morquio's disease. However, their experience with Austin's disease is not reported due to the rarity of this disease elsewhere.

Structural and functional study of K453E mutant protective protein/cathepsin A causing the late infantile form of galactosialidosis.

To clarify the molecular basis of the late infantile form of galactosialidosis, we characterized a defective protective protein/cathepsin A (PPCA) gene product with the K453E mutation newly found in an Arabic patient with this disease. Immunocytochemical, expression, and metabolic studies revealed that the precursor PPCA was synthesized but not processed to the mature form, and it was degraded in the mutant. A structural model of the mutant PPCA was constructed by amino acid substitution of 453glutamic acid for lysine in the crystal structure of the wild type PPCA precursor reported. The results show that the K453E mutation is located at the dimer interface of the PPCA and reduces the hydrogen bond formation in the dimer. This structural change may cause instability of the PPCA dimer.

Hypoglycemia in association with various organic and amino acid disorders.

A number of organic and amino acidemias, particularly those that involve the oxidation of fatty acids, cause hypoglycemia intermittently. This may be associated with distrubances of acid base equilibrium and accumulation of lactic acid and/or ketone bodies. When such diseases are not diagnosed rapidly, they might lead to neurological crippling and, at times, death. As a group, these disorders involve more than 1 organ and their phenotypic expression may include all or a single system. The symptoms may appear soon after birth or as late as 1 year of age. Their early recognition and rapid intervention provide rewarding clinical outcome. With the recent advances in diagnostic techniques, such as the introduction of tandem mass spectrometry (MS), screening for these diseases now can be performed because rapid identification on a large scale is possible. The phenotypes, mutations involved, pathognomonic laboratory findings, prognosis, and treatment procedures available have been reviewed for major diseases.

Glutaric aciduria type II: observations in seven patients with neonatal- and late-onset disease.

The clinical, biochemical, and neuroradiologic findings and clinical follow-up of seven patients with glutaric aciduria type II are reported. Three phenotypes of the disease are encountered: neonatal-onset form with congenital anomalies (two patients) or without congenital anomalies (three patients) and late-onset form (two patients). The neonatal-onset form presents as an overwhelming illness, with severe hypoglycemia and metabolic acidosis leading to rapid death. Frequently it is associated with perinatal energy deprivation, a neonate with low birth weight and prematurity. The late-onset form presents with intermittent episodes of vomiting, hypoglycemia, and acidosis especially after meals rich in fat and/or proteins. All parents are consanguineous and have a first- or second-degree relationship. Initially, in the two phenotypes with neonatal onset and during crisis in the late-onset phenotype, routine laboratory evaluation showed severe metabolic acidosis, with an increased anion gap, hypoglycemia without ketonuria, and disturbed liver function tests. In the majority of patients with neonatal-onset forms, the kidneys, liver, and at times the spleen are enlarged with an increased echogenic pattern; however, no hepatic or renal cysts are detected. Cardiomegaly is observed in most patients. The diagnosis can be easily and rapidly reached through tandem mass spectrometry study of the blood and can further be confirmed by gas chromatography/mass spectrometry analysis of the urine organic acids. In this report, the magnetic resonance imaging/computed tomography brain studies showed brain atrophy, white matter disease, and in one patient, fluid-filled cavities in the periventricular area and putamina. Fluorine-18-labeled 2-fluoro-2-deoxyglucose positron emission tomographic (FDG PET) brain studies in two patients with late-onset disease showed slightly decreased activity in the cerebral cortex in one and in the caudate nuclei in the other. Brain FDG PET scan and magnetic resonance spectroscopy were normal in one patient with neonatal-onset disease. All patients were treated with a diet low in fat and protein, oral riboflavin, and carnitine. The results were promising for the late-onset disease. Intravenous carnitine gave rewarding results in one patient with neonatal-onset disease.

Clinical, fluorine-18 labeled 2-fluoro-2-deoxyglucose positron emission tomography (FDG PET), MRI of the brain and biochemical observations in a patient with 4-hydroxybutyric aciduria; a progressive neurometabolic disease.

We report a five-year-old boy with 4-hydroxybutyric aciduria. The child presented with global developmental delay, severe hypotonia and myoclonic seizures. The urine 4-hydroxybutyric acid was 1038 times that of normal, and other organic acids related to its further metabolism were also increased. Electroencephalography showed findings indicative of cerebral dysfunction. However, other neurophysiological studies were normal. Clinical improvement was observed after the administration of vigabatrin and dextromethorphan. Magnetic resonance imaging of the brain revealed cerebellar vermin atrophy and subtle white matter changes in the cerebral hemispheres. Fluorine-18 labeled 2-fluoro-2-deoxyglucose positron emission tomographic (FDG PET) scan of the brain showed a marked decrease in the cerebellar metabolism, probably related to atrophy of cerebellar vermis and secondary cerebellar deafferentation. FDG PET scan is found to be of value in the understanding and assessment of brain functional alterations. It may be useful in monitoring and optimizing treatment strategies of this rare disease.

Clinical and cerebral FDG PET scan in a patient with Krabbe's disease.

A 2-year, 6-month-old Saudi male with infantile Krabbe's disease was studied with fluorine-18-labeled-2-fluoro-2-deoxyglucose positron emission tomography (FDG PET) scan. The patient presented with a gradual loss of developmental milestones, irritability, and crying. At the advanced stage of the disease, he developed tonic-clonic seizures and became a microcephalic, extremely irritable, blind, spastic quadriplegic child, with no deep tendon reflexes. Laboratory studies revealed normal blood chemistry, muscle enzymes, very long chain fatty acids, and acylcarnitines. No abnormal urinary organic acids were detected. The cerebrospinal fluid protein concentration was increased. Magnetic resonance imaging of the brain revealed mild brain atrophy and white matter disease mainly in the centrum semiovale. Electroretinography was normal; however, electroencephalography and visual-evoked potentials were abnormal. Peripheral nerve conduction studies documented a demyelinating neuropathic process. The FDG PET study of the brain demonstrated a marked decrease in the metabolism of the left cerebral cortex and no uptake in the caudate heads. Normal glucose uptake was observed in the thalami, lentiform nuclei, and cerebellum. The patient did not present for subsequent clinic visits and is presumed dead.

X-linked adrenoleukodystrophy. The Saudi experience.

OBJECTIVES: To evaluate the clinical, biochemical, neuroradiological, and neurophysiological findings of patients with X-linked adrenoleukodystrophy. METHODS: Retrospective study evaluating the data of 10 X-linked adrenoleukodystrophy patients diagnosed at King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia. RESULTS: The common presenting symptoms were deterioration in school performance, vision and hearing, behavioral changes, and seizures. Eight patients survived 1-4 years and one patient 12 years after the initial presentation, while one patient expired. Six patients had the childhood form, 3 had the adolescent form and one had the adrenomyeloneuropathy form. Six are in an advanced stage of the disease and 3 have mild to moderate spasticity. All except 2 manifested moderate to severe dementia with variable degrees of visual loss. Decreased hearing and features of adrenal insufficiency were seen in 7 patients. Very long chain fatty acids were significantly increased in seven and mildly elevated in 2 patients, however the C26 to C22 ratio was increased in all. The characteristic high-signal intensity of parieto-occipital white matter on brain magnetic resonance imaging T2-weighted images was observed in all patients. Two patients had functional study of the brain, which showed hypometabolic activity in gray and white matter of the occipital lobes. Various neurophysiological abnormalities were detected. The response to different treatment modalities was not promising. CONCLUSION: The disease is more common than had been previously recognized due to phenotypic variability and a wide spectrum of presentations. This report describes various aspects of this disorder and emphasizes the importance of early identification and treatment of asymptomatic but biochemically affected individuals, since all current therapeutic approaches are disappointing if overt neurological abnormalities have been already developed.

X-linked adrenoleukodystrophy. The Saudi experience.

OBJECTIVE: To evaluate the clinical, biochemical, neuroradiological, and neurophysiological findings of patients with X-linked adrenoleukodystrophy. METHODS: Retrospective study evaluating the data of 10 X-linked adrenoleukodystrophy patients diagnosed at King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia. RESULTS: The common presenting symptoms were deterioration in school performance, vision and hearing, behavioral changes, and seizures. Eight patients survived 1-4 years and one patient 12 years after the initial presentation, while one patient expired. Six patients had the childhood form, 3 had the adolescent form and one had the adrenomyeloneuropathy form. Six are in an advanced stage of the disease and 3 have mild to moderate spasticity. All except 2 manifested moderate to severe dementia with variable degrees of visual loss. Decreased hearing and features of adrenal insufficiency were seen in 7 patients. Very long chain fatty acids were significantly increased in seven and mildly elevated in 2 patients, however the C26 to C22 ratio was increased in all. The characteristic high-signal intensity of parieto-occipital white matter on brain magnetic resonance imaging T2-weighted images was observed in all patients. Two patients had functional study of the brain, which showed hypometabolic activity in gray and white matter of the occipital lobes. Various neurophysiological abnormalities were detected. The response to different treatment modalities was not promising. CONCLUSION: The disease is more common than had been previously recognized due to phenotypic variability and a wide spectrum of presentations. This report describes various aspects of this disorder and emphasizes the importance of early identification and treatment of asymptomatic but biochemically affected individuals, since all current therapeutic approaches are disappointing if overt neurological abnormalities have been already developed.

Hyperpipecolic acidemia: clinical, biochemical, and radiologic observations.

Pipecolic acid is a biochemical marker frequently detected in group 1 peroxisomal disorders (peroxisomal biogenesis disorders). Its presence, in addition to the constellation of particular phenotypic manifestations and pathologic findings, has led to its recent classification under disorders of peroxisomal biogenesis as a separate disease entity (hyperpipecolic acidemia or hyperpipecolatemia). The clinical, biochemical, and radiologic findings observed in three patients diagnosed with hyperpipecolic acidemia are reported.

Cerebral fluorine-18 labeled 2-fluoro-2-deoxyglucose positron emission tomography (FDG PET), MRI, and clinical observations in a patient with infantile G(M1) gangliosidosis.

The clinical, biochemical, pathological and neuroradiological findings of a 2-year-old Saudi boy with infantile G(M1) gangliosidosis are reported. The patient had a progressive neurologic deterioration, manifesting with developmental regression, sensorimotor and psychointellectual dysfunction and generalized spasticity that started at 4 months of age. Cherry-red macula, facial dysmorphia, hepatomegaly, exaggerated startle response to sounds, skeletal dysplasia, and vacuolated foamy lymphocytes that contain finely fibrillar material in addition to lamellar membranes and electron-dense rounded bodies were seen. MRI of the brain demonstrated mild diffuse brain atrophy and features of delayed dysmyelination and demyelination. Brain FDG PET scan revealed a mild decrease in the basal ganglia uptake, and moderate to severe decrease in thalamic and visual cortex uptake, and an area of increased glucose uptake in the left frontal lobe, probably representing an active seizure focus. The functional changes indicated by FDG PET scan and the structural abnormalities shown on MRI were found to be complementary in the imaging evaluation of infantile G(M1) gangliosidosis.

Clinical and brain 18fluoro-2-deoxyglucose positron emission tomographic findings in ethylmalonic aciduria, a progressive neurometabolic disease.

We report a 2-year-old boy with ethylmalonic aciduria and vasculopathy syndrome evaluated by 18fluoro-2-deoxyglucose positron emission tomographic (18FDG PET) brain scan, with intense uptake of 18FDG in the caudate nucleus and putamen bilaterally but with no morphological changes on magnetic resonance imaging (MRI). A repeat 18FDG PET brain scan 1 year later showed a significant bilateral decreased uptake of glucose in the putamen and the head of the caudate nucleus as well as a decreased uptake in the frontal lobes. On MRI, there was atrophy and watershed infarcts in the basal ganglia, explaining the loss of glucose uptake. These results reflect a selective vulnerability of the basal ganglia, their functional derangement, and ultimate degeneration.

Clinical, biochemical, and molecular characterization of patients with glutathione synthetase deficiency.

Pyroglutamic aciduria (5-oxoprolinuria) is a rare autosomal recessive disorder caused by either glutathione synthetase deficiency (GSSD) or 5-oxoprolinase deficiency. GSSD results in low glutathione levels in erythrocytes and may present with hemolytic anemia alone or together with pyroglutamic aciduria, metabolic acidosis, and CNS damage. Five patients with pyroglutamic aciduria were studied. All presented with hemolytic anemia and metabolic acidosis. Two (brothers) also had Fanconi nephropathy, which is not seen in pyroglutamic aciduria. Molecular analyses of the GSS gene was performed in 3 patients. RT-PCR and heteroduplex analysis identified a homozygous deletion in 1 patient and a homozygous mutation in 2 others (brothers with Fanconi nephropathy). Sequencing of glutathione synthetase (GSS) cDNA from the first patient showed a 141-bp deletion corresponding to the entire exon 4, whilst the corresponding genomic DNA showed a G491 --> A homozygous splice site mutation. Sequencing of GSS cDNA from the Fanconi nephropathy patients showed a C847 --> T [ARG283 --> CYS] mutation in exon 9.

18Fluoro-2-deoxyglucose (18FDG) PET scan of the brain in propionic acidemia: clinical and MRI correlations.

The clinical data and the imaging findings of the positron emission tomography (PET) and the magnetic resonance imaging (MRI) studies in five patients, previously diagnosed to have propionic acidemia, were retrospectively reviewed. The patients were all normal at birth. The first clinical signs, typically hypotonia and failure to thrive, appeared during the first 2 years of life. With progression of the disease, the neurological findings consisted of variable degrees of dementia and extrapyramidal symptoms, notably dystonia, choreoathetosis and rigidity of variable degrees. Initial cerebral PET and MRI studies were normal. Follow-up MRI examinations showed progressive basal ganglia degeneration, with evidence of atrophy and signal abnormalities within the caudate nuclei and the putamina. The thalamic structures were normal. The PET studies demonstrated increased uptake in the basal ganglia and thalami, followed by decreased uptake in the basal ganglia at a later stage of the disease. The structural (MRI) and the functional (PET) studies of the brain were found to be complementary in the evaluation of propionic acidemia, and were in good correlation with the clinical findings.

Clinical, fluorine-18 labeled 2-fluoro-2-deoxyglucose positron emission tomography of the brain, MR spectroscopy, and therapeutic attempts in methylenetetrahydrofolate reductase deficiency.

The cases of three infants, two Saudi and one Bahraini, with methylenetetrahydrofolate reductase (MTHFR) deficiency are reported. They presented in the neonatal period with lethargy, poor feeding, hypotonia, and frequent apneas. Tandem mass spectrometry (MS/MS) of a blood spot indicated very low methionine level and of urine revealed high homocysteine. The diagnosis was confirmed by demonstrating severe deficiency of MTHFR in the cultured skin fibroblast. All patients were treated with folinic acid, vitamin B12, betaine, and methionine, with good initial response to the therapy. In two patients, the diagnosis was late and their disease was severe, resulting in neurological crippling. However, in the third patient, who was diagnosed and treated early, the current neurological status is normal. In her case, at 1 month of age, the brain FDG PET scan documented very faint cerebral and cerebellar cortical activities. After 5 months of intensive therapy, that included 200-600 mg/kg per day methionine, she had a dramatic clinical and biochemical recovery as well as a parallel improvement in FDG PET. Brain MR spectroscopy indicated normal neuronal glial and myelin markers for her age. We conclude that the functional changes confirmed by the FDG PET study were better correlated with the clinical course of the patient and adequately monitored the response to therapy. This disease warrants early detection through neonatal screening program, since the beneficial effect of early administration of adequate therapy with combined use of betaine and a high dose of methionine is rewarding and may be the treatment of choice for MTHFR deficiency.

Application of electrospray tandem mass spectrometry to neonatal screening.

For the past 30 years, neonatal screening programs have been performed largely by using the bacterial inhibition assays developed by Dr Robert Guthrie. These programs focused on a small number of diseases such as phenylketonuria and maple syrup urine disease and involved one test for each disease. During the same period many new diseases were discovered, such as organic acidemias and fatty acid oxidation defects, and they presented a diagnostic challenge to biochemical laboratories. Different mass spectrometric approaches have been the main tools for the diagnosis; however, each has its own limitation. Recently, electrospray tandem mass spectrometry (MS/MS) has provided an alternative automated high throughput, specific, and broad-spectrum approach to screening for a relatively large number of disorders, including those covered by bacterial inhibition assays tests. By using specific scan functions, a large number of amino acids and acylcarnitines in blood spots are quantified in 2 minutes analytical time. A new scan function is described here for quantification and screening for argininosuccinic acid in blood spots, which is a key metabolite in the diagnosis of argininosuccinase deficiency. We describe the results of a 3-year tandem MS/MS-based neonatal study that was performed in our newborn population. We screened 27,624 blood spots and identified 20 cases yielding a frequency of 1:1,381. No false-negative cases were identified, but several false-positive cases were eliminated by repeat analysis by MS/MS of blood or by other means. We also used MS/MS analysis of urine or blood either for confirmation of initial positive results or for follow-up of treatment, such as in glutaric acidemia, citrullinemia, argininosuccinase deficiency, and biopterin-dependent phenylketonuria.