Creatine depletion in a new case with AGAT deficiency: clinical and genetic study in a large pedigree

Arginine:glycine amidinotransferase (AGAT, EC 2.1.4.1) deficiency is a recently recognized autosomal recessive inborn error of creatine biosynthesis, characterized by mental retardation and severe language impairment. We extensively investigated a third 5-year-old patient with AGAT deficiency, discovered in the pedigree of the same Italian family as the two index cases. At the age of 2 years he presented with psychomotor and language delay, and autistic-like behavior. Brain MRI was normal, but brain 1H-MRS disclosed brain creatine depletion, which almost completely normalized following creatine monohydrate supplementation. A remarkable clinical improvement paralleled the restoration of brain creatine concentration. AGAT and GAMT (guanidinoacetate:methyltransferase) genes were analyzed in the proband and in 26 relatives, including the two cousins with AGAT deficiency. Sequencing of the proband's AGAT gene disclosed the same homozygous mutation at nt position 9093 converting a tryptophan (TGG) to a stop codon (TAG) at residue 149 (W149X), as already described in the two previously reported cases. The proband's parents and 10 additional subjects of the pedigree were carriers for this mutation. AGAT deficiency was further confirmed by undetectable AGAT activity in the patient's lymphoblasts. Mutation analysis of the GAMT gene revealed a sequence variation in exon 6 (T209M), not in the proband, but in 15 additional subjects from the pedigree. The silent nature of this sequence variation is supported by its homozygosity in one AGAT deficient cousin and in one asymptomatic adult, both with normal GAMT activity.

Inborn errors of creatine metabolism and epilepsy: clinical features, diagnosis, and treatment

Creatine metabolism disorders have so far been described at the level of two synthetic steps, guanidinoacetate N-methyltransferase and arginine:glycine amidinotransferase, and at the level of the creatine transporter 1. Guanidinoacetate N-methyltransferase and arginine:glycine amidinotransferase deficiency respond positively to substitutive treatment with creatine monohydrate. Guanidinoacetate N-methyltransferase deficiency results in a severe neurologic disease (age of onset 3 months to 2 years) characterized by developmental arrest, neurologic deterioration, movement disorders, mental retardation, autistic-like behavior, and epilepsy. Severe early-onset epilepsy with pleomorphic seizures is a key symptom of this disorder. Data suggest that in patients with guanidinoacetate N-methyltransferase deficiency, epilepsy and associated electroencephalographic abnormalities are more responsive to creatine supplementation than to conventional antiepilepsy drugs. Arginine:glycine amidinotransferase and creatine transporter 1 mainly present with mental retardation and severe language disorder. All cases of creatine disorders reported to date have been detected by brain proton magnetic resonance spectroscopy, an expensive technique not routinely used in pediatric neurology. A potential diagnostic strategy to select patients for evaluation using proton magnetic resonance spectroscopy is proposed in this review.

Autosomal dominant GTP-CH deficiency presenting as a dopa-responsive myoclonus-dystonia syndrome

The authors report a kindred in which GTP-CH deficiency resulted in a myoclonus-dystonia syndrome. The proband, a 17-year-old boy, presented with early-onset myoclonus and later, dystonia and bradykinesia. Blood prolactin was increased and CSF homovanillic acid, 5-hydroxyindoleacetic acid, and biopterin were all reduced. L-Dopa/carbidopa administration resulted in clinical improvement. In the paternal branch, the grandfather and three relatives had myoclonus-dystonia and resting or postural tremor of limbs. The authors found a missense mutation in the exon 6 of GCH-1 gene (K224R).

Guanidinoacetate and creatine plus creatinine assessment in physiologic fluids: an effective diagnostic tool for the biochemical diagnosis of arginine:glycine amidinotransferase and guanidinoacetate methyltransferase deficiencies

BACKGROUND

Disorders of creatine metabolism arise from genetic alterations of arginine:glycine amidinotransferase (AGAT), guanidinoacetate methyltransferase (GAMT), and the creatine transporter. We developed a strategy for the detection of AGAT and GAMT defects by measurement of guanidinoacetate (GAA) and creatine plus creatinine (Cr+Crn) in biological fluids.

METHODS

Three patients with AGAT deficiency from the same pedigree and their eight relatives, as well as a patient affected by a GAMT defect and his parents were analyzed by a new HPLC procedure in comparison with 90 controls. The method, which uses precolumn derivatization with benzoin, separation with a reversed-phase column, and fluorescence detection, has shown good precision and sensitivity and requires minimal sample handling.

RESULTS

In the three AGAT patients, plasma GAA was 0.01-0.04 micro mol/L [mean (SD) for neurologically normal controls was 1.16 (0.59) micromol/L], Cr+Crn was 15-29 micro mol/L [reference limit in our laboratory, 79 (38) micromol/L]. Urinary GAA was 2.4-5.8 micro mol/L [reference, 311 (191) micromol/L], and Cr+Crn was 2.1-3.3 mmol/L [reference, 9.9 (4.1) mmol/L]. We found a smaller decrease in GAA and Cr+Crn in some carriers of an AGAT defect. In the patient with GAMT deficiency, plasma and urine GAA was increased (18.6 and 1783 micromol/L, respectively), and Cr+Crn was decreased in plasma (10.7 micromol/L) and urine (2.1 mmol/L). GAA was increased in the parents' plasmas and in the mother's urine.

CONCLUSION

The assessment of GAA is a new tool for the detection of both GAMT and AGAT deficiencies.

Guanidinoacetate and Creatine plus Creatinine Assessment in Physiologic Fluids: An Effective Diagnostic Tool for the Biochemical Diagnosis of Arginine:Glycine Amidinotransferase and Guanidinoacetate Methyltransferase Deficiencies

Background: Disorders of creatine metabolism arise from genetic alterations of arginine:glycine amidinotransferase (AGAT), guanidinoacetate methyltransferase (GAMT), and the creatine transporter. We developed a strategy for the detection of AGAT and GAMT defects by measurement of guanidinoacetate (GAA) and creatine plus creatinine (Cr+Crn) in biological fluids.

Methods: Three patients with AGAT deficiency from the same pedigree and their eight relatives, as well as a patient affected by a GAMT defect and his parents were analyzed by a new HPLC procedure in comparison with 90 controls. The method, which uses precolumn derivatization with benzoin, separation with a reversed-phase column, and fluorescence detection, has shown good precision and sensitivity and requires minimal sample handling.

Results: In the three AGAT patients, plasma GAA was 0.01–0.04 μmol/L [mean (SD) for neurologically normal controls was 1.16 (0.59) μmol/L], Cr+Crn was 15–29 μmol/L [reference limit in our laboratory, 79 (38) μmol/L]. Urinary GAA was 2.4–5.8 μmol/L [reference, 311 (191) μmol/L], and Cr+Crn was 2.1–3.3 mmol/L [reference, 9.9 (4.1) mmol/L]. We found a smaller decrease in GAA and Cr+Crn in some carriers of an AGAT defect. In the patient with GAMT deficiency, plasma and urine GAA was increased (18.6 and 1783 μmol/L, respectively), and Cr+Crn was decreased in plasma (10.7 μmol/L) and urine (2.1 mmol/L). GAA was increased in the parents’ plasmas and in the mother’s urine.

Conclusion: The assessment of GAA is a new tool for the detection of both GAMT and AGAT deficiencies.

Automated high-performance liquid chromatographic method for the determination of guanidinoacetic acid in dried blood spots: a tool for early diagnosis of guanidinoacetate methyltransferase deficiency

A new automated method for the assay of guanidinoacetic acid (GAA) in dried blood spot (DBS) on filter paper is reported. The method, based on reversed-phase (RP)-HPLC, precolumn derivatisation with benzoin and fluorescence detection, has shown good precision and sensitivity and requires only minimal sample handling. The validity of the method was demonstrated by analysing the neonatal blood spot of a patient affected by guanidinoacetate methyltransferase (GAMT) deficiency. GAA concentration was found to be nearly 12-fold higher than the mean control value. We propose this method as an inexpensive and widely applicable tool for the diagnosis of GAMT deficiency.

Two new severe mutations causing guanidinoacetate methyltransferase deficiency

Primary disorders of creatine metabolism have been only recently described. We report new molecular and biochemical findings obtained from a child affected by guanidinoacetate methyltransferase deficiency. This patient presented with neurological regression, epilepsy, and a movement disorder during the first year of life. HPLC analysis showed high concentrations of guanidinoacetic acid in urine, plasma, and CSF. Molecular analyses of cDNA and genomic DNA revealed two novel mutations, a G insertion following nucleotide 491 of the cDNA (c.491insG) in exon 5 and a transversion at nt -3 in intron 5 (IVS5-3C>G). The c.491insG mutation causes a frameshift and a premature stop codon at the end of the exon. The IVS5-3C>G mutation prevents the splicing of the last exon of the gene precluding the complete maturation of the transcript and, most likely, causes rapid degradation of the mRNA.

Brain creatine depletion: guanidinoacetate methyltransferase deficiency (improving with creatine supplementation)

The authors describe an Italian child with guanidinoacetate methyltransferase deficiency, neurologic regression, movement disorders, and epilepsy during the first year of life. Brain MRI showed pallidal and periaqueductal alterations. In vivo 1H-MRS showed brain creatine depletion. The assessment of guanidinoacetic acid concentration in biologic fluids confirmed the diagnosis. Clinical, biochemical, and neuroradiologic improvement followed creatine supplementation.

Clinical significance of brain phenylalanine concentration assessed by in vivo proton magnetic resonance spectroscopy in phenylketonuria

Recent studies using in vivo proton magnetic resonance spectroscopy (1H MRS) have suggested that plasma phenylalanine (Phe) may not be a reliable indicator of brain Phe level in subjects with phenylketonuria (PKU). Interindividual variation in cerebral Phe can contribute to the phenotypic variability of the disease. We report the results of the direct assessment of brain Phe by 1H MRS in 10 off-diet PKU patients (aged 15.5-30.5 years), 4 detected and treated early, 6 late. In a single patient, brain Phe was evaluated before and 15 days after diet discontinuation. FLAIR MRI and 1H MRS were performed in the same setting by a 1.5 T clinical MR scanner. MR images were scored according to the extent of the lobar white-matter hyperintensity. Brain 1H MRS Phe signal (resonating at 7.36 ppm) was evaluated as a ratio to the creatine+phosphocreatine signal. Brain Phe was correlated with clinical, biochemical and MRI findings. Results were as follows. (1) An abnormal concentration of brain Phe was detected in all 10 PKU subjects (ranging from 0.030 to 0.074), associated with a wide interindividual variability of concurrent plasma Phe (ranging from 724 to 2800 micromol/L). (2) In late-detected subjects, brain Phe concentration correlated with clinical phenotype better than did plasma Phe. The discrepancy between brain and plasma Phe was relevant from a clinical point of view in two cases: in one, a late-detected patient with normal mental development, a high level of plasma Phe was associated with a relatively low concentration of brain Phe; in the other, a late-detected subject with severe neurological impairment, a very high level of brain Phe was associated with plasma Phe compatible with the diagnosis of mild PKU. (3) White-matter alterations were detected in all patients. FLAIR MRI sequences disclosed an involvement of optic chiasma and tracts in 7 subjects. No correlation was found between white-matter alterations and concurrent brain Phe concentrations. (4) In the only case assessed under different intake of Phe, the relevant increase of brain Phe paralleled the concurrent increase of plasma Phe, showing that 1H MRS can be a useful tool in evaluating the individual vulnerability of PKU patients to different values of plasma Phe.

Ataxia, deafness, leukodystrophy: inherited disorder of the white matter in three related patients

The authors report three related patients, two girls and a boy, presenting a distinctive clinical phenotype characterized by early-onset, slowly progressive ataxia. Subsequently these patients experienced sensorineural deafness, resulting in complete hearing loss by the age of 12 years, and exhibited leukodystrophy on brain MRI. There was no mental deterioration. An extensive neurometabolic assessment failed to detect any anomalies in the three patients. The patients originated from a large consanguineous family in southern Italy (Calabria), with a pedigree that was traced back five generations. The disease's pattern of transmission suggests an autosomal recessive trait.

Tyrosine hydroxylase deficiency with severe clinical course: clinical and biochemical investigations and optimization of therapy

Tyrosine hydroxylase deficiency was diagnosed after determination of cerebrospinal fluid neurotransmitters and DNA analysis in a child with severe axial hypotonia and hypokinesia associated with dystonic and ballistic movements. L-dopa therapy was unsuccessful, whereas a combination with selegiline, a selective monoamine oxidase-beta inhibitor, with low-dose L-dopa markedly improved the severe clinical picture.

Biochemical features of mtDNA 14484 (ND6/M64V) point mutation associated with Leber's hereditary optic neuropathy

We report the effect on complex I function of the 14484 Leber's hereditary optic neuropathy (LHON) mutation affecting the ND6 subunit gene. The same gene was also reported to carry another mutation, at position 14459, associated with the LHON/dystonia phenotype that induces a reduction of complex I-specific activity and increases the sensitivity to the product decylubiquinol. Given the proximity of both mutations in the ND6 gene, we tested the specific activity of complex I and its sensitivity to myxothiazol and nonylbenzoquinol, both inhibitors at the ubiquinol product site, in platelet submitochondrial particles from nine 14484 homoplasmic individuals, 8 Italians with Caucasian mtDNA haplogroup J (adjunctive 4216 and 13708 mutations), and 1 Tunisian with an African mtDNA haplogroup. The specific activity of complex I was not affected by the 14484 mutation, but the sensitivity to both inhibitors was significantly increased compared with control subjects regardless of the presence of haplogroup J polymorphisms. Analysis of 70 different amino acid sequences of the ND6 subunit indicated that the 14484 mutation affects an amino acid belonging to its most conserved region, which shows local similarities with cytochrome b regions interacting with ubiquinone or ubiquinol in complex III. Our results suggest that both 14484 and 14459 mutations may affect amino acids forming the interaction site of ubiquinol product, and the 14484 mutation produces a biochemical defect resembling in part that already reported for the common 11778/ND4 LHON mutation.

Childhood Leber's hereditary optic neuropathy (ND1/3460) with visual recovery

The authors report the clinical features and the results of genetic and biochemical studies of a child affected by ND1/3460 Leber's hereditary optic neuropathy, who demonstrates a persistent visual recovery after protracted monitoring. A 10-year-old male suffered from a severe right visual impairment that was incidentally detected. Within 2 months the left eye was also seriously involved, and visual acuity worsened to 20/300 in both eyes, associated with bilateral cecocentral scotomas and dyschromatopsia. During the following months a progressive visual improvement occurred, and 2 years later the visual acuity was 20/20 OU. After 9 years of follow-up the clinical status is unchanged. The mutation at np ND1/3460 was found to be virtually homoplasmic in the proband's mtDNA, which was extracted either from platelets or leukocytes, whereas the mother and the sister tested heteroplasmic for the same mutation. The specific activity of complex I in platelets was reduced in the proband and normal in his relatives. An abnormal resistance of NADH:ubiquinone reductase to the inhibitory effect of rotenone was found in platelet mitochondria from the proband and family members and was consistent with the degree of heteroplasmy. This pattern of biochemical abnormalities suggests a cumulative effect of the increasing percentage of mutated mtDNA on complex I function, which involves the interaction between complex I and its substrate ubiquinone in the heteroplasmic condition (asymptomatic state), and the catalytic function of complex I, as mutated mDNA turns toward the homoplasmic condition (symptomatic state).

Subclinical visual impairment in phenylketonuria. A neurophysiological study (VEP-P) with clinical, biochemical, and neuroradiological (MRI) correlations

During detailed visual function testing, pattern-reversal visual evoked potentials (VEP), generated by different spatial frequencies (3 c/d, 1 c/d and 0.6 c/d) and visual contrasts (100% and 10%) were recorded in 21 adolescent and young adult phenylketonuric (PKU) patients (11 females and 10 males; mean age 14.8 years, range 9-22.8) on and off diet. In 14 of the 21 patients, disease had been detected at neonatal screening and in 7 later. Ten age-matched healthy subjects acted as controls. Recordings in more than 40% of eyes in the whole group and 30% of eyes in the screening subgroup showed a prolonged P100 latency. All visual pattern stimuli elicited a significantly longer P100 latency in PKU patients than in controls. VEP latencies to 3 c/d, 1 c/d and 1 c/d with 10% contrast--but not to 0.6 c/d--were longer in patients off diet than in patients on diet. No differences were found between VEP latencies in early- and later-detected subjects. To study the link between biochemical variables and VEP latencies, we envisaged either a linear relationship between recent exposure to phenylalanine (Phe) and VEP abnormalities or a threshold model considering phenylalanine (Phe) concentrations among the factors influencing VEP latencies. The correlation analysis detected an association between plasma Phe concentrations and abnormal VEP latencies, predicting that plasma Phe concentrations > 901 mumol/L would prolong VEP latencies to 1 c/d; concentrations > 879 mumol/L would prolong latencies to 3 c/d; and concentrations > 898 mumol/L would prolong latencies to 1 c/d with 10% contrast.

LHON mutations in Italian patients affected by multiple sclerosis

The occurrence of a multiple sclerosis (MS)-like phenotype in subjects carrying mitochondrial DNA (mtDNA) mutations associated with Leber hereditary optic neuropathy (LHON) has suggested that mitochondrial genes may contribute to susceptibility to MS. With the present study 74 unrelated Italian patients (53 females and 21 males; mean age 37.9, SD 9.9, range 20-59) affected by MS with early and prominent optic nerve involvement and 99 normal control subjects were analysed for the presence of primary (nps 11778, 3460, 14484) and an alleged secondary one (np 15257) LHON mutations. A single MS patient carrying a virtually homoplasmic LHON mutation at np 11778 was found. Family history revealed a maternal uncle affected by MS, decreased at age of 64 in consequence of a stroke. The patient's mother harboured the same mutation in a homoplasmic way. Primary LHON mutations were not detected in any other MS patient or control. Of the MS patients 5.4% (4 out of 74), and 5.1% (5 out of 99) of the controls carried the 15257 mutation in a homoplasmic state. Present data do not support any contribution of primary LHON mutations to genetically determined susceptibility in MS. There is no evidence that the 15257 mutation has any pathogenetic significance in the Italian population.

Leber's hereditary optic neuropathy: biochemical effect of 11778/ND4 and 3460/ND1 mutations and correlation with the mitochondrial genotype

To clarify the bioenergetic relevance of mtDNA mutations in Leber's hereditary optic neuropathy (LHON), we investigated affected individuals and healthy carriers from six Italian LHON families harboring the 11778/ND4 and the 3460/ND1 mtDNA mutations. The enzymatic activities of mitochondrial complex I and its sensitivity to the potent inhibitors rotenone and rolliniastatin-2 were studied in mitochondrial particles from platelets, in correlation with mtDNA analysis of platelets and leukocytes. In platelets homoplasmic for mutant mtDNA, both 11778/ND4 and 3460/ND1 mutations induced resistance to rotenone and the 3460/ND1 mutation also provoked a marked decrease in the specific activity of complex I. Individuals heteroplasmic in platelets for either mutation showed normal biochemical features, indicating functional complementation of wild-type mtDNA. There was no correlation between the clinical status and mtDNA homo/heteroplasmy in platelets, but the biochemical features correlated with the mitochondrial genotype of platelets. In some cases, the degree of mtDNA heteroplasmy differed in platelets and leukocytes from the same individual with a prevalence of wild-type mtDNA in the platelets. These results imply that biochemical studies on mitochondrial diseases should always be integrated with mtDNA analysis of the same tissue investigated and also suggest that the mtDNA analysis on the leukocyte fraction, as usually performed in LHON, does not necessarily reflect the mutant genotype level of other tissues. The differential tissue heteroplasmy may be more relevant than previously thought in determining disease penetrance.

Haplotype and phylogenetic analyses suggest that one European-specific mtDNA background plays a role in the expression of Leber hereditary optic neuropathy by increasing the penetrance of the primary mutations 11778 and 14484

mtDNAs from 37 Italian subjects affected by Leber hereditary optic neuropathy (LHON) (28 were 11778 positive, 7 were 3460 positive, and 2 were 14484 positive) and from 99 Italian controls were screened for most of the mutations that currently are associated with LHON. High-resolution restriction-endonuclease analysis also was performed on all subjects, in order to define the phylogenetic relationships between the mtDNA haplotypes and the LHON mutations observed in patients and in controls. This analysis shows that the putative secondary/intermediate LHON mutations 4216, 4917, 13708, 15257, and 15812 are ancient polymorphisms, are associated in specific combinations, and define two common Caucasoid-specific haplotype groupings (haplogroups J and T). On the contrary, the same analysis shows that the primary mutations 11778, 3460, and 14484 are recent and are due to multiple mutational events. However, phylogenetic analysis also reveals a different evolutionary pattern for the three primary mutations. The 3460 mutations are distributed randomly along the phylogenetic trees, without any preferential association with the nine haplogroups (H, I, J, K, T, U, V, W, and X) that characterize European populations, whereas the 11778 and 14484 mutations show a strong preferential association with haplogroup J. This finding suggests that one ancient combination of haplogroup J-specific mutations increases both the penetrance of the two primary mutations 11778 and 14484 and the risk of disease expression.

Evolution of daytime quiet sleep components in early treated phenylketonuric infants

The maturational patterns of 'tracé alternant' (TA) and sleep spindles obtained from 16 early detected phenylketonuric (PKU) children during their first months of life were compared with others that were evaluated in recordings taken from 42 controls of the same age group. The TA maturation evolved significantly later in the PKU group than in the control group during the 5th-8th week (the TA score for the PKU group was 64% vs. 10% in the control group, P < 0.001). Afterwards, during the 9th-12th week the score for the PKU group was 27% vs. 0% in the controls (P < 0.002). The sleep spindle evolution score also matured significantly later in the PKU than the control group: the score was 31% in PKU children vs. 85% in controls for the 5th-8th week of age (P < 0.01), and it was 66% vs. 96% for the 9th-12th week (P < 0.02). After the 12th week, TA pattern could not be detected, and spindles reached complete maturation in the PKU children as well. Our results show a consistent delay in the maturation of TA and spindle scores in PKU children. This trend of delay is parallel to the plasma phenylalanine normalization, but not necessarily dependent only on it. In conclusion, we suggest that studies on the critical maturational periods of different sleep components (TA and sleep spindles) might provide a sensitive tool for early diagnosis of neurophysiological brain alterations during the first trimester of life in a population of children "at risk'.

Automated method for the measurement of amino acids in urine by high-performance liquid chromatography

An automatic and sensitive HPLC method for the determination of primary and secondary amino acids included cystine and homocystine in urine samples is described. After a simple ultrafiltration, urine samples were subjected to reduction of disulfides, carboxymethylation of free thiols and double precolumn derivatization with o-phthalaldehyde-3-mercaptopropionic acid and 9-fluroenylmethyl chloroformate. All reactions were fully automated by means of an injector programme and were accomplished in 10 min. Since urine samples contain a large number of amino compounds, a good resolution was required. By optimization of the conditions, separation of 40 amino acids in 92 min was achieved. The recovery of amino acids ranged from 83% for TRP to 105% for CIT. The within-run and between-run R.S.D.s of urinary amino acid concentrations were below 10% for most amino acids except for HYL, LYS and ORN. The method was applied to the diagnosis of genetic disorders of amino acid metabolism.

Patients with clinically definite multiple sclerosis, white matter abnormalities on MRI, and normal CSF: if not multiple sclerosis, what is it?

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Biochemical, clinical and neuroradiological (MRI) correlations in late-detected PKU patients

Brain magnetic resonance imaging (MRI) was performed in 17 late-detected PKU patients (aged 2.8-25 years). Twelve subjects had been treated late (0.7-4.5 years), and 5 not at all. Four were still on diet when the study was performed. Mental development was normal in 4 subjects, mildly retarded in 6, and moderately or severely retarded in 7. None had exhibited mental or neurological deterioration. On MRI examination a symmetrical increase of T2-weighted signal in the periventricular white matter was found in all patients, although to different degrees. Concomitant signal decrease on the T1-weighted sequences was detected in 9 patients. Ten subjects showed focal white-matter abnormalities. A variable degree of cortical and subcortical atrophy was found in 12 subjects, and asymmetry of lateral ventricles in 4. White-matter involvement correlated with phenylalanine concentrations during the year preceding (rs = 0.5706; p < 0.02) and at the time of (rs = 0.6182, p < 0.01) the investigation. Cortical and subcortical atrophy correlated with the patient's age (rs = 0.5889, p < 0.02, and rs = 0.5929, p < 0.02, respectively). We conclude that late-detected PKU patients showed the same MRI abnormalities reported in early-treated subjects and in subjects who underwent neurological deterioration; white-matter abnormalities possibly result from the recent exposure to high phenylalanine concentrations; in late-detected PKU subjects cerebral atrophy could be the late result of chronic exposure to high phenylalanine concentrations.

Visual, auditory, and somatosensorial evoked potentials in early and late treated adolescents with phenylketonuria

Pattern reversal visual, auditory, and somatosensorial evoked potentials were recorded in two groups of phenylketonuric (PKU) adolescents after protracted exposition to high concentrations of phenylalanine following diet discontinuation. The first group consisted of 11 early treated (before age 3 months) PKU patients (ET-PKU); the second group consisted of 11 late detected (after age 8 months), symptomatic, PKU subjects (LT-PKU). Despite the relevant lag between the two groups in mental development and neurological status, no clear-cut difference in evoked potentials could be detected. Only the wave I latency of the brainstem auditory evoked potentials (BAEPs) was significantly shorter in ET- versus LT-PKU children. The P100 latency, I-V interpeak latency (IPL), and I-III IPL seem to discriminate the less severe form of PKU (ET-PKU type 3) from the most severe forms, ET-PKU type 1 plus 2 and LT-PKU. No correlations were found between clinical, biochemical, and neurophysiological parameters. The present data suggest that evoked potentials technique is of limited sensitivity in detecting central nervous system (CNS) alterations in PKU adolescents after diet discontinuation.

Neuroradiological (MRI) abnormalities in phenylketonuric subjects: clinical and biochemical correlations

A clinical, biochemical and neuroradiological (MRI) study was performed in 22 hyperphenylalaninemic patients detected by neonatal screening and early treated (Group A; 5-23 years old, 13 females and 9 males) and in 5 late detected, symptomatic subjects (Group B; 9-23 years old, 3 females and 2 males). The screening subjects were clustered in a Group A1 (10 on diet patients), and a Group A2 (12 after end of diet patients). On MRI examination (1.5-T magnet, SE T1-weighted 530/22/2, T2-weighted 2400/15-90/1 sequences, SL 6 mm, gap 1.8) a symmetrical increase of the T2-weighted signal in the periventricular white matter was found in all patients. The periatrial white matter was always involved, the occipital region was affected in 22 cases, the frontal region in 16. Concomitant signal decrease on the T1-weighted sequences in the same areas with the highest signal intensity on the T2-weighted scans was found in 7 patients (in 3 out of 12 Group A2 and in 4 out of 5 Group B patients). In 6 Group A and in 3 Group B subjects a variable degree of cortical and subcortical atrophy was detected. A significantly positive correlation was found between white matter involvement and the degree of recent exposition to high PHE values. This correlation was also confirmed when only Group A was examined. Moreover, a significant difference in neuroradiological involvement was found between Group A1 and Group A2 subjects, but not between Group A2 and Group B subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurological and cytogenetic study in early-onset ataxia-telangiectasia patients

The clinical diagnosis of ataxia-telangiectasia (AT) is difficult before the age of 4 years. We report clinical and cytogenetic data on three early-onset, early-diagnosed AT patients at the age of 12, 18 and 22 months, respectively. Postural instability of the trunk, characterized by motor impersistence, was the earliest neurological sign detected as early as 1 year of life. Dystonic movements and postures of arms and trunk and a subtle disorder of eye movement (blinking before gaze changing, increased latency and dysmetry of saccades) were observed during the 2nd year of life. All patients exhibited an unusual temper tantrum. We also observed an increased bleomycin-induced chromosomal instability in patient's cells in the early stages of the disease before all the clinical hallmarks were apparent. Our data suggest that detection of clinical indications, leading to early laboratory confirmation of AT, can reduce the age at diagnosis.

Bilateral striatal necrosis, dystonia and optic atrophy in two siblings

Two siblings developed a neurological disorder in the first decade characterised by generalised dystonia, hypokinesia, and subacute visual loss. CT and serial MRI examinations showed bilateral lesions of the striatum, mainly in the putamen. The classification of these patients is discussed in relation to infantile bilateral striatal necrosis (IBSN), Leigh's disease, and Leber's optic neuropathy. The literature shows a clinical and aetiopathogenetic overlap between these syndromes. In our cases parental consanguinity and the involvement of a single generation suggest a new clinical condition with autosomal recessive transmission.

Mitochondrial DNA mutation in an Italian family with Leber hereditary optic neuropathy

Mitochondrial (mt) DNA from a Southern Italian family with Leber hereditary optic neuropathy was analyzed for the presence of the reported mutation at position 11778 of the ND4 subunit gene. The point mutation was found in mt DNA extracted from peripheral blood in all members of the family with the exclusion of the father, and was present in a homoplasmic fashion, despite the phenotypic heterogeneity of disease presentation among family members.

The development of auditory and visual evoked potentials in early treated phenylketonuric children

Brain-stem auditory evoked potentials (BAEPs) and flash visual evoked potentials (F-VEPs) were gathered from 8 early treated phenylketonuric (PKU) children in a prospective longitudinal investigation during the 1st to the 12th months after birth. No consistent differences were found in the wave morphology of evoked potentials in PKU children from that of age-matched controls. Studying the latency of some components showed that in BAEPs, wave I latency was similar to control values for the whole year, but that the I-V interpeak mean latency (I-V IPL) was always significantly longer than in controls. In F-VEPs wave N1 latency was significantly longer than in controls only at 1-2 months of age, but returned to control values at 3-4 months (when all children were on dietary therapy) and remained in this range up to the 12th month. The mean latency of the P2 wave of flash VEPs was always significantly longer in PKU children than in controls. These results show that relevant alterations in evoked potentials may be found in PKU children several months after starting dietary therapy. This suggests that information processing in the brain may be impaired for a long time, due to abnormal metabolic conditions between birth and the onset of dietary therapy.