Vascular outcome in patients with homocystinuria due to cystathionine beta-synthase deficiency treated chronically: a multicenter observational study.

An inborn error of metabolism, homocystinuria due to cystathionine beta-synthase deficiency, results in markedly elevated levels of circulating homocysteine. Premature vascular events are the main life-threatening complication. Half of all untreated patients have a vascular event by 30 years of age. We performed a multicenter observational study to assess the effectiveness of long-term homocysteine-lowering treatment in reducing vascular risk in 158 patients. Vascular outcomes were analyzed and effectiveness of treatment in reducing vascular risk was evaluated by comparison of actual to predicted number of vascular events, with the use of historical controls from a landmark study of 629 untreated patients with cystathionine beta-synthase deficiency. The 158 patients had a mean (range) age of 29.4 (4.5 to 70) years; 57 (36%) were more than 30 years old, and 10 (6%) were older than 50 years. There were 2822 patient-years of treatment, with an average of 17.9 years per patient. Plasma homocysteine levels were markedly reduced from pretreatment levels but usually remained moderately elevated. There were 17 vascular events in 12 patients at a mean (range) age of 42.5 (18 to 67) years: pulmonary embolism (n=3), myocardial infarction (n=2), deep venous thrombosis (n=5), cerebrovascular accident (n=3), transient ischemic attack (n=1), sagittal sinus thrombosis (n=1), and abdominal aortic aneurysm (n=2). Without treatment, 112 vascular events would have been expected, for a relative risk of 0.09 (95% CI 0.036 to 0.228; P<0.0001). Treatment regimens designed to lower plasma homocysteine significantly reduce cardiovascular risk in cystathionine beta-synthase deficiency despite imperfect biochemical control. These findings may be relevant to the significance of mild hyperhomocysteinemia that is commonly found in patients with vascular disease.

Adult care in phenylketonuria and hyperphenylalaninaemia: the relevance of neurological abnormalities.

UNLABELLED: Neurological abnormalities in phenylketonuria were described before dietary treatment became possible. These included tremor, clumsiness, epilepsy, spastic paraparesis and occasionally extrapyramidal features. Neurological deterioration after childhood was recognised. Patients with neurological deterioration described recently have been late diagnosed or intellectually impaired or both. No early diagnosed patient who was well treated and of good intellectual outcome has yet shown neurological deterioration after stopping diet but it may happen. CONCLUSION: The fascinating links between pathology, magnetic resonance imaging appearances, magnetic resonance spectroscopy results and clinical features are not yet clearly understood. Patients must understand the possible risks of stopping diet and make their choice. All patients need help, support and follow-up regardless of the choices they make over continuing diet.

The adult and adolescent clinic for inborn errors of metabolism.

Adolescent and adult clinics for patients with inborn metabolic errors are needed first to provide care to patients who develop distinctive problems as their different disorders impinge on education, career and family life. The selection of patients in this article illustrates the range of the problems. Fundamental research will be a shared interest with paediatricians and others, but outcomes of care and treatment in young adults and in patients in middle life must be a special concern of adult clinics. It is essential to gather that information. The best model is probably an outpatient service for all ages in a single centre with paediatricians and adult physicians contributing and sharing access to dietary and laboratory services. Such a model would be best for generating the meetings, case discussions and initiatives that contribute to a thriving and energetic unit. Clearly identified centres in each country would be an effective means of acquiring the information on the adult follow-up of these uncommon disorders.

Cutis verticis gyrata of the scalp in a patient with autosomal dominant insulin resistance syndrome.

Cutis verticis gyrata (CVG) is a rare disorder; it is characterized by thickening of the scalp which becomes raised to form ridges and furrows resembling the cerebral gyri. We report a case of CVG associated with the autosomal dominant insulin resistance syndrome. This syndrome is characterized by obesity, mild mental retardation, delayed puberty, acanthosis nigricans and hyperinsulinaemia. The association of CVG and autosomal dominant insulin resistance has not been previously described.

Phenylketonuria: treatment in adolescence and adult life.

In our clinic the decision on whether to continue with dietary treatment of phenylketonuria or not is left to each adolescent and adult patient after the advantages and disadvantages, as discussed in this paper, of continuing diet have been presented to them. As a result 61 of 132 patients have stopped diet or declined to restart and only 4 of them have phenylalanine values below 1000 mumol/l. Seventy-one patients have remained on diet or started again with phenylalanine values below 1000 mumol/l in 58 of them. This series of 132 excludes women who returned to diet to conceive.

Maternal phenylketonuria. A study from the United Kingdom.

By November 1994, 39 pregnancies had been completed in phenylketonuric mothers. Dietary control was post-conception in 6 and 2 of these offspring died of congenital heart disease and 1 other needed surgery for coarctation. There were no heart defects in the 34 offspring of the 33 pregnancies following preconception diet controlled by Guthrie assays of maternal phenylalanine three (Phe) weekly. These Phe results were analysed by trimester for the means, the number of days over 300 mumol/l or below 60 mumol/l. Generally good control was achieved suggesting the UK guidelines drawn up by the MRC Working Party are broadly achievable but excessively high and low values occur intermittently in many pregnancies both of which may adversely affect the fetus. Though developmental assessment scores at 1 year were over 100 in all but five, early outcome results suggest that intellectual development may still be impaired at 4 years. Until much more information is available caution is still needed in discussing outcome with phenylketonuria patients who wish to conceive.

Brain MRI changes in phenylketonuria. Associations with dietary status.

Following the introduction 30 years ago of neonatal screening and early dietary treatment for phenylketonuria there has been a dramatic decrease in the severity of neurological dysfunction associated with this disorder. However, there is evidence that subtle neurological impairment remains common in early treated subjects and in the last 3 years there have been a number of reports of overt neurological impairment with white matter abnormalities on MRI. The frequency of white matter changes in phenylketonuria, and the relation of these changes to dietary management, have remained unclear. The present study examines MRI findings in 34 subjects aged 8-33 years. Twenty-five subjects had been detected by routine neonatal screening and nine had been missed in the screening programme. At the time of the investigation 16 of the early treated and two of the late treated subjects were still receiving a diet low in phenylalanine. All but two of the 34 subjects showed abnormalities on MRI. In the early diagnosed group it could be shown that the severity of MRI changes (graded 1-5) was significantly and independently associated with phenylalanine concentrations at the time of investigation and the time since dietary treatment had been withdrawn. These data are consistent with studies in animals showing that hyperphenylalaninaemia increases myelin turnover in a dose dependent manner. It is suggested that the effects of phenylalanine on myelin pose a lifelong hazard to the nervous system.

Linkage analysis of 7 polymorphic markers at chromosome 11p11.2-11q13 in 27 multiple endocrine neoplasia type 1 families.

The multiple endocrine neoplasia type 1 (MEN1) locus has been previously localized to 11q13 by combined tumour deletion mapping and linkage studies. Family linkage analysis has defined the locus order as 11 cen-PGA-(PYGM, MEN1)-(D11S97, D11S146)-INT2-11qter, and tumour deletion mapping studies have suggested that the MEN1 locus is proximal to D11S146 but distal to PYGM. In order to establish further the location of MEN1, we have utilized the seven polymorphic DNA probes: D11S288, D11S149, PGA, PYGM, D11S97, D11S146 and INT2, in linkage studies of 339 members (116 affected) from 27 MEN1 families. Linkage between MEN1 and 6 of the 7 loci was established, and the highest peak lod scores [Z(theta)] were observed with PYGM and D11S97 at Z(theta) = 13.71, theta = 0.047 and Z(theta) = 13.76, theta = 0.076 respectively. Multilocus analysis suggested the most likely locus order as: 11 pter-(D11S288, D11S149)-11 cen-PGA-PYGM-MEN1-D11S97-D11S146-INT2-1 1qter. In addition, an examination of individual recombinants indicated a centromeric location of D11S149 in relation to D11S288. Thus, the results of our study, which favoured a location of MEN1 proximal to D11S97 and distal to PYGM, have established a panel of recombinants that will facilitate further meiotic mapping studies of the MEN1 locus.

Myoglobinuria: the importance of reaching a firm diagnosis--a patient with defective fatty acid oxidation.

A 52 year old man presented with myoglobinuria-induced acute renal failure requiring dialysis. Despite renal biopsy, the cause of the myoglobinuria was not established until he re-presented a year later with a milder episode. At this stage investigations, including a muscle biopsy, demonstrated a defect in fatty acid oxidation amenable to dietary and lifestyle advice. This report emphasizes the importance of reaching a definitive diagnosis in myoglobinuria.

Transport of L-phenylalanine and related amino acids at the ovine blood-brain barrier.

1. Unidirectional influx of amino acids at the blood-brain barrier was studied in the lamb and sheep under barbiturate anaesthesia using the single-pass indicator-dilution technique. 2. In the lamb, influx of both L-phenylalanine (14 +/- 1 nmol g-1 min-1) and L-alanine (12 +/- 2 nmol g-1 min-1) was greater than in the sheep: L-phenylalanine influx, 9 +/- 1 nmol g-1 min-1; L-alanine influx, 5 +/- 1 nmol g-1 min-1 (P less than 0.01). This difference reflected higher blood concentrations of these amino acids in the younger animal. 3. The kinetic parameters of transport for L-phenylalanine were determined in the lamb and sheep from measurements of influx over a range of blood concentrations. The concentration dependence of L-phenylalanine influx was best described by a model with a saturable and non-saturable component. Maximum influx (Jmax) was higher and apparent transport constant (km, app) lower in the lamb. Values obtained (mean +/- S.E.M.) were: lamb, Jmax, 138 +/- 6 nmol g-1 min; km, app, 0.85 +/- 0.10 mmol l-1; sheep, Jmax, 107 +/- 7 nmol g-1 min-1; km, app, 2.25 +/- 0.25 mmol l-1. 4. L-Phenylalanine inhibited influx of L-leucine, L-tyrosine, L-valine and L-glutamine but not L-arginine and L-lysine. Its influx was inhibited by L-histidine, L-valine and L-leucine, but not by L-glutamine or L-alanine. In the lamb, L-phenylalanine inhibited L-histidine influx with an apparent inhibitor constant (kh) of 139 mumol l-1, and a maximum inhibition of 92%. In the sheep, L-phenylalanine inhibited L-methionine influx with an apparent kh of 33 mumol l-1 and a maximum inhibition of 82%. 5. Fractional extraction of phenylalanine and alanine was stereospecific with preference for the L-enantiomer. In the lamb, fractional extraction values (mean +/- S.E.M.) were: L-phenylalanine, 0.58 +/- 0.03; D-phenylalanine, 0.20 +/- 0.02; L-alanine, 0.16 +/- 0.03; D-alanine, 0.05 +/- 0.02. Self-inhibition of extraction was evident for L-phenylalanine and L-alanine in both lamb and sheep.

Dystonia in homocystinuria.

Three patients with homocystinuria due to cystathionine beta-synthase deficiency who developed progressive generalised dystonia are described. Although cerebrovascular thrombosis is usually thought to be responsible for neurological dysfunction in homocystinuric patients, neuropathological studies in one case and clinical and radiological evidence in the other two suggested that dystonia was not caused by brain infarction. Movement disorder associated with homocystinuria may result from the neurochemical changes in the basal ganglia related to the inherited defect in sulphur amino acid metabolism.

Neurological involvement in X-linked hypophosphataemic rickets.

X-linked hypophosphataemic rickets is a familial form of Vitamin D resistant rickets in which gross bony and ligamentous changes may occur. Two patients showing severe spinal disease with evidence of spinal cord compression requiring neurosurgical intervention are reported. The management of such lesions may be problematic as cord compression may be found at several levels at presentation, and further difficulties develop after neurosurgical treatment.

DOOR syndrome (deafness, onycho-osteodystrophy, and mental retardation): elevated plasma and urinary 2-oxoglutarate in three unrelated patients.

We describe three further children with the DOOR syndrome (deafness, onycho-osteodystrophy and mental retardation). A severe seizure disorder and characteristic facial appearance are part of the syndrome. Fourteen similar cases including the present patients are now on record. Autosomal recessive inheritance is likely. An increased level of 2-oxoglutarate in both plasma and urine has been found in our three patients. It is suggested there may be an inherited metabolic defect in this malformation syndrome.