Reversal of metabolic block in glycolysis by enzyme replacement in triosephosphate isomerase-deficient cells.

Inherited deficiency of the housekeeping enzyme triosephosphate isomerase (TPI) is the most severe clinical disorder of glycolysis. Homozygotes manifest congenital hemolytic anemia and progressive neuromuscular impairment, which in most cases pursues an inexorable course with fatal outcome in early childhood. No effective therapy is available. Hitherto specific enzyme replacement has not been attempted in disorders of glycolysis. Primary skeletal muscle myoblasts and Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines generated from homozygous TPI-deficient patients were cultured in the presence of exogenous enzyme or cocultured with human K562 erythroleukemia cells as an exogenous source of TPI. Uptake of active enzyme by TPI-deficient cells resulted in reversal of intracellular substrate accumulation, with a reduction in dihydroxyacetone phosphate (DHAP) concentration to levels seen in TPI-competent cells. Evidence of successful metabolic correction of TPI deficiency in vitro establishes the feasibility of enzyme replacement therapy, and has important implications for the potential role of allogeneic bone marrow transplantation and gene therapy as a means of sustained delivery of functional enzyme in vivo.

Porphyrins in urine, plasma, erythrocytes, bile and faeces in a case of congenital erythropoietic porphyria (Gunther's disease) treated with blood transfusion and iron chelation: lack of benefit from oral charcoal.

Congenital erythropoietic porphyria is a rare genetic disorder in which deficiency of uroporphyrinogen III synthase results in excessive production of Type I porphyrins. The main clinical features are severe photodestruction of the skin and haemolytic anaemia. Treatment consists of shielding from light, blood transfusions and splenectomy, but is generally unsatisfactory. Previous studies have suggested that oral charcoal may be of benefit by binding porphyrins in the gut. A trial was therefore undertaken to evaluate this possibility. Porphyrins in urine, plasma and erythrocytes were measured by HPLC in a 23-year-old male patient with congenital erythropoietic porphyria, during an 8 week "run-in" period, and for a further 3 weeks when oral charcoal was given. Total urinary porphyrin excretion was 79-283 mumol/24 h consisting of 75% uroporphyrin I, 15% coproporphyrin I and smaller amounts of hepta-, hexa-, and pentacarboxylic porphyrins. Similar proportions were found in plasma and erythrocytes. During the first 24 h of charcoal administration a minor decrease in plasma and erythrocyte porphyrins was detected but this was not maintained during the remainder of the trial. In bile and faeces coproporphyrin I constituted approximately 95% of the porphyrins, with 2-3% coproporphyrin III and smaller amounts of pentaporphyrins I and III, but only trace amounts of uroporphyrin I. Oral charcoal was of no value in this case. Reasons are discussed in the context of biochemical differences between this patient with classical Gunther's disease and the similar clinical syndrome due to deficiency of uroporphyrinogen decarboxylase.

Outcome of stroke in patients with sickle cell disease

Cerebral vasculopathy is a major cause of morbidity in sickle cell disease (SCD). We report the first UK population-based study of stroke in SCD. Of 669 SCD patients (HbSS 429, HbSC 193, HbS-thalassaemia 48, HbSO 1) followed at the King's College hospital between 1970 and 1995, 21 (3.1 percent) developed stroke. A further ten patients were referred. 29 had HbSS and 2, HbSC. 3 (10 percent) suffered subarachnoid haemorrhage, the remaining 28 strokes were ischaemic. Median age at initial stroke was 6 years (19 mo- 31 yr) with 24 (80 percent) patients aged >10. Precipitating factors included parvovirus associated aplastic crisis in 2/25 98 percent) evaluable patients and bacterial meningitis in 2 (8 percent). 9 (36 percent) patients experienced transient neurological disturbance prodromally. 27 (87 percent) presented with paresis, 5 (16 percent) cranial nerve defects. 11 (35 percent) dysphasia and 3 (10 percent) seizures. No patient died during the acute episode. Patients with stroke had significantly lower Hb and higher WCC at age 1 compared to matched controls. Exchanged transfusion was performed with 26 patients following which 15 (58 percent) recovered neurologically. 19 patients subsequently entered a transfusion programme to maintain HbS <30 percent. Transfusion was stopped in 10 patients. Of these, 6 (60 percent) had recurrent stroke at a median of 4.5 months. A similar recurrence rate (50 percent) was observed among patients who did not receive regular transfusion whilst no patient maintained on monthly transfusions suffered further stroke. Recurrence was more common in patients suffering initial stroke at an early age and in whom no trigger was identified. Median follow-up after initial stroke is 8 years. 14 (45 percent) patients have no residual neurological deficit, 6 (19 percent) are severely disabled, 13 (42 percent) have learning disabilities and 7 (23 percent) epilepsy. There were two deaths in both patients with recurrent stroke. 1 patient with moyamoya-type disease has undergone extracranial-intracranial bypass and 1 allogeneic-BMT. In conclusion, whilst transfusion is effective in prevention of further stroke, cessation is associated with a high rate of recurrence which frequently results in severe physical and/or neuropsychological disability. The 6.5 percent mortality following stroke supports the rationale for early consideration of allogeneic-BMT in these patients. (AU)

Neonatal Screening for Haemoglobinopathies in South East London: findings and comparisons with Jamaica

INTRODUCTION: Neonatal screening for sickle cell disorders has been shown to reduce mortality and morbidity. Methods of screening vary but in 1994, the local Health Authority funded universal neonatal screening across the whole of Lambeth, Southwark and Lewisham. This paper will report the findings of the first three years of operation of the programme and compare findings with the screening programme currently operating in Jamaica. METHOD: since May 1994 dried bloo[d] spots of all infants have been screened at King's College Hospital and screen positive cases followed up by counsellors. Infants are followed up at four sites (Guy's, King's, Lewisham and St.Thomas') according to parental preference. Minimum standards for follow-ups have been agreed by clinicians across all four sites and information of the success in achieving these standards is now being collected. RESULTS: Overall there have been 122 affected infants detected in the first two years 10 months of the programmes operation. This is made up of 83 HbSS, 35 HbSC, 4HbSBThal. This gives a birth preference of 23.4 per 1000 total population (2.3HbSS, 1.0 HbSC). Allowing for a termination rate of 20 percent this indicates that the expected birth prevalence in the district would be 4.2 per 1000 births. This compares with birth prevalence of of 0.3 per 1000 for congenital hypothyroidism, 06. per 1000 for cystic fibrosis and 0.1 for phenylketonuria. The distribution of the births is unevem with 57 in Southwark, 40 in Lambeth and 25 in Lewisham. The paper will report on the follow-up and outcome of care provided for this population to date. Discussion: South East London has the highest prevalence of sickle cell disorders of any district in the UK. Sickle cell disorder is now as common in South East London as it is in Jamaica. The follow-up arrangements established in South East London provide an opportunity for colloboration with the West Indies which may help to determine some of the reasons for differences in the natural course of the disease in these populations. The population based approach established should allow monitoring of the impact of community education and antenatal screening programmes on the birth prevalence over time. (AU)

The molecular basis for genetic variation in fetal haemoglobin level in sickle cell anaemia

Raised fetal haemoglobin levels ameliorate the clinical severity of sickle cell anaemia. This provides a rationale for therapy and signals the need to elucidate the molecular basis for the variability of HbF level in sickle cell anaemia. Polymorphism within regulatory sites of the globin locus alter the affinity with which transcription factors bind their cogante recognition sites thereby modulating gene expression. A novel chromosomal haplotype utilising polymorphic variation within two enhancers hypersensitive site 2 (HS2) of the locus control region and the pre g y framework and the silencer protein BP1 binding site that spans a 53 kb interval of the globin locus was determined in 205 patients with sickle cell anaemia from the UK and Jamaica. Multiplexed polymerase chain reactions developed to facilitate rapid analysis of polymorphisms within each site allowed individual haplotype construction in a single lane of a single strand conformation polymorphism (SSCP) electrophoresis gel. SSCP banding patterns for the combined polymorphic sites were confirmed as unique chromosomal haplotypes by DNA sequence anaylsis. Three hundred and ten chromosomes with sequence TA7 N 12 TA8, GA and AT(AT)8T4 were designated class 1. Twenty-five class II with sequence TA8 N10 TA11, GG, AC(AT)6T9; 17 class III with TA9 N10 TA10, AG, AC(AT)8T4; 7 class IV with TA10 N10 TA12, AG, AC(AT)9T5 and 13 class Ia haplotype with sequence TA9 N10 TA10, GA, AT(AT)8T4 were identified. The proportion of class I chromosomes in both groups (159/210 UK; 151/200 Jamaican) is identical, however, significantly more chromosomes with sub-classes I and II are present among the Jamaican sample. There is incomplete association between the functional haplotype classes defined and conventional haplotypes based on restriction fragment length polymorphisms. The level of Hbf is significantly higher in patients with functional haplotype classes III and IV compared to those with classes I and II. Both high HbF haplotypes share a high affinity binding motif for the transcription factor GATA-1. This novel approach allows the combined effets of genetic variation in regulatory sequences within the globin locus on HbF level to be defined. (AU)

Metabolic correction of triose phosphate isomerase deficiency in vitro by complementation.

Inherited deficiency of triose phosphate isomerase (TPI), the enzyme that catalyses the interconversion of dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate, is characterised by an accumulation of intracellular DHAP and markedly reduced enzyme activity in cells and tissues, resulting in progressive, usually fatal neuromuscular dysfunction. Since specific enzyme replacement for TPI deficiency is not currently available, the secretion and recapture of the missing enzyme was investigated in a co-culture model comprising K562 human erythroleukaemia cells and lymphoblastoid cells taken from a TPI deficient patient. A sevenfold reduction in intracellular DHAP with concomitant increase in intracellular TPI activity from 7.25 +/- 0.1 to 197.2 +/- 10 units/mg protein was achieved for co-cultured lymphoblastoid cells. These novel results confirm the existence of a transport mechanism which permits transfer of active TPI from K562 cells to deficient cells, and may have important implications for developing different therapeutic approaches for TPI deficiency and other metabolic disorders of glycolysis.

Evidence for founder effect of the Glu104Asp substitution and identification of new mutations in triosephosphate isomerase deficiency.

Triosephosphate isomerase (TPI) deficiency is an autosomal recessive disorder of glycolysis characterized by multisystem disease and lethality in early childhood. Among seven unrelated Northern European kindreds with clinical TPI deficiency studied, a single missense mutation at codon 104 (GAG;Glu-->GAC;Asp) predominated, accounting for 11/14 (79%) mutant alleles. In three families molecular analysis revealed compound heterozygosity for Glu104Asp and novel missense mutations. In two cases the second mutation was a Cys to Tyr substitution at codon 41 (TGT-->TAT) and in one an Ile to Val substitution at codon 170(ATT-->GTT). The origin of the Glu104Asp mutation was defined by haplotype analysis using a novel G/A polymorphism at nucleotide 2898 of the TPI gene. Cosegregation of the low frequency 2898A allele with the G-->C base change at nucleotide 315 supports a single origin for the Glu104Asp mutation in a common ancestor.

Two novel mutations in the reduced nicotinamide adenine dinucleotide (NADH)-cytochrome b5 reductase gene of a patient with generalized type, hereditary methemoglobinemia.

Hereditary methemoglobinemia due to reduced nicotinamide adenine dinucleotide (NADH) cytochrome b5 reductase (b5R) deficiency is classified into two types, an erythrocyte (type I) and a generalized (type II). We investigated the b5R gene of a patient with type II from a white United Kingdom (UK) family and found that the patient was a compound heterozygote for two novel mutations. The first mutation was a C-to-A transversion changing codon 42 (TAC: Tyr) to a stop codon in the one allele. From this mutant allele, the product without the catalytic portion of the enzyme is generated. The second one was a missense mutation at codon 95 (CCC-->CAC) in the other allele with the result that Pro changed to His within the flavin adenine dinucleotide (FAD)-binding domain of the enzyme. To characterize effects of this missense mutation on the enzyme function, we compared glutathione S-transferase (GST)-fused b5R with the GST-fused mutant enzyme with the codon 95 missense mutation (P95H) expressed in Escherichia coll. The mutant enzyme showed less catalytic activity, less thermostability, and a greater susceptibility to trypsin than did the normal counterpart. The absorption spectrum of the mutant enzyme in the visual region differed from that of the wild-type. These results suggest that this amino acid substitution influences both secondary structure and catalytic activity of the enzyme. The compound heterozygosity for the nonsense and the missense mutations apparently caused hereditary methemoglobinemia type II in this patient.

Prenatal diagnosis of triosephosphate isomerase deficiency.

First-trimester prenatal diagnosis was undertaken by chorionic villus DNA analysis in two unrelated families with the inherited glycolytic disorder triosephosphate isomerase (TPI) deficiency. The propositus in each family was shown to be homozygous for a missense mutation (GAG --> GAC) at codon 104 of the TPI gene. In the first case the fetus was heterozygous for the codon 104 mutation and therefore clinically unaffected. Prenatal diagnosis in the second case showed the fetus to be homozygous for the codon 104 mutation and thus affected by TPI deficiency. This represents the first molecular diagnosis during early pregnancy of a human glycolytic enzyme disorder.

Tucaresol increases oxygen affinity and reduces haemolysis in subjects with sickle cell anaemia.

The primary pathophysiological event in sickling is the intracellular polymerization of deoxygenated haemoglobin S. Tucaresol (589C80;4[2-formyl-3-hydroxyphenoxymethyl] benzoic acid), a substituted benzaldehyde, was designed to interact with haemoglobin to increase oxygen affinity and has been shown to inhibit sickling in vitro. We administered tucaresol to sickle cell patients in the steady state to examine the anti-sickling effect in vivo. Oral doses of tucaresol or placebo were given to nine stable sickle cell patients (aged 17-39 years; tucaresol, six; placebo, three) for 10 d. The first two patients on tucaresol were scheduled to receive a loading dose of 800 mg or 1200 mg (depending on bodyweight) for the first 4 d, followed by maintenance doses of 200 or 300 mg for the next 6 d. Due to concerns over the sharp rise in haematocrit in one patient, subsequent cohorts received 300 mg tucaresol daily throughout the dosing period. The oxygen affinity of haemoglobin S was increased in all patients receiving tucaresol, with between 10% and 24% of the haemoglobin modified, dependent on dose. In all patients on tucaresol, haemolysis was reduced with rises in haemoglobin of 0.9- 3.7 g/dl (mean 2.2 g/dl), falls in lactate dehydrogenase of 16-52%, and a halving of the irreversibly sickled cell counts. These effects were apparent within a few days and persisted for 1-2 weeks following discontinuation of the drug. Three of the six patients on tucaresol developed fever and cervical lymphadenopathy, with onset between days 7 and 11 from start of drug. Further evaluation of the tolerability and efficacy of tucaresol in sickle cell patients is necessary.

Emergence of ciprofloxacin resistance during treatment of Salmonella osteomyelitis in three patients with sickle cell disease.

The treatment of salmonella osteomyelitis in sickle cell disease (SCD) is difficult and the emergence of antibiotic resistance in Salmonella spp presents further problems for clinicians treating SCD. Three patients presented with salmonella bacteraemia. Treatment with several intravenous antibiotics did not prevent the subsequent development of osteomyelitis. Emergence of resistance to multiple antibiotics, including ciprofloxacin, during the treatment of salmonella osteomyelitis in SCD patients is reported here for the first time. Ceftriaxone 2 g once daily given for 3 months to 3 years was an effective and convenient treatment for osteomyelitis caused by multiply-resistant salmonella. Two of these patients gave a definite history of diarrhoea, and stool cultures confirmed the presence of Salmonella spp in one. Our experience shows that salmonella osteomyelitis may not be prevented by early treatment of bacteraemia in SCD patients. Other measures to reduce the risk of salmonella infection are therefore necessary.

Hereditary red cell enzymopathies.

The hereditary red cell enzymopathies are an uncommon but important cause of chronic haemolytic anaemia. Their clinical diversity is mirrored by increasingly evident heterogeneity at the molecular level. The structure, function, and expression of the genes encoding red cell enzymes and the nature of the gene defects in the deficient state are examined.

Salmonella bacteraemia in sickle cell disease at King's College Hospital: 1976-1991.

A review of all blood culture isolates for the 16 years from 1976 were collated with prospective laboratory and clinical records of 620 sickle cell patients treated at King's College Hospital. Over half of all salmonella bacteraemias diagnosed in the clinical laboratory occurred in sickle cell disease (SCD) patients. Of 21 bacteraemias in SCD patients, 11 (52.3%) were due to Salmonella spp. compared with 23 (0.4%) of 4884 bacteraemias in patients without SCD (P = < 0.00001). In SCD, Gram-negative bacilli were responsible for 16 (76.2%) bacteraemias, of which 11 (68.8%) were due to Salmonella spp. but there were no cases of S. typhi or S. paratyphi. An increase in the number of salmonella infections over the past 5 years were noted in the SCD and non-SCD patients, nine and 16 cases respectively, compared with two and seven cases in the previous decade. However, the recent increase of S. enteritidis phage type 4 in the UK was not evident in SCD patients. These findings have important preventative and therapeutic implications for the management of SCD patients.

Screening for ophthalmic manifestations of sickle cell disease in the United Kingdom.

There are marked variations in the manifestations of sickle disease in different populations. The ocular complications of this condition amongst the Afro-Caribbeans living in the United Kingdom have not previously been reported. We present the preliminary results of an ophthalmic screening programme at King's College Hospital, London. One hundred eyes of 50 patients with sickle cell disease were assessed. Full ocular examination was performed including fundus fluorescein angiography. We have looked at the haematological and clinical profile of the patients involved as well as the number of days spent in hospital during the year preceding the eye examination. The incidence of grade II retinopathy was found to be significantly higher than grade I in SC disease. This concurs with the results of the Jamaican screening and confirms that these patients are at higher risk of visual impairment than those with SS disease. Our results also agree with the Jamaican experience which suggest that visual morbidity is mostly due to complications of proliferative sickle retinopathy (PSR). However, the findings in patients without proliferative changes are different; in particular, angioid streaks leading to disciforms are an important cause of visual loss in Jamaica, but were not seen in any of the 98 eyes examined in this study. No correlation was found between the grade of retinopathy and age, sex, systemic complications and various haematological parameters except for the percentage of haemoglobin F, which was significantly higher in patients with grade I (7.6) compared with grade II (4.2) retinopathy (p = 0.0127).

Pathology.

In summary, the College is a long way forward in the preparation for the implementation of Calman and the unified training grade. It has identified a number of problems that could hinder its implementation and is anxious to develop, along with its sister Colleges, a unified approach to these problems to ensure that the doctors of tomorrow have an effective and satisfying training experience for the benefit of all the patients for whom we care.

Screening for opthalmic manifestations of sickle cell disease in the United Kingdom

There are marked variations in the manifestations of sickle cell disease in different populations. The occular complications of this condition amongst the Afro-Caribbeans living in the United Kingdom have not previously been reported. We present the preliminary results of an opthalmic screening programme at King's College Hospital, London. One hundred eyes of 50 patients with sickle cell disease were assessed. Full ocular examination was performed including fundus fluorescein angiography. We have looked at the haemotological and clinical profile of the patients involved as well as the number of days spent in the hospital during the year preceding the examination. The incidence of Grade 11 retinopathy was found to be significantly higher than grade 1 in SC disease. This concurs with the results of the Jamaican screening and confirms that the patients are at higher risk of visual impairment than those wuth the SS disease. Our results also agrees with the Jamaican experience which suggests that visual morbidity is mostly due to complications of proliferative sickle cell retinopathy (PSR). However, the findings in patients without proliferative changes are different; in particular, angloid streaks leading to disciforms are an important cause of visual loss in Jamaica, but were not seen in any of the 98 eyes examined in this study. No correlation was found between the grade of retinopathy and age, sex, systemic complications and various haematological parameters except for the percentage of haemoglobin F, which was significantly higher in patients with grade I (7.6) compared with grade II (4.2) retinopathy (p=0.0127)(AU)