Mild Clinical Presentation Research Articles

Biochemical, clinical and molecular findings in LCHAD and general mitochondrial trifunctional protein deficiency

General mitochondrial trifunctional protein (TFP) deficiency leads to a wide clinical spectrum of disease ranging from severe neonatal/infantile cardiomyopathy and early death to mild chronic progressive sensorimotor poly-neuropathy with episodic rhabdomyolysis. Isolated long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency resulting from the common Glu510Gln mutation usually gives rise to a moderately severe phenotype with multiorgan involvement with high morbidity and mortality. However, isolated LCHAD deficiency can also be consistent with long-term survival in patients identified and treated from an early age. We present biochemical, clinical and mutation data in 9 patients spanning the full spectrum of disease. Fibroblast acylcarnitine profiling shows good correlation with clinical phenotype using the ratio C18(OH)/(C14(OH)+C12(OH)). This ratio shows a gradation of values, from high in four patients with severe neonatal disease (2.5+/-0.8), to low in two neuromyopathic patients (0.35, 0.2). Fibroblast fatty acid oxidation flux assays also show correlation with the patient phenotype, when expressed either as percentage residual activity with palmitate or as a ratio of percentage activity of myristate/oleate (M/O ratio). Fibroblasts from four patients with severe neonatal disease gave an M/O ratio of 4.0+/-0.6 compared to 1.97 and 1.62 in two neuromyopathic patients. Specific enzyme assay of LCHAD and long-chain 3-ketothiolase activity in patient cells shows lack of correlation with phenotype. These results show that measurements in intact cells, which allow all determinative and modifying cellular factors to be present, better reflect patient phenotype. Mutation analysis reveals a number of alpha- and beta-subunit mutations. Peripheral sensorimotor polyneuropathy, often as the initial major presenting feature but usually later accompanied by episodic rhabdomyolysis, is a manifestation of mild TFP protein deficiency. The mild clinical presentation and relative difficulty in diagnosis suggest that this form of TFP is probably underdiagnosed.

Brain MRI findings in patients with mucopolysaccharidosis types I and II and mild clinical presentation.

Our objective was to determine the brain magnetic resonance imaging (MRI) abnormalities in a selected group of patients with mucopolysaccharidosis (MPS) types I and II who had only mild clinical manifestations. We retrospectively assessed MRI brain studies in 18 patients with MPS (type I: 6 and type II: 12). We evaluated abnormal signal intensity in the white matter, widening of the cortical sulci, size of the supratentorial ventricles, dilatation of the perivascular spaces (PVS) and enlargement of the subarachnoid spaces. We observed a broad spectrum of findings, and despite severely abnormal MRI studies, no patients had mental retardation. We also observed that dilated PVS, previously believed to be caused by macroscopic deposition of the mucopolysaccharides, had an appearance similar to cerebrospinal fluid (CSF) in all MRI sequences performed, even in FLAIR and trace diffusion weighted images. Based on our results, we believe that with the exception of white matter abnormalities and brain atrophy, all other findings may be related to abnormal resorption of CSF, and there is no relationship between the imaging and clinical manifestations of the disease.

Beta-globin gene cluster haplotypes in sickle cell patients from southwest Iran.

Sickle cell anemia in Iran is accompanied by a high level of HbF and mild clinical presentation. Here we report haplotypes of the beta gene cluster found in 81 randomly selected sickle cell patients, including 47 sickle cell anemia (SS), 17 sickle cell trait (AS), and 17 sickle/thalassemia (S/thal) from southwest Iran. We found all five common typical haplotypes as well as five atypical haplotypes in our patients. Except for four patients with homozygous Benin haplotype, none of the other African typical haplotypes were found in a homozygous state. Arab-Indian was found to be the most prevalent haplotype in the study population. This haplotype accounted for 51.1% as the homozygous form in SS patients, where 69.1% of chromosomes in these patients had the Arab-Indian haplotype. Bantu A2 was the second most prevalent haplotype among all patients. The mean %HbF in SS patients was 27.83 and in the homozygous Arab-Indian haplotype it was still higher (30.40%), while in AS patients the %HbF was only 1.20. The high %Ggamma chain (71.81) in the Arab-Indian homozygous haplotype was concomitant with the presence of an Xmn I site in both chromosomes. The presence of the Arab-Indian haplotype as the predominant haplotype might be suggestive of a gene flow to/from Saudi Arabia or India. More haplotype investigations of a normal population can clarify the high incidence of Bantu A2 haplotype in our population.

Identification of seven novel missense mutations, two splice-site mutations, two microdeletions and a polymorphic amino acid substitution in the gene for ornithine transcarbamylase (OTC) in patients with OTC deficiency.

Ornithine transcarbamylase (OTC) deficiency, a X-linked disorder, is the most frequent inborn error of the urea cycle. Point mutations and small deletions/insertions in the OTC gene are responsible for the majority of the cases and have a "private" character with little recurrence. We report on eleven pathological changes in the OTC gene sequence detected in three males with mild clinical presentations, and in eight symptomatic females. All of these mutations are novel. Only one mutation affects a CpG mutational hot spot, whereas all but one of the mutations caused an abnormal SSCP of the corresponding PCR-amplified exon. Two mutations occurring in females involved one or two base deletions in codons 196 and 330, respectively, causing frameshift changes and premature termination. Another two mutations in a female and a male affected acceptor splice sites at bases -1 and -3 of the intron 6/exon 7 and intron 9/exon 10 junctions, respectively. All other mutations were point changes causing the simple amino acid substitutions (M1I, I160S, L191F, M206I, L301F, P305H and L341P), although the mutation M1I may abolish translation of the OTC polypeptide. This mutation coexisted in a female patient with the change T333A that appears to be a previously unreported polymorphism. The three male patients but only four of the eight female patients inherited the mutation.

Mutation analysis of the methyl-CpG-binding protein 2 gene ( MECP2) in Rett patients with preserved speech

Genomic DNAs from 35 Japanese sporadic patients with Rett syndrome (RTT) were screened for DNA mutations in the entire coding region and exon–intron boundaries of methyl-CpG-binding protein 2 ( MECP2). We detected mutations in 30 (85.7%) of 35 patients. Among these 35 RTT patients, five patients (14%) had the preserved speech variant of this disease. Four respective mutations (R133C, R306C, R294X, 2 base pair (bp) deletion) were found in these five patients. Two patients had the same missense mutation, R133C. The patients with the R133C mutation and one with frameshift mutation presented the relatively mild clinical presentation, and the R133C mutation was not found in any other patient without preserved speech. We confirmed that the preserved speech variant is one of the clinical phenotypes of RTT and is also caused by MECP2 mutation. We speculated that the clinical phenotype of patients with the R133C missense mutation might be mild.

Milder clinical presentation of haemophilia A with severe deficiency of factor VIII as measured by one-stage assay.

During the course of investigations we encountered 11 patients with haemophilia A who had severe factor VIII deficiency as measured by one-stage assay but had surprisingly mild clinical presentation. Four of these patients had either a brother, nephew or maternal uncle with severe clinical manifestations. Two patients had low protein S levels, and one was heterozygous for the factor V Leiden mutation. One patient had a combined deficiency of protein C and antithrombin III. Four patients had a two-stage factor VIII assay value that was much higher than the one-stage assay value. Five patients were heterozygous for the MTHFR gene C677T polymorphism, of whom two patients were also deficient for protein S and one had two-stage factor assay values higher than the one-stage assay values. The patient who was both factor VIII deficient and heterozygous for factor V Leiden had mild clinical presentation as compared to his maternal uncle who was only factor-VIII deficient. The maternal cousin of the same patient was heterozygous for factor V Leiden and had suffered two thrombotic episodes. Thus, the present study advocates that the physiological inhibitors of blood coagulation also play an important role in cases of haemophilia A in the final outcome of haemostasis in vivo.

Milder clinical presentation of haemophilia A with severe deficiency of factor VIII as measured by one‐stage assay

During the course of investigations we encountered 11 patients with haemophilia A who had severe factor VIII deficiency as measured by one‐stage assay but had surprisingly mild clinical presentation. Four of these patients had either a brother, nephew or maternal uncle with severe clinical manifestations. Two patients had low protein S levels, and one was heterozygous for the factor V Leiden mutation. One patient had a combined deficiency of protein C and antithrombin III. Four patients had a two‐stage factor VIII assay value that was much higher than the one‐stage assay value. Five patients were heterozygous for the MTHFR gene C677T polymorphism, of whom two patients were also deficient for protein S and one had two‐stage factor assay values higher than the one‐stage assay values. The patient who was both factor VIII deficient and heterozygous for factor V Leiden had mild clinical presentation as compared to his maternal uncle who was only factor‐VIII deficient. The maternal cousin of the same patient was heterozygous for factor V Leiden and had suffered two thrombotic episodes. Thus, the present study advocates that the physiological inhibitors of blood coagulation also play an important role in cases of haemophilia A in the final outcome of haemostasis in vivo.

Combined factor V and VIII deficiency in Indian population.

The clinical and haematological heterogeneity in cases of the rare combined factor V and VIII deficiency has not been reported so far from India. Nine such cases belonging to five unrelated families have been analysed in the present study for the various haematological and clinical parameters. A very mild clinical presentation is seen in all these cases. The clinical manifestations, however, do not correlate with the plasma levels of these factors.

Pathobiochemical implications of hyperdopaminuria in patients with aromatic L-amino acid decarboxylase deficiency.

Aromatic L-amino acid decarboxylase (AADC, EC 4.1.1.28) catalyses the conversion of 5-hydroxytryptophan to serotonin in serotonergic neurons and of dopa to dopamine in catecholaminergic neurons and adrenal medullary cells. The enzyme thus plays a key role in the synthesis of both groups of neurotransmitter biogenic amines. AADC is found in both neuronal (monoaminergic neurons in the CNS, adrenal medulla) and nonneuronal cells (liver, intestine, kidney), which distribution is ascribed to tissue-specific expression of the AADC gene as a result of alternative promoter usage and differential splicing (Jahng et al 1996). The first human case of AADC deficiency was described (Hyland and Clayton 1990; Hyland et al 1992) in 1990, and since then several new patients have been identified (Abeling et al 1998; Fiumara et al 1998; Hyland et al 1998; Korenke et al 1997; Maller et al 1997). Mutations in the human AADC gene have been described in six patients, but expression studies to prove their association with altered enzyme activity are still in progress (Chang et al 1998). The condition is considered to be a neurotransmitter defect leading to a combined deficiency of the catecholamines and serotonin. The clinical presentation comprises developmental delay, hypotonia and an extrapyramidal movement disorder with oculogyric crises. Temperature instability, sweating and hypersalivation are also observed. Most patients present in the first years of life. The diagnosis is based on abnormal metabolite patterns in CSF, plasma and urine and on greatly reduced activity of AADC in plasma. Recently (Abeling et al 1998) a new case of AADC deficiency in a 2-year-old Dutch girl was published, with mild clinical presentation and unexpected biochemical findings, i.e. a urinary metabolite pattern partly consistent with AADC deficiency, but also with elements that could not easily be explained from the defect. The most prominent finding was hyperdopaminuria. In addition, elevated urinary concentrations of dopamine metabolites were found. This prompted us to perform further investigations in this and other AADC-deficient patients in search of an explanation for this finding.

3-Methylglutaconyl-CoA hydratase deficiency: a new patient with speech retardation as the leading sign.

3-Methylglutaconyl (3-MG)-CoA hydratase (EC 4.2.1.18) catalyses the fourth step in leucine catabolism by converting 3-MG-CoA into 3-hydroxy-3-methylglutaryl (3-HMG)-CoA. Deficiency of 3-MG-CoA hydratase has been defined as 3-methylglutaconic (3-MGC) aciduria type I (McKusick 250950) presenting with increased urinary excretion of 3-MGC, 3-methylglutaric (3-MGR) acid and 3-hydroxyisovaleric (3-HIV) acid and with normal amounts of 3-hydroxy-3-methylglutaric (3-HMG) acid. Additional types of 3-MGC aciduria with normal activities of 3-MG-CoA hydratase have been classified (Gibson et al 1993): type II seems to be of X-linked inheritance and is associated with cardiomyopathy, growth retardation and neutropenia (Kelley et al 1989). Type III has been described as the Costeff Iraqi-Jewish optic atrophy syndrome (Costeff et al 1989). Another type (type IV, unclassified) comprises a heterogeneous group of patients with progressive neurological symptoms. In contrast to 3-MGC aciduria type I, the origin of the specific organic aciduria in these entities is unknown. Since 3-HIV acid seems to be excreted only in patients with deficient 3-MG-CoA hydratase activity, it is an important parameter for differentiation between type I and the other types. Owing to the variability of the clinical picture of the nine patients with deficiency of 3-MG-CoA hydratase reported so far, a specific phenotype of 3-MGC aciduria type I has not yet been established. There seem to be a benign and a more severe form: in several patients the only symptoms were delayed speech development, mild psychomotor retardation and attention deficits (Duran et al 1982; Gibson et al 1992; Sewell et al 1999). Three of the reported patients, however, presented with severe neurological symptoms including spastic quadriplegia, dystonic movements, hypotonia and marked psychomotor retardation in two patients as well as coma and seizures during an episode of Reye syndrome in another patient with speech retardation (Gibson et al 1998; Hou and Wang 1995; Shoji et al 1999). We report on a new patient with a mild clinical presentation of 3-MGC aciduria type I.

Friedreich's ataxia: point mutations and clinical presentation of compound heterozygotes.

Friedreich's ataxia is the most common inherited ataxia. Ninety-six percent of patients are homozygous for GAA trinucleotide repeat expansions in the first intron of the frataxin gene. The remaining cases are compound heterozygotes for a GAA expansion and a frataxin point mutation. We report here the identification of 10 novel frataxin point mutations, and the detection of a previously described mutation (G130V) in two additional families. Most truncating mutations were in exon 1. All missense mutations were in the last three exons coding for the mature frataxin protein. The clinical features of 25 patients with identified frataxin point mutations were compared with those of 196 patients homozygous for the GAA expansion. A similar phenotype resulted from truncating mutations and from missense mutations in the carboxy-terminal half of mature frataxin, suggesting that they cause a comparable loss of function. In contrast, the only two missense mutations located in the amino-terminal half of mature frataxin (D122Y and G130V) cause an atypical and milder clinical presentation (early-onset spastic gait with slow disease progression, absence of dysarthria, retained or brisk tendon reflexes, and mild or no cerebellar ataxia), suggesting that they only partially affect frataxin function. The incidence of optic disk pallor was higher in compound heterozygotes than in expansion homozygotes, which might correlate with a very low residual level of normal frataxin produced from the expanded allele.

Pelizaeus-Merzbacher disease: three novel mutations and implication for locus heterogeneity.

We report a mutational and polymorphic analysis of the proteolipid protein gene in members of 27 Japanese families with Pelizaeus-Merzbacher disease. We found causative mutations in 6 members of 27 families (22.2%); 5 of the 6 mutations, including two novel mutations, Leu45Arg and 231 + 2T --> G, resulted in the typically severe clinical symptoms. Paradoxically, the Cys219Tyr mutation, presumed to disrupt the tertiary structure of proteolipid protein by removing the disulfide bond between Cys200 and Cys219, was associated with a mild clinical presentation wherein the patient could walk with assistance and speak. It was inferred that the structural change prevented the toxicity associated with a gain of function mutation. Moreover, in one family 3 patients exhibited a intragenic polymorphism that did not segregate with the disease, suggesting a locus heterogeneity for Pelizaeus-Merzbacher disease.

Epidemiologic analysis and clinical course of 84 consecutive cases of pemphigus in eastern Sicily.

The purpose of this study was to examine the clinical and epidemiologic features of pemphigus in eastern Sicily. All new cases of pemphigus seen in the Dermatology Clinic at the University of Catania during the period January 1982 to June 1996 were studied retrospectively. Eighty-four patients with pemphigus represented 1.3% of 6653 patients admitted to our clinic in a 13.5-year period, with an average annual incidence of six cases per year. The most common form of presentation was pemphigus vulgaris (PV) (75%), followed by pemphigus erythematosus (17%), pemphigus herpetiformis (6%), and pemphigus vegetans (2%). In 6% of PV patients, the oral lesions were not followed by skin involvement, and the lag time between the onset of illness and the final diagnosis in five PV cases was prolonged, ranging from 4 to 7 years, probably due to the mild clinical presentation of the disease. Two trauma-related PV cases were documented; in one case, the blisters were located in a surgical scar and in the other in a burn scar. Our findings showed that pemphigus has a relatively high prevalence in eastern Sicily compared with other Italian regions; PV is the most common variant, and may have a mild course not always requiring aggressive therapy.

A novel mutation (V191G) in a German‐British type 1 Gaucher disease patient

Gaucher disease results from mutations in the glucocerebrosidase gene located on human chromosome 1q21. Three clinical forms of Gaucher disease have been described: type 1, nonneuropathic; type 2, acute neuropathic; and type 3, subacute neuropathic. We have identified a novel mutation in a German-British patient with type 1 Gaucher disease which results in V191G of the glucocerebrosidase polypeptide. Because the mutation abolishes a HphI cleavage site, its presence was confirmed by HphI RFLP analysis of PCR-amplified genomic DNA. In the second allele of the patient, the mutation identified was g.5841A G (N370S). Sequence analysis of the remainder of the coding region of the gene as well as the exon-intron boundaries showed identity to normal controls. Because mutation N370S has so far been found only in type 1 Gaucher disease and postulated to result in mild clinical presentation, and since the clinical course of this patient has been relatively mild with minimal skeletal involvement, we speculate that the V191G/N370S genotype may also result in good prognosis. Hum Mutat 11:411–412, 1998. © 1998 Wiley-Liss, Inc.

A novel mutation (V191G) in a German-British type 1 Gaucher disease patient. Mutations in brief no. 131. Online.

Gaucher disease results from mutations in the glucocerebrosidase gene located on human chromosome 1q21. Three clinical forms of Gaucher disease have been described: type 1, nonneuropathic; type 2, acute neuropathic; and type 3, subacute neuropathic. We have identified a novel mutation in a German-British patient with type 1 Gaucher disease which results in V191G of the glucocerebrosidase polypeptide. Because the mutation abolishes a HphI cleavage site, its presence was confirmed by HphI RFLP analysis of PCR-amplified genomic DNA. In the second allele of the patient, the mutation identified was g.5841A G(N370S). Sequence analysis of the remainder of the coding region of the gene as well as the exon-intron boundaries showed identity to normal controls. Because mutation N370S has so far been found only in type 1 Gaucher disease and postulated to result in mild clinical presentation, and since the clinical course of this patient has been relatively mild with minimal skeletal involvement, we speculate that the V191G/N370S genotype may also result in good prognosis.

A novel mutation (V191G) in a German-British type 1 Gaucher disease patient

Gaucher disease results from mutations in the glucocerebrosidase gene located on human chromosome 1q21. Three clinical forms of Gaucher disease have been described: type 1, nonneuropathic; type 2, acute neuropathic; and type 3, subacute neuropathic. We have identified a novel mutation in a German-British patient with type 1 Gaucher disease which results in V191G of the glucocerebrosidase polypeptide. Because the mutation abolishes a HphI cleavage site, its presence was confirmed by HphI RFLP analysis of PCR-amplified genomic DNA. In the second allele of the patient, the mutation identified was g.5841A G (N370S). Sequence analysis of the remainder of the coding region of the gene as well as the exon-intron boundaries showed identity to normal controls. Because mutation N370S has so far been found only in type 1 Gaucher disease and postulated to result in mild clinical presentation, and since the clinical course of this patient has been relatively mild with minimal skeletal involvement, we speculate that the V191G/N370S genotype may also result in good prognosis. Hum Mutat 11:411–412, 1998. © 1998 Wiley-Liss, Inc.

Epidemic Bacillus Endophthalmitis after Cataract Surgery I: Acute Presentation and Outcome

Objective: The purpose of the study is to report the clinical outcome of acute Bacillus endophthalmitis after cataract surgery.Design: The study design is a cohort study.Participants: Fourteen eyes of 14 patients with epidemic acute postoperative inflammation after exposure to bacteria-contaminated viscoelastic material were studied. Intervention: Three patients with milder clinical presentations were treated without vitrectomy or antibiotics. Eleven patients with more severe infection were treated with vitrectomy as well as intravitreous and topical fortified antibiotics.Main Outcome Measures: Final visual acuities were obtained in all 14 study patients. Results of microbiologic studies of aqueous and vitreous specimens from 11 vitrectomized eyes also were analyzed.Results: One patient with late presentation had severe inflammation and had phthisis bulbi develop with no light perception. The remaining 13 patients had successful resolution of inflammation after treatment by 1 month of follow-up. Twelve of these 13 patients, including 1 nonvitrectomized patient, had final visual acuities of 20/100 or better at 6 months' follow-up. Six patients, including two patients with nonvitrectomized eyes, had outcomes of 20140 or better visual acuity. Bacillus species were grown from all 11 (100%) vitreous and 7 (88%) of 8 aqueous specimens obtained from vitrectomized patients, as well as from the contaminated viscoelastic material remaining in the operating room.Conclusions: Postoperative Bacillus endophthalmitis need not result in poor outcome. Results depend on factors including bacterial load, specific bacterial species, timing of treatment, and immune status of the patient.

Hereditary spherocytosis with band 3 deficiency. Association with a nonsense mutation of the band 3 gene (allele Lyon), and aggravation by a low-expression allele occurring in trans (allele Genas)

We describe an 18-year-old with moderate hereditary spherocytosis. The condition was associated with a 35% decrease in band 3. The underlying mutation was Arg to stop at codon 150 (CGA-->TGA) and was designated R150X, which defined allele Lyon of the EPB3 gene. The inheritance pattern was dominant. However, the mother, who also carried the allele Lyon, had a milder clinical presentation and only a 16% decrease of band 3. We suggested that the father had transmitted a modifying mutation that remained silent in the heterozygous state. Nucleotide sequencing after single strand conformation polymorphism analysis of the band 3 cDNA and promoter region revealed a G-->A substitution at position 89 from the cap site in the 5′-untranslated region, designated 89G-->A, which defined allele Genas. A ribonuclease protection assay showed that (1) the allele Genas (father) resulted in a 33% decrease in the amount of band 3 mRNA, (2) the reduction caused by the allele Lyon (mother) was 42%, and (3) the compound heterozygous state for both alleles (proband) resulted in a 58% decrease. These results suggest that some mildly deleterious alleles of the EPB3 gene are compensated for by the normal allele in the heterozygous state. They are shown through the aggravation of the clinical picture, based on more obvious molecular alterations when they occur in trans to an allele causing a manifest reduction of band 3 membrane protein concentration.

Hereditary Spherocytosis With Band 3 Deficiency. Association With a Nonsense Mutation of the Band 3 Gene (Allele Lyon), and Aggravation by a Low-Expression Allele Occurring in trans (Allele Genas)

We describe an 18-year-old with moderate hereditary spherocytosis. The condition was associated with a 35% decrease in band 3. The underlying mutation was Arg to stop at codon 150 (CGA-->TGA) and was designated R150X, which defined allele Lyon of the EPB3 gene. The inheritance pattern was dominant. However, the mother, who also carried the allele Lyon, had a milder clinical presentation and only a 16% decrease of band 3. We suggested that the father had transmitted a modifying mutation that remained silent in the heterozygous state. Nucleotide sequencing after single strand conformation polymorphism analysis of the band 3 cDNA and promoter region revealed a G-->A substitution at position 89 from the cap site in the 5'-untranslated region, designated 89G-->A, which defined allele Genas. A ribonuclease protection assay showed that (1) the allele Genas (father) resulted in a 33% decrease in the amount of band 3 mRNA, (2) the reduction caused by the allele Lyon (mother) was 42%, and (3) the compound heterozygous state for both alleles (proband) resulted in a 58% decrease. These results suggest that some mildly deleterious alleles of the EPB3 gene are compensated for by the normal allele in the heterozygous state. They are shown through the aggravation of the clinical picture, based on more obvious molecular alterations when they occur in trans to an allele causing a manifest reduction of band 3 membrane protein concentration.

Epidemic typhoid in Chile: analysis by molecular and conventional methods of Salmonella typhi strain diversity in epidemic (1977 and 1981) and nonepidemic (1990) years.

From 1977 to 1986, Chile experienced an important typhoid fever epidemic, despite statistics that indicated apparently improving levels of sanitation of drinking water and sewage disposal. The lack of antibiotic resistance among the Salmonella typhi strains isolated during this period, the mild clinical presentation of the disease, and the initially low level of efficacy of the S. typhi Ty21a vaccine in the population exposed to the epidemic suggested that this epidemic might have resulted from the dissemination of S. typhi strains with unique characteristics. To investigate this hypothesis, we used conventional methods (bacteriophage typing and biotyping) and molecular methods (restriction fragment length polymorphism analysis, ribotyping, IS200 typing, and PCR amplification of the fliC-d gene) to study a population of 149 S. typhi isolates during 1977, 1981, and 1990, the years that included periods with low (when the disease was endemic) and high (when the disease was epidemic) morbidities. Our results indicate that these S. typhi isolates in Chile represent a number of highly diverse variants of the clone of S. typhi with a worldwide distribution described by Selander et al. (R. K. Selander, P. Beltran, N.H. Smith, R. Helmuth, F.A. Rubin, D.J. Kopecko, K. Ferris, B.D. Tall, A. Cravioto, and J.M. Musser, Infect. Immun. 58:2262-2275, 1990). For example, we detected 26 PstI and 10 ClaI ribotypes among 47 and 16 S. typhi strains belonging to this clone, respectively. These results suggest that the Chilean epidemic was probably produced by multiple sources of infection because of deficient sanitary conditions. These findings illustrate the usefulness of molecular methods for characterizing the potential causes of the typhoid epidemics and the possible routes of transmission of S. typhi strains in typhoid epidemics.