Clinical features and genetic analysis of a Chinese kindred with Fabry's disease
Kai-Chung Tse,
Kwok-Wah Chan1,
Vicky Pui-Chi Tin1,
Pok-Siu Yip,
Sydney Tang2,
Fu-Keung Li,
Yiu-Wing Ho2,
Kar-Neng Lai and
Tak-Mao Chan
Department of Medicine and
1 Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Hong Kong, People's Republic of China and
2 Department of Medicine, United Christian Hospital, Hong Kong, People's Republic of China
 |
Abstract
|
---|
Background. Fabry's disease is an X-linked recessive inborn error of glycosphingolipid catabolism resulting from deficient activity of lysosomal enzyme
-galactosidase A causing occlusive microvascular diseases affecting the kidney, heart, peripheral nerves and brain. It is an uncommon disease in the Oriental population.
Methods and results. We report a Chinese kindred of Fabry's disease and the relevant clinical features are discussed. The diagnosis of Fabry's disease was based on serum
-galactosidase A activity and typical histological features from renal biopsy in the index patient. Genetic analysis of two hemizygous male patients revealed a missense mutation predicting a leucine to proline substitution (L14P) in the
-galactosidase gene causing classical Fabry's disease in this family. This is a novel point mutation not described previously in the literature and the second report describing novel genetic mutations for Fabry's disease in Chinese patients.
Conclusions. Fabry's disease is rare in Chinese patients but this diagnosis should be considered in patients with positive family history of kidney disease and relevant clinical features.
Keywords:
-galactosidase A; Chinese; Fabry's disease; genetic mutation
 |
Introduction
|
---|
Fabry's disease is an X-linked recessive inborn error of glycosphingolipid catabolism that results from the deficient activity of the lysosomal enzyme
-galactosidase A (EC 3.2.1.22). Because of abnormal catabolism of
-galactosyl-terminal lipids, there is accumulation of glycosphingolipid substrates such as globotriaosylceramide in the vascular endothelium causing occlusive microvascular diseases mainly affecting the kidney, heart, peripheral nerves and brain [1]. The classical phenotype manifests with angiokeratoma, acroparestheias, corneal opacities and hypohidrosis. The onset of symptoms in affected males occurs in childhood or adolescence. With advancing age, the intralysosomal accumulation of glycosphingolipids leads to death in the fourth or fifth decade of life. Atypical and milder Fabry variants show residual enzyme activity and late-onset cardiomyopathy. In patients with this cardiac form, single-base substitutions were detected in the upstream region of exon 6 of the
-galactosidase gene. The human
-galactosidase gene locus is in the X-chromosomal region Xq22, and its entire genomic sequence and full-length cDNA have been determined [2]. The 14 kb genomic sequence contains seven coding exons and 12 intronic Alu repetitive elements. The active enzyme is a glycosylated dimer made up of two 398 amino acid subunits.
Fabry's disease is rarely seen in the Oriental population. We present the clinical and genetic studies of Fabry's disease in a Chinese family. Mutation analysis of the
-galactosidase A gene, including the direct sequencing of all exons of the
-galactosidase A gene, identified a novel mutation in exon 1.
 |
Subjects and methods
|
---|
A 50-year-old female of southern Chinese origin with good past health presented with asymptomatic proteinuria that was detected incidentally during a routine body check. Her mother had died of kidney disease of unknown etiology. The patient had four siblings. One younger brother developed end-stage renal failure (ESRF) at the age of 35 years as a result of unknown etiology, and was treated with continuous ambulatory peritoneal dialysis. Cardiomyopathy had been diagnosed in another younger brother. Physical examination for the index patient did not reveal any skin lesion or corneal abnormality. Proteinuria amounted to 0.59 g in 24 h. The levels of serum creatinine and albumin were 0.92 and 39 g/l, respectively. Renal biopsy showed that the podocytes were packed with myelin bodies, suggestive of Fabry's disease. Serum
-galactosidase A activity was 5.2 nmol/ml/h (normal range 8.814.5 nmol/ml/h). The diagnosis was compatible with heterozygous Fabry's disease.
Investigations in the younger brother with ESRF showed markedly reduced serum
-galactosidase A activity of 0.07 nmol/ml/h, confirming the diagnosis of hemizygotic Fabry's disease. There were multiple angiokeratomata over the scrotal skin, but there was no history of acroparasthesia, or cardiovascular problems. Electrocardiogram (ECG) showed sinus rhythm, and echocardiogram showed satisfactory left ventricular systolic function with mild concentric left ventricular hypertrophy. After having been on peritoneal dialysis for 5 years, at the age of 41 years, he developed an episode of ischaemic stroke. A CT scan of the brain revealed an area of infarct over the right frontoparietal area.
The other younger brother, who had been given the diagnosis of cardiomyopathy but had defaulted medical attention, was called back for further investigation. He presented with bilateral lower limb swelling, acroparasthesia, hypohidrosis and itchy skin rash since the age of 33 years. Physical examination showed multiple eczematous skin plaques over the trunk with angiokeratomata and mild non-pitting edema over both legs, but there were no corneal deposits. He had normal blood pressure. Heart sounds were normal, but there was a grade 2/6 ejection systolic murmur at the apex. ECG showed sinus rhythm with left ventricular hypertrophy, T inversion over infero-lateral leads and ST elevation over V2 and V3 precordial leads suggestive of early repolarization changes. ECG showed mild concentric left ventricular hypertrophy with satisfactory function. Serum creatinine was 1.02 mg/dl and serum albumin was 43 g/l. Twenty-four hour urine protein excretion was 0.12 g. Serum
-galactosidase A activity was 0.23 nmol/ml/h, compatible with the diagnosis of hemizygous Fabry's disease.
The elder and younger sisters of the index patient were 53 and 39 years of age, both enjoying good past health all along. Physical examination was unremarkable with no skin lesions or corneal abnormalities in particular. Serum creatinine was 0.97 mg/dl, serum albumin was 46 g/l and serum
-galactosidase A activity was 18.7 nmol/ml/h for the elder sister while that of the younger sister were 0.85 mg/dl, 48 g/l and 27.2 nmol/ml/h, respectively. The serum
-galactosidase A activity was normal for both sisters, confirming that they were unaffected family members.
The two daughters of the index patient, who were 17 and 19 years old, were asymptomatic and there were no skin lesions or corneal abnormalities on physical examination. Serum
-galactosidase A activity of the elder daughter was 6.5 nmol/ml/h, suggestive of heterozygous Fabry's disease. No significant proteinuria or ECG abnormalities were detected for the elder sister. The younger daughter had normal
-galactosidase A activity of 10.9 nmol/ml/h. The clinical features and pedigree of this family are summarized in Table 1
and Figure 1
, respectively.
Genetic studies
Twenty mililitres of peripheral venous blood was obtained from each of the two hemizygous male patients with informed consent. The blood samples were collected into bottles containing EDTA. Genomic DNA was obtained. The
-galactosidase gene sequence was obtained from the European Bioinformatics Institute (EBI) of the European Molecular Biology Laboratory (EMBL) through its web site. The nucleotides were numbered according to EMBL-EBI accession number X14448. The gene has seven exons and is located in Xq22.1 (Figure 2
). The complete coding region including intronexon boundaries of the
-galactosidase gene was amplified from genomic DNA in six fragments by PCR. Table 2
shows the DNA primers used in this study. The numeral in the primer name denoted the exon being amplified. The PCR mixture consisted of 0.3 µM primers, 200 µM dNTP, 0.5 U of Taq DNA polymerase (Promega, Madison, WI, USA), and 50 ng of genomic DNA in a total 20 µl volume. Amplifications were performed for 35 cycles, each cycle consisting of denaturation at 9°C for 30 s, annealing at temperatures indicated in Table 2
and for 45 s, and extension at 72°C for 1 min. Figure 3
shows the amplification products after agarose gel electrophoresis.

View larger version (11K):
[in this window]
[in a new window]
|
Fig. 2. Idiogram of the human G-banded X-chromsome illustrating the position of band Xq22.1 and a map of -galactosidase (Gal) A indicating the relative positions and sizes of its seven exons.
|
|

View larger version (100K):
[in this window]
[in a new window]
|
Fig. 3. The PCR amplification products of the two patients and normal control after agarose gel electrophoresis.
|
|
DNA sequencing was performed using an ABI Prism 377 automated sequencer (PE Biosystems, Foster City, CA, USA) using DYEnamicTM ET terminator cycle sequencing kit (US81050) (Amersham Pharmacia Biotech, Auckland, New Zealand). DNA sequencing procedure was performed in both directions. Genomic DNA from normal subjects was used as control.
Direct DNA sequencing showed single T-to-C transition in codon 14 of exon 1. This was a missense mutation predicting a leucine to proline substitution (L14P). DNA sequences of the other exons were normal in both patients.
 |
Discussion
|
---|
Fabry's disease is a rare disease, mostly reported in Caucasians, with an incidence of 1:117 000 live births [3]. It is also uncommon in Asians, but the exact incidence and prevalence of Fabry's disease in the Oriental population have not been reported previously. Isolated case reports have come from Taiwan and Japan [47]. In one Japanese series of 230 patients the prevalence of atypical cardiac variant of Fabry's disease among male patients with left ventricular hypertrophy was 3% [8]. It is likely that the correct diagnosis of Fabry's disease might have been missed in some patients, as has occurred with the family members of our index patient. A high index of suspicion is therefore important, and a renal biopsy is mandatory in suggesting the correct diagnosis in the context of proteinuria and positive family history of kidney disease particularly when other signs of the disease are lacking in its early stages.
Clinical presentations of Fabry's disease can be variable, depending on the organ(s) affected. Patients with renal involvement may present with proteinuria or renal insufficiency. On the other hand, cardiac involvement may be associated with an incidental cardiac murmur, conduction system disease, ventricular hypertrophy, ischaemic heart disease or cardiomyopathy. The cause of ventricular hypertrophy was due to deposition of glycosphingolipids in cardiac myocytes and an absolute increase in the myocardial muscle mass. Acroparasthesia, with painful neuropathy affecting terminal digits, and hypohidrosis are also commonly seen. Bilateral ankle oedema, which occurred in one of our patients, is often due to lymphoedema secondary to lymph node infiltration by glycosphingolipids. Hypohidrosis can lead to secondary skin changes and the eczematous skin lesions. Other clinical features include angiokeratoma corporis diffusum, corneal opacities and increased risk of ischaemic stroke. It is interesting to note that phenotypic variations can occur with identical genetic mutation in the same family, as illustrated by the different clinical manifestations and severity of renal involvement in the two hemizygous brothers with comparable enzyme activities. Whether the heterogeneous manifestations can be attributed in part to environmental factors has not been determined, but it has been suggested that such phenotypic variations may also be related to different blood groups of affected individuals and patients with blood groups AB and B may have a more aggressive disease course due to a greater body substrate burden [9].
Because of the X-linked inheritance, male patients with Fabry's disease are predominantly affected, while female carriers can be asymptomatic or affected to a variable degree due to random inactivation of the X-chromosome. Various genetic defects have been reported, which include partial gene deletions, partial gene duplication, small deletion and insertion, splice junction consensus site alterations and single-base substitutions [9,10]. A single point mutation has been previously described in two Chinese patients with Fabry's disease [7]. In this report we have identified a novel point mutation (L14P) causing classical Fabry's disease in Chinese.
In conclusion, Fabry's disease is a rare but recognized disease in Chinese, which can present with kidney, cardiovascular or skin manifestations. In view of the genetic implications, clinicians should be alerted to this possibility, especially with a positive family history of relevant clinical features. The correct diagnosis can be promptly arrived at through the measurement of serum
-galactosidase A activity, and confirmed with typical histological features. Genetic analysis for specific genetic aberrations in the
-galactosidase gene may help understand the different phenotypic manifestations and may permit confirmation of heterozygous states in patients with less typical clinical or biochemical features and prenatal diagnosis of Fabry's disease.
 |
Acknowledgments
|
---|
The authors would like to thank Dr Joseph Lee (Department of Biochemistry, Queen Mary Hospital) for providing assay of serum
-galactosidase A activity.
 |
Notes
|
---|
Correspondence and offprint requests to: Prof. Tak-Mao Chan, Department of Medicine, Queen Mary Hospital, 102 Pokfulam Road, Hong Kong, People's Republic of China. Email: kctseqmh{at}sinatown.com 
 |
References
|
---|
- Brady RO, Schiffmann R. Clinical features of and recent advances in therapy for Fabry disease. J Am Med Assoc2002; 284:27712775[Abstract/Free Full Text]
- Calhoun DH, Bishop DF, Bernstein HS, Quinn M, Hantzopoulos P, Desnick RJ. Fabry disease: isolation of a cDNA clone encoding human
-galactosidase A. Proc Natl Acad Sci USA1985; 82:73647368[Abstract]
- Clague AE, Carey WF. Prevalence of lysosomal storage disorders. J Am Med Assoc1999; 281:249254[Abstract/Free Full Text]
- Chang HS, Ro LS, Chen ST, Tang LM, Hsiao KJ. Fabry's disease: report of a case. J Formos Med Assoc1995; 94:346350[ISI][Medline]
- Sheu SS, Chan LP, Liao SC et al. Fabry's disease: clinical, pathologic and biochemical manifestations in two Chinese males. Chung Hua I Hsueh Tsa Chih (Taipei)1994; 54:368372[Medline]
- Miyazaki T, Kajita M, Ohmori S et al. A novel mutation (E358K) in the
-galactosidase A gene detected in a Japanese family with Fabry disease. Hum Mutat 1998; Suppl 1:S139S140
- Chen CH, Shyu PW, Wu SJ, Desnick RJ, Hsiao KJ. Identification of a novel point mutation (S56T) in
-galactosidase A gene in Chinese patients with Fabry disease. Mutations in brief no. 169. Online. Hum Mutat1998; 11:328330[ISI][Medline]
- Nakao S, Takenaka T, Maeda M et al. An atypical variant of Fabry's disease in men with left ventricular hypertrophy. N Engl J Med1995; 333:288293[Abstract/Free Full Text]
- Pastores GM, Lien YH. Biochemical and molecular genetic basis of Fabry disease. J Am Soc Nephrol2002; 13:S130S133[Free Full Text]
- Eng CM, Desnick RJ. Molecular basis of Fabry disease: mutations and polymorphisms in the human
-galactosidase A gene. Hum Mutat1994; 3:103111[ISI][Medline]
Received for publication: 1. 6.02
Accepted in revised form: 15. 8.02