Heterozygote detection in Fabry disease utilizing multiple enzyme activities

Altered globotriaosylceramide accumulation and mucosal neuronal fiber density in the colon of the Fabry disease mouse model

BACKGROUND

Fabry disease (FD) is a hereditary X-linked metabolic storage disorder characterized by deficient or absent lysosomal α-galactosidase A (α-Gal A) activity. This deficiency causes progressive accumulation of glycosphingolipids, primarily globotriaosylceramide (Gb3), in nearly all organ systems. Gastrointestinal (GI) symptoms can be very debilitating and are among the most frequent and earliest of the disease. As the pathophysiology of these symptoms is poorly understood, we carried out a morphological and molecular characterization of the GI tract in α-Gal A knockout mice colon in order to reveal the underlying mechanisms.

METHODS

Here, we performed the first morphological and biomolecular characterization of the colon wall structure in the GI tract of the α-Gal A knock-out mouse (α-Gal A -/0), a murine model of FD.

KEY RESULTS

Our data show a greater thickness of the gastrointestinal wall in α-Gal A (-/0) mice due to enlarged myenteric plexus' ganglia. This change is paralleled by a marked Gb3 accumulation in the gastrointestinal wall and a decreased and scattered pattern of mucosal nerve fibers.

CONCLUSIONS AND INFERENCES

The observed alterations are likely to be a leading cause of gut motor dysfunctions experienced by FD patients and imply that the α-Gal A (-/0) male mouse represents a reliable model for translational studies on enteropathic pain and GI symptoms in FD.

Kidney Transplantation Improves Survival and Is Indicated in Fabry’s Disease

BACKGROUND

Fabry's disease (FD) is an inborn error of glycosphingolipid catabolism with progressive systemic deposition of globotriaosylceramide thereby leading to renal and cardiac failure. Current therapy involves symptomatic medical management, dialysis, enzyme replacement therapy, kidney transplantation (KTx), and more recently gene therapy. Case fatalities occur in the fourth decade of life resulting from uremia unless dialysis or KTx is undertaken.

STUDY DESIGN

This is a retrospective study aimed at determining the effect of KTx on the long-term outcome of patients with FD.

RESULTS

Between 1964 and 1998, ten patients with FD received KTx at our institutions. Actuarial patient and graft survivals were 100% and 90% at 5 years; 76% and 66% at 10 years. One kidney graft was lost due to rejection. Patient survival data compared favorably at 5 years with survival of FD patients on hemodialysis alone (41%, P < .05). Five patients are alive at the time of this study, and five patients died with median survival time after KTx of 128 months (range: 74-160 months).

CONCLUSIONS

This study demonstrates an excellent outcome in patients with FD in the first decade after KTx. In the absence of a severe contraindication, we advocate KTx to improve the overall prognosis of patients with renal failure due to FD. Based on the data, enzyme replacement therapy after KTx seems indicated, as FD progresses posttransplant, leading to case fatalities in the second decade after KTx.

Urinary lipid profiling for the identification of fabry hemizygotes and heterozygotes

BACKGROUND

Fabry disease is an X-linked lysosomal storage disorder resulting from a deficiency of the lysosomal hydrolase, alpha-galactosidase, for which enzyme replacement therapy is now available. In this study, we aimed to identify Fabry heterozygotes not only for genetic counseling of families but because it is becoming increasingly obvious that many heterozygous (carrier) females are symptomatic and should be considered for treatment.

METHODS

We measured 29 individual lipid species, including ceramide, glucosylceramide, lactosylceramide, and ceramide trihexoside, in urine samples from Fabry hemizygotes and heterozygotes and from control individuals by electrospray ionization tandem mass spectrometry. Individual analyte species and analyte ratios were analyzed for their ability to differentiate the control and patient groups.

RESULTS

The Fabry hemizygotes had increased concentrations of the substrate for the deficient enzyme, ceramide trihexoside, as well as lactosylceramide and ceramide, along with decreased concentrations of both glucosylceramide and sphingomyelin. Ratios of these analytes improved differentiation between the control and Fabry groups, with the Fabry heterozygotes generally falling between the Fabry hemizygotes and the control group.

CONCLUSIONS

These lipid profiles hold particular promise for the identification of Fabry individuals, may aid in the prediction of phenotype, and are potentially useful for the monitoring of therapy in patients receiving enzyme replacement.

Remarkable variability in renal disease in a large Slovenian family with Fabry disease

Following the diagnosis of Fabry disease in a 45-year-old male, in 31 family members alpha-galactosidase A (alpha-Gal) activity in leucocytes was measured and mutation analysis of the alpha-Gal gene was performed. In the proband, the unique mutation A10523G/N272S in exon 6 was found, which was subsequently detected in seven males (of which one twin) and 10 female subjects. All males showed decreased to absent alpha-Gal A activity in leucocytes, but three out of 10 female subjects had alpha-Gal A activities within normal range. Although all male patients had symptoms of classical Fabry disease, such as acroparesthesias, hypohydrosis and heat-intolerance, there was considerable variability in organ involvement, especially in deterioration of renal function. Detailed studies of large families with Fabry disease may give insight into factors that influence the phenotype of this disorder.

Molecular genetic, biochemical, and clinical studies in three families with cardiac Fabry's disease

The variant form of Fabry's disease, called cardiac Fabry's disease, which has left ventricular hypertrophy as its main clinical manifestation is not uncommon. Because there has been no pedigree analysis in families with cardiac Fabry's disease, we performed gene analyses, enzyme assays, and cardiac evaluations in 3 distinct families with cardiac Fabry's disease. Gene analyses were performed in all 18 members of 3 families including 3 male probands. Five hemizygotes and 6 heterozygotes were identified. Plasma alpha-galactosidase A activity was measured in all 18 family members. Echocardiography and electrocardiography were performed in the 5 hemizygotes and in 5 of the 6 heterozygotes. The proband and 3 heterozygotes from a pedigree with a mutation in exon 6 of the alpha-galactosidase A sequence leading to a Met296Ile substitution showed a decrease in alpha-galactosidase A activity. In a separate pedigree, a proband and his hemizygous brother, with a mutation in exon 2 leading to a Glu66Gln substitution, had a decrease in alpha-galactosidase A activity, whereas 3 heterozygotes had normal values. In the third pedigree, a decrease in alpha-galactosidase A activity was observed in 2 hemizygotes who have a mutation in exon 1 leading to an Ala2OPro substitution. Although all 5 hemizygotes exhibited left ventricular hypertrophy on echocardiography, all 5 heterozygotes lacked this finding. Because plasma alpha-galactosidase A activity was normal in some heterozygotes with cardiac Fabry's disease, gene analysis is essential for an accurate diagnosis. Patients with cardiac Fabry's disease thus show an x-linked form of hypertrophic cardiomyopathy.

A Fabry's disease heterozygote with a new mutation: biochemical, ultrastructural, and clinical investigations

A Fabry heterozygote with early clinical manifestations of this X linked disorder is described. Her symptoms, including febrile attacks, arthralgia, abdominal pain, and neurological signs, were characteristic of Fabry's disease hemizygotes. The neurological findings were compatible with a brain stem infarction. The diagnosis was confirmed by the finding of low activities of alpha-galactosidase A (alpha-galA) in plasma, lymphocytes, and cultured fibroblasts, and by the observation of typical lamellar inclusions in the lysosomes of cultured fibroblasts. Increased levels of ceramide trihexoside were also found by TLC of urine sediment. The family history gave no indication of Fabry's disease in the patient's relatives, and biochemical and ultrastructural investigations of their cells were also normal. Our findings therefore suggest that the defective gene in the heterozygote has resulted from a new mutation.

Corneal changes in Fabry's disease: a clinico-pathologic case report of a heterozygote

Fabry's disease is an X-linked recessive inborn error of metabolism, caused by a deficiency of alpha galactosidase A. This report describes a heterozygote patient with multiple system problems diagnosed eventually as Fabry's disease by the ocular findings. The clinical diagnosis was confirmed by enzymatic assay. Our report emphasizes: The variability of the non-ocular manifestations in the heterozygote of Fabry's disease. The diagnosis of Fabry's disease in our patient was made by the ophthalmologist. The ultra-structural changes in the cornea and conjunctiva of the heterozygote confirm those reported in the literature; in addition we describe changes in the goblet cells. The clinical and ultra-structural similarities of the deposits in Fabry's disease, Chloroquin keratopathy and Amiodarone keratopathy are striking and will be discussed.

Metabolism of ceramide trihexoside in cultured skin fibroblasts from Fabry's patients, carriers and normal controls

The metabolism of ceramide trihexoside (CTH) was studied in cultured skin fibroblasts from Fabry's patients, carriers, and controls. The in vitro activities of alpha-galactosidase in fibroblasts using either artificial substrate or CTH led to a clear identification of 4 Fabry's patients, 6 carriers and 8 controls. Normal findings were noted in one carrier. In fibroblasts from Fabry's patients, the residual activities assayed with CTH were less than those with the artificial substrate. In the CTH-loading test, the incorporation and hydrolysis of CTH in the fibroblasts were closely related with the culture time and CTH-concentration in the medium. With 0.5 nmol CTH per flask (25 cm2 growth area, 3 ml of medium), the hydrolysis rate of CTH, based on its incorporation, was 2.1% in fibroblasts from 4 Fabry's patients, 82.0% in 10 controls and 47.1% in 6 out of 7 carriers on the 7th day of culture. The impaired hydrolysis in carriers' fibroblasts differs from the hydrolysis noted in fibroblasts from carriers of autosomal recessive sphingolipidoses with a normal hydrolysis. These findings explain that some of the carriers show clinical symptoms and a mild accumulation of CTH in their tissues, such as seen in Fabry's patients. In one carrier there was a normal hydrolysis of CTH, both in vitro and in the CTH-loading study. This may be explained by Lyon's random X-chromosome inactivation theory.

Electrocardiograms in Fabry's disease

We studied the ECGs of 47 kindred members from three families with Fabry's disease. The control group (19) with normal plasma alpha-galactosidase levels had normal ECGs. Of the 12 affected males (mean age 15 years, plasma alpha-galactosidase levels less than 10% of normals), ten had ECG evidence of LVH, and five had ST-T wave changes. The conduction time of the cardiac impulse was accelerated (decreased PR index) in one male. Of the 16 heterozygous females (mean age 19 years, plasma alpha-galactosidase level and alpha/beta galactosidase ratio in the carrier range) none had ECG evidence of LVH, but six had conduction abnormalities--decreased PR index (four) and delayed conduction (two). The ECG abnormalities were uniformly distributed in different age groups.