Ultrastructural study of renal involvement in two females with Anderson-Fabry disease

[Renal lesions in patients with Fabry's disease]

Kidney involvement is one of the main manifestations of Fabry's disease. In the absence of enzyme replacement therapy, hemizygous males and some heterozygous females progress to end stage renal failure. In hemizygous males, diffuse glycolipid accumulation is observed in all glomerular and vascular cells whereas distal tubular cells are focally involved. In heterozygous females, the glycolipid storage is irregular in glomeruli and vessels, some cells being massively involved, others being normal. In both sexes, degenerative changes occur, linked to the necrosis of overloaded mesangial and vascular smooth muscle cells. Their progression leads to unspecific arteriopathy and glomerulosclerosis not prone to reverse under enzymotherapy. Kidney biopsy is useful for confirming the diagnosis if clinical presentation of Fabry's disease is atypical. Moreover, histological analysis of renal tissue allows to assess the severity of degenerative changes and to evaluate the beneficial impact of enzyme replacement therapy.

Electron microscopy in end stage renal disease: a case of Fabry's disease

Fabry's disease is an X-linked error of metabolism with deficiency of the enzyme α-glycosidase A, and glycosphingolipid accumulation in multiple tissues. Patients may be asymptomatic and present with advanced disease. We report a case of a 38 year old white male who presented with end stage renal disease of unknown etiology. He received a living-related donor kidney transplant (mother), but lost the graft after 10 years to multiple episodes of rejection. Review of the native renal biopsy with added ultrastructural studies established the diagnosis of Fabry's disease. Evaluation of renal biopsies showing advanced chronic injury should include electron microscopic studies, which may reveal characteristic diagnostic features, as seen in this case of Fabry's disease. Identification of hereditary disorders involving the kidney is important for appropriate treatment and prevention of disease recurrence. Potential living related donors should be screened for genetic involvement.

Scoring system for renal pathology in Fabry disease: report of the International Study Group of Fabry Nephropathy (ISGFN)

BACKGROUND

In Fabry nephropathy, alpha-galactosidase deficiency leads to accumulation of glycosphingolipids in all kidney cell types, proteinuria and progressive loss of kidney function.

METHODS

An international working group of nephrologists from 11 Fabry centres identified adult Fabry patients, and pathologists scored histologic changes on renal biopsies. A standardized scoring system was developed with a modified Delphi technique assessing 59 Fabry nephropathy cases. Each case was scored independently of clinical information by at least three pathologists with an average final score reported.

RESULTS

We assessed 35 males (mean age 36.4 years) and 24 females (43.9 years) who mostly had clinically mild Fabry nephropathy. The average serum creatinine was 1.3 mg/dl (114.9 micromol/l); estimated glomerular filtration rate was 81.7 ml/min/1.73 m(2) and urine protein to creatinine ratio was 1.08 g/g (122.0 mg/mmol). Males had greater podocyte vacuolization on light microscopy (mean score) and glycosphingolipid inclusions on semi-thin sections than females. Males also had significantly more proximal tubule, peritubular capillary and vascular intimal inclusions. Arteriolar hyalinosis was similar, but females had significantly more arterial hyalinosis. Chronic kidney disease stage correlated with arterial and glomerular sclerosis scores. Significant changes, including segmental and global sclerosis, and interstitial fibrosis were seen even in patients with stage 1-2 chronic kidney disease with minimal proteinuria.

CONCLUSIONS

The development of a standardized scoring system of both disease-specific lesions, i.e. lipid deposition related, and general lesions of progression, i.e. fibrosis and sclerosis, showed a spectrum of histologic appearances even in early clinical stage of Fabry nephropathy. These findings support the role of kidney biopsy in the baseline evaluation of Fabry nephropathy, even with mild clinical disease. The scoring system will be useful for longitudinal assessment of prognosis and responses to therapy for Fabry nephropathy.

Vasculopathy in patients with Fabry disease: current controversies and research directions

Fabry disease is an X-linked lysosomal storage disorder due to deficiency of the enzyme alpha-galactosidase A. The principal clinical manifestations of Fabry disease consist of cardiovascular complications including cerebrovascular, renal and cardiac disease but the pathophysiology of this specific vasculopathy is unclear. With the development of targeted treatment for Fabry disease, i.e. enzyme replacement therapy, it has become apparent that the removal of stored glycosphingolipid from the endothelial cells does not prevent progression of vascular disease in many patients. The aim of this study is to review the current available literature on vascular function tests, imaging and pathology studies and propose a hypothesis on the evolution of arterial complications in Fabry disease. Clearly, although premature atherosclerosis is suggested to occur, most studies describe absence of characteristic plaque formation. Smooth muscle cell hypertrophy, is probably the earliest feature of a complex vasculopathy, as in females and atypical cardiac variants, who have residual enzyme activity, no endothelial storage of significance is found. Subsequently, processes occur as observed in neo intima formation however with formation of more fibrotic structures. In the presence of a hyperdynamic circulation in combination with a less compliant vascular wall, it is hypothesized that upregulation of local renin angiotensine systems may occur. Angiotensin II is known to increase adhesion molecules, cytokines and chemokines and exerts a pro-inflammatory effect on leucocytes, endothelial cells and vascular smooth muscle cells. This enhances release of pro-thrombotic factors and opposes actions mediated through angiotensin 2 (AT2) receptor, including the release of nitric oxide (NO). A combination of reduced vascular compliance and activation of pro-thrombotic factors can lead to vascular complications in Fabry disease.

A 4-year study of the efficacy and tolerability of enzyme replacement therapy with agalsidase alfa in 36 women with Fabry disease

PURPOSE

Although Fabry disease is X linked and considered to affect primarily male hemizygotes, female heterozygotes may experience all the signs and symptoms of this metabolic disorder. This prospective, single-center, open-label, clinical trial was performed to evaluate the long-term response of female patients with Fabry disease to enzyme replacement therapy.

METHODS

Symptomatic women (average age = 47 years) enrolled in this 4-year study were treated with agalsidase alfa (Replagal, Shire HGT, Inc.) at a dose of 0.2 mg/kg, every other week for 4 years (N = 36). Clinical and biochemical assessments were conducted at 12-month intervals.

RESULTS

The Mainz Severity Score Index, a measure of total disease burden, was significantly reduced after 12 months (P < 0.01) of treatment and continuously improved over 4 years. Brief Pain Inventory "pain at its worst" score was reduced from 4.6 +/- 2.9 at baseline to 3.3 +/- 2.9 after 12 months (P = 0.001) and remained reduced through 4 years. Mean left-ventricular mass decreased from 89.4 +/- 29.3(2.7) g/m at baseline to 66.5 +/- 29.3(2.7) g/m after 12 months (P < 0.001) and remained reduced through 4 years. Average kidney function (estimated glomerular filtration rate and proteinuria) remained constant during the study. No safety issues were identified.

CONCLUSIONS

Long-term agalsidase alfa is effective and was well tolerated in women with Fabry disease.

Kidney biopsy findings in heterozygous Fabry disease females with early nephropathy

Fabry disease is an X-linked glycosphingolipidosis caused by deficiency of alpha-galactosidase. Progressive chronic kidney disease (CKD) is a major cause of morbidity and mortality in males. Although 40% of heterozygous females may develop renal involvement, pathologic data on Fabry nephropathy in heterozygotes are scarce. We reviewed the kidney biopsies of four affected females who had normal to slightly sub-normal renal function, two of them with overt proteinuria. Chronic non-specific degenerative lesions and glycosphingolipid accumulation per cell type were semi-quantitatively assessed by light and electron microscopy. Cellular distribution of glycosphingolipid deposits was best assessed on semithin sections. Podocyte effacement was seen only in proteinuric patients. Combined analysis of our data with those of two earlier series showed that glomerular sclerosis and tubulointerstitial fibrosis are predictors of proteinuria and CKD stage. There was no histopathological evidence supporting a major role of vascular damage in the early pathogenesis of Fabry nephropathy in females.