Long-read single molecule real-time (SMRT) sequencing of GBA1 locus in Gaucher disease national cohort from Argentina reveals high frequency of complex allele underlying severe skeletal phenotypes: Collaborative study from the Argentine Group for Diagnosis and Treatment of Gaucher Disease

Gaucher disease is reckoned for extreme phenotypic diversity that does not show consistent genotype/phenotype correlations. In Argentina, a national collaborative group, Grupo Argentino de Diagnóstico y Tratamiento de la Enfermedad de Gaucher, GADTEG, have delineated uniformly severe type 1 Gaucher disease manifestations presenting in childhood with large burden of irreversible skeletal disease. Here using Long-Read Single Molecule Real-Time (SMRT) Sequencing of GBA1 locus, we show that RecNciI allele is highly prevalent and associates with severe skeletal manifestations in childhood.

Incidental finding of cornea verticillata or lamellar inclusions in kidney biopsy: measurement of lyso-Gb3 in plasma defines between Fabry disease and drug-induced phospholipidosis

INTRODUCTION

Therapy with cationic amphiphilic drugs (Amiodarone or hydroxychloroquine) may result in biochemically and ultrastructurally similar lipid inclusions in many cells also affected by Fabry disease (FD). In addition, it often results in similar clinical manifestations such as cornea verticillata. This may lead to a FD misdiagnosis, especially when a complete medical history is not available to the ophthalmologist confronted with cornea verticillata or to the pathologist examining a kidney biopsy. When enzymatic/genetic test or pathological studies are not conclusive, a specific biomarker may help clarify this dilemma. The plasma globotriaosylsphingosine (lyso-Gb3) assay has high sensitivity and specificity and is elevated above normal levels in FD.

MATERIALS AND METHODS

We measured plasma lyso-Gb3 levels in male patients receiving Amiodarone or hydroxychloroquine and compared it with male patients with classic and late onset variant of FD.

RESULTS

In all Fabry patients (classic and late onset variant) α-GalA activity was deficient in dried blood spot and plasma lyso-Gb3 was above normal levels. Patients on treatment with Amiodarone or hydroxychloroquine had normal values for α-GalA activity and lyso-Gb3 in plasma.

CONCLUSIONS

Even when Amiodarone or hydroxychloroquine may decrease α-GalA activity in vitro or in cell culture, our results showed that in all patients lyso-Gb3 plasma levels remain normal with no evidence of reduction in α-GalA activity, confirming the specificity of this biomarker for the diagnosis of FD.

Clinical parameters, LysoGb3, podocyturia, and kidney biopsy in children with Fabry disease: is a correlation possible?

BACKGROUND

Fabry disease is an X-linked lysosomal storage disorder caused by α-galactosidase enzyme deficiency. We present clinical, biochemical, and histologic findings in children with classical phenotypic presentation of Fabry disease.

METHODS

A retrospective analysis was performed using charts from 14 children with confirmed diagnosis. Clinical parameters were evaluated. Globotriaosylsphingosine -lysoGb3- detection in plasma, podocyturia, and kidney biopsy were carried out in all cases.

RESULTS

All patients except one demonstrated at least one symptom of Fabry disease. LysoGb3 levels were above the normal range in all patients. Podocyturia was documented in all patients. Kidney biopsy revealed glomerular, interstitial, vascular, and tubular changes on light microscopy in nearly all patients. Electron microscopy showed podocyte inclusions in all patients.

CONCLUSIONS

No difference in symptomatology was discernible between boys and girls. Podocyturia was detectable in children serving as a possible early marker of kidney injury. LysoGb3 was elevated in all cases, emphasizing the importance for diagnosis especially in female patients with normal αGal A activity. A possible association between lysoGb3 and symptom severity and histological involvement in kidney biopsy should be assessed in prospective studies with enough statistical power to determine if lysoGb3 can be used to predict nephropathy in children with Fabry disease.