Mutations in the GLA Gene and LysoGb3: Is It Really Anderson-Fabry Disease?

Anderson-Fabry disease (FD) is a rare, progressive, multisystem storage disorder caused by the partial or total deficit of the lysosomal enzyme α-galactosidase A (α-Gal A). It is an X-linked, lysosomal enzymopathy due to mutations in the galactosidase alpha gene (GLA), encoding the α-Gal A. To date, more than 900 mutations in this gene have been described. In our laboratories, the study of genetic and enzymatic alterations related to FD was performed in about 17,000 subjects with a symptomatology referable to this disorder. The accumulation of globotriaosylsphingosine (LysoGb3) was determined in blood of positives. Exonic mutations in the GLA gene were detected in 471 patients (207 Probands and 264 relatives): 71.6% of mutations were associated with the classic phenotype, 19.8% were associated with the late-onset phenotype, and 8.6% of genetic variants were of unknown significance (GVUS). The accumulation of LysoGb3 was found in all male patients with a mutation responsible for classic or late-onset FD. LysoGb3 levels were consistent with the type of mutations and the symptomatology of patients. α-Gal A activity in these patients is absent or dramatically reduced. In recent years, confusion about the pathogenicity of some mutations led to an association between non-causative mutations and FD. Our study shows that the identification of FD patients is possible by associating clinical history, GLA gene analysis, α-Gal A assay, and blood accumulation of LysoGB3. In our experience, LysoGB3 can be considered a reliable marker, which is very useful to confirm the diagnosis of Fabry disease.

Fabry disease and multiple sclerosis misdiagnosis: the role of family history and neurological signs.

Fabry disease (FD) is an X-linked inherited lysosomal storage disorder caused by α galactosidase A (α-gal A) deficiency. Central nervous system involvement and chronic white matter lesions are observed in both FD and multiple sclerosis (MS), which can confound the differential diagnosis. We analyzed the GLA gene, which encodes α-gal A, in 86 patients with clinical and neuroradiological findings consistent with MS to determine whether they had FD. We identified four women initially diagnosed with MS who had GLA mutations associated with FD. Our results indicate that family history besides neurological findings should be evaluated in patients with an uncertain diagnosis of MS. Also the involvement of organs outside the central nervous system can support the FD diagnosis.

Metformin-related lactic acidosis: is it a myth or an underestimated reality?

Metformin, belonging to a class of drugs called biguanides, is the recommended first-line treatment for overweight patients with type 2 diabetes mellitus. It has multiple mechanisms of action, such as reduction of gluconeogenesis, increases peripheral uptake of glucose, and decreases fatty acid oxidation. However, a potential serious complication, defined metformin-associated lactic acidosis (MALA), is related to increased plasma lactate levels, linked to an elevated plasma metformin concentrations and/or a coexistent condition altering lactate production or clearance. The mortality rate for MALA approaches 50% and metformin has been contraindicated in moderate and severe renal impairment, to minimize its potential toxic levels. Nevertheless, metformin prescription or administration, despite the presence of contraindications or precipitating factors for MALA, was a common topic highlighted in all reviewed papers. Routine assessment of metformin plasma concentration is not easily available in all laboratories, but plasma metformin concentrations measured in the emergency room could ensure the correct diagnosis, eliminating metformin as the cause of lactic acidosis if low plasma levels occurred. Renal replacement therapies have been successfully employed to achieve the correction of metabolic acidosis and rapidly remove metformin and lactate, but the optimal treatment modality for MALA is still controversial.

[Periorbital purpura: a pathognomonic but late sign of AL amyloidosis]. / Porpora periorbitaria: un segnale patognomonico ma tardivo di amiloidosi AL.

INTRODUCTION: AL amyloidosis is the most common type of systemic amyloidosis and is caused by the deposition of an amyloidogenic protein composed of immunoglobulin light chains produced by a clonal population of plasma cells. CASE REPORT: We report the case of a 77-year-old woman with arterial hypotension, peripheral edema and renal failure. Electrocardiogram reveals low voltage on peripheral leads. Echocardiogram shows normal values for left ventricle size with increased wall thickness and cardiac wall reflectance with ground glass appearance. Serum immunofixation electrophoresis (IFE) is negative while urine IFE detects type monoclonal light chains. Abdominal Fat Pad biopsy is positive for Congo red with typical apple green birefringence after polarization under optical microscopy (OM) while ultrastructural analysis does not show presence of amyloid deposition. Two months later, the patient undergoes further worsening of general clinical condition and development of purpura in the periorbital area, at the base of the neck and in the anterior chest wall. DISCUSSION: This clinical case presents classic signs of AL amyloidosis, such as cardiac and renal involvement with the presence of a urine monoclonal component. Periorbital purpura is a pathognomonic sign of AL amyloidosis but it appears late. Final diagnosis is "AL amyloidosis with prevalent cardiac, renal and soft tissue involvement".

Anderson-Fabry disease: a protean clinical behavior and a chance diagnosis.

Anderson-Fabry disease is a rare inborn X-linked glycosphingolipid storage disorder in which the deficient activity of the enzyme alfa-galactosidase A (alfa-gal A) leads to the progressive tissular accumulation of lipidic molecules which, in turn, cause a protean pattern of multi-organ disfunction. Enzyme replacement therapy has recently become available and has proved to be effective in controlling the disorder. We present and discuss the case of a family with this disease, with special attention to the variability of clinical features and the difficulty of a correct diagnosis.