Uncertain diagnosis of Fabry disease: consensus recommendation on diagnosis in adults with left ventricular hypertrophy and genetic variants of unknown significance.

BACKGROUND: Screening in subjects with left ventricular hypertrophy (LVH) reveals a high prevalence of Fabry disease (FD). Often, a diagnosis is uncertain because characteristic clinical features are absent and genetic variants of unknown significance (GVUS) in the α-galactosidase A (GLA) gene are identified. This carries a risk of misdiagnosis, inappropriate counselling and extremely expensive treatment. We developed a diagnostic algorithm for adults with LVH (maximal wall thickness (MWT) of >12 mm), GLA GVUS and an uncertain diagnosis of FD. METHODS: A Delphi method was used to reach a consensus between FD experts. We performed a systematic review selecting criteria on electrocardiogram, MRI and echocardiography to confirm or exclude FD. Criteria for a definite or uncertain diagnosis and a gold standard were defined. RESULTS: A definite diagnosis of FD was defined as follows: a GLA mutation with ≤ 5% GLA activity (leucocytes, mean of reference value, males only) with ≥ 1 characteristic FD symptom or sign (neuropathic pain, cornea verticillata, angiokeratoma) or increased plasma (lyso)Gb3 (classical male range) or family members with definite FD. Subjects with LVH failing these criteria have a GVUS and an uncertain diagnosis. The gold standard was defined as characteristic storage in an endomyocardial biopsy on electron microscopy. Abnormally low voltages on ECG and severe LVH (MWT>15 mm) <20 years exclude FD. Other criteria were rejected due to insufficient evidence. CONCLUSIONS: In adults with unexplained LVH and a GLA GVUS, severe LVH at young age and low voltages on ECG exclude FD. If absent, an endomyocardial biopsy with electron microscopy should be performed.

Uncertain diagnosis of fabry disease in patients with neuropathic pain, angiokeratoma or cornea verticillata: consensus on the approach to diagnosis and follow-up.

INTRODUCTION: Individuals with neuropathic pain, angiokeratoma (AK) and/or cornea verticillata (CV) may be tested for Fabry disease (FD). Classical FD is characterised by a specific pattern of these features. When a patient presents with a non-specific pattern, the pathogenicity of a variant in the α-galactosidase A (GLA) gene may be unclear. This uncertainty often leads to considerable distress and inappropriate counselling and treatment. We developed a clinical approach for these individuals with an uncertain diagnosis of FD. MATERIALS AND METHODS: A document was presented to an FD expert panel with background information based on clinical experience and the literature, followed by an online survey and a written recommendation. RESULTS: The 13 experts agreed that the recommendation is intended for individuals with neuropathic pain, AK and/or CV only, i.e. without kidney, heart or brain disease, with an uncertain diagnosis of FD. Only in the presence of FD-specific neuropathic pain (small fibre neuropathy with FD-specific pattern), AK (FD-specific localisations) or CV (without CV inducing medication), FD is confirmed. When these features have a non-specific pattern, there is insufficient evidence for FD. If no alternative diagnosis is found, follow-up is recommended. CONCLUSIONS: In individuals with an uncertain diagnosis of FD, the presence of an FD-specific pattern of CV, AK or neuropathic pain is sufficient to confirm the diagnosis of FD. When these features are non-specific, a definite diagnosis cannot (yet) be established and follow-up is indicated. ERT should be considered only in those patients with a confirmed diagnosis of FD.

A systematic review on screening for Fabry disease: prevalence of individuals with genetic variants of unknown significance.

Screening for Fabry disease (FD) reveals a high prevalence of individuals with α-galactosidase A (GLA) genetic variants of unknown significance (GVUS). These individuals often do not express characteristic features of FD. A systematic review on FD screening studies was performed to interpret the significance of GLA gene variants and to calculate the prevalence of definite classical and uncertain cases. We searched PubMed and Embase for screening studies on FD. We collected data on screening methods, clinical, biochemical and genetic assessments. The pooled prevalence of identified subjects and those with a definite diagnosis of classical FD were calculated. As criteria for a definite diagnosis, we used the presence of a GLA variant, absent or near-absent leukocyte enzyme activity and characteristic features of FD. Fifty-one studies were selected, 45 in high-risk and 6 in newborn populations. The most often used screening method was an enzyme activity assay. Cut-off values comprised 10-55% of the mean reference value for men and up to 80% for women. Prevalence of GLA variants in newborns was 0.04%. In high-risk populations the overall prevalence of individuals with GLA variants was 0.62%, while the prevalence of a definite diagnosis of FD was 0.12%. The majority of identified individuals in high-risk and newborn populations harbour GVUS or neutral variants in the GLA gene. To determine the pathogenicity of a GVUS in an individual, improved diagnostic criteria are needed. We propose a diagnostic algorithm to approach the individual with an uncertain diagnosis.