Machtelt G. Bouwman

Plasma globotriaosylsphingosine: Diagnostic value and relation to clinical manifestations of Fabry disease

Fabry disease is an X-linked lysosomal storage disorder due to deficiency of alpha-Galactosidase A, causing accumulation of globotriaosylceramide and elevated plasma globotriaosylsphingosine (lysoGb3). The diagnostic value and clinical relevance of plasma lysoGb3 concentration was investigated. All male and adult female patients with classical Fabry disease could be discerned by an elevated plasma lysoGb3. In young pre-symptomatic Fabry heterozygotes, lysoGb3 levels can be normal. Individuals carrying the R112H and P60L mutations, without classical Fabry symptoms, showed no elevated plasma lysoGb3. Multiple regression analysis showed that there is no correlation of plasma lysoGb3 concentration with total disease severity score in Fabry males. However, plasma lysoGb3 concentration did correlate with white matter lesions (odds ratio: 6.1 per 100 nM lysoGb3 increase (95% CI: 1.4-25.9, p=0.015). In females, plasma lysoGb3 concentration correlated with overall disease severity. Furthermore, plasma lysoGb3 level was related to left ventricular mass (19.5+/-5.5 g increase per 10 nM lysoGb3 increase; p=0.001). In addition, it was assessed whether lifetime exposure to lysoGb3 correlates with disease manifestations. Male Fabry patients with a high lysoGb3 exposure (>10,000 U), were moderately or severely affected, only one mildly. Female patients with a low exposure (<1000 U) were asymptomatic or mildly affected. A large proportion of the females with an exposure >1000 U showed disease complications. Plasma lysoGb3 is useful for the diagnosis of Fabry disease. LysoGb3 is an independent risk factor for development of cerebrovascular white matter lesions in male patients and left ventricular hypertrophy in females. Disease severity correlates with exposure to plasma lysoGb3.

Screening for Fabry disease in high risk populations: a systematic review

Introduction Fabry disease (FD) may present with left ventricular hypertrophy (LVH), renal insufficiency or stroke. Several studies investigated FD prevalence in populations expressing these symptoms. A systematic review was conducted to calculate the overall prevalence of FD in these cohorts. Methods Online databases were searched for studies on screening for FD. Study population selection, screening methods and outcome of screening were recorded. Results 20 studies were identified, 10 of which included both male and female patients. In all (n=19) studies with male and almost all (n=10) with female patients, α-galactosidase A (α-Gal A) activity was used as the screening method. In men on dialysis (10 studies), overall FD prevalence was 0.33% (95% CI 0.20% to 0.47%) and in women (6 studies) 0.10% (95% CI 0% to 0.19%). Combined prevalence of FD in patients with renal transplant was 0.38% in men (95% CI 0.07% to 0.69%) and 0% in women. In patients with LVH, selection of study population and differences in the method of screening hampered the calculation of an overall prevalence (ranging from 0.9% to 3.9% in men and 1.1% to 11.8% in women). In premature strokes (n=2 studies), overall FD prevalence was 4.2% (95% CI 2.4% to 6.0%) in men and 2.1% (95% CI 0.5% to 3.7%) in women. Discussion The prevalence of FD in dialysis patients is 0.33% for men and 0.10% for women. The prevalence of FD in LVH is at least 1% for both genders. In women, most studies were performed with α-Gal A activity measurements as the screening tool, although this method fails to detect one third of female patients with FD, underestimating the overall prevalence in women.

Long term enzyme replacement therapy for Fabry disease: effectiveness on kidney, heart and brain

BackgroundFabry disease is an X-linked lysosomal storage disorder caused by α-galactosidase A deficiency leading to renal, cardiac, cerebrovascular disease and premature death. Treatment with α-galactosidase A (enzyme replacement therapy, ERT) stabilises disease in some patients, but long term effectiveness is unclear.MethodsRenal, cardiac, and cerebral outcomes were prospectively studied in males and females with Fabry disease treated with ERT. Additionally, the occurrence of major cardiac events, stroke, end-stage renal disease and death was compared to a natural history (NH) cohort meeting treatment criteria.ResultsOf 75 patients on ERT (median treatment duration 5.2 years, range 0.05-11.0), prospective follow-up was available for 57 adult patients (30 males) and 6 adolescents. Renal function declined in males (-3.4 ml/min/1.73 m2 per year, SE 0.2; p < 0.001) despite ERT, but followed the normal course in females (-0.8 ml/min/1.73 m2 per year, SE 0.3; p = 0.001). Cardiac mass increased during ERT in males (+ 1.2 gram/m2.7, SE 0.3; p < 0.001), but remained stable in females (-0.3 gram/m2.7 per year, SE 0.4; p = 0.52). ERT did not prevent the occurrence of cerebral white matter lesions. Comparison of ERT treated to untreated patients revealed that the odds to develop a first complication increased with age (OR 1.05 (95% CI: 1.0-1.1) per year, p = 0.012). For development of a first or second complication the odds declined with longer treatment duration (OR 0.81 (95% CI: 0.68-0.96) per year of ERT, p = 0.015;OR 0.52 (0.31-0.88), p = 0.014 respectively).ConclusionsLong term ERT does not prevent disease progression, but the risk of developing a first or second complication declines with increasing treatment duration. ERT in advanced Fabry disease seems of doubtful benefit.

'Doctor Google' ending the diagnostic odyssey in lysosomal storage disorders: parents using internet search engines as an efficient diagnostic strategy in rare diseases.

The expansion of the internet has resulted in widespread availability of medical information for both patients and physicians. People increasingly spend time on the internet searching for an explanation, diagnosis or treatment for their symptoms. Regarding rare diseases, the use of the internet may be an important tool in the diagnostic process. The authors present two cases in which concerned parents made a correct diagnosis of a lysosomal storage disorder in their child by searching the internet after a long doctors delay. These cases illustrate the utility of publicly available internet search engines in diagnosing rare disorders and in addition illustrate the lengthy diagnostic odyssey which is common in these disorders.

Experiences of parents and patients with the timing of Mucopolysaccharidosis type I (MPS I) diagnoses and its relevance to the ethical debate on newborn screening

INTRODUCTION Newborn screening (NBS) techniques have been developed for several lysosomal storage disorders (LSDs), including Mucopolysaccharidosis type I (MPS I). MPS I is an LSD with a wide phenotypic spectrum that ranges from the severe Hurler phenotype to the attenuated Scheie phenotype. To improve the ethical discussion about NBS for MPS I, we performed an interview study to explore the experiences of MPS I patients and their parents with the timings of their diagnoses. METHODS We used a qualitative research approach consisting of 17 interviews with the parents of patients with all MPS I phenotypes and with patients with attenuated forms of MPS I. The interviews were audio-recorded, transcribed and subsequently analyzed to identify the main themes identified by the participants. RESULTS Five important themes, focusing on the experienced disadvantages of delayed diagnosis and the advantages and disadvantages of a hypothetical earlier diagnosis, were identified in our group of participants: 1) delayed diagnosis causing parental frustration, 2) delayed diagnosis causing patient frustration, 3) early diagnosis enabling reproductive decision-making, 4) early diagnosis enabling focusing on the diagnosis, and 5) early diagnosis enabling timely initiation of treatment. There was a remarkable similarity in the experiences with timing of diagnosis between parents of patients with the severe and the attenuated forms. CONCLUSION This was the first study to explore the personal experiences of MPS I patients and their parents with diagnostic timing. Our study identified five important themes that are highly relevant to the ethical discussion on expanding NBS programs for MPS I.

Prevalence of symptoms in female Fabry disease patients: a case-control survey

BackgroundFabry disease (FD) is an X-linked lysosomal storage disorder, caused by a deficiency of α-galactosidase A. Several studies demonstrated that heterozygotes have symptoms such as acroparesthesia, abdominal pain and chronic fatigue. However, as these symptoms are aspecific and relatively common in the general population, it is important to compare the prevalence of these symptoms with an appropriate control group. The aim of this study was to explore the prevalence of signs and symptoms in FD females in comparison to a control group.MethodsFD females and age-matched controls were approached to complete a questionnaire. This questionnaire was developed by the Dutch Fabry patient organisation (Fabry Support en Informatie Groep Nederland, FSIGN) with input from Fabry expert-physicians from the AMC. We compared the prevalence symptoms using Pearson’s chi-square test. Bonferroni correction was used to correct for multiple comparisons.ResultsA total of 63 heterozygotes and 52 controls completed the questionnaire. Many symptoms were also common in controls. Yet, fatigue, palpitations, pains in hands and feet, joint pain, dizziness, loss of libido and proteinuria during pregnancy were more common in Fabry females (all p < 0.001).ConclusionIn addition to acroparesthesia - fatigue, palpitations, dizziness, proteinuria during pregnancy, libido loss and joint pain are more prevalent in FD females as compared to a control group. Although, these symptoms are present in a significant proportion of normal controls they deserve further attention by treating physicians to better understand their significance, treatment and relationship with FD.

Early cerebral manifestations in a young female with Fabry disease with skewed X-inactivation.

To the Editor : Fabry disease (FD) is an X-linked lysosomal storage disorder caused by deficiency of the enzyme alpha-galactosidase A (αGal A). Accumulation of globotriaosylceramide (Gb3) in different cell types eventually leads to renal insufficiency, cardiomyopathy and central nervous system (CNS) involvement (1). CNS involvement is mainly characterized by white matter lesions (WMLs) and strokes (2, 3). Several cohort studies revealed that females with FD often do develop clinical manifestations, although the disease generally follows a milder course (4–7). WMLs and strokes have been reported in young males with FD (8–10), but not in young females. In this letter, we report the enzymatic, biochemical and molecular characteristics of a young female patient with FD who had signs of CNS involvement from the very early age of 13 years. The proband was the patient’s grandmother, diagnosed with FD after the evaluation of unexplained renal insufficiency. Patient’s aunt, mother and sister were subsequently also diagnosed with FD. The patient had several early signs and symptoms of FD: minor acroparesthesia during exercise, a few angiokeratoma on the trunk, cornea verticillata and bilateral high-frequency hearing loss. Renal and cardiac assessments were normal. Brain magnetic resonance imaging (MRI) at the age of 15 years showed a 4-mm periventricular WML on T2 and fluid-attenuated inversion recovery (FLAIR) images near the right posterior horn (Fig. 1a). In retrospect, this lesion was already present on the MRI performed at the age of 13 years. Intravenous enzyme replacement and antiplatelet therapy was started. One year later, a hemorrhagic infarction was present in the left globus pallidus (Fig. 1b) without any symptoms. Risk factors for cardiovascular disease only revealed a history of cigarette smoking. Fibrinogen, clotting factor VIII, antithrombin deficiency, lupus anticoagulant, factor II mutation, factor V Leiden mutation, protein (a) (b)

Analysis of Placental Tissue in Fabry Disease With and Without Enzyme Replacement Therapy

There are only a few reports on the histology of placental tissue of pregnancies from mothers with Fabry disease. Fabry disease is a lysosomal disorder caused by alpha-galactosidase A deficiency. Extensive glycosphingolipid (GSL) accumulation in fetal and maternal placenta tissue obtained from a Fabry mother and her affected male newborn has previously been reported. Here we report the evaluation of placenta tissue of two pregnancies in Fabry mothers, one of an unaffected male newborn (placenta A) and one of an affected female newborn (placenta B). The mother of the female affected offspring was treated with recombinant alpha-galactosidase A (enzyme replacement therapy, ERT) during the pregnancy (placenta B). Storage material was only detected in smooth muscle cells of the umbilical cord of placenta B. No accumulation was seen in both placentae. Combing these results with the outcome in two earlier described placentae, a heterogeneous picture emerges. This may be due to differences in disease severity in the mothers or severity of disease in their offspring. In addition, a possible effect of ERT on placental GSL accumulation could also explain lack of GSL storage in placenta B.