Gaucher disease: when molecular testing and clinical presentation disagree -the novel c.1226A>G(p.N370S)--RecNcil allele.

We report a 31 year old woman who had prenatal carrier screening for Ashkenazi Jewish (AJ) genetic diseases and was found to have two acid ß-glucosidase (GBA) mutations, c.1226A>G(p.N370S) and c.1448T>C(p.L444P), consistent with the diagnosis of Type 1 Gaucher disease (GD1). This genotype typically manifests in late-adolescence with hepatosplenomegaly and early-onset bone involvement. The Proband had a normal physical examination, no organomegaly, and normal blood counts, skeletal survey, and bone density. Leukocyte acid ß-glucosidase and plasma chitotriosidase activities were normal. To investigate these unexpected results, her GBA alleles were RT-PCR amplified and sequenced. Five RT-PCR clones were negative for both mutations, while five clones had the c.1226A>G(p.N370S) and c.1448T>C(p.L444P) mutations, along with c.1483G>C(p.A456P), and c.1497G>C(p.V460V) mutations, the latter three lesions composing the rare GBA pseudogene-derived RecNcil allele. Genetic testing misdiagnosed the asymptomatic Proband as affected with Type 1 Gaucher disease; however, molecular studies revealed a novel allele with the two common GBA mutations on the RecNcil background. This allele presumably arose by crossing-over between a c.1226A>G allele and the pseudogene, gene conversion, or a new c.1226A>G mutation on the RecNcil background. This novel complex allele highlights a limitation of carrier screening for GD.

Frequency of unrecognized Fabry disease among young European-American and African-American men with first ischemic stroke.

BACKGROUND AND PURPOSE: The cause of initial ischemic stroke in up to 30% of young patients remains unclear. Fabry disease, due to deficient alpha-galactosidase A (alpha-Gal A) activity, is a vascular endothelial glycosphingolipid storage disease typically presenting in childhood. With advancing age, patients develop renal, cardiac, and cerebrovascular disease and die prematurely. A European study suggested an increased prevalence of unrecognized Fabry disease in patients with cryptogenic stroke. We hypothesized that alpha-Gal A deficiency is a rare cause of initial early-onset ischemic stroke in men. METHODS: The Stroke Prevention in Young Men Study enrolled >550 men (15 to 49 years) with first ischemic stroke in the Baltimore-Washington area in 2004 to 2007. Frozen plasma samples were assayed for alpha-Gal A activity, and DNA from patients with consistently low plasma alpha-Gal A activities were sequenced. RESULTS: The study sample consisted of 558 men (42% African-American; median age 44 years). Stroke was cryptogenic in 154 men (40% African-American). In 10 patients with low plasma alpha-Gal A activities, DNA sequencing identified alterations in the alpha-Gal A gene in 2 patients. The polymorphism, D313Y, which results in low plasma enzyme activity, but near normal levels of cellular activity was seen in one European-American male. The Fabry disease-causing A143T mutation was seen in an African-American male with cryptogenic stroke (0.18% of all strokes: upper 95% CI=0.53%; 0.65% of cryptogenic strokes: upper 95% CI=1.92%). CONCLUSIONS: In this biracial population, unrecognized Fabry disease is a rare but treatable cause of initial ischemic stroke in young men.

Type 1 Gaucher disease: null and hypomorphic novel chitotriosidase mutations-implications for diagnosis and therapeutic monitoring.

Human plasma chitotriosidase (Chito) is a useful diagnostic and therapeutic biomarker for Type 1 Gaucher disease (GD). However, approximately 40% of Caucasians are heterozygous or homozygous for a common null mutation, c.1049_1072dup24 (dup24) in the chitotriosidase gene (chitinase 1, CHIT1), that complicates interpretation for heterozygotes and precludes use for null homozygotes. 320 Type 1 GD patients were screened for CHIT1 genotype and plasma Chito enzyme levels; 37% were heterozygous and 4% were homozygous for the CHIT1 dup24 allele. Four patients who had no or very low plasma Chito activities had wild-type (wt)/dup24 or wt/wt CHIT1 genotypes, suggesting the presence of other mutations. Sequencing their CHIT1 genes revealed three novel mutations: p.E74K (E74K), p.G102S (G102S), and a complex exon 10 lesion (c.[1060G>A; 1155G>A; 1156+5_1156+8delGTAA], p.[G354R; L385L; missplicing], designated "complex E/I-10"). The G102S mutation was common in Type 1 GD patients and controls ( approximately 30% of alleles). In contrast, the E74K mutation was rare, present only in three Type 1 GD patients ( approximately 1% of alleles), all of Ashkenazi Jewish (AJ) descent, but it was not found in normal controls. The complex E/I-10 mutation occurred in two Caribbean Hispanic/African Type 1 GD patients and was present in 0 to 6% of alleles among normal controls from different populations. In vitro expression demonstrated that the E74K and G102S alleles had approximately 51% and approximately 23% of wild-type Chito catalytic efficiency, respectively. Expression of the G354R allele alone or with the L385L silent substitution did not produce detectable Chito activity or protein. RNA studies indicated that the complex E/I-10 allele also caused missplicing. Recognition of these mutations, particularly G102S, will facilitate the use and interpretation of plasma Chito activities for disease diagnosis, estimating disease severity, and monitoring therapeutic efficacy in GD.

Pulmonary hypertension in type 1 Gaucher's disease: genetic and epigenetic determinants of phenotype and response to therapy.

Type 1 Gaucher's disease (GD) is recognized for striking but unexplained phenotypic diversity. Rarely, severe pulmonary hypertension (PH) may occur in GD but its clinical spectrum, determinants or its response to enzyme replacement therapy (ERT)+/-vasodilators is not known. One hundred and thirty-four consecutive patients with Type 1 GD were screened to estimate right ventricular systolic pressure (RVSP) by Doppler echocardiography. Ninety-four patients were on ERT and 40 were untreated. Eight additional GD patients were studied that represented consecutive tertiary referrals with severe PH. Angiotensin converting enzyme (ACE) gene polymorphisms and acid beta-glucosidase gene (GBA) mutations were determined by DNA analysis. Mild, asymptomatic PH (RVSP>35<50 mmHg) was prevalent in Type 1 GD: 30% in untreated patients and 7.4% among patients receiving ERT (P<0.001). Splenectomy was strongly associated with severe, life-threatening PH: all patients with severe PH (RVSP 50-130 mmHg) were asplenic compared to only 31% of patients with RVSP<50 mmHg (Odds ratio [OR] 28.8, 95% CI 1.6-531.6, P<0.001). Other characteristics of patients presenting with severe PH were poor compliance to ERT (4/9 patients) or no ERT (5/9 patients), a family history of a sib with GD and PH (2/2 patients), an excess of ACE I allele (OR 2.3, 95% CI 1.1-4.9, P=0.034) and an excess of non-N370S GBA mutation (OR 6.0, 95% CI 1.1-33, P=0.003). Severe PH was ameliorated by ERT+/-vasodilators during 4.6+/-4.0 yr (range 1-12 yr) follow-up; three patients were initially considered for lung transplantation but improved such that they are no longer active transplant candidates. Our study reveals a remarkable predisposition for PH in type 1 GD. Progression to severe, life-threatening PH occurs in the presence of additional genetic factors (non-N370S GBA mutation, positive family history, and ACE I gene polymorphism) and epigenetic modifiers (i.e., asplenia and female sex). Splenectomy should be avoided and in high-risk patients, ERT+/-vasodilators/coumadin should be initiated.