Case Report: Cerebral Revascularization in a Child With Mucopolysaccharidosis Type I.

Mucopolysaccharidosis (MPS) type I is a rare lysosomal storage disorder caused by an accumulation of glycosaminoglycans (GAGs) resulting in multisystem disease. Neurological morbidity includes hydrocephalus, spinal cord compression, and cognitive decline. While many neurological symptoms have been described, stroke is not a widely-recognized manifestation of MPS I. Accordingly, patients with MPS I are not routinely evaluated for stroke, and there are no guidelines for managing stroke in patients with this disease. We report the case of a child diagnosed with MPS I who presented with overt stroke and repeated neurological symptoms with imaging findings for severe ventriculomegaly, infarction, and bilateral terminal carotid artery stenosis. Direct intracranial pressure evaluation proved negative for hydrocephalus. The patient was subsequently treated with cerebral revascularization and at a 3-year follow-up, the patient reported no further neurological events or new ischemia on cerebral imaging. Cerebral arteriopathy in patients with MPS I may be associated with GAG accumulation within the cerebrovascular system and may predispose patients to recurrent strokes. However, further studies are required to elucidate the etiology of cerebrovascular arteriopathy in the setting of MPS I. Although the natural history of steno-occlusive arteriopathy in patients with MPS I remains unclear, our findings suggest that cerebral revascularization is a safe treatment option that may mitigate the risk of future strokes and should be strongly considered within the overall management guidelines for patients with MPS I.

Mitochondrial Ultrastructural Defects in NDUFS3-Related Disorder.

Complex I, the largest multisubunit enzyme complex of the respiratory chain, has a vital role in the energy production of the cell, and the clinical spectrum of complex I deficiency varies from severe lactic acidosis in infants to muscle weakness in adults. Pathogenic variants of NDUFS3 (constitutes the catalytic core of the complex I) have been reported in a small number of patients with variable phenotypes. We describe a girl with a history of infantile-onset nonepileptic myoclonus, who developed myopathy at the age of 2 years. Next-generation sequencing revealed compound heterozygous for two variants in the NDUSF3 gene. The electron-microscopic study of the skeletal muscle showed an increase in the number of mitochondria inside the myofibers; mitochondria were variably enlarged with some irregularity and were aligned perpendicular to the myofibrils in a stacked-up manner. This is the first description of mitochondrial ultrastructural abnormality in an individual with NDUFS3-related disorder.

Outcomes of screening for gammopathies in children and adults with Gaucher disease type 1 in a cohort from Brazil and the United States.

Multiple myeloma is the most common hematological malignancy in Gaucher disease type 1 (GD1). There is a lack of outcome data and consensus regarding screening of gammopathies. This study explores utility of screening in Porto Alegre, Brazil, and Cincinnati, Ohio. A retrospective analysis of clinical information and laboratory data from GD1 patients was performed. Over 19 years, 68 individuals with GD1 (31 males, 37 females) underwent screening, and 20 (29.4%) had abnormalities. Twelve (17.6%) had polyclonal gammopathy (mean age 24.2 years, p = .02), seven (10%) had monoclonal gammopathy of uncertain significance (MGUS; mean age 52.7 years, p = .009). One had multiple myeloma (age 61 years). Risk factors for MGUS included male gender (p = .05), p.N409S allele (p = .032). MGUS developed in six of 62 treated and two of four untreated individuals. Of those with MGUS receiving treatment, four were on enzyme replacement therapy (ERT) and one on substrate reduction therapy (SRT). Gammopathy normalized in 13 treated individuals (10 polyclonal, three MGUS) and remained abnormal in two treated individuals (two polyclonal, two MGUS). Gammopathy relapse was seen in one individual with MGUS and three with polyclonal gammopathy. This study describes screening for gammopathies and identifies risk factors in individuals with GD1.

Multiple Autoimmune Disorders in Aicardi-Goutières Syndrome.

BACKGROUND: Aicardi-Goutières syndrome is an early-onset encephalopathy with presumed immune pathogenesis caused by inherited defects in nucleic acid metabolism. It is a model disease to study systemic autoimmunity, and there are many clinical, genetic, and basic science considerations that underline a possible overlap between Aicardi-Goutières syndrome and systemic lupus erythematosus. RESULTS: We describe a 15-year-old girl with Aicardi-Goutières syndrome due to compound heterozygous pathogenic variants in SAMHD1 (sterile alpha motif domain and HD domain-containing protein 1). Over time, she developed multiple autoimmune diseases (vitiligo, alopecia areata, immune thrombocytopenia, positive antithyroglobulin antibodies) without positive antinuclear antibody or features of systemic lupus erythematosus. Her thrombocytopenia was refractory to treatment with corticosteroids and intravenous immunoglobulin but responded to a standard course of rituximab. CONCLUSION: This is the first report of a multiple autoimmune syndrome in a patient with molecularly proven Aicardi-Goutières syndrome. This study illustrates an emerging pattern of the natural history of Aicardi-Goutières syndrome characterized by early encephalopathic presentation followed by symptoms of systemic autoimmunity.

KCTD7 deficiency defines a distinct neurodegenerative disorder with a conserved autophagy-lysosome defect.

OBJECTIVE: Several small case series identified KCTD7 mutations in patients with a rare autosomal recessive disorder designated progressive myoclonic epilepsy (EPM3) and neuronal ceroid lipofuscinosis (CLN14). Despite the name KCTD (potassium channel tetramerization domain), KCTD protein family members lack predicted channel domains. We sought to translate insight gained from yeast studies to uncover disease mechanisms associated with deficiencies in KCTD7 of unknown function. METHODS: Novel KCTD7 variants in new and published patients were assessed for disease causality using genetic analyses, cell-based functional assays of patient fibroblasts and knockout yeast, and electron microscopy of patient samples. RESULTS: Patients with KCTD7 mutations can exhibit movement disorders or developmental regression before seizure onset, and are distinguished from similar disorders by an earlier age of onset. Although most published KCTD7 patient variants were excluded from a genome sequence database of normal human variations, most newly identified patient variants are present in this database, potentially challenging disease causality. However, genetic analysis and impaired biochemical interactions with cullin 3 support a causal role for patient KCTD7 variants, suggesting deleterious alleles of KCTD7 and other rare disease variants may be underestimated. Both patient-derived fibroblasts and yeast lacking Whi2 with sequence similarity to KCTD7 have impaired autophagy consistent with brain pathology. INTERPRETATION: Biallelic KCTD7 mutations define a neurodegenerative disorder with lipofuscin and lipid droplet accumulation but without defining features of neuronal ceroid lipofuscinosis or lysosomal storage disorders. KCTD7 deficiency appears to cause an underlying autophagy-lysosome defect conserved in yeast, thereby assigning a biological role for KCTD7. Ann Neurol 2018;84:774-788.

Transformation in pretreatment manifestations of Gaucher disease type 1 during two decades of alglucerase/imiglucerase enzyme replacement therapy in the International Collaborative Gaucher Group (ICGG) Gaucher Registry.

This study tests the hypothesis that the prevalence of severe clinical manifestations in Gaucher disease type 1 (GD1) patients at the time of treatment initiation has changed since alglucerase/imiglucerase enzyme replacement therapy (ERT) was approved in the United States (US) in 1991. US alglucerase/imiglucerase-treated GD1 patients from the International Collaborative Gaucher Group Gaucher Registry clinicaltrials.gov NCT00358943 were stratified by age at ERT initiation (<18, 18 to <50, ≥50 years), era of ERT initiation (1991-1995, 1996-2000, 2001-2005, 2006-2009), and splenectomy status pre-ERT. Prevalence of splenectomy decreased dramatically across the eras among all age groups. Bone manifestations were more prevalent in splenectomized patients than non-splenectomized patients in all age groups. Prevalence of bone manifestations differed across eras in certain age groups: non-splenectomized patients had a lower prevalence of ischemic bone events (pediatric patients) and bone crisis (pediatric patients and adults 18 to <50 years) in later eras; splenectomized adult (18 to <50 years) patients had a lower prevalence of ischemic bone events and bone crisis in later eras. Over two decades after the introduction of ERT, the prevalence of splenectomy and associated skeletal complications has declined dramatically. Concomitantly, the interval between diagnosis and initiation of ERT has decreased, most strikingly in pediatric patients who have the most severe disease. Together, these findings suggest that since the introduction of alglucerase/imiglucerase ERT, optimal standard of care has become established in the US to prevent destructive complications of GD1.

Complement drives glucosylceramide accumulation and tissue inflammation in Gaucher disease.

Gaucher disease is caused by mutations in GBA1, which encodes the lysosomal enzyme glucocerebrosidase (GCase). GBA1 mutations drive extensive accumulation of glucosylceramide (GC) in multiple innate and adaptive immune cells in the spleen, liver, lung and bone marrow, often leading to chronic inflammation. The mechanisms that connect excess GC to tissue inflammation remain unknown. Here we show that activation of complement C5a and C5a receptor 1 (C5aR1) controls GC accumulation and the inflammatory response in experimental and clinical Gaucher disease. Marked local and systemic complement activation occurred in GCase-deficient mice or after pharmacological inhibition of GCase and was associated with GC storage, tissue inflammation and proinflammatory cytokine production. Whereas all GCase-inhibited mice died within 4-5 weeks, mice deficient in both GCase and C5aR1, and wild-type mice in which GCase and C5aR were pharmacologically inhibited, were protected from these adverse effects and consequently survived. In mice and humans, GCase deficiency was associated with strong formation of complement-activating GC-specific IgG autoantibodies, leading to complement activation and C5a generation. Subsequent C5aR1 activation controlled UDP-glucose ceramide glucosyltransferase production, thereby tipping the balance between GC formation and degradation. Thus, extensive GC storage induces complement-activating IgG autoantibodies that drive a pathway of C5a generation and C5aR1 activation that fuels a cycle of cellular GC accumulation, innate and adaptive immune cell recruitment and activation in Gaucher disease. As enzyme replacement and substrate reduction therapies are expensive and still associated with inflammation, increased risk of cancer and Parkinson disease, targeting C5aR1 may serve as a treatment option for patients with Gaucher disease and, possibly, other lysosomal storage diseases.

Eliglustat maintains long-term clinical stability in patients with Gaucher disease type 1 stabilized on enzyme therapy.

In the phase 3 Study of Eliglustat Tartrate (Genz-112638) in Patients With Gaucher Disease Who Have Reached Therapeutic Goals With Enzyme Replacement Therapy (ENCORE), at 1 year, eliglustat was noninferior to imiglucerase enzyme therapy in maintaining stable platelet counts, hemoglobin concentrations, and spleen and liver volumes. After this primary analysis period, patients entered a long-term extension phase in which all received eliglustat. Duration on eliglustat ranged from 2 to 5 years, depending on timing of enrollment (which spanned 2 years), treatment group to which patients were randomized, and whether they lived in the United States when commercial eliglustat became available. Here we report long-term safety and efficacy of eliglustat for 157 patients who received eliglustat in the ENCORE trial; data are available for 46 patients who received eliglustat for 4 years. Mean hemoglobin concentration, platelet count, and spleen and liver volumes remained stable for up to 4 years. Year to year, all 4 measures remained collectively stable (composite end point relative to baseline values) in ≥85% of patients as well as individually in ≥92%. Mean bone mineral density z scores (lumbar spine and femur) remained stable and were maintained in the healthy reference range throughout. Eliglustat was well tolerated over 4 years; 4 (2.5%) patients withdrew because of adverse events that were considered related to the study drug. No new or long-term safety concerns were identified. Clinical stability assessed by composite and individual measures was maintained in adults with Gaucher disease type 1 treated with eliglustat who remained in the ENCORE trial for up to 4 years. This trial was registered at www.clinicaltrials.gov as #NCT00943111.

Clinical delineation of the PACS1-related syndrome--Report on 19 patients.

We report on 19 individuals with a recurrent de novo c.607C>T mutation in PACS1. This specific mutation gives rise to a recognizable intellectual disability syndrome. There is a distinctive facial appearance (19/19), characterized by full and arched eyebrows, hypertelorism with downslanting palpebral fissures, long eye lashes, ptosis, low set and simple ears, bulbous nasal tip, wide mouth with downturned corners and a thin upper lip with an unusual "wavy" profile, flat philtrum, and diastema of the teeth. Intellectual disability, ranging from mild to moderate, was present in all. Hypotonia is common in infancy (8/19). Seizures are frequent (12/19) and respond well to anticonvulsive medication. Structural malformations are common, including heart (10/19), brain (12/16), eye (10/19), kidney (3/19), and cryptorchidism (6/12 males). Feeding dysfunction is presenting in infancy with failure to thrive (5/19), gastroesophageal reflux (6/19), and gastrostomy tube placement (4/19). There is persistence of oral motor dysfunction. We provide suggestions for clinical work-up and management and hope that the present study will facilitate clinical recognition of further cases.

Recommendations for the use of eliglustat in the treatment of adults with Gaucher disease type 1 in the United States.

In Gaucher disease, deficient activity of acid ß-glucosidase results in accumulation of its substrates, glucosylceramide and glucosylsphingosine, within the lysosomes of cells primarily in the spleen, liver, bone marrow, and occasionally the lung. The multisystem disease is predominantly characterized by hepatosplenomegaly, anemia, thrombocytopenia, and skeletal disease. Enzyme replacement therapy with recombinant human acid ß-glucosidase has been the first-line therapy for Gaucher disease type 1 for more than two decades. Eliglustat, a novel oral substrate reduction therapy, was recently approved in the United States and the European Union as a first-line treatment for adults with Gaucher disease type 1. Eliglustat inhibits glucosylceramide synthase, thereby decreasing production of the substrate glucosylceramide and reducing its accumulation. Although existing recommendations for the care of patients with Gaucher disease remain in effect, unique characteristics of eliglustat require additional investigation and monitoring. A panel of physicians with expertise in Gaucher disease and experience with eliglustat in the clinical trials provide guidance regarding the use of eliglustat, including considerations before starting therapy and monitoring of patients on eliglustat therapy.

Defects of B-cell terminal differentiation in patients with type-1 Kabuki syndrome.

BACKGROUND: Kabuki syndrome (KS) is a complex multisystem developmental disorder associated with mutation of genes encoding histone-modifying proteins. In addition to craniofacial, intellectual, and cardiac defects, KS is also characterized by humoral immune deficiency and autoimmune disease, yet no detailed molecular characterization of the KS-associated immune phenotype has been reported. OBJECTIVE: We sought to characterize the humoral immune defects found in patients with KS with lysine methyltransferase 2D (KMT2D) mutations. METHODS: We comprehensively characterized B-cell function in a cohort (n = 13) of patients with KS (age, 4 months to 27 years). RESULTS: Three quarters (77%) of the cohort had a detectable heterozygous KMT2D mutation (50% nonsense, 20% splice site, and 30% missense mutations), and 70% of the reported mutations are novel. Among the patients with KMT2D mutations (KMT2D(Mut/+)), hypogammaglobulinemia was detected in all but 1 patient, with IgA deficiency affecting 90% of patients and a deficiency in at least 1 other isoform seen in 40% of patients. Numbers of total memory (CD27(+)) and class-switched memory B cells (IgM(-)) were significantly reduced in patients with KMT2D(Mut/+) mutations compared with numbers in control subjects (P < .001). Patients with KMT2D(Mut/+) mutations also had significantly reduced rates of somatic hypermutation in IgG (P = .003) but not IgA or IgM heavy chain sequences. Impaired terminal differentiation was noted in primary B cells from patients with KMT2D(Mut/+) mutations. Autoimmune pathology was observed in patients with missense mutations affecting the SET domain and its adjacent domains. CONCLUSIONS: In patients with KS, autosomal dominant KMT2D mutations are associated with dysregulation of terminal B-cell differentiation, leading to humoral immune deficiency and, in some cases, autoimmunity. All patients with KS should undergo serial clinical immune evaluations.

Clinical Impact and Cost-Effectiveness of Whole Exome Sequencing as a Diagnostic Tool: A Pediatric Center's Experience.

BACKGROUND: There are limited reports of the use of whole exome sequencing (WES) as a clinical diagnostic tool. Moreover, there are no reports addressing the cost burden associated with genetic tests performed prior to WES. OBJECTIVE: We demonstrate the performance characteristics of WES in a pediatric setting by describing our patient cohort, calculating the diagnostic yield, and detailing the patients for whom clinical management was altered. Moreover, we examined the potential cost-effectiveness of WES by examining the cost burden of diagnostic workups. METHODS: To determine the clinical utility of our hospital's clinical WES, we performed a retrospective review of the first 40 cases. We utilized dual bioinformatics analyses pipelines based on commercially available software and in-house tools. RESULTS: Of the first 40 clinical cases, we identified genetic defects in 12 (30%) patients, of which 47% of the mutations were previously unreported in the literature. Among the 12 patients with positive findings, seven have autosomal dominant disease and five have autosomal recessive disease. Ninety percent of the cohort opted to receive secondary findings and of those, secondary medical actionable results were returned in three cases. Among these positive cases, there are a number of novel mutations that are being reported here. The diagnostic workup included a significant number of genetic tests with microarray and single-gene sequencing being the most popular tests. Significantly, genetic diagnosis from WES led to altered patient medical management in positive cases. CONCLUSION: We demonstrate the clinical utility of WES by establishing the clinical diagnostic rate and its impact on medical management in a large pediatric center. The cost-effectiveness of WES was demonstrated by ending the diagnostic odyssey in positive cases. Also, in some cases it may be most cost-effective to directly perform WES. WES provides a unique glimpse into the complexity of genetic disorders.

De novo mutations in KIF1A cause progressive encephalopathy and brain atrophy.

OBJECTIVE: To determine the cause and course of a novel syndrome with progressive encephalopathy and brain atrophy in children. METHODS: Clinical whole-exome sequencing was performed for global developmental delay and intellectual disability; some patients also had spastic paraparesis and evidence of clinical regression. Six patients were identified with de novo missense mutations in the kinesin gene KIF1A. The predicted functional disruption of these mutations was assessed in silico to compare the calculated conformational flexibility and estimated efficiency of ATP binding to kinesin motor domains of wild-type (WT) versus mutant alleles. Additionally, an in vitro microtubule gliding assay was performed to assess the effects of de novo dominant, inherited recessive, and polymorphic variants on KIF1A motor function. RESULTS: All six subjects had severe developmental delay, hypotonia, and varying degrees of hyperreflexia and spastic paraparesis. Microcephaly, cortical visual impairment, optic neuropathy, peripheral neuropathy, ataxia, epilepsy, and movement disorders were also observed. All six patients had a degenerative neurologic course with progressive cerebral and cerebellar atrophy seen on sequential magnetic resonance imaging scans. Computational modeling of mutant protein structures when compared to WT kinesin showed substantial differences in conformational flexibility and ATP-binding efficiency. The de novo KIF1A mutants were nonmotile in the microtubule gliding assay. INTERPRETATION: De novo mutations in KIF1A cause a degenerative neurologic syndrome with brain atrophy. Computational and in vitro assays differentiate the severity of dominant de novo heterozygous versus inherited recessive KIF1A mutations. The profound effect de novo mutations have on axonal transport is likely related to the cause of progressive neurologic impairment in these patients.

Eliglustat compared with imiglucerase in patients with Gaucher's disease type 1 stabilised on enzyme replacement therapy: a phase 3, randomised, open-label, non-inferiority trial.

BACKGROUND: The mainstay of treatment for Gaucher's disease type 1 is alternate-week infusion of enzyme replacement therapy (ERT). We investigated whether patients stable on such treatment would remain so after switching to oral eliglustat, a selective inhibitor of glucosylceramide synthase. METHODS: In this phase 3, randomised, multinational, open-label, non-inferiority trial, we enrolled adults (aged ≥18 years) who had received ERT for 3 years or more for Gaucher's disease. Patients were randomly allocated 2:1 at 39 clinics (stratified by ERT dose; block sizes of four; computer-generated centrally) to receive either oral eliglustat or imiglucerase infusions for 12 months. Participants and investigators were aware of treatment assignment, but the central reader who assessed organ volumes was masked. The composite primary efficacy endpoint was percentage of patients whose haematological variables and organ volumes remained stable for 12 months (ie, haemoglobin decrease not more than 15 g/L, platelet count decrease not more than 25%, spleen volume increase not more than 25%, and liver volume increase not more than 20%, in multiples of normal from baseline). The non-inferiority margin was 25% for eliglustat relative to imiglucerase, assessed in all patients who completed 12 months of treatment. This trial is registered with ClinicalTrials.gov, number NCT00943111, and EudraCT, number 2008-005223-28. FINDINGS: Between Sept 15, 2009, and Nov 9, 2011, we randomly allocated 106 (66%) patients to eliglustat and 54 (34%) to imiglucerase. In the per-protocol population, 84 (85%) of 99 patients who completed eliglustat treatment and 44 (94%) of 47 patients who completed imiglucerase treatment met the composite primary endpoint (between-group difference -8·8%; 95% CI -17·6 to 4·2). The lower bound of the 95% CI of -17·6% was within the prespecified threshold for non-inferiority. Dropouts occurred due to palpitations (one patient on eliglustat), myocardial infarction (one patient on eliglustat), and psychotic disorder (one patient on imiglucerase). No deaths occurred. 97 (92%) of 106 patients in the eliglustat group had treatment-emergent adverse events, as did 42 (79%) of 53 in the imiglucerase group (mostly mild or moderate in severity). INTERPRETATION: Oral eliglustat maintained haematological and organ volume stability in adults with Gaucher's disease type 1 already controlled by intravenous ERT and could be a useful therapeutic option. FUNDING: Genzyme, a Sanofi company.

CNS, lung, and lymph node involvement in Gaucher disease type 3 after 11 years of therapy: clinical, histopathologic, and biochemical findings.

A Caucasian male with Gaucher disease type 3, treated with continuous enzyme therapy (ET) for 11 years, experienced progressive mesenteric and retroperitoneal lymphadenopathy, lung disease, and neurological involvement leading to death at an age of 12.5 years. Autopsy showed significant pathology of the brain, lymph nodes, and lungs. Liver and spleen glucosylceramide (GluCer) and glucosylsphingosine (GluS) levels were nearly normal and storage cells were cleared. Clusters of macrophages and very elevated GluCer and GluS levels were in the lungs, and brain parenchymal and perivascular regions. Compared to normal brain GluCer (GC 18:0), GluCer species with long fatty acid acyl chains were increased in the patient's brain. This profile was similar to that in the patient's lungs, suggesting that these lipids were present in brain perivascular macrophages. In the patient's brain, generalized astrogliosis, and enhanced LC3, ubiquitin, and Tau signals were identified in the regions surrounding macrophage clusters, indicating proinflammation, altered autophagy, and neurodegeneration. These findings highlight the altered phenotypes resulting from increased longevity due to ET, as well as those in poorly accessible compartments of brain and lung, which manifested progressive disease involvement despite ET.

Velaglucerase alfa in the treatment of Gaucher disease type 1.

Gaucher disease is an autosomal recessively inherited lysosomal storage disease that results from the defective activity of the enzyme acid ß-glucosidase (glucocerebrosidase). Velaglucerase alfa was recently developed and approved as an alternative form to imiglucerase enzyme therapy. Despite differences in primary structure and glycosylation patterns, recent preclinical and clinical trials of the preparation have shown similar efficacy and safety profiles to those of imiglucerase. The development of alternative therapies, such as velaglucerase alfa for Gaucher disease, is providing clinicians with a larger armamentarium of therapies, allowing for a more personalized approach to patient care.

Glycogen storage disease type IV: novel mutations and molecular characterization of a heterogeneous disorder.

Glycogen storage disease type IV (GSD IV; Andersen disease) is caused by a deficiency of glycogen branching enzyme (GBE), leading to excessive deposition of structurally abnormal, amylopectin-like glycogen in affected tissues. The accumulated glycogen lacks multiple branch points and thus has longer outer branches and poor solubility, causing irreversible tissue and organ damage. Although classic GSD IV presents with early onset of hepatosplenomegaly with progressive liver cirrhosis, GSD IV exhibits extensive clinical heterogeneity with respect to age at onset and variability in pattern and extent of organ and tissue involvement. With the advent of cloning and determination of the genomic structure of the human GBE gene (GBE1), molecular analysis and characterization of underlying disease-causing mutations is now possible. A variety of disease-causing mutations have been identified in the GBE1 gene in GSD IV patients, many of whom presented with diverse clinical phenotypes. Detailed biochemical and genetic analyses of three unrelated patients suspected to have GSD IV are presented here. Two novel missense mutations (p.Met495Thr and p.Pro552Leu) and a novel 1-bp deletion mutation (c.1999delA) were identified. A variety of mutations in GBE1 have been previously reported, including missense and nonsense mutations, nucleotide deletions and insertions, and donor and acceptor splice-site mutations. Mutation analysis is useful in confirming the diagnosis of GSD IV--especially when higher residual GBE enzyme activity levels are seen and enzyme analysis is not definitive--and allows for further determination of potential genotype/phenotype correlations in this disease.