Williams-Beuren Syndrome Patients Research Articles

Development of a Low Cost Semiquantitative Polymerase Chain Reaction Assay for Molecular Diagnosis of Williams Syndrome.

Williams Beuren Syndrome (WBS) is a well-recognized and common genetic cause of congenital heart defects, developmental delay, hypercalcemia, and characteristic facial features. It is caused by a 1.5 - 1.8 Mb heterozygous deletion of chromosome 7q11.23 with loss of around 28 coding genes. The aim of this study was to develop a low-cost, semi-quantitative PCR (sqPCR) method to detect the chromosome 7q11.23 deletion. Twenty-four suspected WBS cases were recruited following ethical clearance and informed consent. Blood was obtained, DNA extracted and spectrophotometrically quantified using standard methods. To detect the deletion by dosage analysis, a target region within a gene located in the WBS commonly deleted region of 7q11.23 was amplified together with a control region in a duplex sqPCR assay. The control region was telomeric to the WBS commonly deleted region and was located in chromosome 7q31.2. The two target regions within the deleted region namely a locus within ELN and a marker in the intergenic region between FZD9 and FKBP6 and designated IFF, were amplified in separate duplex sqPCR assays. The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene was used as the control for normalization. Included in the assay were a non-deleted and deleted individuals' samples. Nineteen patients were identified to have the deletion while five did not. All 24 patients' results were confirmed by whole exome sequencing and 11 also by fluorescence in-situ hybridization (FISH). The data obtained indicates the sqPCR assay developed in this study to be an accurate and reliable diagnostic test for WBS. Most Sri Lankan patients with WBS are diagnosed clinically, as many parents of affected WBS children are unable to afford currently available molecular diagnostic testing. This low cost sqPCR test is therefore likely to benefit Sri Lankan WBS patients, by enabling genetic testing for confirming or refuting a clinical diagnosis of WBS and may be of use in other low and middle income countries.

Brazilian growth charts for Williams–Beuren Syndrome at ages 2 to 18 years

ObjectiveTo develop growth charts for weight-for-age, height-for-age, and body mass index (BMI)-for-age for both genders aged 2 to 18 years for Brazilian patients with Williams-Beuren Syndrome (WBS). MethodsThis is a multicenter, retrospective, and longitudinal study, data were collected from the medical records of boys and girls with a confirmed diagnosis of WBS in three large university centers in the state of Sao Paulo, Brazil. Growth charts stratified by gender and age in years were developed using LMSchartmaker Pro software. The LMS (Lambda Mu Sigma) method was used to model the charts . The quality of the settings was checked by worm plots. ResultsThe first Brazilian growth charts for weight-for-age, height-for-age, and BMI-for-age stratified by gender were constructed for WBS patients aged 2 to 18 years. ConclusionThe growth charts developed in this study can help to guide family members and to improve the health care offered by health professionals.

Analysis of gut microbiota in patients with Williams–Beuren Syndrome reveals dysbiosis linked to clinical manifestations

Williams–Beuren syndrome (WBS) is a multisystem genetic disease caused by the deletion of a region of 1.5–1.8 Mb on chromosome 7q11.23. The elastin gene seems to account for several comorbidities and distinct clinical features such including cardiovascular disease, connective tissue abnormalities, growth retardation, and gastrointestinal (GI) symptoms. Increasing evidence points to alterations in gut microbiota composition as a primary or secondary cause of some GI or extra-intestinal characteristics. In this study, we performed the first exploratory analysis of gut microbiota in WBS patients compared to healthy subjects (CTRLs) using 16S rRNA amplicon sequencing, by investigating the gut dysbiosis in relation to diseases and comorbidities. We found that patients with WBS have significant dysbiosis compared to age-matched CTRLs, characterized by an increase in proinflammatory bacteria such as Pseudomonas, Gluconacetobacter and Eggerthella, and a reduction of anti-inflammatory bacteria including Akkermansia and Bifidobacterium. Microbial biomarkers associated with weight gain, GI symptoms and hypertension were identified. Gut microbiota profiling could represent a new tool that characterise intestinal dysbiosis to complement the clinical management of these patients. In particular, the administration of microbial-based treatments, alongside traditional therapies, could help in reducing or preventing the burden of these symptoms and improve the quality of life of these patients.

Dysfunctional Mitochondria in the Cardiac Fibers of a Williams-Beuren Syndrome Mouse Model.

Williams-Beuren syndrome (WBS) is a rare neurodevelopmental disorder that, together with a rather characteristic neurocognitive profile, presents a strong cardiovascular phenotype. The cardiovascular features of WBS are mainly related to a gene dosage effect due to hemizygosity of the elastin (ELN) gene; however, the phenotypic variability between WBS patients indicates the presence of important modulators of the clinical impact of elastin deficiency. Recently, two genes within the WBS region have been linked to mitochondrial dysfunction. Numerous cardiovascular diseases are related to mitochondrial dysfunction; therefore, it could be a modulator of the phenotype present in WBS. Here, we analyze mitochondrial function and dynamics in cardiac tissue from a WBS complete deletion (CD) model. Our research reveals that cardiac fiber mitochondria from CD animals have altered mitochondrial dynamics, accompanied by respiratory chain dysfunction with decreased ATP production, reproducing alterations observed in fibroblasts from WBS patients. Our results highlight two major factors: on the one hand, that mitochondrial dysfunction is probably a relevant mechanism underlying several risk factors associated with WBS disease; on the other, the CD murine model mimics the mitochondrial phenotype of WBS and could be a great model for carrying out preclinical tests on drugs targeting the mitochondria.

Bilateral Congenital Nasolacrimal Duct Obstruction in Williams-Beuren Syndrome.

A 23-year-old patient with Williams-Beuren syndrome presented with ocular irritation and bilateral persistent tearing. Despite probing as an infant which showed bilateral nasolacrimal duct obstruction, dacryocystorhinostomy had been avoided due to the patient's syndromic supravalvular stenosis and related anesthesia risk. As the known diminished production of elastin in Williams-Beuren syndrome causes an array of associated vascular diseases, this case report hypothesizes that the lacrimal duct becomes obstructed through a similar mechanism. This case presents the unique findings of bilateral congenital nasolacrimal duct stenosis in a Williams-Beuren syndrome patient.

Hibridização in situ fluorescente (FISH) como ferramenta diagnóstica insubstituível para a síndrome de Williams-Beuren em países em desenvolvimento: uma revisão de literatura

ABSTRACT Objective: The aim of this study was to sum up and characterize all Williams-Beuren syndrome cases diagnosed by fluorescence in situ hybridization (FISH) since its implementation, as well as to discuss FISH as a cost-effective methodology in developing countries. Data source: From January 1986 to January 2022, articles were selected using the databases in PubMed (Medline) and SciELO. The following terms were used: Williams syndrome and In Situ Hybridization, Fluorescence. Inclusion criteria included Williams-Beuren syndrome cases diagnosed by FISH with a stratified phenotype of each patient. Only studies written in English, Spanish, and Portuguese were included. Studies with overlapping syndromes or genetic conditions were excluded. Data synthesis After screening, 64 articles were included. A total of 205 individuals with Williams-Beuren syndrome diagnosed by FISH were included and further analyzed. Cardiovascular malformations were the most frequent finding (85.4%). Supravalvular aortic stenosis (62.4%) and pulmonary stenosis (30.7%) were the main cardiac alterations described. Conclusions: Our literature review reinforces that cardiac features may be the key to early diagnosis in Williams-Beuren syndrome patients. In addition, FISH may be the best diagnostic tool for developing nations that have limited access to new technologic resources.

Celiac disease prevalence and predisposing-HLA in a cohort of 93 Williams-Beuren syndrome patients.

Williams-Beuren syndrome is considered to be at increased risk for celiac disease, as for recent literature data and celiac disease guidelines, despite pathogenic mechanisms are still unclear. Our study analyzed the prevalence of autoimmune disorders, HLA DQ2 and/or DQ8 haplotypes, of transglutaminase antibodies and of diagnosis of celiac disease in a cohort of 93 Williams-Beuren syndrome's patients (mean age 21.26 years). Our study showed an increased prevalence of celiac disease equal to 10.8% (10/93 patients). We did not find a significant different frequency of predisposing HLA in subjects with Williams-Beuren syndrome compared to literature data in the general population (49.5% vs. 42.9%, with p> .1), nor a susceptibility to autoimmunity. This suggests that the increased prevalence of celiac disease in Williams-Beuren syndrome cannot be ascribed to HLA haplotype and may be related to other factors that still need to be identified in these patients.

Galnt17 loss-of-function leads to developmental delay and abnormal coordination, activity, and social interactions with cerebellar vermis pathology

GALNT17 encodes a N-acetylgalactosaminyltransferase (GalNAc-T) protein specifically involved in mucin-type O-linked glycosylation of target proteins, a process important for cell adhesion, cell signaling, neurotransmitter activity, neurite outgrowth, and neurite sensing. GALNT17, also known as WBSCR17, is located at the edge of the Williams-Beuren Syndrome (WBS) critical region and adjacent to the AUTS2 locus, genomic regions associated with neurodevelopmental phenotypes that are thought to be co-regulated. Although previous data have implicated Galnt17 in neurodevelopment, the in vivo functions of this gene have not been investigated. In this study, we have analyzed behavioral, brain pathology, and molecular phenotypes exhibited by Galnt17 knockout (Galnt17−/−) mice. We show that Galnt17−/− mutants exhibit developmental neuropathology within the cerebellar vermis, along with abnormal activity, coordination, and social interaction deficits. Transcriptomic and protein analysis revealed reductions in both mucin type O-glycosylation and heparan sulfate synthesis in the developing mutant cerebellum along with disruption of pathways central to neuron differentiation, axon pathfinding, and synaptic signaling, consistent with the mutant neuropathology. These brain and behavioral phenotypes and molecular data confirm a specific role for Galnt17 in brain development and suggest new clues to factors that could contribute to phenotypes in certain WBS and AUTS2 syndrome patients.

Novel ophthalmic findings and deep phenotyping in Williams-Beuren syndrome

Background/AimsTo characterise the ocular manifestations of Williams-Beuren syndrome (WBS) and compare these to patients with isolated elastin mediated supravalvular aortic stenosis (SVAS).MethodsFifty-seven patients with a diagnosis of WBS and five...

Behavioral features in Williams Beuren syndrome: A Tunisian Cohort study

IntroductionThe low prevalence of some genetic neuro-developmental syndromes associated to psychiatric disorders requests to be integrated in human genome-phenome databases from which pleiotropy can be compiled from by systematic integration of phenotypes associated with genetic loci using phenomic inference tools. Williams-Beuren syndrome (WBS) is a neurodevelopmental disorder related to elastin gene at 7q11.23. Anxiety, depression and attention problems are the main behavioral problems found in WBS with no gender differences. Significant differences between cohorts are reported in particular regarding somatic complaints and aggressive behavior.ObjectivesHere, we report a Tunisian cohort of WBS patients for whom clinical behavioral phenotypes as well as genetic features are detailed.MethodsSixteen patients from Sfax, Tunisia were referred for genetic assessment due to a suspected WBS syndrome.ResultsGenetic evaluation using fluorescent in situ hybridization confirmed 7q11.23 microdeletion in only eight patients. Comparison of detailed behavioral phenotypes revealed differences between age groups, gender groups and genetic groups. Anxiety and depression were recorded in the two older male patients and aggressive behavior was recorded in only two boys. The severity of behavioral features were dependent to familial environment and to parental socio-economic and educational levels.ConclusionsA more complete understanding of phenomic space is critical for elucidating genome-phenome relationships mediating neurodevelopmental disorder associated to psychiatric diseases for assessing and managing psychiatric and behavioral risks in young syndromic children.DisclosureNo significant relationships.

Co-Treatment With Verapamil and Curcumin Attenuates the Behavioral Alterations Observed in Williams-Beuren Syndrome Mice by Regulation of MAPK Pathway and Microglia Overexpression.

Williams–Beuren syndrome (WBS) is a rare neurodevelopmental disorder characterized by a distinctive cognitive phenotype for which there are currently no effective treatments. We investigated the progression of behavioral deficits present in WBS complete deletion (CD) mice, after chronic treatment with curcumin, verapamil, and a combination of both. These compounds have been proven to have beneficial effects over different cognitive aspects of various murine models and, thus, may have neuroprotective effects in WBS. Treatment was administered orally dissolved in drinking water. A set of behavioral tests demonstrated the efficiency of combinatorial treatment. Some histological and molecular analyses were performed to analyze the effects of treatment and its underlying mechanism. CD mice showed an increased density of activated microglia in the motor cortex and CA1 hippocampal region, which was prevented by co-treatment. Behavioral improvement correlated with the molecular recovery of several affected pathways regarding MAPK signaling, in tight relation to the control of synaptic transmission, and inflammation. Therefore, the results show that co-treatment prevented behavioral deficits by recovering altered gene expression in the cortex of CD mice and reducing activated microglia. These findings unravel the mechanisms underlying the beneficial effects of this novel treatment on behavioral deficits observed in CD mice and suggest that the combination of curcumin and verapamil could be a potential candidate to treat the cognitive impairments in WBS patients.

Epileptic Phenotype and Cannabidiol Efficacy in a Williams–Beuren Syndrome Patient With Atypical Deletion: A Case Report

Epilepsy is a rare clinical manifestation in Williams–Beuren syndrome patients. However, some studies report the presence of infantile spasms and epilepsy in patients carrying larger deletions. Herein, we describe a 13-year-old female affected by Williams–Beuren syndrome and pharmacoresistant epilepsy reporting a de novo large heterozygous 7q11.21q21 deletion (19.4 Mb) also including the YWHAG gene. Studies indicate that cannabidiol is effective as adjunctive therapy for seizures associated with tuberous sclerosis complex, and it is under investigation also in focal cortical dysplasia. When treated with cannabidiol, our patient showed a significant reduction in seizure frequency and intensity, and improved motor and social skills. We hypothesized that CBD could exert a gene/disease-specific effect.

Differential diagnosis of vitamin D-related hypercalcemia using serum vitamin D metabolite profiling.

Genetic causes of vitamin D-related hypercalcemia are known to involve mutation of 25-hydroxyvitamin D-24-hydroxylase CYP24A1 or the sodium phosphate co-transporter SLC34A1, which result in excessive 1,25-(OH)2 D hormonal action. However, at least 20% of idiopathic hypercalcemia (IH) cases remain unresolved. In this case-control study, we used precision vitamin D metabolite profiling based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) of an expanded range of vitamin D metabolites to screen German and French cohorts of hypercalcemia patients, to identify patients with altered vitamin D metabolism where involvement of CYP24A1 or SLC34A1 mutation had been ruled out and who possessed normal 25-OH-D3 :24,25-(OH)2 D3 ratios. Profiles were compared to those of hypercalcemia patients with hypervitaminosis D, Williams-Beuren syndrome (WBS), CYP24A1 mutation, and normal subjects with a range of 25-OH-D levels. We observed that certain IH and WBS patients exhibited a unique profile comprising eightfold to 10-fold higher serum 23,25,26-(OH)3 D3 and 25-OH-D3 -26,23-lactone than normals, as well as very low serum 1,25-(OH)2 D3 (2-5 pg/ml) and elevated 1,24,25-(OH)3 D3 , which we interpret implies hypersensitive expression of vitamin D-dependent genes, including CYP24A1, as a general underlying mechanism of hypercalcemia in these patients. Because serum 25-OH-D3 and 24,25-(OH)2 D3 remained normal, we excluded the possibility that the aberrant profile was caused by hypervitaminosis D, but instead points to an underlying genetic cause that parallels the effect of Williams syndrome transcription factor deficiency in WBS. Furthermore, we observed normalization of serum calcium and vitamin D metabolite profiles at follow-up of an IH patient where 25-OH-D was reduced to 9 ng/ml, suggesting that symptomatic IH may depend on vitamin D nutritional status. Other hypercalcemic patients with complex conditions exhibited distinct vitamin D metabolite profiles. Our work points to the importance of serum vitamin D metabolite profiling in the differential diagnosis of vitamin D-related hypercalcemia that can rationalize expensive genetic testing, and assist healthcare providers in selecting appropriate treatment. © 2021 American Society for Bone and Mineral Research (ASBMR).

Generation of induced pluripotent stem cells (iPSCs) by retroviral transduction of skin fibroblasts from four patients suffering Williams-Beuren syndrome (7q11.23 deletion).

Skin fibroblasts were obtained from four patients with Williams-Beuren syndrome (WBS) carrying the typical 1.5Mb or 1.8Mb deletion at the 7q11.23 genomic region. Induced pluripotent stem cells (iPSCs) were generated by retroviral infection of fibroblasts with polycystronic vectors. The generated iPSC clones ESi059A, ESi060B and ESi068A had the 1.5Mb deletion of 7q11.23 and ESi069A the 1.8Mb, with no novel additional genomic alterations, stable karyotype, expressed pluripotency markers and could differentiate towards the three germ layers in vitro via embryoid body formation and in vivo by teratoma formation. WBS patient's lines are a valuable resource for in vitro modelling of WBS.

Pulmonary function in Williams-Beuren syndrome: Spirometric data of 22 Italian patients.

Williams-Beuren syndrome (WBS) is caused by an haploinsufficiency of the 7q11.2 region which involves the elastin gene (ELN). A deficiency of elastin is a known pathophysiological mechanism of emphysema/chronic obstructive pulmonary disease (COPD). A previous study hypothesized a higher risk of COPD in WBS patients. Herein, this phenomenon was further investigated looking for a possible correlation between COPD and WBS. Dynamic lung volumes (forced vital capacity [FVC], FEV1, FEV1/FVC) were measured in 22 patients (age range 18.9 ± 7.4 years) affected with WBS, genetically confirmed, correlating these parameters to respiratory risk factors. Dyspnea, cough and wheezing were detected in 6/22 (27%) patients. Obstructive and restrictive patterns were identified in 6/22 (27%) and 2/22 (9%) cases, respectively with no evidence of irreversible obstruction. CVF, FEV1 and FEV1/CVF mean values were all normal, with values of 91.3% (n.v. > 80%), 84.2% (n.v. > 80%) and 0.82 (n.v. > 0.7), respectively. The severity of the comorbidities did not show a cause-effect relation with the respiratory patterns, nevertheless patients treated with anti-hypertensive drugs had poorer pulmonary function. Our findings are in accordance with previous observations, showing that emphysema/COPD is not a typical finding in young patients with WBS. However, a respiratory function assessment should be included in the follow-up of WBS patients, especially in adolescents/young adults under treatment with anti-hypertensive drugs.

TFII-I/Gtf2i and Erythro-Megakaryopoiesis.

TFII-I is a ubiquitously expressed transcription factor that positively or negatively regulates gene expression. TFII-I has been implicated in neuronal and immunologic diseases as well as in thymic epithelial cancer. Williams–Beuren Syndrome (WBS) is caused by a large hemizygous deletion on chromosome 7q11.23 which encompasses 26–28 genes, including GTF2I, the human gene encoding TFII-I. A subset of WBS patients has recently been shown to present with macrocytosis, a mild anemia characterized by enlarged erythrocytes. We conditionally deleted the TFII-I/Gtf2i gene in adult mice by tamoxifen induced Cre-recombination. Bone marrow cells revealed defects in erythro-megakaryopoiesis and an increase in expression of the adult β-globin gene. The data show that TFII-I acts as a repressor of β–globin gene transcription and that it is implicated in the differentiation of erythro-megakaryocytic cells.

Williams-Beuren Syndrome and celiac disease: A real association?

Celiac disease (CD) screening in patients with Williams-Beuren Syndrome (WBS) is suggested, although data described in literature are discordant regarding CD prevalence in WBS. We retrospectively collected data from 101 WBS Italian patients [mean age: 13.5 years], to clarify the CD prevalence in a large cohort. All patients underwent a CD biochemical screening: IgA and anti-transglutaminase reflex antibodies (tTGA). CD-specific HLA typing was available for 42 patients. Small intestinal biopsy was performed in patients according to ESPGHAN guidelines. In 7 WBS patients an overt celiac disease was diagnosed. In 3 patients CD was confirmed by symptoms, HLA-DQ heterodimers and CD specific antibodies title, whereas in 4 patients, it was confirmed by a small intestinal biopsy. CD prevalence in our cohort is 6.9% (7/101). In 42/101 patients the CD-specific HLA typing was available, detecting 29/42 (69%) patients genetically predisposed to CD. The CD prevalence and CD-specific HLA prevalence are both higher than in the general population (p < 0.001; p < 0.001). Our cohort is the most numerous described confirming that the CD risk in WBS patients is significantly greater than in general population. Moreover, our HLA typing results, as well as scientific literature, suggest that the higher CD prevalence in WBS patients might not be intrinsically related to the genetic disease itself but with the higher HLA prevalence. However, HLA typing should be performed in bigger WBS cohorts to confirm this hypothesis. Our data confirms that HLA typing is mandatory in WBS patients and that CD screening should be performed only if genetically predisposed.

Growth assessment in children with Williams-Beuren syndrome: a systematic review.

Williams-Beuren syndrome (WBS) is a rare genetic disease caused by a sporadic heterozygous microdeletion in 7q11.23. It is characterized by distinctive facial appearance, cardiopathy, short stature, intellectual disability, and endocrine abnormalities. To evaluate the growth pattern of patients with WBS and to identify the prevalence of malnutrition, overweight, and obesity in this population, a systematic review of studies published in English, between 1987 and 2018, was performed following the PRISMA protocol using the PubMed, Cochrane, and BIREME databases. Original articles and articles that evaluated growth status using weight, or height, or head circumference (HC), or body mass index (BMI) of individuals with WBS were included. Case reports, articles with data from other syndromes, and articles that did not present as a central theme the evaluation of growth were not included. WBS presented specific growth pattern, characterized by intrauterine growth restriction, low weight, length, and HC at birth. This global growth delay persisted during childhood and adolescence. BMI was not different to the reference population, and obesity was not observed in childhood. The mechanisms that determine this typical growth pattern are not totally clear; however, the typical pubertal development of these patients and the intrinsic and secondary lesions caused by microdeletion at 7q11.23 seem to be the major factors involved. Conclusion: Patients with WBS have a growth pattern different from the general reference population. The reference charts for normal population should notbe used for WBS patients because it often underestimate their growth. Specific growth charts for WBS patients are necessary.

Stenosis coexists with compromised \u03b11-adrenergic contractions in the ascending aorta of a mouse model of Williams-Beuren syndrome

Williams-Beuren syndrome (WBS) is a rare disorder caused by a heterozygous deletion of 26–28 contiguous genes that affects the brain and cardiovascular system. Here, we investigated whether WBS affects aortic structure and function in the complete deletion (CD) mouse model harbouring the most common deletion found in WBS patients. Thoracic aortas from 3–4 months-old male CD mice and wild-type littermates were mounted in wire myographs or were processed for histomorphometrical analysis. Nitric oxide synthase (NOS) isoforms and oxidative stress levels were assessed. Ascending aortas from young adult CD mice showed moderate (50%) luminal stenosis, whereas endothelial function and oxidative stress were comparable to wild-type. CD mice showed greater contractions to KCl. However, α1-adrenergic contractions to phenylephrine, but not with a thromboxane analogue, were compromised. Decreased phenylephrine responses were not affected by selective inducible NOS blockade with 1400 W, but were prevented by the non-selective NOS inhibitor L-NAME and the selective neuronal NOS inhibitor SMTC. Consistently, CD mice showed increased neuronal NOS expression in aortas. Overall, aortic stenosis in CD mice coexists with excessive nNOS-derived NO signaling that compromises ascending aorta α1-adrenergic contractions. We suggest that increased neuronal NOS signaling may act as a physiological ‘brake’ against the detrimental effects of stenosis.

Mild macrocytosis in Williams-Beuren syndrome

ObjectiveTo evaluate the occurrence and estimate the frequency of macrocytosis in Williams-Beuren syndrome (WBS). Study designComplete blood count (CBC) data from 179 subjects with WBS aged 1-69 were collected, with common parameters assessed for trends. Z-transformed mean corpuscular volume (MCV) was compared with each laboratory's reference range as well as with control data from the National Health and Nutrition Examination Survey (NHANES) 2013-2014 data archives. ResultsJust over a third (35%) subjects had at least one recorded incidence of macrocytosis. In comparisons of CBC parameters with an expected population mean, MCV and MCH were greater than, while Hct and RDW were lower than, expected values. The distribution of erythrocyte MCV is shifted to the right in WBS compared to controls, as was the mean value. Despite this, anemia was absent, except in a single medically complex WBS subject. Though there was a paucity of data available of variables that could potentially cause an elevated MCV, no obvious etiology could be elucidated. ConclusionsMild macrocytosis without anemia affects a moderate subset of WBS patients, leading to a rightward shift in the MCV distribution curve. Providers encountering isolated mild macrocytosis in WBS can consider observation over further workup.