Clinical Findings in a Series of Thirty Eight Patients with Williams-Beuren Syndrome

In 1961, Williams et al. [1] described 4 unrelated patients presenting with supravalvar aortic stenosis (SVAS), neurodevelopmental disorder, and peculiar facial features. The following year, Beuren et al. [2] also reported 4 patients with the same combination of features. This new recognizable condition was then named Williams-Beuren syndrome (MIM 194050) or simply Williams syndrome.

WBS is now known to be a multisystemic disease with an incidence as high as 1:7,500 individuals and is caused by a heterozygous microdeletion in the locus 7q11.23, usually arising from a de novo mutation. This deletion results in the loss of a copy of about 25–27 genes, among them ELN, the gene that encodes elastin, as well as GTF2I and GTF2IRD1, which are transcription factor genes. Due to this, a series of abnormalities occur, especially cardiovascular, neurological, behavioral, dysmorphic, gastrointestinal, and endocrine. However, any organ can be affected since a spectrum of different individual characteristics exists. The cardinal features are neurodevelopmental delay in variable degrees, congenital cardiac defects (mainly SVAS), outgoing personality, typical facies, and other performance and growth deficiencies [3].

Traditionally, WBS diagnosis has been made through clinical features since it is a well-known, clinically recognizable condition. The definite diagnosis can be confirmed with the use of cytogenetic and cytogenomic techniques that detect copy number variation events of the 7q11.23 region, such as fluorescent in situ hybridization (FISH), multiplex ligation-dependent probe amplification, or chromosomal microarray analysis. A diagnostic index for WBS was established in 1984 [4], and the more discriminative findings among FISH-positive patients were later validated using the Sugayama scoring system [5, 6].

Data were obtained retrospectively from medical records in the Clinical Genetics Service in a single reference center for rare diseases and included a cohort of consecutive individuals with WBS diagnosed by clinical geneticists; cases with unsure clinical diagnosis or negative cytogenetic tests were excluded. Patients were separated into two groups: definite clinical diagnosis only (group A) or suspicious clinical diagnosis followed by a positive laboratory confirmation test (group B). Data encompassed sex, age of first appointment in the hospital, family history, and clinical findings according to Preus criteria modified by the Sugayama scoring system [4‒6]. Comorbidities and atypical findings were also registered. Atypical findings were defined as features that did not have a high frequency overall or a characteristic that is not classically found in patients with WBS or is not part of the Preus criteria. Data were transcribed to a semi-structured Table with a χ² calculator for each clinical finding to compare the results to validate p value statistical significance (<0.05) and data homogeneity.

Thirty-eight individuals were enrolled, with a sex ratio of 17:21 male to female patients. The age in their first appointment in the hospital where this study was conducted ranged from 1 month to 660 months (55 years of age), with a mean of 93.7 months (7 years) and a median of 72 months (6 years). Regarding the diagnostic groups, there was a balanced proportion of 17 patients with exclusive clinical diagnosis (group A) and 21 patients with laboratory confirmatory diagnosis (group B) (Fig. 1).

Parental consanguinity (first cousins) was reported for patient 25, and recurrence of WBS in a second cousin once removed for patient 26. Patient 16 had an abnormal karyotype showing a de novo chromosomal translocation 46,XX,t(2;7)(p23;q11.2) involving the WBS critical region; for this patient, FISH testing confirmed that this region was deleted.

Tables 1 and 2 show the most frequent clinical findings in both groups, and Table 3 shows the statistical comparison and frequency of the whole sample. In the group of patients with exclusive clinical diagnosis, the most prevalent findings were typical face (100%), intellectual deficiency (100%), arterial hypertension (100%), and developmental delay (93.3%). In the group with cytogenetic/cytogenomic confirmatory testing, the most frequent findings were intellectual deficiency (100%), developmental delay (100%), typical face (85.7%), and overfriendliness (75%). Besides the standard features in WBS shown in Tables 1 and 2, five individuals in this sample presented unusual features: patient 1 with 13 pairs of ribs, 3 patients (individuals 5, 24, and 29) with unilateral renal agenesis, and patient 34 with unilateral microphthalmia.

Comorbidities were also identified in this sample, comprising 9 cases of hypothyroidism (patients 1, 5, 20, 25, 26, 30, 32, 33, and 38) and 1 case each of precocious puberty (patient 15), segmental vitiligo (patient 25, Fig. 2), type 1 diabetes mellitus (patient 38), and congenital adrenal hyperplasia (CAH) (patient 28).

Regarding patient 34, she is the only child of a nonconsanguineous couple; the father was 28, and the mother was 36 years old at the time of conception. Pregnancy was complicated by maternal tabagism and episodes of alcohol intoxication; delivery was by cesarean section, and anthropometric data at birth were not informed, although being referred to as “small.” Besides the clinical findings of WBS described in Table 2, she presented with micro/anophthalmia of the left eye (Fig. 3), confirmed by a cranial CT scan that also detected a reduction in the diameter of the left auricular canal.

Patient 28 is the only child of a young and nonconsanguineous couple; pregnancy and delivery were uneventful. He had an abnormal newborn screening test with elevated levels of 17-hydroxyprogesterone and a diagnosis of CAH due to 21-hydroxylase deficiency, which was later confirmed by molecular analysis of the CYP21A2 gene that detected compound heterozygous for a maternal c.290-13A/C>G and a paternal p.Gln318* variant. Due to facial dysmorphic features, he was referred for clinical genetic evaluation at 3 months, when a clinical diagnosis of WBS syndrome was established and confirmed by FISH analysis.

Comparing the frequency of the clinical findings in this study with the ones in the literature, there was a similar frequency within the most prevalent results in this cohort, including typical face, developmental delay, and overfriendliness, which seems to represent some of the three most characteristic features of WBS [3]. Concerning cardiac disease, the typical SVAS was seen in only 32.4%, while other congenital heart diseases were present in 56.7% of this sample, mainly represented by pulmonic stenosis and septal defects. Except for arterial hypertension, there was no statistical difference in frequencies of the clinical findings among groups A and B, demonstrating homogeneity within the two groups included in this study.

The number of not informed fields for some features in both groups most probably reflects a bias of data collection regarding some age-dependent findings, such as overfriendliness, hypertension, and hyperacusis, since some of the individuals were evaluated in infancy and data on long-term follow-up were unavailable for some of the subjects. For the same reason, formal IQ testing was unfeasible for participants below the school age, but intellectual deficiency was confirmed in all individuals who underwent validated assessment. As discussed below, the same lack of information occurred for data such as pubertal development and late-onset hypothyroidism.

Renal abnormalities are common in WBS, with frequencies ranging from 3 to 86% of individuals in studies in the pre-FISH years [7, 8]; a more plausible prevalence of nearly 50% has been suggested in studies comprising FISH-positive cases [9]. The most common feature is renal artery stenosis, leading to hypertension [10]. Still, structural abnormalities of the kidneys and the urinary tract include renal aplasia or hypoplasia, duplicated kidneys, nephrocalcinosis, hydronephrosis, duplicated collecting system, and kidney stones [9, 11, 12].

Unilateral renal agenesis was found in 5/130 (3.8%) individuals in a large cohort study and 2/27 (7%) in another study with WBS patients recruited in a cardiology clinic [12, 13]. A similar frequency (3/38; 7.9%) of unilateral renal agenesis in the present cohort was found. A previous study of 20 Brazilian patients investigated with FISH analysis detected renal abnormalities in 5/17 (29%) FISH-positive patients and 1/3 FISH-negative ones, but none presented renal agenesis [14].

Except for short stature and scoliosis, skeletal features are not listed among the most relevant findings in WBS. Recently, Schmitz et al. [15] reported that supernumerary lumbar ribs arising from the first lumbar vertebra, often accompanied by lumbosacral transitional vertebrae, are common in children with WBS, present in 73.6% of their cohort and usually being bilateral. In the current case series, only 1 patient was identified with 13 pairs of ribs. Still, spinal radiological assessment was not part of routine surveillance in this group, and the incidence of such anomalies in this cohort was probably underestimated.

The most frequent ocular findings in WBS are strabismus, esotropia, light-colored irises with a typical stellate pattern, and retinal vascular tortuosity [16]. Unilateral microphthalmia, as seen in patient 34, had been described only once in the literature [17]. Also, for this patient, the maternal history of alcohol abuse during pregnancy could be considered a risk factor for such association since microphthalmos is more prevalent and/or severe in children with fetal alcohol spectrum disorders when compared to controls [18].

Considering the comorbidities, among the 9 cases of hypothyroidism in this series, two were subclinical, and two were congenital. Hypothyroidism is an age-dependent finding in WBS, but subclinical hypothyroidism is frequent in young children, while the great majority of patients over 10 years of age, either with normal or hypoplastic thyroid, have normal thyroid function [19]. As expected [20], none of the patients in this cohort presented with autoimmune thyroid disease. On the other hand, the frequency of overt hypothyroidism in this sample (13.1%) seems to be slightly higher than previously reported [21].

Patient 15 also presented with precocious puberty. The frequency in this cohort is lower than reported by Partsch et al. [22], who estimated a prevalence of central precocious puberty of 1 in every 5 to 6 girls with WBS, being less frequent in boys with WBS.

The other comorbidities were vitiligo and type 1 diabetes mellitus, each affecting one individual in this sample. Both have been described in other chromosomal conditions, such as trisomy 21 (Down syndrome), monosomy X (Turner syndrome), and 22q11.2 deletion syndrome, but seem to be undescribed findings in WBS [20]. Type 2 diabetes mellitus and impaired glucose tolerance were reported to be unusually high among adults with WBS, representing one of the highest diabetes risk groups in human populations, with obesity as a significant risk factor [23, 24], but type 1 diabetes mellitus has never been reported in WBS. However, the presence of these conditions in the present study was not overvalued, being considered most probably a casual co-occurrence considering that those disorders are common in the general population.

Patient 28 represents another coincidental association of diagnosis due to the frequencies of both disorders. The prevalence of WBS is 1:7,500 [25], and the incidence of 21-hydroxylase deficiency CAH in Brazil is one of the highest in the world, with an estimated rate of 1:10,325 live births. In contrast, the estimated worldwide CAH incidences of 1:14,199 live births have been calculated from data on neonatal screening in different countries [26].

Except for hypertension, no statistically significant difference was found among patients with exclusive clinical diagnoses compared to patients with laboratory-confirmed WBS, validating Preus criteria modified by the Sugayama scoring system as a diagnostic tool when cytogenomic tests are not universally available. The most frequent findings in this whole sample were developmental delay/intellectual deficiency, typical face, and overfriendliness, while SVAS was not the most frequent congenital heart defect in this cohort, as would be expected in WBS. Many age-dependent features were probably underestimated since a long-term follow-up of the patients is recommended for more informative data collection of these findings. Atypical findings included unilateral renal agenesis with a frequency similar to the literature, while supernumerary ribs and precocious puberty were below expected, and overt hypothyroidism was slightly higher than previously reported. A second report of microphthalmia in WBS was added to the literature, and this was the first study to describe the association of CAH and the findings of segmental vitiligo and type 1 diabetes mellitus with WBS.

The authors thank the Clinical Genetics Service’s clinical staff for the patients’ evolution. Special thanks are extended to Dr. Társis Paiva Vieira and the staff from Laboratório de Citogenética e Citogenômica Humana (FCM/Unicamp) for the FISH analysis. The authors would also like to thank Dr. Maricilda Palandi de Mello from Centro de Biologia Molecular e Engenharia Genética (CBMEG/Unicamp) for the molecular analysis of the patient with congenital adrenal hyperplasia.

The State University of Campinas Ethics Committee Board approved this study under protocol CAAE No. 33970820.0.3014.5404. The State University of Campinas Ethics Committee Board approved informed consent as not required as this is a retrospective study with data collected from medical records. The parents of patients 25 and 28 gave written permission to use the images in this publication.

K.M.K.O., L.O.S., and A.M.S. have received grants from the National Council for Scientific and Technological Development and the Brazilian Ministry of Health.

This study was supported by the Rede Nacional de Doenças Raras (RARAS), and a multicentric research project funded by the National Council for Scientific and Technological Development and the Brazilian Ministry of Health (CNPq/MS/SCTIE/DECIT research protocol No. 25/2019).

K.M.K.O., L.O.S., and A.M.S. collected and analyzed clinical data, performed statistical analysis, and wrote the manuscript draft. C.E.S. was responsible for funding acquisition, supervised the research, and reviewed and edited the final version. All authors have read and agreed to the published version of the manuscript.

The data supporting this study’s findings are available on request from the corresponding author.