Genotypes and phenotypes heterogeneity in PIK3CA-related overgrowth spectrum and overlapping conditions: 150 novel patients and systematic review of 1007 patients with PIK3CA pathogenetic variants

BACKGROUND

Postzygotic activating PIK3CA variants cause several phenotypes within the PIK3CA-related overgrowth spectrum (PROS). Variant strength, mosaicism level, specific tissue involvement and overlapping disorders are responsible for disease heterogeneity. We explored these factors in 150 novel patients and in an expanded cohort of 1007 PIK3CA-mutated patients, analysing our new data with previous literature to give a comprehensive picture.

METHODS

We performed ultradeep targeted next-generation sequencing (NGS) on DNA from skin biopsy, buccal swab or blood using a panel including phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin pathway genes and GNAQ, GNA11, RASA1 and TEK. Additionally, 914 patients previously reported were systematically reviewed.

RESULTS

93 of our 150 patients had PIK3CA pathogenetic variants. The merged PROS cohort showed that PIK3CA variants span thorough all gene domains, some were exclusively associated with specific PROS phenotypes: weakly activating variants were associated with central nervous system (CNS) involvement, and strongly activating variants with extra-CNS phenotypes. Among the 57 with a wild-type PIK3CA allele, 11 patients with overgrowth and vascular malformations overlapping PROS had variants in GNAQ, GNA11, RASA1 or TEK.

CONCLUSION

We confirm that (1) molecular diagnostic yield increases when multiple tissues are tested and by enriching NGS panels with genes of overlapping 'vascular' phenotypes; (2) strongly activating PIK3CA variants are found in affected tissue, rarely in blood: conversely, weakly activating mutations more common in blood; (3) weakly activating variants correlate with CNS involvement, strong variants are more common in cases without; (4) patients with vascular malformations overlapping those of PROS can harbour variants in genes other than PIK3CA.

Natural history of KBG syndrome in a large European cohort

KBG syndrome (KBGS) is characterized by distinctive facial gestalt, short stature and variable clinical findings. With ageing, some features become more recognizable, allowing a differential diagnosis. We aimed to better characterize natural history of KBGS. In the context of a European collaborative study, we collected the largest cohort of KBGS patients (49). A combined array- based Comparative Genomic Hybridization and next generation sequencing (NGS) approach investigated both genomic Copy Number Variants and SNVs. Intellectual disability (ID) (82%) ranged from mild to moderate with severe ID identified in two patients. Epilepsy was present in 26.5%. Short stature was consistent over time, while occipitofrontal circumference (median value: -0.88 SD at birth) normalized over years. Cerebral anomalies, were identified in 56% of patients and thus represented the second most relevant clinical feature reinforcing clinical suspicion in the paediatric age when short stature and vertebral/dental anomalies are vague. Macrodontia, oligodontia and dental agenesis (53%) were almost as frequent as skeletal anomalies, such as brachydactyly, short fifth finger, fifth finger clinodactyly, pectus excavatum/carinatum, delayed bone age. In 28.5% of individuals, prenatal ultrasound anomalies were reported. Except for three splicing variants, leading to a premature termination, variants were almost all frameshift. Our results, broadening the spectrum of KBGS phenotype progression, provide useful tools to facilitate differential diagnosis and improve clinical management. We suggest to consider a wider range of dental anomalies before excluding diagnosis and to perform a careful odontoiatric/ear-nose-throat (ENT) evaluation in order to look for even submucosal palate cleft given the high percentage of palate abnormalities. NGS approaches, following evidence of antenatal ultrasound anomalies, should include ANKRD11.

Expanded cardiovascular phenotype of Myhre syndrome includes tetralogy of Fallot suggesting a role for SMAD4 in human neural crest defects

Tetralogy of Fallot (ToF) can be associated with a wide range of extracardiac anomalies, with an underlying etiology identified in approximately 10% of cases. Individuals affected with Myhre syndrome due to recurrent SMAD4 mutations frequently have cardiovascular anomalies, including congenital heart defects. In addition to two patients in the literature with ToF, we describe five additional individuals with Myhre syndrome and classic ToF, ToF with pulmonary atresia and multiple aorto-pulmonary collaterals, and ToF with absent pulmonary valve. Aorta hypoplasia was documented in one patient and suspected in another two. In half of these individuals, postoperative cardiac dysfunction was thought to be more severe than classic postoperative ToF repair. There may be an increase in right ventricular pressure, and right ventricular dysfunction due to free pulmonic regurgitation. Noncardiac developmental abnormalities in our series and the literature, including corectopia, heterochromia iridis, and congenital miosis suggest an underlying defect of neural crest cell migration in Myhre syndrome. We advise clinicians that Myhre syndrome should be considered in the genetic evaluation of a child with ToF, short stature, unusual facial features, and developmental delay, as these children may be at risk for increased postoperative morbidity. Additional research is needed to investigate the hypothesis that postoperative hemodynamics in these patients may be consistent with restrictive myocardial physiology.

Unilateral testicular enlargement in a teenager with Beckwith-Wiedemann syndrome: a case report

BACKGROUND

Beckwith-Wiedemann syndrome (BWS) is a rare congenital overgrowth disorder. A major feature is lateralized overgrowth, which can variably involve a single body district up to the entire hemisome. Visceral asymmetrical involvement has been observed, commonly represented by enlargement of one kidney or adrenal gland, rather than one gonad.

CASE PRESENTATION

We report the case of a pubertal boy affected by BWS, who developed a progressive testicular enlargement, ipsilateral to the pre-existing external body overgrowth. Asymptomatic unilateral testis enlargement started after regular pubertal onset and worsened over time, without any associated pathological findings in a long-term follow-up. Since biopsy is not indicated in case of benign macro-orchidism, we hypothesize that this asymmetric enlargement could be an expression of visceral lateralized overgrowth in BWS.

CONCLUSIONS

At the best of our knowledge, this is the first detailed report of unilateral testicular overgrowth in BWS. We revised common causes of painless unilateral scrotal masses in the pediatric age. Considering both the overall frequency of neoplasia and the malignancies predisposition in BWS, a testicular cancer should be carefully ruled out through a close follow-up, before stating a benign condition. A normal ultrasound pattern, together with normal serum hormonal levels and negative tumor markers, make testicular neoplasms highly unlikely.

Could a chimeric condition be responsible for unexpected genetic syndromes? The role of the single nucleotide polymorphism-array analysis

In this paper, is reported the identification of two chimeric patients, a rare finding if sexual abnormalities are absent. However, their chimeric condition is responsible at least for the Silver-Russell phenotype observed in one of the two patients. By single nucleotide polymorphism-array analyses, it was possible to clearly define the mechanism responsible for this unusual finding, underlining the importance of this technique in bringing out the perhaps submerged world of chimeras.

Contribution of MUTYH Variants to Male Breast Cancer Risk: Results From a Multicenter Study in Italy

Inherited mutations in BRCA1, and, mainly, BRCA2 genes are associated with increased risk of male breast cancer (MBC). Mutations in PALB2 and CHEK2 genes may also increase MBC risk. Overall, these genes are functionally linked to DNA repair pathways, highlighting the central role of genome maintenance in MBC genetic predisposition. MUTYH is a DNA repair gene whose biallelic germline variants cause MUTYH-associated polyposis (MAP) syndrome. Monoallelic MUTYH variants have been reported in families with both colorectal and breast cancer and there is some evidence on increased breast cancer risk in women with monoallelic variants. In this study, we aimed to investigate whether MUTYH germline variants may contribute to MBC susceptibility. To this aim, we screened the entire coding region of MUTYH in 503 BRCA1/2 mutation negative MBC cases by multigene panel analysis. Moreover, we genotyped selected variants, including p.Tyr179Cys, p.Gly396Asp, p.Arg245His, p.Gly264Trpfs^*7, and p.Gln338His, in a total of 560 MBC cases and 1,540 male controls. Biallelic MUTYH pathogenic variants (p.Tyr179Cys/p.Arg241Trp) were identified in one MBC patient with phenotypic manifestation of adenomatous polyposis. Monoallelic pathogenic variants were identified in 14 (2.5%) MBC patients, in particular, p.Tyr179Cys was detected in seven cases, p.Gly396Asp in five cases, p.Arg245His and p.Gly264Trpfs^*7 in one case each. The majority of MBC cases with MUTYH pathogenic variants had family history of cancer including breast, colorectal, and gastric cancers. In the case-control study, an association between the variant p.Tyr179Cys and increased MBC risk emerged by multivariate analysis [odds ratio (OR) = 4.54; 95% confidence interval (CI): 1.17-17.58; p = 0.028]. Overall, our study suggests that MUTYH pathogenic variants may have a role in MBC and, in particular, the p.Tyr179Cys variant may be a low/moderate penetrance risk allele for MBC. Moreover, our results suggest that MBC may be part of the tumor spectrum associated with MAP syndrome, with implication in the clinical management of patients and their relatives. Large-scale collaborative studies are needed to validate these findings.

Nutrition and Lung Growth

Experimental evidence from animal models and epidemiology studies has demonstrated that nutrition affects lung development and may have a lifelong impact on respiratory health. Chronic restriction of nutrients and/or oxygen during pregnancy causes structural changes in the airways and parenchyma that may result in abnormal lung function, which is tracked throughout life. Inadequate nutritional management in very premature infants hampers lung growth and may be a contributing factor in the pathogenesis of bronchopulmonary dysplasia. Recent evidence seems to indicate that infant and childhood malnutrition does not determine lung function impairment even in the presence of reduced lung size due to delayed body growth. This review will focus on the effects of malnutrition occurring at critical time periods such as pregnancy, early life, and childhood, on lung growth and long-term lung function.

Phenotypic expression of 19q13.32 microdeletions: Report of a new patient and review of the literature

The phenotypic manifestations of microdeletions in the 19q13.32 region are still poorly known. In this paper we report a patient who presented with hypotonia, developmental delay, facial dysmorphism, micrognathia, kyphoscoliosis, and buried penis. Chromosomal microarray revealed an interstitial 327 kb de novo microdeletion in the 19q13.32 region comprising eight genes (ARGHAP35, NPAS1, TMEM160, ZC3H4, SAE1, BBC3, MIR3190, and MIR3191). Previously reported cases of microdeletions in the 19q13.32 region were reviewed and compared to our patient, highlighting the common features of a possible 19q13.32 microdeletion syndrome.