Phenotypic overlap in Melnick-Needles, serpentine fibula-polycystic kidney and Hajdu-Cheney syndromes: a clinical and molecular study in three patients

Mutation of FLNA attenuating the migration of abdominal muscles contributed to Melnick-Needles syndrome (MNS) in a family with recurrent miscarriage

BACKGROUND

Filamin A, encoded by the X-linked gene FLNA, links the cell membrane with the cytoskeleton and acts as a regulator of the actin cytoskeleton. Mutations in FLNA cause a large spectrum of congenital malformations during embryonic development, including Melnick-Needles syndrome (MNS). However, reports of MNS, especially in males, are rare, and the pathogenesis molecular mechanisms are not well understood.

METHODS

We found a family with two consecutive miscarriages of similar fetuses with multiple malformations. DNA was extracted from peripheral blood and tissues, and whole exome sequencing was performed for genetic analysis. Then, we created a C57BL/6 mouse with a point mutation by CRISPR/Cas-mediated genome engineering. The migration of primary abdominal muscle cell was detected by wound healing assay.

RESULTS

The first fetus showed congenital hygroma colli and omphalocele identified by ultrasound at 12 wks; the second fetus showed hygroma colli and thoraco abdominoschisis at 12 wks, with a new hemizygous mutation c.4420G>A in exon 26 of the FLNA gene, which is predicted to cause an amino acid substitution (p.Asp1474Asn). The mother and grandmother were both present in the c.4420G>A heterozygous state, and the mother's healthy brother had wild-type FLNA. These FLNA-mutated mice exhibited a broader central gap between the rectus abdominis than the wild type (WT), similar to the midline structure dysplasia of the abdominal wall in the two fetuses. Wound healing assays showed the attenuated migration capacity of abdominal muscle cells in mice with mutated FLNA. Finally, we summarized the cases of MNS with FLNA mutation from the accessible published literature thus far.

CONCLUSION

Our research revealed a mutation site of the FLNA for MNS and explored the mechanism of midline structure dysplasia in the abdominal wall of male patients, which could provide more evidence for the clinical diagnosis and genetic counseling of families with these disorders.

Hajdu-Cheney syndrome with atypical cardiovascular abnormalities

Hajdu-Cheney syndrome is an ultra-rare autosomal dominant disorder caused by a heterozygous variant in NOTCH2 gene. Characteristic features include osteolysis, distinct facial appearance, skull deformity, joint laxity, osteoporosis, and short stature. Associated abnormalities are congenital heart disease, congenital defects of the kidney, and neurological problems. Here, we present the first reported case of an African child with a variant in NOTCH2 gene and features of Hajdu-Cheney syndrome in whom we detected a congenital heart defect that has not been previously reported in association with the syndrome. To appropriately characterize this disease and document correct proportion of cardiovascular malformation associations, echocardiography is recommended for all cases of Hajdu Cheney syndrome.

Novel phenotypic feature in a patient with a recurrent NOTCH2 nonsense mutation

Pathogenic variants in NOTCH2 which encodes a single-pass transmembrane protein have been identified as a cause of several autosomal dominant congenital disorders. In particular, truncating mutations in exon 34 have been found in patients with skeletal abnormalities and dysmorphic features. We describe a patient with a de novo variant in NOTCH2 who displayed features of both Hajdu-Cheney syndrome (HJCYS) and serpentine fibula-polycystic kidney syndrome (SFPKS). The recurrent nonsense variant in exon 34 has been reported in seven other patients with syndromic presentations, making it the most common pathogenic variant for NOTCH2 in congenital disorders. In addition to the core features of HJCYS and SFPKS, there was a gastrointestinal tract malformation of an imperforate anus which has not been reported in patients with pathogenic variants in NOTCH2.

Interstitial lung disease in infancy

There is a wide differential diagnosis of early onset respiratory distress especially in term babies, and interstitial lung disease (chILD) is a rare but important consideration in this context. chILD manifesting immediately after birth is usually related to mutations in surfactant protein genes, or conditions related to the Congenital Acinar Dysplasia -Alveolar capillary dysplasia - Congenital Alveolar Dysplasia (CAD-ACD) spectrum. There is currently no specific treatment for these conditions, and management is supportive. Prognosis is very poor in most of these babies if onset is early, with relentless respiratory deterioration unless transplanted. Ideally, the diagnosis is made on genetic analysis, but this may be time-consuming and complex in CAD-ACD spectrum, so lung biopsy may be needed to avoid prolonged and futile treatment being instituted. Milder forms with prolonged survival have been reported. Early onset, less severe chILD is usually related to neuroendocrine cell hyperplasia of infancy (NEHI), pulmonary interstitial glycogenosis (PIG) and less severe disorders of surfactant proteins. PIG and NEHI are not specific entities, but are pulmonary dysmaturity syndromes, and there may be a number of underlying genetic and other cause. If the child is stable and thriving, many will not be subject to lung biopsy, and slow improvement and weaning of supplemental oxygen can be anticipated. Where possible, a precise genetic diagnosis should be made in early onset cHILD allow for genetic counselling. chILD survivors and their families have complex respiratory and other needs, and co-ordinated, multi-disciplinary support in the community is essential.

Hajdu-Cheney Syndrome: A Systematic Review of the Literature

Hajdu–Cheney syndrome (HCS) is a rare genetic disease that causes acroosteolysis and generalized osteoporosis, accompanied by a series of developmental skeletal disorders and multiple clinical and radiological manifestations. It has an autosomal dominant inheritance, although there are several sporadic non-hereditary cases. The gene that has been associated with Hajdu-Cheney syndrome is NOTCH2. The described phenotype and clinical signs and symptoms are many, varied, and evolve over time. As few as 50 cases of this disease, for which there is currently no curative treatment, have been reported to date. The main objective of this systematic review was to evaluate the results obtained in research regarding Hajdu–Cheney Syndrome. The findings are reported in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines and were registered on the web PROSPERO under the registration number CRD42020164377. A bibliographic search was carried out using the online databases Orphanet, PubMed, and Scielo; articles from other open access sources were also considered. Finally, 76 articles were included, and after their analysis, we have obtained a series of hypotheses as results that will support further studies on this matter.

Bisphosphonate therapy for spinal osteoporosis in Hajdu-Cheney syndrome - new data and literature review

Background

Hajdu-Cheney syndrome (HCS) (#OMIM 102500) is a rare, autosomal dominant condition that presents in early childhood. It is caused by mutations in the terminal exon of NOTCH2, which encodes the transmembrane NOTCH2 receptor. This pathway is involved in the coupled processes of bone formation and resorption. The skeletal features of HCS include acro-osteolysis of the digits and osteoporosis commonly affecting vertebrae and long bones. Fractures are a prominent feature and are associated with significant morbidity. There is no specific treatment, but with both acro-osteolysis and generalized osteoporosis, it is possible that anti-resorptive treatment might be of benefit. However, to date only a few case reports have evaluated the effectiveness of bisphosphonate treatment.

Methods

We describe the clinical features, treatment regimens and response to bisphosphonate treatment in 7 newly described patients aged 6–39 with HCS, and pooled the data with that from 8 previously published cases (a total of 17 courses of treatment in 15 individuals).

Results

The mean lumbar spine bone mineral density (BMD) z-score before treatment was − 2.9 (SD 1.2). In 14 courses of treatment (82%), there was an increase in BMD with bisphosphonate treatment, but the impact (in terms of change in spinal BMD z-score) appeared to be less with advancing age (p = 0.01). There was no evidence that acro-osteolysis was prevented.

Conclusions

Although individual response is variable and age-related, the data support a role for bisphosphonates in preventing or treating spinal osteoporosis in HCS, but bone loss from the lumbar spine may be rapid after cessation.

End-Stage Renal Disease in an Infant With Hajdu-Cheney Syndrome

Hajdu-Cheney syndrome (HJCYS) is a rare, autosomal dominant, skeletal disorder caused by mutations in the NOTCH2 signaling pathway for which genetic testing has recently become available. Renal abnormalities are associated in at least 10% of cases. We present an 8-year-old Caucasian boy, born with multiple dysmorphic features consistent with HJCYS. Imaging of the urinary tract revealed bilateral cystic dysplastic kidneys with associated vesicoureteral reflux. Renal function has been impaired since birth and deteriorated progressively to end-stage renal disease (ESRD) by the age of two and a half years, when peritoneal dialysis was initiated and only recently renal transplantation was performed. Additional congenital abnormalities and multisystem involvement in HJCYS further complicated management, and he developed refractory anemia. Molecular diagnosis was confirmed by identification of a truncating mutation in exon 34 of NOTCH2. Although, renal abnormalities are considered an integral part of the HJCYS, published reports on ESRD are scarce. In those few published cases, where ESRD was recognized, renal failure developed either in late adolescence or adulthood. This is the first report of early ESRD occurring in a child. Patients with HJCYS may need chronic renal replacement therapy even in early childhood. The management of these children can be challenging given the multisystemic manifestations of HJCYS.

Clinical consequences in truncating mutations in exon 34 of NOTCH2: report of six patients with Hajdu-Cheney syndrome and a patient with serpentine fibula polycystic kidney syndrome

It is debatable whether Hajdu-Cheney syndrome (HCS) and serpentine fibula-polycystic kidney syndrome (SFPKS) represent a single clinical entity with a variable degree of expression or two different entities, because both disorders share common clinical and radiological manifestations, including similar craniofacial characteristics, and defective bone mineralization. Since it was shown that heterozygous truncating mutations in NOTCH2 are responsible for both HCS and SFPKS, 37 patients with HCS and four patients with SFPKS are reported. To elucidate the clinical consequences of NOTCH2 mutations, we present detailed clinical information for seven patients with truncating mutations in exon 34 of NOTCH2, six with HCS and one with SFPKS. In addition, we review all the reported patients whose clinical manifestations are available. We found 13 manifestations including craniofacial features, acroosteolysis, Wormian bones, and osteoporosis in >75% of NOTCH2-positive patients. Acroosteolysis was observed in two patients with SFPKS and bowing fibulae were found in two patients with HCS. These clinical and molecular data would support the notion that HCS and SFPKS are a single disorder.

Severe osteoporosis and mutation in NOTCH2 gene in a woman with Hajdu-Cheney syndrome

Hajdu-Cheney syndrome (HCS) is a rare genetic disorder characterised by acro-osteolysis, skull deformation and generalised osteoporosis. Recently, truncating mutations in the last exon of NOTCH2, a protein-coding gene, were found to be responsible. We present the case of a young woman with HCS in whom clinical and radiologic diagnosis was confirmed with DNA tests.

Serpentine fibula-polycystic kidney syndrome caused by truncating mutations in NOTCH2

Serpentine fibula-polycystic kidney syndrome (SFPKS) is a rare disorder characterized by the association of craniofacial anomalies, radiological findings (wormian bones, elongated and bowed fibulae), polycystic kidneys, and normal intelligence. SFPKS shares many similarities with Hajdu-Cheney syndrome (HCS). We and others recently showed that truncating mutations in the last exon of NOTCH2 cause HCS. Here, we identify by Sanger sequencing two different heterozygous truncating mutations in the last exon of NOTCH2 in two unrelated patients with SFPKS. In one family, we show that the mutation occurred de novo. These findings demonstrate that SFPKS and HCS are both conditions caused by NOTCH2 mutations.

Serpentine fibula polycystic kidney syndrome is part of the phenotypic spectrum of Hajdu-Cheney syndrome

Serpentine fibula polycystic kidney syndrome (SFPKS; MIM600330) is a rare skeletal dysplasia that has polycystic kidneys and dysmorphic facies as additional defining phenotypic components. The nosological classification of this disease has been debated as the condition shares features common to other skeletal dysplasias such as Melnick Needles syndrome (MNS; MIM309350) and Hajdu-Cheney Syndrome (HCS; MIM102500). Here, two previously reported cases of SFPKS are presented with emphasis on their phenotypic evolution. With the recent discovery that HCS is caused by mutations in NOTCH2, DNA from the both cases was examined and both were found to have truncating mutations in exon 34 of NOTCH2. The phenotypic evolution of SFPKS and this molecular analysis strongly suggest that SFPKS is part of the phenotypic spectrum of HCS and should no longer be classified as a distinct disease entity.

Mutations in NOTCH2 cause Hajdu-Cheney syndrome, a disorder of severe and progressive bone loss

We used an exome-sequencing strategy and identified an allelic series of NOTCH2 mutations in Hajdu-Cheney syndrome, an autosomal dominant multisystem disorder characterized by severe and progressive bone loss. The Hajdu-Cheney syndrome mutations are predicted to lead to the premature truncation of NOTCH2 with either disruption or loss of the C-terminal proline-glutamate-serine-threonine-rich proteolytic recognition sequence, the absence of which has previously been shown to increase Notch signaling.

Hajdu-Cheney syndrome with severe dural ectasia

Hajdu-Cheney syndrome (HCS) is an autosomal dominant condition comprising osteolysis of the terminal phalanges, characteristic craniofacial abnormalities, dental anomalies, and proportionate short stature. The clinical and radiological findings develop and progress with age. Here, we report on a HCS patient with severe scoliosis and exceptionally massive dural ectasia. Congenital scoliosis and dural ectasia have not been reported previously in HCS.

Hajdu-Cheney syndrome associated with serpentine fibulae and polycystic kidney disease

Six patients who presented with craniofacial anomalies, musculoskeletal anomalies including elongated and bowed (serpentine) fibulae, and polycystic kidneys are reported. This association of anomalies is referred to as serpentine fibula polycystic kidney syndrome (SFPKS) and is currently interpreted as a manifestation of Hajdu-Cheney syndrome (HCS). We report a new instance of this association of anomalies and review the clinical and radiographic features of HCS and of the reported cases of SFPKS.