Serpentine fibula--polycystic kidney syndrome and Melnick-Needles syndrome are different disorders

Notch Pathway and Inherited Diseases: Challenge and Promise

The evolutionary highly conserved Notch pathway governs many cellular core processes including cell fate decisions. Although it is characterized by a simple molecular design, Notch signaling, which first developed in metazoans, represents one of the most important pathways that govern embryonic development. Consequently, a broad variety of independent inherited diseases linked to defective Notch signaling has now been identified, including Alagille, Adams-Oliver, and Hajdu-Cheney syndromes, CADASIL (cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy), early-onset arteriopathy with cavitating leukodystrophy, lateral meningocele syndrome, and infantile myofibromatosis. In this review, we give a brief overview on molecular pathology and clinical findings in congenital diseases linked to the Notch pathway. Moreover, we discuss future developments in basic science and clinical practice that may emerge from recent progress in our understanding of the role of Notch in health and disease.

Congenital Glaucoma: a Novel Ocular Manifestation of Hajdu-Cheney Syndrome

Hajdu-Cheney Syndrome (HSC) is a rare multisystem disease in which the phenotype involves acro-osteolysis, severe osteoporosis, short stature, wormian bones, facial dysmorphism, central neurological abnormalities, cardiovascular defects, and polycystic kidneys. We describe an infant with severe manifestations of HCS in whom congenital glaucoma was a significant early feature, which has not been reported to date. HCS cases reported to date have involved truncating mutations in exon 34 of NOTCH2 upstream the PEST domain that lead to the development of a truncated and stable NOTCH2 protein which upregluates notch signaling. We describe a hitherto undescribed missense mutation that is predicted to be pathogenic, with functional characterization remaining to be performed. Serpentine fibula-polycystic kidney syndrome (SFPKS) is allelic to HCS and commonly associated with missense NOTCH2 mutations. Our patient provides new ophthalmological manifestations of HCS and provides insight into the potential role of notch signaling in the anterior chamber development.

Clinical and experimental aspects of notch receptor signaling: Hajdu-Cheney syndrome and related disorders

BACKGROUND

There are four Notch transmembrane receptors that determine the fate and function of cells. Notch is activated following its interactions with ligands of the Jagged and Delta-like families that lead to the cleavage and release of the Notch intracellular domain (NICD); this translocates to the nucleus to induce the transcription of Notch target genes. Genetic disorders of loss- and gain-of-NOTCH function present with severe clinical manifestations.

BASIC PROCEDURES

In this article, current knowledge of Hajdu Cheney Syndrome (HCS) and related disorders is reviewed.

MAIN FINDINGS

HCS is a rare genetic disorder characterized by acroosteolysis, fractures, short stature, neurological manifestations, craniofacial developmental abnormalities, cardiovascular defects and polycystic kidneys. HCS is associated with NOTCH2 gain-of-function mutations. An experimental mouse model of the disease revealed that the bone loss is secondary to increased osteoclastogenesis and bone resorption due to enhanced expression of receptor activator of nuclear factor kappa B ligand (Rankl). This would suggest that inhibitors of bone resorption might prove to be beneficial in the treatment of the bone loss associated with HCS. Notch2 is a determinant of B-cell allocation in the marginal zone of the spleen and "somatic" mutations analogous to those found in HCS are associated with B-cell lymphomas of the marginal zone, but there are no reports of lymphomas associated with HCS.

CONCLUSION

In conclusion, HCS is a serious genetic disorder associated with NOTCH2 mutations. New experimental models have offered insight on mechanisms responsible for the manifestations of HCS.

Hajdu-Cheney Syndrome, a Disease Associated with NOTCH2 Mutations

Notch plays an important function in skeletal homeostasis, osteoblastogenesis, and osteoclastogenesis. Hajdu-Cheney syndrome (HCS) is a rare disease associated with mutations in NOTCH2 leading to the translation of a truncated NOTCH2 stable protein. As a consequence, a gain-of-NOTCH2 function is manifested. HCS is inherited as an autosomal dominant disease although sporadic cases exist. HCS is characterized by craniofacial developmental defects, including platybasia and wormian bones, osteoporosis with fractures, and acro-osteolysis. Subjects may suffer severe neurological complications, and HCS presents with cardiovascular defects and polycystic kidneys. An experimental mouse model harboring a HCSNotch2 mutation exhibits osteopenia secondary to enhanced bone resorption suggesting this as a possible mechanism for the skeletal disease. If the same mechanisms were operational in humans, anti-resorptive therapy could correct the bone loss, but not necessarily the acro-osteolysis. In conclusion, HCS is a devastating disease associated with a gain-of-NOTCH2 function resulting in diverse clinical manifestations.

Hajdu-Cheney syndrome: a review

Hajdu Cheney Syndrome (HCS), Orpha 955, is a rare disease characterized by acroosteolysis, severe osteoporosis, short stature, specific craniofacial features, wormian bones, neurological symptoms, cardiovascular defects and polycystic kidneys. HCS is rare and is inherited as autosomal dominant although many sporadic cases have been reported. HCS is associated with mutations in exon 34 of NOTCH2 upstream the PEST domain that lead to the creation of a truncated and stable NOTCH2 protein with enhanced NOTCH2 signaling activity. Although the number of cases with NOTCH2 mutations reported are limited, it would seem that the diagnosis of HCS can be established by sequence analysis of exon 34 of NOTCH2. Notch receptors are single-pass transmembrane proteins that determine cell fate, and play a critical role in skeletal development and homeostasis. Dysregulation of Notch signaling is associated with skeletal developmental disorders. There is limited information about the mechanisms of the bone loss and acroosteolysis in HCS making decisions regarding therapeutic intervention difficult. Bone antiresorptive and anabolic agents have been tried to treat the osteoporosis, but their benefit has not been established. In conclusion, Notch regulates skeletal development and bone remodeling, and gain-of-function mutations of NOTCH2 are associated with HCS.

Notch signaling in skeletal health and disease

Notch receptors are single-pass transmembrane proteins that determine cell fate. Upon Notch ligand interactions, proteolytic cleavages release the Notch intracellular domain, which translocates to the nucleus to regulate the transcription of target genes, including Hairy enhancer of split (Hes) and Hes related to YRPW motif (Hey). Notch is critical for skeletal development and activity of skeletal cells, and dysregulation of Notch signaling is associated with human diseases affecting the skeleton. Inherited or sporadic mutations in components of the Notch signaling pathway are associated with spondylocostal dysostosis, spondylothoracic dysostosis and recessive brachydactyly, diseases characterized by skeletal patterning defects. Inactivating mutations of the Notch ligand JAG1 or of NOTCH2 are associated with Alagille syndrome, and activating mutations in NOTCH2 are associated with Hajdu-Cheney syndrome (HCS). Individuals affected by HCS exhibit osteolysis in distal phalanges and osteoporosis. NOTCH is activated in selected tumors, such as osteosarcoma, and in breast cancer cells that form osteolytic bone metastases. In conclusion, Notch regulates skeletal development and bone remodeling, and gain- or loss-of-function mutations of Notch signaling result in important skeletal diseases.

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.

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.

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.

Hajdu-Cheney syndrome: report of a case

Hajdu-Cheney syndrome is a rare disorder characterized by short stature, joint hypermobility, distinctive craniofacial and skull abnormalities, dental anomalies, and acroosteolysis of the distal phalanges. Cystic kidneys have been associated with some cases. We report a case of a 12-year-old girl with renal failure who underwent bilateral nephrectomies. Histopathological examination revealed polycystic kidneys with numerous nodules located throughout the kidney composed of basaloid epithelial cells.

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

Several disorders characterized primarily by anomalies of the skeleton have recently been shown to be caused by mutations in the X-linked gene, FLNA. One of these conditions, the Melnick-Needles syndrome exhibits a phenotype that shares overlap with that of serpentine fibula-polycystic kidney syndrome and the autosomal dominant condition, Hajdu-Cheney syndrome. Here, we describe three individuals with these diagnoses. The individual with serpentine fibula-polycystic kidney syndrome, the fifth case reported in the literature, exhibited wormian bones which further expands the phenotypic spectrum for this condition and extends the overlap with Hajdu-Cheney syndrome. All three members of the filamin gene family, FLNA, and its functionally related paralogues, FLNB and FLNC, were screened for pathogenic mutations in all three individuals. We found a mutation in FLNA in the individual with Melnick-Needles syndrome, but no pathogenic variants in any filamin gene in the two individuals with Hajdu-Cheney syndrome and serpentine fibula-polycystic kidney syndrome. Clinical and molecular evidence indicates that Melnick-Needles syndrome is aetiologically distinct from Hajdu-Cheney syndrome and serpentine fibula-polycystic kidney syndrome, but these two latter conditions share many clinical similarities and may prove to be allelic to one another.

Fronto-otopalatodigital osteodysplasia: clinical evidence for a single entity encompassing Melnick-Needles syndrome, otopalatodigital syndrome types 1 and 2, and frontometaphyseal dysplasia

Otopalatodigital syndrome type 2 is an X-linked disorder with minimal expression in carrier females and comprises typical facial anomalies and a generalized bone dysplasia with osteodysplastic changes, brachydactyly, and impaired survival. Recently several other severe malformations were reported in the condition. Melnick-Needles syndrome is an X-linked dominant disorder. Affected males are usually sporadic cases. The exceptional males born to symptomatic women present with a lethal disorder comprising generalized osteodysplasia, deficiency of the first ray, and facial anomalies strikingly similar to those of otopalatodigital syndrome type 2. We report here on three boys with classical, severe, and lethal otopalatodigital type 2 syndrome, and three boys with severe (lethal) Melnick-Needles syndrome, born to affected mothers. We suggest that otopalatodigital type 1 and 2, Melnick-Needles syndrome and frontometaphyseal dysplasia, sharing many clinical manifestations and a similar mode of inheritance, are variants of the same condition: fronto-otopalatodigital osteodysplasia. The relationships to similar syndromes (i.e., Saint-Martin-Gardner-Morrisson syndrome, serpentine fibula syndrome, atelosteogenesis type 3, boomerang dysplasia, and Yunis-Varon syndrome) are discussed.

Clinical and radiological aspects in Melnick-Needles syndrome

Melnick-Needles syndrome is an X-linked dominant bone dysplasia, lethal in males, characterized by a typical facies and characteristic radiological findings: including sclerosis of skull base and mastoids. S-shaped appearance of tibia; cortical irregularities with a ribbon appearance of the ribs. About 48 well-documented cases have been reported, most of them were sporadic. Parental transmission has been published in only 11 kindreds. We are presenting the first Brazilian family with mother-daughter transmission. The proposita presented the typical clinical and radiological features with characteristic facies, severe thoracic cage restriction and pulmonary hypertension. Her mother was more mildly affected.

Further evidence that the Hajdu-Cheney syndrome and the "serpentine fibula-polycystic kidney syndrome" are a single entity

The Hajdu-Cheney syndrome (HCS) is a rare autosomal dominant disorder. It comprises a coarse face, short neck, hirsutism, joint laxity, and normal intelligence. Bone dysplasias, include acro-osteolysis, bathrocephaly, and vertebral anomalies. In 1988, Exner [1988: Eur J Pediatr 147:544-546] coined the term "serpentine fibula-polycystic kidney syndrome" (SFPKS) when he reported on a girl with short stature, unusual facial appearance, polycystic kidneys, and elongated curved fibulae. He postulated that it was a new entity different from the Melnick-Needles syndrome. Since his report, five similar cases have been published. Similarities between both HCS and SFPKS were noticed first by us and then by other authors. In this report we show that many clinical and radiological characteristics are shared by the HCS and the SFPKS and hypothesize that they represent a single entity with a variable degree of expression.

Vocal cord paralysis and cystic kidney disease in Hajdu-Cheney syndrome

In this report we describe the clinical history and symptoms in a 36-year-old male with Hajdu-Cheney syndrome, an autosomal dominant condition with dissolution of the terminal phalanges (acro-osteolysis), characteristic craniofacial dysmorphism, and musculoskeletal alterations. He was admitted at that age because of progressive respiratory problems, with Cheyne-Stokes respiration and bilateral vocal cord paralysis. Terminal renal failure with cystic renal disease was diagnosed at the age of 14 years. The findings in the present patient illustrate the risk of progressive neurologic degeneration with involvement of the cranial nerves in patients with Hajdu-Cheney syndrome. Moreover, we confirm that cystic renal changes are an integral part of Hajdu-Cheney syndrome, and agree that Hajdu-Cheney syndrome and Serpentine fibula syndrome are probably variant examples of the same disease.

Mental retardation, distinct craniofacial dysmorphism, and central nervous system malformation: confirmation of a syndrome

We present a child with severe mental retardation, a central nervous system malformation, signs of ectodermal dysplasia, and a distinct craniofacial dysmorphism. Similar but less pronounced craniofacial features were present in the mildly mentally retarded mother. This observation confirms a previous report of a boy with the same MCA-MR syndrome and suggests X linked or autosomal dominant inheritance.

Cystic kidney disease in Hajdu-Cheney syndrome

We report on 2 unrelated patients with Hajdu-Cheney acroosteolysis syndrome, who had cystic kidneys with ultrasonographic changes similar to those of autosomal dominant polycystic kidney disease. Neither had a family history of Hajdu-Cheney syndrome or polycystic kidneys, nor manifestations of any other syndrome. On the basis of the findings in these 2 patients and a review of published cases, we suggest that cystic kidneys are an important component of Hajdu-Cheney syndrome.