Neuropathology of Raine syndrome

Raine's syndrome: rare disease from neurosurgical perspective

Raine's syndrome (RS) is a rare genetic disorder. Only 25 cases are in literature. Occurs due to genetic mutation resulting in deranged bone metabolism. Few cases are reported discussing the neurosurgical ramifications of the disease. We report a child diagnosed with RS. He was presented with multisutural synostosis requiring craniofacial intervention with two vault expansions. Additionally, required VP shunt due to hydrocephalus. We consider our case unique among reports of RS, as our patient has survived for 10. He died due to valve obstruction of the VP shunt. We also present a review of relevant medical literature.

Mutations of family with sequence similarity 20-member C gene causing lethal and nonlethal Raine syndrome causes hypophosphatemia rickets

Family with sequence similarity 20-member C (FAM20C) is a kinase specific to most of the secreted phosphoproteome. FAM20C has been identified as the causative gene of Raine syndrome, initially characterized by lethal osteosclerosis bone dysplasia. However, since the identification of the cases of nonlethal Raine syndrome characterized by hypophosphatemia rickets, the previous definition of Raine syndrome has become debatable and raised a question about the role of mutations of FAM20C in controversial skeletal manifestation in the two forms of the disease. In this study, we aimed to investigate the influence of FAM20C mutations on skeletogenesis. We developed transgenic mice expressing Fam20c mutations mimicking those associated with human lethal and nonlethal Raine syndrome. The results revealed that transgenic mice expressing the mutant Fam20c found in the lethal (KO;G374R) and nonlethal (KO;D446N) Raine syndrome exhibited osteomalacia without osteosclerotic features. Additionally, both mutants significantly increased the expression of the Fgf23, indicating that Fam20c deficiency in skeletal compartments causes hypophosphatemia rickets. Furthermore, as FAM20C kinase activity catalyzes the phosphorylation of secreted proteomes other than those in the skeletal system, global FAM20C deficiency may trigger alterations in other systems resulting in osteosclerosis secondary to hypophosphatemia rickets. Together, the findings of this study suggest that FAM20C deficiency primarily causes hypophosphatemia rickets or osteomalacia; however, the heterogeneous skeletal manifestation in Raine syndrome was not determined solely by specific mutations of FAM20C. The findings also implicated that rickets or osteomalacia caused by FAM20C deficiency would deteriorate into osteosclerosis by the defects from other systems or environmental impacts.

Intracranial calcification in Fam20c-deficient mice recapitulates human Raine syndrome

FAM20C (family with sequence similarity 20-member C) is a protein kinase that phosphorylates secretory proteins, including the proteins that are essential to the formation and mineralization of calcified tissues. FAM20C loss-of-function mutations cause Raine syndrome in humans, characterized by generalized osteosclerosis, distinctive craniofacial dysmorphism, along with extensive intracranial calcification. Our previous studies revealed that inactivation of Fam20c in mice led to hypophosphatemic rickets. In this study, we examined the expression of Fam20c in the mouse brain and investigated brain calcification in Fam20c-deficient mice. Reverse transcription polymerase chain reaction (RT-PCR), Western-blotting and in situ hybridization analyses demonstrated the broad expression of Fam20c in the mouse brain tissue. X-ray and histological analyses showed that the global deletion of Fam20c (mediated by Sox2-cre) resulted in brain calcification in mice after postnatal 3 months and that the calcifications were bilaterally distributed within the brain. There was mild perifocal microgliosis as well as astrogliosis around calcospherites. The calcifications were first observed in the thalamus, and later in the forebrain and hindbrain. Furthermore, brain-specific deletion (mediated by Nestin-cre) of Fam20c in mice also led to cerebral calcification at an older age (postnatal 6 months), but no obvious skeletal or dental defects. Our results suggest that the local loss of FAM20C function in the brain may directly account for intracranial calcification. We propose that FAM20C plays an essential role in maintaining normal brain homeostasis and preventing ectopic brain calcification.

FAM20C Overview: Classic and Novel Targets, Pathogenic Variants and Raine Syndrome Phenotypes

FAM20C is a gene coding for a protein kinase that targets S-X-E/pS motifs on different phosphoproteins belonging to diverse tissues. Pathogenic variants of FAM20C are responsible for Raine syndrome (RS), initially described as a lethal and congenital osteosclerotic dysplasia characterized by generalized atherosclerosis with periosteal bone formation, characteristic facial dysmorphisms and intracerebral calcifications. The aim of this review is to give an overview of targets and variants of FAM20C as well as RS aspects. We performed a wide phenotypic review focusing on clinical aspects and differences between all lethal (LRS) and non-lethal (NLRS) reported cases, besides the FAM20C pathogenic variant description for each. As new targets of FAM20C kinase have been identified, we reviewed FAM20C targets and their functions in bone and other tissues, with emphasis on novel targets not previously considered. We found the classic lethal and milder non-lethal phenotypes. The milder phenotype is defined by a large spectrum ranging from osteonecrosis to osteosclerosis with additional congenital defects or intellectual disability in some cases. We discuss our current understanding of FAM20C deficiency, its mechanism in RS through classic FAM20C targets in bone tissue and its potential biological relevance through novel targets in non-bone tissues.

Raine syndrome: Prenatal diagnosis based on recognizable fetal facial features and characteristic intracranial calcification

OBJECTIVE

The purpose of this study was to elucidate the facial morphology and the pattern of internal malformations in three fetuses with RS born to first cousins of Egyptian decent.

METHODS

The fetal ultrasonography findings were highly suggestive of RS leading to targeted Sanger sequencing of FAM20C and postnatal assessment.

RESULTS

The prenatal ultrasound findings of osteosclerotic skull, exorbitism, hypoplastic nose, midface hypoplasia, small mouth with down-curved corners, and a distinct and recognizable pattern of intracranial calcification were identified in three fetuses with RS. The calcifications were evident specifically around the corpus callosum and/or ventricular walls. Ectopic renal and hepatic calcifications, pulmonary hypoplasia, mild rhizomelic shortening of the upper limbs, intrauterine fractures, and cerebellar hypoplasia were also noted. Molecular analysis identified three novel homozygous variants, two frameshift: [c.456delC (p.Gly153Alafs*34)] in exon 1 and [c.905delT (Phe302Serfs*35)] in exon 4 and one nonsense mutation in exon 10, [c.1557C>G(p.Tyrs519*)]. The three variants were segregated with the phenotype. This is the first description of a phenotype associated with homozygous truncating variants of FAM20C.

CONCLUSION

RS has characteristic prenatal ultrasound findings which can improve the prenatal identification of this condition and help in guiding the molecular diagnosis and counseling.

Two Novel FAM20C Variants in A Family with Raine Syndrome

Two siblings from a Mexican family who carried lethal Raine syndrome are presented. A newborn term male (case 1) and his 21 gestational week brother (case 2), with a similar osteosclerotic pattern: generalized osteosclerosis, which is more evident in facial bones and cranial base. Prenatal findings at 21 weeks and histopathological features for case 2 are described. A novel combination of biallelic FAM20C pathogenic variants were detected, a maternal cytosine duplication at position 456 and a paternal deletion of a cytosine in position 474 in exon 1, which change the reading frame with a premature termination at codon 207 and 185 respectively. These changes are in concordance with a negative detection of the protein in liver and kidney as shown in case 2. Necropsy showed absence of pancreatic Langerhans Islets, which are reported here for the first time. Corpus callosum absence is added to the few reported cases of brain defects in Raine syndrome. This report shows two new FAM20C variants not described previously, and negative protein detection in the liver and the kidney. We highlight that lethal Raine syndrome is well defined as early as 21 weeks, including mineralization defects and craniofacial features. Pancreas and brain defects found here in FAM20C deficiency extend the functional spectrum of this protein to previously unknown organs.

A case of Raine syndrome presenting with facial dysmorphy and review of literature

Background

Raine syndrome (RS) – an extremely rare autosomal recessive genetic disorder, is caused by a biallelic mutation in the FAM20C gene. Some of the most common clinical features include generalized osteosclerosis with a periosteal bone formation, dysmorphic face, and thoracic hypoplasia. Many cases have also been reported with oro-dental abnormalities, and developmental delay. Most of the cases result in neonatal death. However, a few non-lethal RS cases have been reported where patients survive till adulthood and exhibits a heterogeneous clinical phenotype. Clinical diagnosis of RS has been done through facial appearance and radiological findings, while confirmatory diagnosis has been conducted through a molecular study of the FAM20C gene.

Case presentation

A 6-year-old girl was born to healthy third degree consanguineous parents. She presented with facial dysmorphy, delayed speech, and delayed cognition. Radiography showed small sclerotic areas in the lower part of the right femur, and an abnormally-shaped skull with minimal sclerosis in the lower occipital region. Computer tomography scan of the brain revealed mild cortical atrophy, and MRI scan of the brain showed corpus callosal dysgenesis with the absence of the rostral area. Chromosome banding at 500 band resolution showed a normal female karyotype. No quantitative genomic imbalance was detected by aCGH. Further study conducted using Clinical Exome Sequencing identified a homozygous missense variation c.1228 T > A (p.Ser410Thr) in the exon 6 of FAM20C gene – a likely pathogenic variant that confirmed the clinical diagnosis of RS. The variant was confirmed in the proband and her parents using Sanger sequencing. Prenatal diagnosis during subsequent pregnancy revealed heterozygous status of the fetus, and a normal carrier child was delivered at term.

Conclusions

The syndrome revealed markedly variable presentations such as facial dysmorphy and developmental delay, and was localized to diffuse bone osteosclerosis. Clinical indications, striking radiological findings and molecular testing of FAM20C gene confirmed the diagnosis of RS. A rarity of the disorder and inconsistent phenotype hindered the establishment of genotype-phenotype correlations in RS. Therefore, reporting more cases and conducting further research would be crucial in defining the variable radiologic and molecular defects of the lethal and non-lethal forms of this syndrome.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0593-x) contains supplementary material, which is available to authorized users.

Fetal ultrasonographic findings including cerebral hyperechogenicity in a patient with non-lethal form of Raine syndrome

Raine syndrome is a rare osteosclerotic bone dysplasia characterized by craniofacial anomalies and intracranial calcification. Most patients with Raine syndrome are of Arab ancestry and die during the neonatal period. We herein report a Japanese patient with non-lethal Raine syndrome who presented with characteristic cerebral hyperechogenicity and a hypoplastic nose by fetal ultrasonography. She was admitted to the NICU due to pyriform aperture stenosis. Craniofacial abnormalities, intracranial calcification, osteosclerosis, chondrodysplasia punctata, and a mutation of FAM20C was identified. She was subsequently discharged without surgical intervention and is now 2 years old with mild neurodevelopmental delays. Images of cerebral hyperechogenicity by fetal ultrasonography in a non-lethal case were described herein for the first time. This patient represents a rare occurrence of a child with Raine syndrome born to Japanese parents and confirms that this syndrome is not always lethal. Even if Raine syndrome is suspected in a fetus due to cerebral hyperechogenicity and a hypoplastic nose, cerebral hyperechogenicity without pulmonary hypoplasia does not always predict lethality or severe neurodevelopmental delays. The information provided herein will be useful for prenatal counseling.

Raine Syndrome (OMIM #259775), Caused By FAM20C Mutation, Is Congenital Sclerosing Osteomalacia With Cerebral Calcification (OMIM 259660)

In 1985, we briefly reported infant sisters with a unique, lethal, autosomal recessive disorder designated congenital sclerosing osteomalacia with cerebral calcification. In 1986, this condition was entered into Mendelian Inheritance In Man (MIM) as osteomalacia, sclerosing, with cerebral calcification (MIM 259660). However, no attestations followed. Instead, in 1989 Raine and colleagues published an affected neonate considering unprecedented the striking clinical and radiographic features. In 1992, "Raine syndrome" entered MIM formally as osteosclerotic bone dysplasia, lethal (MIM #259775). In 2007, the etiology emerged as loss-of-function mutation of FAM20C that encodes family with sequence similarity 20, member C. FAM20C is highly expressed in embryonic calcified tissues and encodes a kinase (dentin matrix protein 4) for most of the secreted phosphoproteome including FGF23, osteopontin, and other regulators of skeletal mineralization. Herein, we detail the clinical, radiological, biochemical, histopathological, and FAM20C findings of our patients. Following premortem tetracycline labeling, the proposita's non-decalcified skeletal histopathology after autopsy indicated no rickets but documented severe osteomalacia. Archival DNA revealed the sisters were compound heterozygotes for a unique missense mutation and a novel deletion in FAM20C. Individuals heterozygous for the missense mutation seemed to prematurely fuse their metopic suture and develop a metopic ridge sometimes including trigonocephaly. Our findings clarify FAM20C's role in hard tissue formation and mineralization, and show that Raine syndrome is congenital sclerosing osteomalacia with cerebral calcification. © 2016 American Society for Bone and Mineral Research.

Raine syndrome: an overview

Raine syndrome (RS) is a bone dysplasia characterised by generalised osteosclerosis with periosteal bone formation, characteristic face, and brain abnormalities [MIM # 259775]. Its prevalence is estimated to be < 1/1,000,000. Although it was originally thought always to be lethal, there have now been six reports of patients surviving into childhood and this phenotype is still being defined. The skeletal dysplasia predominantly affects craniofacial development explaining the severe proptosis, underdeveloped midface, depressed nasal bridge and short nose. The main radiological manifestation is a diffuse, marked osteosclerosis of the base of skull and long bones. Raine syndrome is caused by biallelic mutations in FAM20C, located on chromosome 7p22.3. This gene encodes a Golgi casein kinase, which phosphorylates serine residues of extracellular proteins involved in biomineralisation. Facial appearance and radiological findings allow the clinical diagnosis, and molecular testing of FAM20C can confirm this. Desmosterolosis and congenital cytomegalovirus infection may resemble Raine syndrome. If Raine syndrome is suspected prenatally the newborn should be admitted at a neonatal intensive care unit as significant respiratory distress is often present immediately after birth. We present here a review of the pertinent literature in clinical manifestations, molecular background, diagnosis and management.

Raine syndrome

Raine syndrome is a rare genetic disorder with characteristic features of exophthalmos, choanal atresia or stenosis, osteosclerosis and cerebral calcifications. Most of babies with this disorder die immediately after birth. We report a baby who was 7 weeks old at the time of presentation.

Exome sequencing reveals FAM20c mutations associated with fibroblast growth factor 23-related hypophosphatemia, dental anomalies, and ectopic calcification

Fibroblast growth factor 23 (FGF23) plays a crucial role in renal phosphate regulation, exemplified by the causal role of PHEX and DMP1 mutations in X-linked hypophosphatemic rickets and autosomal recessive rickets type 1, respectively. Using whole exome sequencing we identified compound heterozygous mutations in family with sequence similarity 20, member C (FAM20C) in two siblings referred for hypophosphatemia and severe dental demineralization disease. FAM20C mutations were not found in other undiagnosed probands of a national Norwegian population of familial hypophosphatemia. Our results demonstrate that mutations in FAM20C provide a putative new mechanism in human subjects leading to dysregulated FGF23 levels, hypophosphatemia, hyperphosphaturia, dental anomalies, intracerebral calcifications and osteosclerosis of the long bones in the absence of rickets.

Raine Syndrome

Raine syndrome is a lethal, osteosclerotic bone dysplasia. There is a generalized increase in bone density, but the increased ossification in the skull results in a unique “fish-like” appearance to the face. Specific characteristics include a prominent forehead, exophthalmos, midfacial hypoplasia with hypoplastic nose, triangular-shaped mouth, and gum hyperplasia. Fewer than 20 cases have been reported in the literature with survival times varying from minutes to weeks. A retrospective review of the sonographic findings in the presented case documents the unique facial phenotype associated with this rare syndrome.

Raine syndrome: expanding the radiological spectrum

We describe ante- and postnatal imaging of a 1-year-old otherwise healthy girl with Raine syndrome. She presented with neonatal respiratory distress related to a pyriform aperture stenosis, which was diagnosed on CT. Signs of chondrodysplasia punctata, sagittal vertebral clefting and intervertebral disc and renal calcifications were also found on imaging. This new case confirms that Raine syndrome is not always lethal. The overlapping imaging signs with chondrodysplasia punctata and the disseminated calcifications give new insights into its pathophysiology.

Amygdalae and striatum calcification in lipoid proteinosis

Lipoid proteinosis is a rare genodermatosis characterized by multisystem involvement due to intracellular deposition of an amorphous hyaline material. Lipoid proteinosis is caused by mutations in the ECM1 gene. In many patients, skin and mucosa abnormalities are the first manifestation. When the CNS is affected, a wide variety of neurologic abnormalities may be present. The hallmark findings are calcifications, mostly occurring in the amygdalae, hippocampus, parahippocampal gyrus, or even the striatum. Present in half of the patients, moniliform blepharosis is considered a pathognomonic finding. In the other half of patients imaging could assist in the diagnosis. The authors present a series of 3 cases of lipoid proteinosis with brief clinical data and imaging findings.

Raine syndrome: a rare lethal osteosclerotic bone dysplasia. Prenatal diagnosis, autopsy, and neuropathological findings

Raine syndrome is an autosomal recessive condition with generalized osteosclerosis, characteristic facial dysmorphism and brain abnormalities including intracerebral calcifications. We report on a case with Raine syndrome born to nonconsanguineous couple and report the prenatal sonogram/MRI, the fetopathology, and neuropathology findings.

Raine syndrome: report of a family with three affected sibs and further delineation of the syndrome

We describe three affected sibs with Raine syndrome born to a consanguineous Turkish couple. Clinical findings and post-mortem assessment are presented. We have added previously unreported meso and severe telebrachyphalangy and urogenital anomalies to the clinical spectrum. Appositional new bone formation may be mistaken for fractures and callus formation--both prenatally by ultrasound and postnatally in radiographs. Further research is required to detect the underlying metabolic and molecular defects of this autosomal recessive syndrome.

Mineralization of the basal ganglia: implications for neuropsychiatry, pathology and neuroimaging

This article examines the evidence for and against the existence of basal ganglia mineralization as a defined clinico-pathological entity. In reviewing the literature on basal ganglia mineralization, this article emphasizes evidence derived from different neuroimaging modalities, genetics, metabolic studies, postmortem series and their possible neuropsychiatric correlates. Relevant articles were collected through Medline and Index Medicus searches. Researchers have encountered multiple difficulties in accepting basal ganglia mineralization as a distinct entity. This syndrome lacks set clinical criteria or a unique etiology; not surprisingly, numerous articles have applied varied definitions. Because many of the reported cases have not been examined postmortem, both the extent and nature of their mineralization remains uncertain. Furthermore, researchers have considered small foci of basal ganglia mineralization a normal phenomenon of aging. However, when brain deposits are extensive, they are associated with a set of age-dependent, progressive clinical symptoms. They include cognitive impairment, extrapyramidal symptoms and psychosis. Most cases are related to abnormalities of calcium metabolism, but rare familial cases of idiopathic origin have been reported. Overabundant mineralization of the brain is judged pathological based on its amount, distribution and accompanying clinical symptoms. Although its relation with calcium dysregulation is well known, modern studies have emphasized abnormalities of iron and dopamine metabolism. The authors suggest that these metabolic abnormalities may link basal ganglia mineralization to psychotic symptomatology.