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Classifications

ISDS Skeletal Nosology

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Inheritance

1

Autosomal recessive HP:0000007

Raine syndrome is inherited in an autosomal recessive manner; affected individuals carry homozygous or compound heterozygous pathogenic FAM20C variants. Parental consanguinity is frequently reported, and unaffected parents are obligate heterozygous carriers.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:19250384 SUPPORT Human Clinical

"Mutations in FAM20C, consistent with autosomal recessive inheritance, were identified in both cases."

Documents autosomal recessive segregation of FAM20C variants in Raine syndrome families.

PMID:24039075 SUPPORT Human Clinical

"We report on a child who is homozygous for a 487-kb deletion in 7p22.3 that contains FAM20C. Both parents were heterozygous for the deletion."

Homozygous whole-gene deletion with heterozygous carrier parents demonstrates recessive inheritance.

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Subtypes

2

Lethal (classic) Raine syndrome

FAM20C hgnc:22140

The originally described, neonatal-lethal form. Affected neonates present at birth with generalized osteosclerosis, periosteal bone formation, the characteristic craniofacial phenotype and intracranial calcification, and die within the first days to weeks of life, usually from respiratory insufficiency secondary to midface hypoplasia with choanal atresia and a narrow, hypoplastic thorax. Typically associated with complete loss-of-function FAM20C alleles.

Show evidence (1 reference)

PMID:17924334 SUPPORT Human Clinical

"Lethal osteosclerotic bone dysplasia (or, Raine syndrome) is an autosomal recessive disorder characterized by generalized osteosclerosis with periosteal bone formation and a distinctive facial phenotype. Affected individuals survive only days or weeks."

Defines the lethal subtype and its neonatal course.

Non-lethal (attenuated) Raine syndrome

FAM20C hgnc:22140

An attenuated form recognized since 2009, in which affected individuals survive infancy — into childhood, adolescence and adulthood (reported to at least 39 years). The phenotype is highly heterogeneous and dominated by FGF23-related hypophosphatemic rickets, hypoplastic amelogenesis imperfecta and dentin anomalies, ectopic soft-tissue and solid-organ calcification, facial dysmorphism, and variable neurodevelopmental delay, seizures and sensory involvement; osteosclerosis may be mild or absent. Associated with hypomorphic FAM20C alleles retaining residual kinase activity or partially preserved protein function.

Show evidence (2 references)

PMID:19250384 SUPPORT Human Clinical

"the identification of mutations in these two patients confirms a broader phenotypic spectrum and that mutation of FAM20C does not always lead to the infantile lethality previously seen as a prerequisite for Raine syndrome diagnosis."

Establishes the existence of a non-lethal FAM20C-related Raine syndrome subtype.

PMID:32299476 SUPPORT Human Clinical

"However, there exists a non-lethal RS form, the phenotype of which is extremely heterogeneous."

Confirms the non-lethal subtype and its marked phenotypic heterogeneity.

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Discussions and Knowledge Gaps

1

Why does Fam20c loss in mice produce hypophosphatemic rickets rather than the generalized osteosclerosis that defines human Raine syndrome, and what does that imply about the origin of the human sclerotic phenotype?

HUMAN MODEL MISMATCH raine_osteosclerosis_vs_osteomalacia_model_mismatch

Attached to

pathophysiology#Abnormal Bone Matrix Mineralization

Global and tissue-specific Fam20c knockout mice, and transgenic mice expressing lethal (G374R) and non-lethal (D446N) Raine syndrome alleles, consistently develop hypophosphatemic rickets or osteomalacia without osteosclerosis. Only occasional conventional knock-in mice show an osteosclerotic radiographic appearance, and micro-CT of those bones shows reduced mineral density and increased porosity. Human autopsy histology likewise shows severe osteomalacia rather than true hypermineralization. This raises the possibility that human "osteosclerosis" is a radiographic semblance superimposed on an underlying osteomalacic/rachitic process, driven by extraskeletal systems (or FAM20C substrates outside bone) not captured by the mouse models.

Proposed experiments

Quantitative bone mineral density distribution in human Raine syndrome bone

raine_bse_histomorphometry

Quantitative backscattered-electron imaging and static/dynamic histomorphometry of non-decalcified human Raine syndrome bone, compared directly against the radiographic density of the same specimens, to test whether radiographic "osteosclerosis" reflects true hypermineralization or an osteomalacic matrix with altered geometry.

Supporting outcome

Radiographic osteosclerosis overlies an undermineralized osteomalacic matrix

Refuting outcome

Raine syndrome bone is genuinely hypermineralized, matching the radiographic appearance

Tissue-restricted Fam20c rescue outside the skeleton

raine_extraskeletal_rescue

Re-express Fam20c in candidate extraskeletal compartments (kidney, liver, brain, vasculature) on a global Fam20c-null background and assay whether an osteosclerotic skeletal phenotype emerges or is prevented, testing the hypothesis that the human sclerotic phenotype is driven by non-skeletal FAM20C substrates.

Supporting outcome

Osteosclerosis in Raine syndrome depends on loss of FAM20C activity outside bone

Refuting outcome

The skeletal phenotype is entirely cell-autonomous to bone

Show evidence (2 references)

PMID:37698039 SUPPORT Model Organism

"transgenic mice expressing the mutant Fam20c found in the lethal (KO;G374R) and nonlethal (KO;D446N) Raine syndrome exhibited osteomalacia without osteosclerotic features."

Documents the mouse-human mismatch for the defining osteosclerotic phenotype.

PMID:36572689 SUPPORT Model Organism

"Fam20c deficiency in mice does not recapitulate the human disorder, so the underlying pathoetiological mechanisms remain poorly understood."

States the model-human mismatch explicitly.

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Pathophysiology

12

Loss of FAM20C Golgi Casein Kinase Activity

FAM20C is the Golgi casein kinase: an atypical, secretory-pathway protein kinase that localizes to the Golgi apparatus and phosphorylates serine residues within S-x-E/pS motifs of secreted proteins. Biallelic loss-of-function variants in FAM20C abolish or markedly reduce this kinase activity. Raine syndrome missense substitutions impair both Golgi localization and catalytic activity of the recombinant enzyme; a non-lethal splice-altering variant produces an in-frame insertion that mislocalizes the protein and reduces its secretion without disrupting dimerization.

FAM20C hgnc:22140 ↓ DECREASED

peptidyl-serine phosphorylation of secreted proteins GO:0018105 ↓ DECREASED

Golgi casein kinase (protein serine/threonine kinase) activity GO:0004674 ↓ DECREASED

Golgi apparatus GO:0005794

Downstream

Hypophosphorylation of Secreted Biomineralization Proteins Loss of kinase activity leaves the FAM20C secreted phosphoproteome unphosphorylated.

Gingival Fibroblast Activation via TGF-beta and YAP/TAZ Loss of FAM20C activity engages a TGF-beta-YAP/TAZ profibrotic loop in resident gingival fibroblasts.

Show evidence (5 references)

PMID:22582013 SUPPORT In Vitro

"Fam20C appears to be the Golgi casein kinase that phosphorylates secretory pathway proteins within S-x-E motifs."

Identifies FAM20C as the Golgi casein kinase and defines its S-x-E substrate motif.

PMID:22900076 SUPPORT In Vitro

"Introduction of point mutations identified in Raine syndrome patients into recombinant FAM20C impairs its normal localization and kinase activity."

Directly demonstrates that Raine syndrome variants impair FAM20C localization and catalysis.

PMID:25026495 SUPPORT In Vitro

"all the mutant FAM20C proteins showed decreased kinase activities compared to wild-type (WT) FAM20C, and most of them also showed impaired secretion."

Functional analysis of six Raine syndrome FAM20C mutants shows loss of kinase activity.

+ 2 more references

Hypophosphorylation of Secreted Biomineralization Proteins

FAM20C phosphorylates well over one hundred substrates in the secretory pathway, including the caseins and members of the SIBLING (small integrin-binding ligand, N-linked glycoprotein) family — DMP1, MEPE, osteopontin (SPP1), bone sialoprotein and DSPP — which regulate extracellular matrix biomineralization. Loss of FAM20C activity leaves these substrates hypophosphorylated, removing a key post-translational control on mineral nucleation and inhibition in bone and dental hard tissue.

DMP1 hgnc:2932 ↓ DECREASED MEPE (FAM20C substrate, hypophosphorylated) hgnc:13361 ⚠ ABNORMAL SPP1 / osteopontin (FAM20C substrate, hypophosphorylated) hgnc:11255 ⚠ ABNORMAL DSPP (FAM20C substrate, hypophosphorylated) hgnc:3054 ⚠ ABNORMAL

biomineral tissue development GO:0031214 ⚠ ABNORMAL

Downstream

Dysregulated FGF23 and Renal Phosphate Wasting Reduced DMP1 expression and loss of direct FGF23 phosphorylation dysregulate FGF23 processing and output.

Abnormal Bone Matrix Mineralization Loss of SIBLING phosphorylation deranges matrix mineral nucleation and inhibition.

Ectopic Intracranial and Soft Tissue Calcification Loss of phosphorylation on mineralization-inhibiting secreted substrates removes a brake on mineral nucleation outside the skeleton.

Dental Hard Tissue Mineralization Failure Ameloblast and odontoblast substrates are left hypophosphorylated.

Show evidence (4 references)

PMID:22582013 SUPPORT In Vitro

"Fam20C phosphorylates the caseins and several secreted proteins implicated in biomineralization, including the small integrin-binding ligand, N-linked glycoproteins (SIBLINGs)."

Establishes the SIBLING family as FAM20C substrates relevant to biomineralization.

PMID:22900076 SUPPORT In Vitro

"We show that FAM20C can phosphorylate secreted phosphoproteins, including both Casein and members of the SIBLING protein family, which modulate biomineralization, and we find that FAM20C phosphorylates a biologically active peptide at amino acids essential for inhibition of biomineralization."

Shows FAM20C phosphorylation directly targets residues that control mineralization inhibition.

PMID:33759783 SUPPORT In Vitro

"The protein kinase, Fam20C, conserved from nematodes to humans, phosphorylates well over 100 substrates in the secretory pathway"

Documents the breadth of the FAM20C secreted phosphoproteome.

+ 1 more reference

Dysregulated FGF23 and Renal Phosphate Wasting

FAM20C directly phosphorylates FGF23 on Ser180 within its R176XXR179/S180AE subtilisin-like proprotein convertase motif; this phosphorylation blocks GalNAc-T3 O-glycosylation and promotes furin cleavage and inactivation of FGF23. FAM20C also sustains DMP1 expression, which suppresses FGF23 production. Loss of FAM20C therefore raises circulating intact, biologically active FGF23, causing renal phosphate wasting, hypophosphatemia, and FGF23-related hypophosphatemic rickets or osteomalacia — the dominant endocrine feature of the non-lethal form.

FGF23 hgnc:3680 ↑ INCREASED

phosphate ion homeostasis GO:0055062 ⚠ ABNORMAL

Downstream

Abnormal Bone Matrix Mineralization Hypophosphatemia produces rickets/osteomalacia, on which the sclerotic radiographic phenotype is superimposed.

Show evidence (4 references)

PMID:24706917 SUPPORT In Vitro

"Here we show that Fam20C directly phosphorylates FGF23 on Ser(180), within the FGF23 R(176)XXR(179)/S(180)AE subtilisin-like proprotein convertase motif. This phosphorylation event inhibits O-glycosylation of FGF23 by polypeptide N-acetylgalactosaminyltransferase 3 (GalNAc-T3), and promotes..."

Defines the molecular mechanism by which FAM20C limits intact bioactive FGF23.

PMID:24706917 SUPPORT Other

"humans with FAM20C mutations and Fam20C KO mice develop hypophosphatemia due to an increase in full-length, biologically active FGF23"

Background statement summarising prior human and mouse work (this PNAS paper itself reports in vitro biochemistry), and it mixes human and mouse observations in one sentence - hence OTHER rather than HUMAN_CLINICAL. The human arm is independently evidenced by PMID:31471673 and PMID:25026495, the mouse arm by PMID:22615579.

PMID:25026495 SUPPORT In Vitro

"our results suggest that FAM20C suppresses FGF23 production by enhancing DMP1 expression, and inactivating mutations in FAM20C cause FGF23-related hypophosphatemia by decreasing transcription of DMP1."

Provides the DMP1-dependent arm of FGF23 dysregulation in Raine syndrome.

+ 1 more reference

Abnormal Bone Matrix Mineralization

The matrix-level lesion. Loss of FAM20C-dependent substrate phosphorylation, compounded by FGF23-driven hypophosphatemia, leaves bone matrix abnormally mineralized with disorganized, thickened collagen fibrils and a widened, disorganized growth plate. Critically, this is an UNDER-mineralization lesion: non-decalcified human histology after tetracycline labeling documented severe osteomalacia (not rickets), and knock-in mouse tibiae that look osteosclerotic on radiography show reduced mineral density and increased porosity on micro-CT. FAM20C additionally fine-tunes chondroitin sulfate 4-O/6-O sulfation, an activity lost with Raine syndrome mutations, providing a further route to dysregulated osteoblast biomineralization. The relationship between this osteomalacic matrix and the sclerotic radiographic appearance is the entry's principal open question (see discussions).

osteoblast CL:0000062 osteocyte CL:0000137

bone mineralization GO:0030282 ⚠ ABNORMAL ossification GO:0001503 ⚠ ABNORMAL

Downstream

Generalized Osteosclerosis and Periosteal Bone Formation The abnormal matrix presents radiographically as generalized osteosclerosis with periosteal new bone formation.

Show evidence (5 references)

PMID:17924334 SUPPORT Human Clinical

"This study defines the causative role of FAM20C in this lethal osteosclerotic disorder and its crucial role in normal bone development."

Establishes FAM20C loss as the cause of the osteosclerotic skeletal phenotype.

PMID:27862258 SUPPORT Human Clinical

"Following premortem tetracycline labeling, the proposita's non-decalcified skeletal histopathology after autopsy indicated no rickets but documented severe osteomalacia."

Human bone histopathology shows the radiographically sclerotic skeleton is severely undermineralized.

PMID:36572689 SUPPORT In Vitro

"FAM20C with Raine-originated mutations loses the ability to interact with chondroitin 4-O-sulfotransferase-1, and is associated with reduced 4-sulfation/6-sulfation (4S/6S) ratio of CS chains and upregulated biomineralization in human osteosarcoma cells."

Identifies a chondroitin-sulfate sulfation route by which Raine syndrome mutations dysregulate biomineralization.

+ 2 more references

Generalized Osteosclerosis and Periosteal Bone Formation

The radiographic readout of the abnormal matrix: a diffuse, marked increase in radiodensity of all bones, most striking at the skull base and long bones, together with periosteal new bone formation — the feature that distinguishes Raine syndrome from osteopetrosis and other sclerosing dysplasias. Modeled as a distinct node from the matrix lesion because the two dissociate: the sclerotic radiographic appearance overlies an osteomalacic, porous matrix, and osteosclerosis may be mild or absent in the non-lethal form.

ossification GO:0001503 ↑ INCREASED

Downstream

Craniofacial Skeletal Overgrowth Excess ossification of the skull and facial bones drives the craniofacial phenotype.

Thoracic Hypoplasia and Pulmonary Hypoplasia Skeletal involvement of the ribs and thoracic cage produces a narrow, hypoplastic thorax.

Show evidence (2 references)

PMID:25019372 SUPPORT Human Clinical

"The main radiological manifestation is a diffuse, marked osteosclerosis of the base of skull and long bones."

Defines the radiographic osteosclerosis and its anatomical distribution.

PMID:33676444 SUPPORT Human Clinical

"Periosteal bone formation is also a characteristic feature of this disorder differentiating it from osteopetrosis and other known lethal and nonlethal osteosclerotic bone dysplasias."

Establishes periosteal new bone formation as the discriminating radiographic feature.

Thoracic Hypoplasia and Pulmonary Hypoplasia

A narrow, hypoplastic thorax restricts lung growth, producing pulmonary hypoplasia. This arm is mechanistically independent of the craniofacial arm; the two converge on neonatal respiratory failure.

Downstream

Neonatal Respiratory Failure Pulmonary hypoplasia limits gas exchange from the first minutes of life.

Show evidence (1 reference)

PMID:33676444 SUPPORT Human Clinical

"Severe midface hypoplasia and narrow thorax leading to choanal atresia and pulmonary hypoplasia respectively, contribute to respiratory distress and have been regarded as the causes for early death."

Attributes pulmonary hypoplasia specifically to the narrow thorax, separate from the midface/choanal arm.

Neonatal Respiratory Failure

The convergent terminal node of the lethal form: upper-airway obstruction from choanal atresia/stenosis plus pulmonary hypoplasia from the narrow thorax produce severe respiratory distress from birth, the usual proximate cause of death within days to weeks.

Show evidence (2 references)

PMID:32299476 SUPPORT Human Clinical

"RS is usually lethal during the neonatal period due to severe respiratory distress."

Identifies neonatal respiratory failure as the proximate cause of death.

PMID:17924334 SUPPORT Human Clinical

"Affected individuals survive only days or weeks."

Documents the neonatal-lethal course driven by respiratory failure.

Craniofacial Skeletal Overgrowth

The dysplasia predominantly affects craniofacial development. Increased ossification of the skull and facial bones underlies the characteristic facies — narrow prominent forehead, severe proptosis, underdeveloped midface, depressed nasal bridge and short nose — and in the most severe cases multisuture craniosynostosis. Severe midface hypoplasia in turn produces choanal atresia or stenosis, obstructing the neonatal upper airway.

ossification GO:0001503 ↑ INCREASED

Downstream

Neonatal Respiratory Failure Midface hypoplasia with choanal atresia/stenosis obstructs the neonatal upper airway.

Show evidence (3 references)

PMID:25019372 SUPPORT Human Clinical

"The skeletal dysplasia predominantly affects craniofacial development explaining the severe proptosis, underdeveloped midface, depressed nasal bridge and short nose."

Directly links the craniofacial skeletal overgrowth to the characteristic facial phenotype.

PMID:33676444 SUPPORT Human Clinical

"Severe midface hypoplasia and narrow thorax leading to choanal atresia and pulmonary hypoplasia respectively, contribute to respiratory distress and have been regarded as the causes for early death."

Explains the mechanism by which craniofacial and thoracic involvement cause neonatal lethality.

PMID:25019372 SUPPORT Human Clinical

"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."

Confirms respiratory distress as the immediate perinatal threat.

Ectopic Intracranial and Soft Tissue Calcification

Ectopic mineral is deposited outside the skeleton. The leading hypothesis is that loss of FAM20C-dependent phosphorylation of mineralization-INHIBITING secreted substrates removes a brake on mineral nucleation, but this has been demonstrated biochemically rather than at ectopic sites in patients, and a parallel in silico analysis proposes distinct brain-expressed FAM20C targets; the mechanism should be read as provisional. Intracranial calcifications are a cardinal feature, typically periventricular and involving basal ganglia and corpus callosum, and are accompanied in severe cases by periventricular gliosis, infarction, hemorrhage and leukomalacia. Brain-specific deletion of Fam20c in mice produces cerebral calcification without skeletal or dental defects, indicating that local loss of FAM20C function within the brain is sufficient. Ectopic calcification also occurs in soft tissue and solid organs in longer-surviving patients.

Show evidence (5 references)

PMID:36914045 SUPPORT Model Organism

"Our results suggest that the local loss of FAM20C function in the brain may directly account for intracranial calcification."

Brain-specific Fam20c deletion in mice shows a cell-autonomous CNS route to the calcification phenotype.

PMID:36914045 SUPPORT Model Organism

"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"

Dissociates the CNS calcification mechanism from the skeletal and dental phenotypes.

PMID:38163266 SUPPORT Human Clinical

"Histological sections of the brain showed marked periventricular gliosis with regions of infarction, hemorrhage, and cavitation with global periventricular leukomalacia. Numerous dystrophic calcifications were diffusely present."

Human neuropathology documenting dystrophic intracranial calcification and associated brain injury.

+ 2 more references

Dental Hard Tissue Mineralization Failure

FAM20C acts intracellularly within ameloblasts and odontoblasts, where its substrates (including DSPP and other SIBLINGs) direct enamel and dentin mineralization. Its loss produces a distinctive hypoplastic amelogenesis imperfecta affecting all teeth together with dentin abnormalities, a hallmark of the non-lethal form that should prompt FAM20C testing. Hypophosphatemic rickets adds spontaneous recurrent abscesses on non-carious teeth.

ameloblast CL:0000059 odontoblast CL:0000060

biomineral tissue development GO:0031214 ⚠ ABNORMAL

Show evidence (3 references)

PMID:25928877 SUPPORT Human Clinical

"a profound failure of dental enamel formation leading to a distinctive hypoplastic AI in all teeth should alert clinicians to the possibility of FAM20C mutations."

Establishes hypoplastic amelogenesis imperfecta as a defining dental manifestation of FAM20C loss.

PMID:23703840 SUPPORT Model Organism

"FAM20C localized intracellularly within ameloblasts and odontoblasts in a pattern consistent with Golgi localization."

Localizes FAM20C to the Golgi of the two cell types that build enamel and dentin, grounding the dental mineralization defect.

PMID:33505751 SUPPORT Human Clinical

"Spontaneous recurrent abscesses on noncarious teeth result in significant odontogenic pain and multiple dental interventions."

Documents the dental consequence of hypophosphataemic rickets in non-lethal Raine syndrome.

Gingival Fibroblast Activation via TGF-beta and YAP/TAZ

In non-lethal Raine syndrome, resident gingival fibroblasts are activated along the conserved pro-fibrotic axis. Proteomic and functional analyses of patient gingival tissue and primary gingival fibroblasts show upregulated TGF-beta/SMAD signaling together with engagement of the fibrogenic transcriptional cofactors YAP and TAZ; FAM20C knockdown reproduces the TGF-beta-YAP/TAZ interplay, defining a self-reinforcing profibrotic loop. This is the disease-specific instance of the conserved mesenchymal cell activation step of the fibrotic response, with the gingival fibroblast substituted for the generic fibroblast.

gingival fibroblast CL:0002552

TGF-beta Receptor Signaling GO:0007179 ↑ INCREASED

Downstream

Excessive Gingival ECM Deposition and Calcification Activated gingival fibroblasts overproduce and disorganize extracellular matrix.

Show evidence (2 references)

PMID:38664418 SUPPORT In Vitro

"Knocking down of FAM20C confirmed the TGFβ-YAP/TAZ interplay indicating that a profibrotic loop enabled gingival fibrosis in RNS patients."

Functional knockdown evidence for the TGF-beta-YAP/TAZ profibrotic loop driven by FAM20C loss.

PMID:38664418 SUPPORT In Vitro

"They furthermore uncover the contribution of increased TGFβ-YAP/TAZ signaling in the pathogenesis of the gingival fibrosis."

States the increased TGF-beta-YAP/TAZ signaling contribution to the gingival phenotype.

Excessive Gingival ECM Deposition and Calcification

Activated gingival fibroblasts overproduce and disorganize extracellular matrix, with increased profibrotic and pro-osteogenic proteins (POSTN, SPARC, VIM). The result is gingival fibrosis together with pathological ectopic gingival calcification — the tissue substrate of the gum hyperplasia seen clinically. The pro-osteogenic component distinguishes this from generic soft-tissue fibrosis and reflects the loss of FAM20C-dependent mineralization control.

gingival fibroblast CL:0002552

Show evidence (2 references)

PMID:38664418 SUPPORT Human Clinical

"We showed that fibrosis, pathological gingival calcifications and increased expression of various profibrotic and pro-osteogenic proteins such as POSTN, SPARC and VIM were common findings."

Patient gingival tissue findings documenting fibrosis with pro-osteogenic protein upregulation.

PMID:38664418 SUPPORT Human Clinical

"gingival fibrosis and calcifications are associated with, and most likely caused by excessed ECM production and disorganization"

Attributes the gingival fibrosis and calcification to excessive, disorganized ECM production.

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Pathograph

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Phenotypes

25

Ear 2

Hearing impairment FREQUENT HP:0000365

Show evidence (1 reference)

PMID:32299476 SUPPORT Human Clinical

"seizures and hearing or vision involvement were also frequent"

Hearing involvement reported as frequent in surviving patients.

Low-set ears HP:0000369

Show evidence (1 reference)

PMID:24959018 SUPPORT Human Clinical

"small nose with depressed nasal bridge, gum hyperplasia, high-arched narrow palate, long philtrum and dysplastic ears"

Case report documents dysplastic ears; low-set/dysplastic ears are part of the characteristic facies.

Eye 2

Proptosis (exophthalmos) HP:0000520

Show evidence (1 reference)

PMID:32299476 SUPPORT Human Clinical

"The most common clinical features are microcephaly, exophthalmos, hypoplastic nose and severe midface hypoplasia, leading to choanal atresia."

Lists exophthalmos among the most common clinical features.

Visual impairment HP:0000505

Show evidence (2 references)

PMID:38664418 SUPPORT Human Clinical

"hypophosphatemic rickets, intracranial calcifications, visual impairment and an oral phenotype characterized by AI, dentinal anomalies and gingival hyperplasia with calcifications"

Documents visual impairment in a molecularly confirmed non-lethal Raine syndrome patient.

PMID:32299476 SUPPORT Human Clinical

"seizures and hearing or vision involvement were also frequent"

Cohort data report vision involvement as frequent, but hearing and vision are not separated.

Head and Neck 8

Midface hypoplasia Midface retrusion HP:0011800

Show evidence (1 reference)

PMID:32299476 SUPPORT Human Clinical

"The most common clinical features are microcephaly, exophthalmos, hypoplastic nose and severe midface hypoplasia, leading to choanal atresia."

Severe midface hypoplasia is listed as a most-common feature.

Depressed nasal bridge HP:0005280

Show evidence (1 reference)

PMID:25019372 SUPPORT Human Clinical

"The skeletal dysplasia predominantly affects craniofacial development explaining the severe proptosis, underdeveloped midface, depressed nasal bridge and short nose."

Depressed nasal bridge is part of the characteristic facies.

Microcephaly HP:0000252

Show evidence (1 reference)

PMID:32299476 SUPPORT Human Clinical

"The most common clinical features are microcephaly, exophthalmos, hypoplastic nose and severe midface hypoplasia, leading to choanal atresia."

Microcephaly is listed among the most common clinical features.

Choanal atresia or stenosis HP:0000453

Both complete atresia and stenosis are reported. The phenotype is bound to HP:0000453 Choanal atresia, which is narrower than the claim; HP:0000452 Choanal stenosis covers the milder end and is not separately modeled because the cited sources do not consistently distinguish the two.

Show evidence (2 references)

PMID:32299476 SUPPORT Human Clinical

"The most common neonatal comorbidity was respiratory distress secondary to choanal atresia."

Identifies choanal atresia as the leading neonatal comorbidity. "Most common" is a rank within the set of comorbidities, not a proportion of patients, so no frequency band is assigned.

PMID:24959018 SUPPORT Human Clinical

"Raine syndrome is a rare genetic disorder with characteristic features of exophthalmos, choanal atresia or stenosis, osteosclerosis and cerebral calcifications."

Lists choanal atresia/stenosis as a characteristic feature.

Hypoplastic amelogenesis imperfecta HP:0000705

Show evidence (1 reference)

PMID:25928877 SUPPORT Human Clinical

"Family 1 included 3 siblings with hypoplastic Amelogenesis Imperfecta (AI) (inherited abnormal dental enamel formation)."

Documents hypoplastic amelogenesis imperfecta in non-lethal Raine syndrome siblings.

Cleft palate HP:0000175

Show evidence (1 reference)

PMID:10482879 SUPPORT Human Clinical

"We describe a newborn girl with a lethal sclerosing bone dysplasia leading to prenatal skeletal alterations and microcephaly, proptosis, hypoplastic nose and midface, small jaw, cleft palate, hypertrophied gums, intracranial calcifications, and generalized osteosclerosis."

Case description of a Raine syndrome neonate documenting cleft palate within the craniofacial complex.

Craniosynostosis HP:0001363

Show evidence (1 reference)

PMID:38163266 SUPPORT Human Clinical

"He had particularly significant CNS manifestations consisting of multisuture craniosynostosis with protrusion of the brain parenchyma through fontanelles and cranial lacunae."

Documents multisuture craniosynostosis in a severe prenatally identified case.

Wormian bones HP:0002645

Show evidence (1 reference)

PMID:24039075 SUPPORT Human Clinical

"In addition, he had wormian bones and pyriform aperture stenosis, features that are usually under diagnosed."

Documents wormian bones as an under-recognised radiographic feature.

Metabolism 2

Hypophosphatemia HP:0002148

Show evidence (1 reference)

PMID:31471673 SUPPORT Human Clinical

"midface hypoplasia, exophthalmos, amelogenesis imperfecta, shortening of distal phalanges, pectus excavatum, and hypophosphatemia due to renal phosphate wasting"

Documents hypophosphatemia from renal phosphate wasting in an adult with non-lethal Raine syndrome.

Hypophosphatemic rickets HP:0004912

Show evidence (1 reference)

PMID:32299476 SUPPORT Human Clinical

"Persistent hypophosphatemic rickets was the most striking endocrinological manifestation, which was scarcely responsive to therapy with phosphate salts and alfacalcidol."

Natural-history cohort documents persistent, treatment-refractory hypophosphatemic rickets. "Most striking" describes salience rather than a proportion of patients, so no frequency band is assigned.

Nervous System 3

Neurodevelopmental delay FREQUENT Global developmental delay HP:0001263

Show evidence (1 reference)

PMID:32299476 SUPPORT Human Clinical

"A variable degree of neurodevelopmental delay was seen in the majority of our cases and seizures and hearing or vision involvement were also frequent."

Natural-history data on developmental delay in surviving patients.

Seizures FREQUENT HP:0001250

Show evidence (1 reference)

PMID:32299476 SUPPORT Human Clinical

"A variable degree of neurodevelopmental delay was seen in the majority of our cases and seizures and hearing or vision involvement were also frequent."

Seizures reported as frequent in the non-lethal natural-history cohort.

Intellectual disability HP:0001249

Show evidence (2 references)

PMID:34360805 SUPPORT Human Clinical

"The milder phenotype is defined by a large spectrum ranging from osteonecrosis to osteosclerosis with additional congenital defects or intellectual disability in some cases."

Systematic phenotype review reports intellectual disability in a subset of non-lethal cases.

PMID:37240249 SUPPORT Computational

"Individuals with RNS can have developmental delay, intellectual disability, seizures, and structural brain defects"

Confirms intellectual disability within the reported neurological spectrum. Tagged COMPUTATIONAL to match the paper type (an in silico analysis) and this entry's other two uses of the same reference.

Respiratory 2

Neonatal respiratory distress VERY_FREQUENT HP:0002643

Show evidence (1 reference)

PMID:32299476 SUPPORT Human Clinical

"RS is usually lethal during the neonatal period due to severe respiratory distress."

Documents respiratory distress as the cause of neonatal lethality.

Pulmonary hypoplasia HP:0002089

Show evidence (2 references)

PMID:33676444 SUPPORT Human Clinical

"Severe midface hypoplasia and narrow thorax leading to choanal atresia and pulmonary hypoplasia respectively, contribute to respiratory distress and have been regarded as the causes for early death."

Documents pulmonary hypoplasia from the narrow thorax as a cause of early death.

PMID:17924334 SUPPORT Human Clinical

"Affected individuals survive only days or weeks."

Documents the neonatal-lethal course that pulmonary hypoplasia and airway obstruction drive.

Other 6

Generalized osteosclerosis HP:0005789

Show evidence (1 reference)

PMID:25019372 SUPPORT Human Clinical

"The main radiological manifestation is a diffuse, marked osteosclerosis of the base of skull and long bones."

Describes the cardinal radiological osteosclerosis of Raine syndrome.

Periosteal bone formation Periosteal thickening of long tubular bones HP:0006465

Show evidence (1 reference)

PMID:33676444 SUPPORT Human Clinical

"Periosteal bone formation is also a characteristic feature of this disorder differentiating it from osteopetrosis and other known lethal and nonlethal osteosclerotic bone dysplasias."

Establishes periosteal bone formation as a differentiating diagnostic feature.

Intracranial calcification Cerebral calcification HP:0002514

Show evidence (3 references)

PMID:32299476 SUPPORT Human Clinical

"The radiological findings include generalized osteosclerosis and brain calcifications."

Confirms brain calcification as a core radiological finding.

PMID:24959018 SUPPORT Human Clinical

"Computed tomography scan of the brain showed diffuse hyperdense areas of calcification in periventricular region, corpus callosum and basal ganglia on both sides"

Case-level imaging documenting the anatomical distribution of the calcification.

PMID:36914045 SUPPORT Other

"FAM20C loss-of-function mutations cause Raine syndrome in humans, characterized by generalized osteosclerosis, distinctive craniofacial dysmorphism, along with extensive intracranial calcification."

Human background framing in the introduction of a mouse study (hence OTHER, not this paper's own data), establishing intracranial calcification as a defining feature of Raine syndrome. No proportion is stated, so no frequency band is assigned.

Gum hyperplasia Gingival overgrowth HP:0000212

Show evidence (2 references)

PMID:24959018 SUPPORT Human Clinical

"There was exophthalmos, small nose with depressed nasal bridge, gum hyperplasia, high-arched narrow palate, long philtrum and dysplastic ears"

Case description documenting gum hyperplasia in Raine syndrome.

PMID:10482879 SUPPORT Human Clinical

"We describe a newborn girl with a lethal sclerosing bone dysplasia leading to prenatal skeletal alterations and microcephaly, proptosis, hypoplastic nose and midface, small jaw, cleft palate, hypertrophied gums, intracranial calcifications, and generalized osteosclerosis."

Independent case documenting hypertrophied gums as part of the Raine syndrome phenotype.

Ectopic soft tissue and solid organ calcification Ectopic calcification HP:0010766

Show evidence (2 references)

PMID:25928877 SUPPORT Human Clinical

"There was hypophosphataemia, soft tissue ectopic mineralization, but no osteosclerosis."

Documents soft-tissue ectopic mineralization in attenuated Raine syndrome.

PMID:31471673 SUPPORT Human Clinical

"presenting with pain in the extremities, osteosclerosis with periosteal bone formation, multiple calcifications in solid organs"

Solid-organ calcification in an adult with non-lethal Raine syndrome.

Short distal phalanges Short distal phalanx of finger HP:0009882

Show evidence (1 reference)

PMID:24039075 SUPPORT Human Clinical

"Our patient had the common craniofacial features as well as, uncommon features such as protruding tongue, short stature, and hypoplastic distal phalanges."

Documents hypoplastic distal phalanges in a patient with a whole-gene FAM20C deletion.

🧬

Genetic Associations

1

FAM20C

Gene: FAM20C hgnc:22140 relationship_type: CAUSATIVE variant_origin: GERMLINE

Autosomal recessive

Show evidence (6 references)

PMID:17924334 SUPPORT Human Clinical

"Sequence analysis of FAM20C, located within the deleted region, in six additional affected subjects revealed four homozygous mutations and two compound heterozygotes."

Original identification of FAM20C as the Raine syndrome disease gene.

PMID:40794899 SUPPORT Human Clinical

"Biallelic mutations in the FAM20C gene, which encodes a Golgi serine/threonine protein kinase that phosphorylates secretory pathway proteins, are responsible for RNS."

Confirms biallelic FAM20C variants as the cause of Raine syndrome.

PMID:33676444 SUPPORT Human Clinical

"FAM20C gene, located on chromosome 7p22.3, spanning ~ 107 kb consists of 10 exons and encodes a protein of 584 amino acids in length. A critical kinase domain resides in its C-terminal, encompassing amino acids 354 to 565"

Gene structure and kinase-domain location.

+ 3 more references

💊

Medical Actions

4

Neonatal intensive care and airway management

Category: Therapeutic Action: neonatal respiratory support and airway management Ontology label: Supportive Care NCIT:C15747

When Raine syndrome is suspected prenatally, delivery should be planned with immediate neonatal intensive care availability because significant respiratory distress is usually present from birth; airway management for choanal atresia/stenosis is the immediate priority. Care remains supportive — there is no disease-modifying therapy.

Target Phenotypes: Neonatal respiratory distress HP:0002643

Show evidence (1 reference)

PMID:25019372 SUPPORT Human Clinical

"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."

Directly supports planned neonatal intensive care as management.

Phosphate salts and alfacalcidol for hypophosphatemic rickets

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: oral phosphate salts CHEBI:37853 alfacalcidol CHEBI:31186

Conventional therapy for hypophosphatemic rickets with oral phosphate salts and the active vitamin D analogue alfacalcidol has been used in non-lethal Raine syndrome, but the rickets is reported as scarcely responsive to this regimen.

Mechanism Target:

Dysregulated FGF23 and Renal Phosphate Wasting — Aims to replace the phosphate lost through FGF23-driven renal wasting and support mineralization.

Show evidence (1 reference)

PMID:32299476 SUPPORT Human Clinical

"Persistent hypophosphatemic rickets was the most striking endocrinological manifestation, which was scarcely responsive to therapy with phosphate salts and alfacalcidol."

Identifies the FGF23-driven phosphate-wasting mechanism as the therapeutic target, with limited response.

Target Phenotypes: Hypophosphatemic rickets HP:0004912

Show evidence (2 references)

PMID:32299476 SUPPORT Human Clinical

"Persistent hypophosphatemic rickets was the most striking endocrinological manifestation, which was scarcely responsive to therapy with phosphate salts and alfacalcidol."

Documents the treatment used and its limited efficacy in non-lethal Raine syndrome.

PMID:32101876 SUPPORT Model Organism

"Plain X-ray radiography and micro-CT radiography analyses showed that the hPi diet improved the shape and mineral density of the Fam20c-deficient femurs/tibiae, and rescued the growth plate defects in the long bone."

Preclinical rationale for phosphate repletion; mouse data only, not established human therapy.

Restorative and oral surgical dental management

Category: Therapeutic Action: surgical procedure Ontology label: Surgical Procedure NCIT:C15329

Extensive restorative and oral surgical intervention is required for the dental sequelae of non-lethal Raine syndrome, including hypoplastic amelogenesis imperfecta and spontaneous recurrent abscesses on non-carious teeth.

Target Phenotypes: Amelogenesis imperfecta HP:0000705

Show evidence (1 reference)

PMID:33505751 SUPPORT Human Clinical

"This article presents the dental manifestations and extensive restorative and oral surgical intervention of three siblings with hypophosphataemic rickets secondary to Raine Syndrome treated at Great Ormond Street Hospital for Children, a tertiary referral hospital."

Describes the restorative and surgical dental management used for these patients.

Genetic counseling

Category: Counseling / Informational Action: genetic counseling Ontology label: Genetic Counseling NCIT:C15240

Autosomal recessive inheritance with a 25% recurrence risk for siblings; consanguinity is common. Carrier testing and prenatal or preimplantation diagnosis are possible once the familial FAM20C variants are known.

Show evidence (1 reference)

PMID:24039075 SUPPORT Human Clinical

"We report on a child who is homozygous for a 487-kb deletion in 7p22.3 that contains FAM20C. Both parents were heterozygous for the deletion."

Carrier status of both parents underpins recurrence-risk counseling.

🔬

Biochemical Markers

2

Elevated intact FGF23 (INCREASED)

Show evidence (2 references)

PMID:24706917 SUPPORT Other

"humans with FAM20C mutations and Fam20C KO mice develop hypophosphatemia due to an increase in full-length, biologically active FGF23"

Background statement summarising prior human and mouse work rather than this paper's own data, and it mixes species in one sentence - hence OTHER.

PMID:31471673 SUPPORT Human Clinical

"hypophosphatemia due to renal phosphate wasting"

Human-only evidence for the renal phosphate-wasting mechanism.

Low serum phosphate (DECREASED)

Show evidence (1 reference)

PMID:31471673 SUPPORT Human Clinical

"pectus excavatum, and hypophosphatemia due to renal phosphate wasting"

Biochemical documentation of hypophosphatemia with renal phosphate wasting.

🔬

Diagnosis

4

Molecular genetic testing of FAM20C

Sequencing of FAM20C confirms the clinical diagnosis. Copy-number analysis must accompany sequencing because whole-gene and multi-exon deletions (including a 487-kb 7p22.3 deletion and a chromosome 7 uniparental isodisomy with 7p telomeric microdeletion) are established causes; a sequencing-only workflow that finds a single heterozygous allele can miss the second hit.

molecular genetic testing NCIT:C19770

Show evidence (2 references)

PMID:25019372 SUPPORT Human Clinical

"molecular testing of FAM20C can confirm this"

Establishes FAM20C molecular testing as the confirmatory test.

PMID:24039075 SUPPORT Human Clinical

"We report on a child who is homozygous for a 487-kb deletion in 7p22.3 that contains FAM20C."

Whole-gene deletion as a disease mechanism is the rationale for adding copy-number analysis.

Skeletal radiography

Skeletal survey / infantogram demonstrating generalized osteosclerosis with periosteal new bone formation, most marked at the skull base and long bones.

radiograph imaging procedure NCIT:C38101

Show evidence (1 reference)

PMID:24959018 SUPPORT Human Clinical

"Infantogram of the baby showed generalized osteosclerosis"

Radiography is the modality that demonstrates the cardinal skeletal finding.

Prenatal ultrasound and fetal MRI

Raine syndrome can be identified prenatally; fetal phenotyping by ultrasound and MRI has demonstrated the characteristic craniofacial and CNS features, allowing delivery to be planned with neonatal intensive care available.

prenatal genetic testing NCIT:C15709

Show evidence (1 reference)

PMID:38163266 SUPPORT Human Clinical

"Fetal phenotyping was based on ultrasound and MRI."

Documents prenatal ultrasound and fetal MRI as the modalities used for antenatal identification.

Clinical and radiographic diagnosis with molecular confirmation

The characteristic facial appearance together with radiological findings (generalized osteosclerosis with periosteal bone formation and intracranial calcification) permits a clinical diagnosis; molecular testing of FAM20C confirms it. Prenatal identification is possible by ultrasound and fetal MRI.

Show evidence (1 reference)

PMID:25019372 SUPPORT Human Clinical

"Facial appearance and radiological findings allow the clinical diagnosis, and molecular testing of FAM20C can confirm this."

States the diagnostic pathway for Raine syndrome.

🩻

Imaging Findings

2

Generalized osteosclerosis on radiography

Infantogram/skeletal survey shows a generalized increase in bone density of all bones with marked sclerosis of the skull base and long bones, plus periosteal new bone formation.

Xray Diagnostic

Generalized osteosclerosis HP:0005789

Show evidence (1 reference)

PMID:24959018 SUPPORT Human Clinical

"Infantogram of the baby showed generalized osteosclerosis"

Radiographic documentation of generalized osteosclerosis.

Intracranial calcification on CT

Brain CT shows hyperdense calcification in the periventricular region, corpus callosum and basal ganglia, characteristically bilateral.

Ct Diagnostic

Cerebral calcification HP:0002514

Show evidence (1 reference)

PMID:24959018 SUPPORT Human Clinical

"Computed tomography scan of the brain showed diffuse hyperdense areas of calcification in periventricular region, corpus callosum and basal ganglia on both sides"

CT documentation of the characteristic intracranial calcification distribution.

📊

Prevalence

2

Worldwide

Point Prevalence ≤0.1 per 100,000 <1 in 1,000,000

Reported as "< 1/1,000,000" in the disease overview literature; upper bound of 1 per 1,000,000 normalizes to 0.1 per 100,000. Fewer than ~50 cases had been reported worldwide as of 2021.

Show evidence (2 references)

PMID:25019372 SUPPORT Human Clinical

"Its prevalence is estimated to be < 1/1,000,000."

Published prevalence estimate for Raine syndrome.

PMID:38163266 SUPPORT Human Clinical

"with an estimated prevalence of <1/1,000,000"

Independent confirmation of the ultra-rare prevalence estimate.

Worldwide

Cases In Literature Ultra Rare

Cumulative case counts remain very small; 47 cases reported worldwide as of the 2021 case report below. Published counts disagree because they use different inclusion criteria and cut-off dates: the 2021 FAM20C/Raine syndrome review by Palma-Lara et al. (PMID:34360805) tabulates a larger series of roughly 70 published patients (about 41 lethal and 29 non-lethal) in its full text. That figure is not quotable from the abstract, so it is recorded here as a curator note rather than as an evidence item; the 47 figure below is retained as the snippet-verifiable count. Either way the order of magnitude - a few tens of published cases worldwide - is the same, and both are published-case tallies subject to ascertainment bias rather than population surveillance.

Show evidence (1 reference)

PMID:33676444 SUPPORT Human Clinical

"Of the 47 cases of RS reported worldwide; four are from India"

Documents the cumulative reported-case count for Raine syndrome.

🔀

Differential Diagnoses

4

Conditions with similar clinical presentations that must be differentiated from Raine Syndrome:

Desmosterolosis

Overlapping Features Desmosterolosis may resemble Raine syndrome clinically and should be considered in the differential diagnosis.

Show evidence (2 references)

PMID:25019372 SUPPORT Human Clinical

"Desmosterolosis and congenital cytomegalovirus infection may resemble Raine syndrome."

Named as a phenocopy in the disease overview.

PMID:9450875 SUPPORT Human Clinical

"A phenotypic overlap of this case with Raine syndrome was noted; however, desmosterol accumulation was not found on postmortem tissue samples from a previously reported case of this disorder."

Primary report documenting the desmosterolosis-Raine syndrome phenotypic overlap and the biochemical test that separates them.

Congenital cytomegalovirus infection

Overlapping Features Congenital CMV infection can mimic Raine syndrome, particularly the intracranial calcification; CMV serology was negative in reported Raine syndrome cases where it was tested.

Show evidence (1 reference)

PMID:25019372 SUPPORT Human Clinical

"Desmosterolosis and congenital cytomegalovirus infection may resemble Raine syndrome."

Named as a phenocopy in the disease overview.

Osteopetrosis

Overlapping Features Osteopetrosis and other sclerosing bone dysplasias share generalized increased bone density but lack the periosteal new bone formation characteristic of Raine syndrome.

Distinguishing Features

Periosteal bone formation is present in Raine syndrome and absent in osteopetrosis

Show evidence (1 reference)

PMID:33676444 SUPPORT Human Clinical

"Periosteal bone formation is also a characteristic feature of this disorder differentiating it from osteopetrosis and other known lethal and nonlethal osteosclerotic bone dysplasias."

Names the radiographic feature distinguishing Raine syndrome from osteopetrosis.

🐁

Animal Models

4

Fam20c conditional knockout (Sox2-Cre global; 3.6 kb Col1a1-Cre mineralized tissue) Mus musculus KNOCKOUT

Global and mineralized-tissue-specific Fam20c knockout mice develop hypophosphatemic rickets with markedly elevated FGF23 rather than osteosclerosis — a partial, not faithful, model of the human disease.

Species

Mus musculus

Genotype

Fam20c conditional knockout (Sox2-Cre global; 3.6 kb Col1a1-Cre mineralized tissue)

Genes

FAM20C hgnc:22140

Show evidence (2 references)

PMID:22615579 SUPPORT Model Organism

"both the global and mineralized tissue-specific cKO mice developed hypophosphatemic rickets (but not osteosclerosis)"

Establishes the mouse knockout as a model of the hypophosphatemic-rickets arm only.

PMID:32101876 SUPPORT Model Organism

"These results suggested that the hPi diet significantly improved the skeletal development of the Fam20c-deficient mice, implying that hypophosphatemia partially contributed to the skeletal defects in Fam20c-deficient subjects."

Dietary phosphate rescue in the same model shows hypophosphatemia is a causal, partially reversible contributor to the skeletal phenotype.

Fam20c D446N knock-in (conditional Col1a1-Cre and conventional Hprt-Cre) Mus musculus KNOCKIN

Knock-in of the non-lethal Raine syndrome D446N allele produces hypophosphatemic rickets in most mice with elevated Fgf23 and decreased Dmp1; a minority of conventional knock-ins die before weaning with osteosclerotic radiography, partially recapitulating the lethal human phenotype.

Species

Mus musculus

Genotype

Fam20c D446N knock-in (conditional Col1a1-Cre and conventional Hprt-Cre)

Genes

FAM20C hgnc:22140

Show evidence (1 reference)

PMID:39748245 SUPPORT Model Organism

"Our results suggested that hypophosphatemia rickets was the predominant phenotype in both conditional and conventional Fam20c deficient mice, while the lethal osteosclerotic phenotype occasionally took place in the conventional Fam20c mutant mice."

Documents partial recapitulation of both human subtypes in the knock-in model.

Fam20c brain-specific knockout (Nestin-Cre) Mus musculus KNOCKOUT

Brain-specific deletion produces cerebral calcification without skeletal or dental defects, isolating the CNS calcification mechanism.

Species

Mus musculus

Genotype

Fam20c brain-specific knockout (Nestin-Cre)

Genes

FAM20C hgnc:22140

Show evidence (1 reference)

PMID:36914045 SUPPORT Model Organism

"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"

Isolates the brain-intrinsic contribution to intracranial calcification.

FAM20C missense variant (dental hypomineralization) Canis lupus familiaris SPONTANEOUS

A naturally occurring canine FAM20C missense variant causes dental hypomineralization, providing a spontaneous large-animal model relevant to the dental arm of Raine syndrome.

Species

Canis lupus familiaris

Genotype

FAM20C missense variant (dental hypomineralization)

Genes

FAM20C hgnc:22140

Show evidence (1 reference)

PMID:27187611 SUPPORT Model Organism

"to investigate the clinico-pathological features and genetic causes of three developmental syndromes in dogs, including craniomandibular osteopathy (CMO), a previously undescribed skeletal syndrome, and dental hypomineralization, for which we identified pathogenic variants in the canine SLC37A2..."

Identifies a spontaneous canine FAM20C model of dental hypomineralization.

{ }

Source YAML

click to show

name: Raine Syndrome
creation_date: "2026-07-30T00:00:00Z"
category: Mendelian
description: >
  Raine syndrome (lethal osteosclerotic bone dysplasia, MIM #259775) is an
  ultra-rare autosomal recessive bone dysplasia caused by biallelic
  loss-of-function variants in FAM20C, which encodes the Golgi casein kinase
  that phosphorylates secreted proteins within S-x-E/pS motifs. It is
  characterized by generalized osteosclerosis with periosteal bone formation, a
  distinctive craniofacial phenotype (proptosis/exophthalmos, midface
  hypoplasia, depressed nasal bridge, gum hyperplasia, cleft palate, low-set
  ears), choanal atresia or stenosis, and intracranial (cerebral)
  calcification. The classic presentation is neonatal lethal, with death within
  days to weeks from respiratory insufficiency. A non-lethal (attenuated) form
  caused by hypomorphic FAM20C alleles is now well recognized, with survival
  into childhood and adulthood, FGF23-related hypophosphatemic rickets, dental
  anomalies including hypoplastic amelogenesis imperfecta, ectopic soft-tissue
  calcification, hearing or vision involvement, seizures, and variable
  neurodevelopmental delay. Historically the same entity was reported as
  congenital sclerosing osteomalacia with cerebral calcification (MIM 259660).
disease_term:
  preferred_term: lethal osteosclerotic bone dysplasia
  term:
    id: MONDO:0009821
    label: lethal osteosclerotic bone dysplasia
parents:
- Neonatal osteosclerotic dysplasia
- Sclerosing bone dysplasia
synonyms:
- Raine syndrome
- RAINE syndrome
- Osteosclerotic bone dysplasia, lethal
- Osteomalacia, sclerosing, with cerebral calcification
- RNS
- Raine dysplasia, FAM20C-related
inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >
    Raine syndrome is inherited in an autosomal recessive manner; affected
    individuals carry homozygous or compound heterozygous pathogenic FAM20C
    variants. Parental consanguinity is frequently reported, and unaffected
    parents are obligate heterozygous carriers.
  evidence:
  - reference: PMID:19250384
    reference_title: "Mutations in FAM20C also identified in non-lethal osteosclerotic bone dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in FAM20C, consistent with autosomal recessive inheritance, were identified in both cases."
    explanation: Documents autosomal recessive segregation of FAM20C variants in Raine syndrome families.
  - reference: PMID:24039075
    reference_title: "Hereditary deletion of the entire FAM20C gene in a patient with Raine syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report on a child who is homozygous for a 487-kb deletion in 7p22.3 that contains FAM20C. Both parents were heterozygous for the deletion."
    explanation: Homozygous whole-gene deletion with heterozygous carrier parents demonstrates recessive inheritance.
has_subtypes:
- name: Lethal RS
  display_name: Lethal (classic) Raine syndrome
  description: >
    The originally described, neonatal-lethal form. Affected neonates present
    at birth with generalized osteosclerosis, periosteal bone formation, the
    characteristic craniofacial phenotype and intracranial calcification, and
    die within the first days to weeks of life, usually from respiratory
    insufficiency secondary to midface hypoplasia with choanal atresia and a
    narrow, hypoplastic thorax. Typically associated with complete
    loss-of-function FAM20C alleles.
  genes:
  - preferred_term: FAM20C
    term:
      id: hgnc:22140
      label: FAM20C
  evidence:
  - reference: PMID:17924334
    reference_title: "Mutations in FAM20C are associated with lethal osteosclerotic bone dysplasia (Raine syndrome), highlighting a crucial molecule in bone development."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Lethal osteosclerotic bone dysplasia (or, Raine syndrome) is an autosomal recessive disorder characterized by generalized osteosclerosis with periosteal bone formation and a distinctive facial phenotype. Affected individuals survive only days or weeks."
    explanation: Defines the lethal subtype and its neonatal course.
- name: Non-lethal RS
  display_name: Non-lethal (attenuated) Raine syndrome
  description: >
    An attenuated form recognized since 2009, in which affected individuals
    survive infancy — into childhood, adolescence and adulthood (reported to at
    least 39 years). The phenotype is highly heterogeneous and dominated by
    FGF23-related hypophosphatemic rickets, hypoplastic amelogenesis
    imperfecta and dentin anomalies, ectopic soft-tissue and solid-organ
    calcification, facial dysmorphism, and variable neurodevelopmental delay,
    seizures and sensory involvement; osteosclerosis may be mild or absent.
    Associated with hypomorphic FAM20C alleles retaining residual kinase
    activity or partially preserved protein function.
  genes:
  - preferred_term: FAM20C
    term:
      id: hgnc:22140
      label: FAM20C
  evidence:
  - reference: PMID:19250384
    reference_title: "Mutations in FAM20C also identified in non-lethal osteosclerotic bone dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the identification of mutations in these two patients confirms a broader phenotypic spectrum and that mutation of FAM20C does not always lead to the infantile lethality previously seen as a prerequisite for Raine syndrome diagnosis."
    explanation: Establishes the existence of a non-lethal FAM20C-related Raine syndrome subtype.
  - reference: PMID:32299476
    reference_title: "Natural history of non-lethal Raine syndrome during childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "However, there exists a non-lethal RS form, the phenotype of which is extremely heterogeneous."
    explanation: Confirms the non-lethal subtype and its marked phenotypic heterogeneity.
classifications:
  isds_skeletal_category:
  - classification_value: osteosclerotic_disorders
    notes: >-
      ISDS Nosology of Genetic Skeletal Disorders. Assigned from the 2019 revision
      (Mortier et al., PMID:31633310), Table 1 group 22 "Neonatal osteosclerotic
      dysplasias"; listed as "Raine dysplasia (lethal and nonlethal forms)". The 2023
      revision (Unger et al., PMID:36779427) dissolved that group into group 25
      "Osteosclerotic disorders", fusing the neonatal osteosclerotic dysplasias with the
      other sclerosing bone disorders, so the value is carried forward here. Membership
      has not been re-verified against the 2023 table.
prevalence:
- population: Worldwide
  measure_type: POINT_PREVALENCE
  prevalence_class: BELOW_1_IN_1000000
  rate_high: 0.1
  notes: >
    Reported as "< 1/1,000,000" in the disease overview literature; upper bound
    of 1 per 1,000,000 normalizes to 0.1 per 100,000. Fewer than ~50 cases had
    been reported worldwide as of 2021.
  evidence:
  - reference: PMID:25019372
    reference_title: "Raine syndrome: an overview."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Its prevalence is estimated to be < 1/1,000,000."
    explanation: Published prevalence estimate for Raine syndrome.
  - reference: PMID:38163266
    reference_title: "Raine syndrome: Prenatally identified severe craniofacial phenotype with multisuture synostosis and brain abnormalities associated with variants in FAM20C."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "with an estimated prevalence of <1/1,000,000"
    explanation: Independent confirmation of the ultra-rare prevalence estimate.
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >
    Cumulative case counts remain very small; 47 cases reported worldwide as of
    the 2021 case report below. Published counts disagree because they use
    different inclusion criteria and cut-off dates: the 2021 FAM20C/Raine
    syndrome review by Palma-Lara et al. (PMID:34360805) tabulates a larger
    series of roughly 70 published patients (about 41 lethal and 29 non-lethal)
    in its full text. That figure is not quotable from the abstract, so it is
    recorded here as a curator note rather than as an evidence item; the 47
    figure below is retained as the snippet-verifiable count. Either way the
    order of magnitude - a few tens of published cases worldwide - is the same,
    and both are published-case tallies subject to ascertainment bias rather
    than population surveillance.
  evidence:
  - reference: PMID:33676444
    reference_title: "Recurrent variant c.1680C>A in FAM20C gene and genotype-phenotype correlation in a patient with Raine syndrome: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Of the 47 cases of RS reported worldwide; four are from India"
    explanation: Documents the cumulative reported-case count for Raine syndrome.
pathophysiology:
- name: Loss of FAM20C Golgi Casein Kinase Activity
  biological_scale: MOLECULAR
  description: >
    FAM20C is the Golgi casein kinase: an atypical, secretory-pathway protein
    kinase that localizes to the Golgi apparatus and phosphorylates serine
    residues within S-x-E/pS motifs of secreted proteins. Biallelic
    loss-of-function variants in FAM20C abolish or markedly reduce this kinase
    activity. Raine syndrome missense substitutions impair both Golgi
    localization and catalytic activity of the recombinant enzyme; a
    non-lethal splice-altering variant produces an in-frame insertion that
    mislocalizes the protein and reduces its secretion without disrupting
    dimerization.
  gene:
    preferred_term: FAM20C
    modifier: DECREASED
    term:
      id: hgnc:22140
      label: FAM20C
  molecular_functions:
  - preferred_term: Golgi casein kinase (protein serine/threonine kinase) activity
    modifier: DECREASED
    term:
      id: GO:0004674
      label: protein serine/threonine kinase activity
  cellular_components:
  - preferred_term: Golgi apparatus
    term:
      id: GO:0005794
      label: Golgi apparatus
  biological_processes:
  - preferred_term: peptidyl-serine phosphorylation of secreted proteins
    modifier: DECREASED
    term:
      id: GO:0018105
      label: peptidyl-serine phosphorylation
  downstream:
  - target: Hypophosphorylation of Secreted Biomineralization Proteins
    description: >
      Loss of kinase activity leaves the FAM20C secreted phosphoproteome
      unphosphorylated.
    evidence:
    - reference: PMID:22582013
      reference_title: Secreted kinase phosphorylates extracellular proteins that regulate biomineralization.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Fam20C phosphorylates the caseins and several secreted proteins implicated in biomineralization, including the small integrin-binding ligand, N-linked glycoproteins (SIBLINGs). Consequently, mutations in Fam20C cause an osteosclerotic bone dysplasia in humans known as Raine syndrome."
      explanation: Establishes that the substrates left unphosphorylated when FAM20C is lost are the biomineralization phosphoproteins, and ties that directly to Raine syndrome.
  - target: Gingival Fibroblast Activation via TGF-beta and YAP/TAZ
    description: >
      Loss of FAM20C activity engages a TGF-beta-YAP/TAZ profibrotic loop in
      resident gingival fibroblasts.
    evidence:
    - reference: PMID:38664418
      reference_title: Gingival proteomics reveals the role of TGF beta and YAP/TAZ signaling in Raine syndrome fibrosis.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Knocking down of FAM20C confirmed the TGFβ-YAP/TAZ interplay indicating that a profibrotic loop enabled gingival fibrosis in RNS patients."
      explanation: siRNA knockdown of FAM20C is sufficient to engage the profibrotic loop, establishing the causal direction from kinase loss to fibroblast activation.
  evidence:
  - reference: PMID:22582013
    reference_title: "Secreted kinase phosphorylates extracellular proteins that regulate biomineralization."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Fam20C appears to be the Golgi casein kinase that phosphorylates secretory pathway proteins within S-x-E motifs."
    explanation: Identifies FAM20C as the Golgi casein kinase and defines its S-x-E substrate motif.
  - reference: PMID:22900076
    reference_title: "The Raine syndrome protein FAM20C is a Golgi kinase that phosphorylates bio-mineralization proteins."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Introduction of point mutations identified in Raine syndrome patients into recombinant FAM20C impairs its normal localization and kinase activity."
    explanation: Directly demonstrates that Raine syndrome variants impair FAM20C localization and catalysis.
  - reference: PMID:25026495
    reference_title: "Functional analysis of mutant FAM20C in Raine syndrome with FGF23-related hypophosphatemia."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "all the mutant FAM20C proteins showed decreased kinase activities compared to wild-type (WT) FAM20C, and most of them also showed impaired secretion."
    explanation: Functional analysis of six Raine syndrome FAM20C mutants shows loss of kinase activity.
  - reference: PMID:40794899
    reference_title: "A synonymous single nucleotide variant on the FAM20C gene causes non-lethal Raine syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "this variant protein failed to localize properly to the Golgi apparatus and exhibited poor secretion from the cell."
    explanation: Shows a non-lethal Raine syndrome variant acts by mislocalizing FAM20C away from the Golgi.
  - reference: PMID:23754375
    reference_title: "Crystal structure of the Golgi casein kinase."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The nucleotide-free and Mn/ADP-bound structures unveil an atypical protein kinase-like fold and highlight residues critical for activity."
    explanation: >
      Provides the structural framework for the atypical Fam20 kinase fold and its
      catalytically critical residues. Note this is the C. elegans Fam20C ortholog
      and the paper does not itself map Raine syndrome variants onto residues; the
      variant-level loss of catalysis is evidenced separately by PMID:22900076 and
      PMID:25026495.
- name: Hypophosphorylation of Secreted Biomineralization Proteins
  biological_scale: MOLECULAR
  description: >
    FAM20C phosphorylates well over one hundred substrates in the secretory
    pathway, including the caseins and members of the SIBLING (small
    integrin-binding ligand, N-linked glycoprotein) family — DMP1, MEPE,
    osteopontin (SPP1), bone sialoprotein and DSPP — which regulate
    extracellular matrix biomineralization. Loss of FAM20C activity leaves
    these substrates hypophosphorylated, removing a key post-translational
    control on mineral nucleation and inhibition in bone and dental hard
    tissue.
  biological_processes:
  - preferred_term: biomineral tissue development
    modifier: ABNORMAL
    term:
      id: GO:0031214
      label: biomineral tissue development
  genes:
  - preferred_term: DMP1
    modifier: DECREASED
    term:
      id: hgnc:2932
      label: DMP1
  - preferred_term: MEPE (FAM20C substrate, hypophosphorylated)
    modifier: ABNORMAL
    term:
      id: hgnc:13361
      label: MEPE
  - preferred_term: SPP1 / osteopontin (FAM20C substrate, hypophosphorylated)
    modifier: ABNORMAL
    term:
      id: hgnc:11255
      label: SPP1
  - preferred_term: DSPP (FAM20C substrate, hypophosphorylated)
    modifier: ABNORMAL
    term:
      id: hgnc:3054
      label: DSPP
  downstream:
  - target: Dysregulated FGF23 and Renal Phosphate Wasting
    description: >
      Reduced DMP1 expression and loss of direct FGF23 phosphorylation
      dysregulate FGF23 processing and output.
    evidence:
    - reference: PMID:25026495
      reference_title: Functional analysis of mutant FAM20C in Raine syndrome with FGF23-related hypophosphatemia.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Fam20c knockdown decreased Dmp1 mRNA and increased Fgf23 mRNA in UMR-106 cells."
      explanation: Directly demonstrates the DMP1-down/FGF23-up consequence of losing FAM20C activity.
  - target: Abnormal Bone Matrix Mineralization
    description: >
      Loss of SIBLING phosphorylation deranges matrix mineral nucleation and
      inhibition.
    evidence:
    - reference: PMID:22900076
      reference_title: The Raine syndrome protein FAM20C is a Golgi kinase that phosphorylates bio-mineralization proteins.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "we find that FAM20C phosphorylates a biologically active peptide at amino acids essential for inhibition of biomineralization"
      explanation: Shows the phosphorylation events lost in Raine syndrome control mineralization inhibition directly.
  - target: Ectopic Intracranial and Soft Tissue Calcification
    description: >
      Loss of phosphorylation on mineralization-inhibiting secreted substrates
      removes a brake on mineral nucleation outside the skeleton.
    evidence:
    - reference: PMID:22900076
      reference_title: The Raine syndrome protein FAM20C is a Golgi kinase that phosphorylates bio-mineralization proteins.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "we find that FAM20C phosphorylates a biologically active peptide at amino acids essential for inhibition of biomineralization"
      explanation: Shows FAM20C phosphorylates residues essential for INHIBITION of biomineralization, the biochemical basis for loss of a mineralization brake; the extension to ectopic (extraskeletal) sites is inferred, hence PARTIAL.
  - target: Dental Hard Tissue Mineralization Failure
    description: >
      Ameloblast and odontoblast substrates are left hypophosphorylated.
    evidence:
    - reference: PMID:25928877
      reference_title: Variability of systemic and oro-dental phenotype in two families with non-lethal Raine syndrome with FAM20C mutations.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "a profound failure of dental enamel formation leading to a distinctive hypoplastic AI in all teeth should alert clinicians to the possibility of FAM20C mutations."
      explanation: Connects loss of FAM20C substrate phosphorylation to failure of dental hard tissue mineralization.
  evidence:
  - reference: PMID:22582013
    reference_title: "Secreted kinase phosphorylates extracellular proteins that regulate biomineralization."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Fam20C phosphorylates the caseins and several secreted proteins implicated in biomineralization, including the small integrin-binding ligand, N-linked glycoproteins (SIBLINGs)."
    explanation: Establishes the SIBLING family as FAM20C substrates relevant to biomineralization.
  - reference: PMID:22900076
    reference_title: "The Raine syndrome protein FAM20C is a Golgi kinase that phosphorylates bio-mineralization proteins."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We show that FAM20C can phosphorylate secreted phosphoproteins, including both Casein and members of the SIBLING protein family, which modulate biomineralization, and we find that FAM20C phosphorylates a biologically active peptide at amino acids essential for inhibition of biomineralization."
    explanation: Shows FAM20C phosphorylation directly targets residues that control mineralization inhibition.
  - reference: PMID:33759783
    reference_title: "The ABCs of the atypical Fam20 secretory pathway kinases."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The protein kinase, Fam20C, conserved from nematodes to humans, phosphorylates well over 100 substrates in the secretory pathway"
    explanation: Documents the breadth of the FAM20C secreted phosphoproteome.
  - reference: PMID:28620244
    reference_title: Specific ablation of mouse Fam20C in cells expressing type I collagen leads to skeletal defects and hypophosphatemia.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The Fam20C-deficient bone had a lower level of dentin matrix protein 1, and higher levels of osteopontin and bone sialoprotein than the normal."
    explanation: In vivo demonstration that FAM20C loss deranges the SIBLING proteins DMP1, osteopontin and bone sialoprotein in bone.
- name: Dysregulated FGF23 and Renal Phosphate Wasting
  biological_scale: ORGANISM
  description: >
    FAM20C directly phosphorylates FGF23 on Ser180 within its
    R176XXR179/S180AE subtilisin-like proprotein convertase motif; this
    phosphorylation blocks GalNAc-T3 O-glycosylation and promotes furin
    cleavage and inactivation of FGF23. FAM20C also sustains DMP1 expression,
    which suppresses FGF23 production. Loss of FAM20C therefore raises
    circulating intact, biologically active FGF23, causing renal phosphate
    wasting, hypophosphatemia, and FGF23-related hypophosphatemic rickets or
    osteomalacia — the dominant endocrine feature of the non-lethal form.
  gene:
    preferred_term: FGF23
    modifier: INCREASED
    term:
      id: hgnc:3680
      label: FGF23
  biological_processes:
  - preferred_term: phosphate ion homeostasis
    modifier: ABNORMAL
    term:
      id: GO:0055062
      label: phosphate ion homeostasis
  downstream:
  - target: Abnormal Bone Matrix Mineralization
    description: >
      Hypophosphatemia produces rickets/osteomalacia, on which the sclerotic
      radiographic phenotype is superimposed.
    evidence:
    - reference: PMID:32101876
      reference_title: High-Phosphate Diet Improved the Skeletal Development of Fam20c-Deficient Mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "These results suggested that the hPi diet significantly improved the skeletal development of the Fam20c-deficient mice, implying that hypophosphatemia partially contributed to the skeletal defects in Fam20c-deficient subjects."
      explanation: Dietary phosphate rescue establishes hypophosphatemia as a causal contributor to the skeletal mineralization defect.
  evidence:
  - reference: PMID:24706917
    reference_title: "Dynamic regulation of FGF23 by Fam20C phosphorylation, GalNAc-T3 glycosylation, and furin proteolysis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Here we show that Fam20C directly phosphorylates FGF23 on Ser(180), within the FGF23 R(176)XXR(179)/S(180)AE subtilisin-like proprotein convertase motif. This phosphorylation event inhibits O-glycosylation of FGF23 by polypeptide N-acetylgalactosaminyltransferase 3 (GalNAc-T3), and promotes FGF23 cleavage and inactivation by the subtilisin-like proprotein convertase furin."
    explanation: Defines the molecular mechanism by which FAM20C limits intact bioactive FGF23.
  - reference: PMID:24706917
    reference_title: "Dynamic regulation of FGF23 by Fam20C phosphorylation, GalNAc-T3 glycosylation, and furin proteolysis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "humans with FAM20C mutations and Fam20C KO mice develop hypophosphatemia due to an increase in full-length, biologically active FGF23"
    explanation: >
      Background statement summarising prior human and mouse work (this PNAS paper
      itself reports in vitro biochemistry), and it mixes human and mouse
      observations in one sentence - hence OTHER rather than HUMAN_CLINICAL.
      The human arm is independently evidenced by PMID:31471673 and PMID:25026495,
      the mouse arm by PMID:22615579.
  - reference: PMID:25026495
    reference_title: "Functional analysis of mutant FAM20C in Raine syndrome with FGF23-related hypophosphatemia."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "our results suggest that FAM20C suppresses FGF23 production by enhancing DMP1 expression, and inactivating mutations in FAM20C cause FGF23-related hypophosphatemia by decreasing transcription of DMP1."
    explanation: Provides the DMP1-dependent arm of FGF23 dysregulation in Raine syndrome.
  - reference: PMID:22615579
    reference_title: "Inactivation of a novel FGF23 regulator, FAM20C, leads to hypophosphatemic rickets in mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "both the global and mineralized tissue-specific cKO mice developed hypophosphatemic rickets (but not osteosclerosis), along with a significant downregulation of osteoblast differentiation markers and a dramatic elevation of fibroblast growth factor 23 (FGF23) in the serum and bone."
    explanation: Mouse Fam20c inactivation reproduces the FGF23-driven hypophosphatemic rickets arm of the human disease.
- name: Abnormal Bone Matrix Mineralization
  biological_scale: TISSUE
  description: >
    The matrix-level lesion. Loss of FAM20C-dependent substrate phosphorylation,
    compounded by FGF23-driven hypophosphatemia, leaves bone matrix abnormally
    mineralized with disorganized, thickened collagen fibrils and a widened,
    disorganized growth plate. Critically, this is an UNDER-mineralization
    lesion: non-decalcified human histology after tetracycline labeling
    documented severe osteomalacia (not rickets), and knock-in mouse tibiae that
    look osteosclerotic on radiography show reduced mineral density and
    increased porosity on micro-CT. FAM20C additionally fine-tunes chondroitin
    sulfate 4-O/6-O sulfation, an activity lost with Raine syndrome mutations,
    providing a further route to dysregulated osteoblast biomineralization.
    The relationship between this osteomalacic matrix and the sclerotic
    radiographic appearance is the entry's principal open question (see
    discussions).
  cell_types:
  - preferred_term: osteoblast
    term:
      id: CL:0000062
      label: osteoblast
  - preferred_term: osteocyte
    term:
      id: CL:0000137
      label: osteocyte
  biological_processes:
  - preferred_term: bone mineralization
    modifier: ABNORMAL
    term:
      id: GO:0030282
      label: bone mineralization
  - preferred_term: ossification
    modifier: ABNORMAL
    term:
      id: GO:0001503
      label: ossification
  downstream:
  - target: Generalized Osteosclerosis and Periosteal Bone Formation
    description: >
      The abnormal matrix presents radiographically as generalized
      osteosclerosis with periosteal new bone formation.
    evidence:
    - reference: PMID:27862258
      reference_title: "Raine Syndrome (OMIM #259775), Caused By FAM20C Mutation, Is Congenital Sclerosing Osteomalacia With Cerebral Calcification (OMIM 259660)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Following premortem tetracycline labeling, the proposita's non-decalcified skeletal histopathology after autopsy indicated no rickets but documented severe osteomalacia."
      explanation: Human histopathology showing the radiographically sclerotic skeleton is in fact an osteomalacic matrix, grounding the matrix-to-radiograph edge.
  evidence:
  - reference: PMID:17924334
    reference_title: "Mutations in FAM20C are associated with lethal osteosclerotic bone dysplasia (Raine syndrome), highlighting a crucial molecule in bone development."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This study defines the causative role of FAM20C in this lethal osteosclerotic disorder and its crucial role in normal bone development."
    explanation: Establishes FAM20C loss as the cause of the osteosclerotic skeletal phenotype.
  - reference: PMID:27862258
    reference_title: "Raine Syndrome (OMIM #259775), Caused By FAM20C Mutation, Is Congenital Sclerosing Osteomalacia With Cerebral Calcification (OMIM 259660)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Following premortem tetracycline labeling, the proposita's non-decalcified skeletal histopathology after autopsy indicated no rickets but documented severe osteomalacia."
    explanation: Human bone histopathology shows the radiographically sclerotic skeleton is severely undermineralized.
  - reference: PMID:36572689
    reference_title: "Altered sulfation status of FAM20C-dependent chondroitin sulfate is associated with osteosclerotic bone dysplasia."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "FAM20C with Raine-originated mutations loses the ability to interact with chondroitin 4-O-sulfotransferase-1, and is associated with reduced 4-sulfation/6-sulfation (4S/6S) ratio of CS chains and upregulated biomineralization in human osteosarcoma cells."
    explanation: Identifies a chondroitin-sulfate sulfation route by which Raine syndrome mutations dysregulate biomineralization.
  - reference: PMID:39748245
    reference_title: "Mutant Fam20c knock-in mice recapitulate both lethal and non-lethal human Raine Syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "a few conventional Fam20cD446N knock-in mice died before weaning with the osteosclerotic X-ray radiography, though micro-CT assay displayed a reduced mineral density and increased porosity in the osteosclerotic tibia."
    explanation: Knock-in mouse data indicate the osteosclerotic radiographic appearance overlies undermineralized, porous bone.
  - reference: PMID:28620244
    reference_title: Specific ablation of mouse Fam20C in cells expressing type I collagen leads to skeletal defects and hypophosphatemia.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "This study showed that the long bones of cKO mice were shorter and had a lower level of mineralization compared to the normal mice. The collagen fibrils in Fam20C-deficient bone were disorganized and thicker while the growth plate cartilage in cKO mice was disorganized and wider compared to the normal mice."
    explanation: Bone-cell-restricted Fam20C loss produces undermineralized bone with disorganized collagen fibrils, defining the matrix-level lesion.
- name: Generalized Osteosclerosis and Periosteal Bone Formation
  biological_scale: TISSUE
  description: >
    The radiographic readout of the abnormal matrix: a diffuse, marked increase
    in radiodensity of all bones, most striking at the skull base and long
    bones, together with periosteal new bone formation — the feature that
    distinguishes Raine syndrome from osteopetrosis and other sclerosing
    dysplasias. Modeled as a distinct node from the matrix lesion because the
    two dissociate: the sclerotic radiographic appearance overlies an
    osteomalacic, porous matrix, and osteosclerosis may be mild or absent in
    the non-lethal form.
  biological_processes:
  - preferred_term: ossification
    modifier: INCREASED
    term:
      id: GO:0001503
      label: ossification
  downstream:
  - target: Craniofacial Skeletal Overgrowth
    description: >
      Excess ossification of the skull and facial bones drives the craniofacial
      phenotype.
    evidence:
    - reference: PMID:33676444
      reference_title: "Recurrent variant c.1680C>A in FAM20C gene and genotype-phenotype correlation in a patient with Raine syndrome: a case report."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The increased ossification of the skull and facial bones underlies the characteristic facial features of RS, which include narrow prominent forehead, proptosis, depressed nasal bridge, and midface hypoplasia."
      explanation: States the causal link from skeletal over-ossification to the craniofacial phenotype.
  - target: Thoracic Hypoplasia and Pulmonary Hypoplasia
    description: >
      Skeletal involvement of the ribs and thoracic cage produces a narrow,
      hypoplastic thorax.
    evidence:
    - reference: PMID:33676444
      reference_title: "Recurrent variant c.1680C>A in FAM20C gene and genotype-phenotype correlation in a patient with Raine syndrome: a case report."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Clinical manifestations include generalized osteosclerosis, craniofacial dysplasia, thoracic hypoplasia and oro-dental anomalies."
      explanation: Lists thoracic hypoplasia alongside osteosclerosis as a skeletal manifestation; the causal ordering is inferred, hence PARTIAL.
  evidence:
  - reference: PMID:25019372
    reference_title: "Raine syndrome: an overview."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The main radiological manifestation is a diffuse, marked osteosclerosis of the base of skull and long bones."
    explanation: Defines the radiographic osteosclerosis and its anatomical distribution.
  - reference: PMID:33676444
    reference_title: "Recurrent variant c.1680C>A in FAM20C gene and genotype-phenotype correlation in a patient with Raine syndrome: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Periosteal bone formation is also a characteristic feature of this disorder differentiating it from osteopetrosis and other known lethal and nonlethal osteosclerotic bone dysplasias."
    explanation: Establishes periosteal new bone formation as the discriminating radiographic feature.
- name: Thoracic Hypoplasia and Pulmonary Hypoplasia
  biological_scale: ORGANISM
  description: >
    A narrow, hypoplastic thorax restricts lung growth, producing pulmonary
    hypoplasia. This arm is mechanistically independent of the craniofacial
    arm; the two converge on neonatal respiratory failure.
  downstream:
  - target: Neonatal Respiratory Failure
    description: >
      Pulmonary hypoplasia limits gas exchange from the first minutes of life.
    evidence:
    - reference: PMID:33676444
      reference_title: "Recurrent variant c.1680C>A in FAM20C gene and genotype-phenotype correlation in a patient with Raine syndrome: a case report."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Severe midface hypoplasia and narrow thorax leading to choanal atresia and pulmonary hypoplasia respectively, contribute to respiratory distress and have been regarded as the causes for early death."
      explanation: Attributes neonatal respiratory distress and early death to pulmonary hypoplasia arising from the narrow thorax.
  evidence:
  - reference: PMID:33676444
    reference_title: "Recurrent variant c.1680C>A in FAM20C gene and genotype-phenotype correlation in a patient with Raine syndrome: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Severe midface hypoplasia and narrow thorax leading to choanal atresia and pulmonary hypoplasia respectively, contribute to respiratory distress and have been regarded as the causes for early death."
    explanation: Attributes pulmonary hypoplasia specifically to the narrow thorax, separate from the midface/choanal arm.
- name: Neonatal Respiratory Failure
  biological_scale: ORGANISM
  description: >
    The convergent terminal node of the lethal form: upper-airway obstruction
    from choanal atresia/stenosis plus pulmonary hypoplasia from the narrow
    thorax produce severe respiratory distress from birth, the usual proximate
    cause of death within days to weeks.
  evidence:
  - reference: PMID:32299476
    reference_title: Natural history of non-lethal Raine syndrome during childhood.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "RS is usually lethal during the neonatal period due to severe respiratory distress."
    explanation: Identifies neonatal respiratory failure as the proximate cause of death.
  - reference: PMID:17924334
    reference_title: "Mutations in FAM20C are associated with lethal osteosclerotic bone dysplasia (Raine syndrome), highlighting a crucial molecule in bone development."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals survive only days or weeks."
    explanation: Documents the neonatal-lethal course driven by respiratory failure.
- name: Craniofacial Skeletal Overgrowth
  biological_scale: ORGANISM
  description: >
    The dysplasia predominantly affects craniofacial development. Increased
    ossification of the skull and facial bones underlies the characteristic
    facies — narrow prominent forehead, severe proptosis, underdeveloped
    midface, depressed nasal bridge and short nose — and in the most severe
    cases multisuture craniosynostosis. Severe midface hypoplasia in turn
    produces choanal atresia or stenosis, obstructing the neonatal upper airway.
  biological_processes:
  - preferred_term: ossification
    modifier: INCREASED
    term:
      id: GO:0001503
      label: ossification
  downstream:
  - target: Neonatal Respiratory Failure
    description: >
      Midface hypoplasia with choanal atresia/stenosis obstructs the neonatal
      upper airway.
    evidence:
    - reference: PMID:32299476
      reference_title: Natural history of non-lethal Raine syndrome during childhood.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The most common neonatal comorbidity was respiratory distress secondary to choanal atresia."
      explanation: Directly links choanal atresia to neonatal respiratory compromise.
  evidence:
  - reference: PMID:25019372
    reference_title: "Raine syndrome: an overview."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The skeletal dysplasia predominantly affects craniofacial development explaining the severe proptosis, underdeveloped midface, depressed nasal bridge and short nose."
    explanation: Directly links the craniofacial skeletal overgrowth to the characteristic facial phenotype.
  - reference: PMID:33676444
    reference_title: "Recurrent variant c.1680C>A in FAM20C gene and genotype-phenotype correlation in a patient with Raine syndrome: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Severe midface hypoplasia and narrow thorax leading to choanal atresia and pulmonary hypoplasia respectively, contribute to respiratory distress and have been regarded as the causes for early death."
    explanation: Explains the mechanism by which craniofacial and thoracic involvement cause neonatal lethality.
  - reference: PMID:25019372
    reference_title: "Raine syndrome: an overview."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "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."
    explanation: Confirms respiratory distress as the immediate perinatal threat.
- name: Ectopic Intracranial and Soft Tissue Calcification
  biological_scale: TISSUE
  description: >
    Ectopic mineral is deposited outside the skeleton. The leading hypothesis is
    that loss of FAM20C-dependent phosphorylation of mineralization-INHIBITING
    secreted substrates removes a brake on mineral nucleation, but this has been
    demonstrated biochemically rather than at ectopic sites in patients, and a
    parallel in silico analysis proposes distinct brain-expressed FAM20C targets;
    the mechanism should be read as provisional.
    Intracranial calcifications are a cardinal feature, typically periventricular
    and involving basal ganglia and corpus callosum, and are accompanied in
    severe cases by periventricular gliosis, infarction, hemorrhage and
    leukomalacia. Brain-specific deletion of Fam20c in mice produces cerebral
    calcification without skeletal or dental defects, indicating that local loss
    of FAM20C function within the brain is sufficient. Ectopic calcification also
    occurs in soft tissue and solid organs in longer-surviving patients.
  evidence:
  - reference: PMID:36914045
    reference_title: "Intracranial calcification in Fam20c-deficient mice recapitulates human Raine syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Our results suggest that the local loss of FAM20C function in the brain may directly account for intracranial calcification."
    explanation: Brain-specific Fam20c deletion in mice shows a cell-autonomous CNS route to the calcification phenotype.
  - reference: PMID:36914045
    reference_title: "Intracranial calcification in Fam20c-deficient mice recapitulates human Raine syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "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"
    explanation: Dissociates the CNS calcification mechanism from the skeletal and dental phenotypes.
  - reference: PMID:38163266
    reference_title: "Raine syndrome: Prenatally identified severe craniofacial phenotype with multisuture synostosis and brain abnormalities associated with variants in FAM20C."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Histological sections of the brain showed marked periventricular gliosis with regions of infarction, hemorrhage, and cavitation with global periventricular leukomalacia. Numerous dystrophic calcifications were diffusely present."
    explanation: Human neuropathology documenting dystrophic intracranial calcification and associated brain injury.
  - reference: PMID:37240249
    reference_title: "Potential Role of Protein Kinase FAM20C on the Brain in Raine Syndrome, an In Silico Analysis."
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: "However, FAM20C has many targets, including brain proteins and the cerebrospinal fluid phosphoproteome."
    explanation: In silico analysis proposing brain-expressed FAM20C substrates as a route to the neurological and calcification phenotype; hypothesis-generating only.
  - reference: PMID:37240249
    reference_title: "Potential Role of Protein Kinase FAM20C on the Brain in Raine Syndrome, an In Silico Analysis."
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: "Individuals with RNS can have developmental delay, intellectual disability, seizures, and structural brain defects, but little is known about FAM20C brain-target-protein dysregulation or about a potential pathogenesis associated with neurologic features."
    explanation: States the open question about the mechanism linking FAM20C loss to the neurological phenotype.
- name: Dental Hard Tissue Mineralization Failure
  biological_scale: TISSUE
  description: >
    FAM20C acts intracellularly within ameloblasts and odontoblasts, where its
    substrates (including DSPP and other SIBLINGs) direct enamel and dentin
    mineralization. Its loss produces a distinctive hypoplastic amelogenesis
    imperfecta affecting all teeth together with dentin abnormalities, a
    hallmark of the non-lethal form that should prompt FAM20C testing.
    Hypophosphatemic rickets adds spontaneous recurrent abscesses on non-carious
    teeth.
  cell_types:
  - preferred_term: ameloblast
    term:
      id: CL:0000059
      label: ameloblast
  - preferred_term: odontoblast
    term:
      id: CL:0000060
      label: odontoblast
  biological_processes:
  - preferred_term: biomineral tissue development
    modifier: ABNORMAL
    term:
      id: GO:0031214
      label: biomineral tissue development
  evidence:
  - reference: PMID:25928877
    reference_title: "Variability of systemic and oro-dental phenotype in two families with non-lethal Raine syndrome with FAM20C mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a profound failure of dental enamel formation leading to a distinctive hypoplastic AI in all teeth should alert clinicians to the possibility of FAM20C mutations."
    explanation: Establishes hypoplastic amelogenesis imperfecta as a defining dental manifestation of FAM20C loss.
  - reference: PMID:23703840
    reference_title: FAM20C functions intracellularly within both ameloblasts and odontoblasts in vivo.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "FAM20C localized intracellularly within ameloblasts and odontoblasts in a pattern consistent with Golgi localization."
    explanation: Localizes FAM20C to the Golgi of the two cell types that build enamel and dentin, grounding the dental mineralization defect.
  - reference: PMID:33505751
    reference_title: "Hypophosphataemic Rickets Secondary to Raine Syndrome: A Review of the Literature and Case Reports of Three Paediatric Patients' Dental Management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Spontaneous recurrent abscesses on noncarious teeth result in significant odontogenic pain and multiple dental interventions."
    explanation: Documents the dental consequence of hypophosphataemic rickets in non-lethal Raine syndrome.
- name: Gingival Fibroblast Activation via TGF-beta and YAP/TAZ
  biological_scale: CELLULAR
  conforms_to: "fibrotic_response#Mesenchymal Cell Activation"
  description: >
    In non-lethal Raine syndrome, resident gingival fibroblasts are activated
    along the conserved pro-fibrotic axis. Proteomic and functional analyses of
    patient gingival tissue and primary gingival fibroblasts show upregulated
    TGF-beta/SMAD signaling together with engagement of the fibrogenic
    transcriptional cofactors YAP and TAZ; FAM20C knockdown reproduces the
    TGF-beta-YAP/TAZ interplay, defining a self-reinforcing profibrotic loop.
    This is the disease-specific instance of the conserved mesenchymal cell
    activation step of the fibrotic response, with the gingival fibroblast
    substituted for the generic fibroblast.
  cell_types:
  - preferred_term: gingival fibroblast
    term:
      id: CL:0002552
      label: fibroblast of gingiva
  biological_processes:
  - preferred_term: TGF-beta Receptor Signaling
    modifier: INCREASED
    term:
      id: GO:0007179
      label: transforming growth factor beta receptor signaling pathway
  downstream:
  - target: Excessive Gingival ECM Deposition and Calcification
    description: >
      Activated gingival fibroblasts overproduce and disorganize extracellular
      matrix.
    evidence:
    - reference: PMID:38664418
      reference_title: Gingival proteomics reveals the role of TGF beta and YAP/TAZ signaling in Raine syndrome fibrosis.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Proteomic analysis of differentially expressed proteins demonstrated that proteins involved in extracellular matrix (ECM) regulation and related to the TGFβ/SMAD signaling pathway were increased."
      explanation: Links activated TGF-beta signaling to increased ECM-regulatory protein expression in patient gingiva.
  evidence:
  - reference: PMID:38664418
    reference_title: Gingival proteomics reveals the role of TGF beta and YAP/TAZ signaling in Raine syndrome fibrosis.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Knocking down of FAM20C confirmed the TGFβ-YAP/TAZ interplay indicating that a profibrotic loop enabled gingival fibrosis in RNS patients."
    explanation: Functional knockdown evidence for the TGF-beta-YAP/TAZ profibrotic loop driven by FAM20C loss.
  - reference: PMID:38664418
    reference_title: Gingival proteomics reveals the role of TGF beta and YAP/TAZ signaling in Raine syndrome fibrosis.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "They furthermore uncover the contribution of increased TGFβ-YAP/TAZ signaling in the pathogenesis of the gingival fibrosis."
    explanation: States the increased TGF-beta-YAP/TAZ signaling contribution to the gingival phenotype.
- name: Excessive Gingival ECM Deposition and Calcification
  biological_scale: TISSUE
  conforms_to: "fibrotic_response#Excessive ECM Deposition"
  description: >
    Activated gingival fibroblasts overproduce and disorganize extracellular
    matrix, with increased profibrotic and pro-osteogenic proteins (POSTN,
    SPARC, VIM). The result is gingival fibrosis together with pathological
    ectopic gingival calcification — the tissue substrate of the gum
    hyperplasia seen clinically. The pro-osteogenic component distinguishes
    this from generic soft-tissue fibrosis and reflects the loss of
    FAM20C-dependent mineralization control.
  cell_types:
  - preferred_term: gingival fibroblast
    term:
      id: CL:0002552
      label: fibroblast of gingiva
  evidence:
  - reference: PMID:38664418
    reference_title: Gingival proteomics reveals the role of TGF beta and YAP/TAZ signaling in Raine syndrome fibrosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We showed that fibrosis, pathological gingival calcifications and increased expression of various profibrotic and pro-osteogenic proteins such as POSTN, SPARC and VIM were common findings."
    explanation: Patient gingival tissue findings documenting fibrosis with pro-osteogenic protein upregulation.
  - reference: PMID:38664418
    reference_title: Gingival proteomics reveals the role of TGF beta and YAP/TAZ signaling in Raine syndrome fibrosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "gingival fibrosis and calcifications are associated with, and most likely caused by excessed ECM production and disorganization"
    explanation: Attributes the gingival fibrosis and calcification to excessive, disorganized ECM production.
phenotypes:
- category: Skeletal
  name: Generalized osteosclerosis
  description: >
    Diffuse, marked increase in bone density affecting all bones, most striking
    at the skull base and long bones.
  diagnostic: true
  phenotype_term:
    preferred_term: Generalized osteosclerosis
    term:
      id: HP:0005789
      label: Generalized osteosclerosis
  evidence:
  - reference: PMID:25019372
    reference_title: "Raine syndrome: an overview."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The main radiological manifestation is a diffuse, marked osteosclerosis of the base of skull and long bones."
    explanation: Describes the cardinal radiological osteosclerosis of Raine syndrome.
- category: Skeletal
  name: Periosteal bone formation
  description: >
    Periosteal new bone formation along the long bones and ribs — the feature
    that distinguishes Raine syndrome from osteopetrosis and other sclerosing
    bone dysplasias.
  diagnostic: true
  phenotype_term:
    preferred_term: Periosteal new bone formation of long bones
    term:
      id: HP:0006465
      label: Periosteal thickening of long tubular bones
  evidence:
  - reference: PMID:33676444
    reference_title: "Recurrent variant c.1680C>A in FAM20C gene and genotype-phenotype correlation in a patient with Raine syndrome: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Periosteal bone formation is also a characteristic feature of this disorder differentiating it from osteopetrosis and other known lethal and nonlethal osteosclerotic bone dysplasias."
    explanation: Establishes periosteal bone formation as a differentiating diagnostic feature.
- category: Neurologic
  name: Intracranial calcification
  description: >
    Cerebral calcification, typically periventricular and involving the basal
    ganglia and corpus callosum; a cardinal radiological feature.
  diagnostic: true
  phenotype_term:
    preferred_term: Cerebral calcification
    term:
      id: HP:0002514
      label: Cerebral calcification
  evidence:
  - reference: PMID:32299476
    reference_title: "Natural history of non-lethal Raine syndrome during childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The radiological findings include generalized osteosclerosis and brain calcifications."
    explanation: Confirms brain calcification as a core radiological finding.
  - reference: PMID:24959018
    reference_title: "Raine syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Computed tomography scan of the brain showed diffuse hyperdense areas of calcification in periventricular region, corpus callosum and basal ganglia on both sides"
    explanation: Case-level imaging documenting the anatomical distribution of the calcification.
  - reference: PMID:36914045
    reference_title: Intracranial calcification in Fam20c-deficient mice recapitulates human Raine syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "FAM20C loss-of-function mutations cause Raine syndrome in humans, characterized by generalized osteosclerosis, distinctive craniofacial dysmorphism, along with extensive intracranial calcification."
    explanation: Human background framing in the introduction of a mouse study (hence OTHER, not this paper's own data), establishing intracranial calcification as a defining feature of Raine syndrome. No proportion is stated, so no frequency band is assigned.
- category: Craniofacial
  name: Proptosis (exophthalmos)
  description: >
    Severe proptosis due to shallow orbits from craniofacial skeletal
    overgrowth and midface underdevelopment.
  phenotype_term:
    preferred_term: Exophthalmos
    term:
      id: HP:0000520
      label: Proptosis
  evidence:
  - reference: PMID:32299476
    reference_title: "Natural history of non-lethal Raine syndrome during childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common clinical features are microcephaly, exophthalmos, hypoplastic nose and severe midface hypoplasia, leading to choanal atresia."
    explanation: Lists exophthalmos among the most common clinical features.
- category: Craniofacial
  name: Midface hypoplasia
  phenotype_term:
    preferred_term: Midface hypoplasia
    term:
      id: HP:0011800
      label: Midface retrusion
  evidence:
  - reference: PMID:32299476
    reference_title: "Natural history of non-lethal Raine syndrome during childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common clinical features are microcephaly, exophthalmos, hypoplastic nose and severe midface hypoplasia, leading to choanal atresia."
    explanation: Severe midface hypoplasia is listed as a most-common feature.
- category: Craniofacial
  name: Depressed nasal bridge
  phenotype_term:
    preferred_term: Depressed nasal bridge
    term:
      id: HP:0005280
      label: Depressed nasal bridge
  evidence:
  - reference: PMID:25019372
    reference_title: "Raine syndrome: an overview."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The skeletal dysplasia predominantly affects craniofacial development explaining the severe proptosis, underdeveloped midface, depressed nasal bridge and short nose."
    explanation: Depressed nasal bridge is part of the characteristic facies.
- category: Craniofacial
  name: Microcephaly
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: PMID:32299476
    reference_title: "Natural history of non-lethal Raine syndrome during childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common clinical features are microcephaly, exophthalmos, hypoplastic nose and severe midface hypoplasia, leading to choanal atresia."
    explanation: Microcephaly is listed among the most common clinical features.
- category: Respiratory
  name: Choanal atresia or stenosis
  description: >
    Choanal atresia or stenosis secondary to severe midface hypoplasia; a major
    contributor to neonatal respiratory compromise and the most common neonatal
    comorbidity in non-lethal cases.
  notes: >
    Both complete atresia and stenosis are reported. The phenotype is bound to
    HP:0000453 Choanal atresia, which is narrower than the claim; HP:0000452
    Choanal stenosis covers the milder end and is not separately modeled because
    the cited sources do not consistently distinguish the two.
  phenotype_term:
    preferred_term: Choanal atresia or stenosis
    term:
      id: HP:0000453
      label: Choanal atresia
  evidence:
  - reference: PMID:32299476
    reference_title: "Natural history of non-lethal Raine syndrome during childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common neonatal comorbidity was respiratory distress secondary to choanal atresia."
    explanation: Identifies choanal atresia as the leading neonatal comorbidity. "Most common" is a rank within the set of comorbidities, not a proportion of patients, so no frequency band is assigned.
  - reference: PMID:24959018
    reference_title: "Raine syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Raine syndrome is a rare genetic disorder with characteristic features of exophthalmos, choanal atresia or stenosis, osteosclerosis and cerebral calcifications."
    explanation: Lists choanal atresia/stenosis as a characteristic feature.
- category: Respiratory
  name: Neonatal respiratory distress
  description: >
    Severe respiratory distress present immediately after birth, from combined
    choanal atresia and thoracic/pulmonary hypoplasia; the usual proximate cause
    of neonatal death in the lethal form.
  frequency: VERY_FREQUENT
  subtype: Lethal RS
  phenotype_term:
    preferred_term: Neonatal respiratory distress
    term:
      id: HP:0002643
      label: Neonatal respiratory distress
  evidence:
  - reference: PMID:32299476
    reference_title: "Natural history of non-lethal Raine syndrome during childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "RS is usually lethal during the neonatal period due to severe respiratory distress."
    explanation: Documents respiratory distress as the cause of neonatal lethality.
- category: Oral
  name: Gum hyperplasia
  description: >
    Gingival overgrowth with fibrosis and pathological gingival calcification.
  phenotype_term:
    preferred_term: Gingival hyperplasia
    term:
      id: HP:0000212
      label: Gingival overgrowth
  evidence:
  - reference: PMID:24959018
    reference_title: "Raine syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There was exophthalmos, small nose with depressed nasal bridge, gum hyperplasia, high-arched narrow palate, long philtrum and dysplastic ears"
    explanation: Case description documenting gum hyperplasia in Raine syndrome.
  - reference: PMID:10482879
    reference_title: "Osteosclerosis, hypoplastic nose, and proptosis (Raine syndrome): further delineation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We describe a newborn girl with a lethal sclerosing bone dysplasia leading to prenatal skeletal alterations and microcephaly, proptosis, hypoplastic nose and midface, small jaw, cleft palate, hypertrophied gums, intracranial calcifications, and generalized osteosclerosis."
    explanation: Independent case documenting hypertrophied gums as part of the Raine syndrome phenotype.
- category: Oral
  name: Hypoplastic amelogenesis imperfecta
  description: >
    Profound failure of dental enamel formation producing a distinctive
    hypoplastic amelogenesis imperfecta affecting all teeth, often with dentin
    abnormalities; a hallmark of the non-lethal form.
  subtype: Non-lethal RS
  diagnostic: true
  phenotype_term:
    preferred_term: Hypoplastic amelogenesis imperfecta
    term:
      id: HP:0000705
      label: Amelogenesis imperfecta
  evidence:
  - reference: PMID:25928877
    reference_title: "Variability of systemic and oro-dental phenotype in two families with non-lethal Raine syndrome with FAM20C mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Family 1 included 3 siblings with hypoplastic Amelogenesis Imperfecta (AI) (inherited abnormal dental enamel formation)."
    explanation: Documents hypoplastic amelogenesis imperfecta in non-lethal Raine syndrome siblings.
- category: Endocrine
  name: Hypophosphatemia
  description: >
    Hypophosphatemia due to FGF23-mediated renal phosphate wasting.
  subtype: Non-lethal RS
  phenotype_term:
    preferred_term: Hypophosphatemia
    term:
      id: HP:0002148
      label: Hypophosphatemia
  evidence:
  - reference: PMID:31471673
    reference_title: "Non-lethal Raine Syndrome in a Middle-Aged Woman Caused by a Novel FAM20C Mutation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "midface hypoplasia, exophthalmos, amelogenesis imperfecta, shortening of distal phalanges, pectus excavatum, and hypophosphatemia due to renal phosphate wasting"
    explanation: Documents hypophosphatemia from renal phosphate wasting in an adult with non-lethal Raine syndrome.
- category: Skeletal
  name: Hypophosphatemic rickets
  description: >
    Persistent hypophosphatemic rickets, the most striking endocrinological
    manifestation of non-lethal Raine syndrome, poorly responsive to phosphate
    salts and alfacalcidol.
  subtype: Non-lethal RS
  phenotype_term:
    preferred_term: Hypophosphatemic rickets
    term:
      id: HP:0004912
      label: Hypophosphatemic rickets
  evidence:
  - reference: PMID:32299476
    reference_title: "Natural history of non-lethal Raine syndrome during childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Persistent hypophosphatemic rickets was the most striking endocrinological manifestation, which was scarcely responsive to therapy with phosphate salts and alfacalcidol."
    explanation: Natural-history cohort documents persistent, treatment-refractory hypophosphatemic rickets. "Most striking" describes salience rather than a proportion of patients, so no frequency band is assigned.
- category: Neurologic
  name: Neurodevelopmental delay
  description: >
    Variable degree of neurodevelopmental delay seen in the majority of
    surviving (non-lethal) patients.
  frequency: FREQUENT
  subtype: Non-lethal RS
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:32299476
    reference_title: "Natural history of non-lethal Raine syndrome during childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A variable degree of neurodevelopmental delay was seen in the majority of our cases and seizures and hearing or vision involvement were also frequent."
    explanation: Natural-history data on developmental delay in surviving patients.
- category: Neurologic
  name: Seizures
  frequency: FREQUENT
  subtype: Non-lethal RS
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:32299476
    reference_title: "Natural history of non-lethal Raine syndrome during childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A variable degree of neurodevelopmental delay was seen in the majority of our cases and seizures and hearing or vision involvement were also frequent."
    explanation: Seizures reported as frequent in the non-lethal natural-history cohort.
- category: Sensory
  name: Hearing impairment
  frequency: FREQUENT
  subtype: Non-lethal RS
  phenotype_term:
    preferred_term: Hearing impairment
    term:
      id: HP:0000365
      label: Hearing impairment
  evidence:
  - reference: PMID:32299476
    reference_title: "Natural history of non-lethal Raine syndrome during childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "seizures and hearing or vision involvement were also frequent"
    explanation: Hearing involvement reported as frequent in surviving patients.
- category: Craniofacial
  name: Cleft palate
  description: >
    Cleft palate as part of the craniofacial malformation complex.
  phenotype_term:
    preferred_term: Cleft palate
    term:
      id: HP:0000175
      label: Cleft palate
  evidence:
  - reference: PMID:10482879
    reference_title: "Osteosclerosis, hypoplastic nose, and proptosis (Raine syndrome): further delineation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We describe a newborn girl with a lethal sclerosing bone dysplasia leading to prenatal skeletal alterations and microcephaly, proptosis, hypoplastic nose and midface, small jaw, cleft palate, hypertrophied gums, intracranial calcifications, and generalized osteosclerosis."
    explanation: Case description of a Raine syndrome neonate documenting cleft palate within the craniofacial complex.
- category: Sensory
  name: Visual impairment
  description: >
    Visual involvement reported in surviving patients, including a patient with
    an activation-loop FAM20C variant.
  subtype: Non-lethal RS
  phenotype_term:
    preferred_term: Visual impairment
    term:
      id: HP:0000505
      label: Visual impairment
  evidence:
  - reference: PMID:38664418
    reference_title: Gingival proteomics reveals the role of TGF beta and YAP/TAZ signaling in Raine syndrome fibrosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "hypophosphatemic rickets, intracranial calcifications, visual impairment and an oral phenotype characterized by AI, dentinal anomalies and gingival hyperplasia with calcifications"
    explanation: Documents visual impairment in a molecularly confirmed non-lethal Raine syndrome patient.
  - reference: PMID:32299476
    reference_title: Natural history of non-lethal Raine syndrome during childhood.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "seizures and hearing or vision involvement were also frequent"
    explanation: Cohort data report vision involvement as frequent, but hearing and vision are not separated.
- category: Neurologic
  name: Intellectual disability
  description: >
    Intellectual disability reported in a subset of longer-surviving patients.
  subtype: Non-lethal RS
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:34360805
    reference_title: "FAM20C Overview: Classic and Novel Targets, Pathogenic Variants and Raine Syndrome Phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The milder phenotype is defined by a large spectrum ranging from osteonecrosis to osteosclerosis with additional congenital defects or intellectual disability in some cases."
    explanation: Systematic phenotype review reports intellectual disability in a subset of non-lethal cases.
  - reference: PMID:37240249
    reference_title: "Potential Role of Protein Kinase FAM20C on the Brain in Raine Syndrome, an In Silico Analysis."
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: "Individuals with RNS can have developmental delay, intellectual disability, seizures, and structural brain defects"
    explanation: Confirms intellectual disability within the reported neurological spectrum. Tagged COMPUTATIONAL to match the paper type (an in silico analysis) and this entry's other two uses of the same reference.
- category: Craniofacial
  name: Craniosynostosis
  description: >
    Multisuture craniosynostosis has been documented prenatally in a severe
    case, with protrusion of brain parenchyma through fontanelles and cranial
    lacunae.
  phenotype_term:
    preferred_term: Multisuture craniosynostosis
    term:
      id: HP:0001363
      label: Craniosynostosis
  evidence:
  - reference: PMID:38163266
    reference_title: "Raine syndrome: Prenatally identified severe craniofacial phenotype with multisuture synostosis and brain abnormalities associated with variants in FAM20C."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "He had particularly significant CNS manifestations consisting of multisuture craniosynostosis with protrusion of the brain parenchyma through fontanelles and cranial lacunae."
    explanation: Documents multisuture craniosynostosis in a severe prenatally identified case.
- category: Multisystem
  name: Ectopic soft tissue and solid organ calcification
  description: >
    Ectopic mineralization outside the skeleton and brain, including soft
    tissue and multiple solid organs in longer-surviving patients.
  subtype: Non-lethal RS
  phenotype_term:
    preferred_term: Ectopic calcification
    term:
      id: HP:0010766
      label: Ectopic calcification
  evidence:
  - reference: PMID:25928877
    reference_title: "Variability of systemic and oro-dental phenotype in two families with non-lethal Raine syndrome with FAM20C mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There was hypophosphataemia, soft tissue ectopic mineralization, but no osteosclerosis."
    explanation: Documents soft-tissue ectopic mineralization in attenuated Raine syndrome.
  - reference: PMID:31471673
    reference_title: "Non-lethal Raine Syndrome in a Middle-Aged Woman Caused by a Novel FAM20C Mutation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presenting with pain in the extremities, osteosclerosis with periosteal bone formation, multiple calcifications in solid organs"
    explanation: Solid-organ calcification in an adult with non-lethal Raine syndrome.
- category: Craniofacial
  name: Low-set ears
  phenotype_term:
    preferred_term: Dysplastic/low-set ears
    term:
      id: HP:0000369
      label: Low-set ears
  evidence:
  - reference: PMID:24959018
    reference_title: "Raine syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "small nose with depressed nasal bridge, gum hyperplasia, high-arched narrow palate, long philtrum and dysplastic ears"
    explanation: Case report documents dysplastic ears; low-set/dysplastic ears are part of the characteristic facies.
- category: Skeletal
  name: Short distal phalanges
  description: >
    Hypoplastic or shortened distal phalanges. Bound to the finger term, which
    is what the cited case describes; toe involvement is reported in the
    literature but is not separately evidenced here.
  phenotype_term:
    preferred_term: Hypoplastic distal phalanges
    term:
      id: HP:0009882
      label: Short distal phalanx of finger
  evidence:
  - reference: PMID:24039075
    reference_title: "Hereditary deletion of the entire FAM20C gene in a patient with Raine syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our patient had the common craniofacial features as well as, uncommon features such as protruding tongue, short stature, and hypoplastic distal phalanges."
    explanation: Documents hypoplastic distal phalanges in a patient with a whole-gene FAM20C deletion.
- category: Skeletal
  name: Wormian bones
  phenotype_term:
    preferred_term: Wormian bones
    term:
      id: HP:0002645
      label: Wormian bones
  evidence:
  - reference: PMID:24039075
    reference_title: "Hereditary deletion of the entire FAM20C gene in a patient with Raine syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In addition, he had wormian bones and pyriform aperture stenosis, features that are usually under diagnosed."
    explanation: Documents wormian bones as an under-recognised radiographic feature.
- category: Respiratory
  name: Pulmonary hypoplasia
  description: >
    Pulmonary hypoplasia secondary to the narrow, hypoplastic thorax; with
    choanal atresia it is a principal determinant of neonatal lethality, with
    affected individuals in the classic form surviving only days or weeks.
  subtype: Lethal RS
  phenotype_term:
    preferred_term: Pulmonary hypoplasia
    term:
      id: HP:0002089
      label: Pulmonary hypoplasia
  evidence:
  - reference: PMID:33676444
    reference_title: "Recurrent variant c.1680C>A in FAM20C gene and genotype-phenotype correlation in a patient with Raine syndrome: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Severe midface hypoplasia and narrow thorax leading to choanal atresia and pulmonary hypoplasia respectively, contribute to respiratory distress and have been regarded as the causes for early death."
    explanation: Documents pulmonary hypoplasia from the narrow thorax as a cause of early death.
  - reference: PMID:17924334
    reference_title: "Mutations in FAM20C are associated with lethal osteosclerotic bone dysplasia (Raine syndrome), highlighting a crucial molecule in bone development."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals survive only days or weeks."
    explanation: Documents the neonatal-lethal course that pulmonary hypoplasia and airway obstruction drive.
imaging_findings:
- name: Generalized osteosclerosis on radiography
  modality: XRAY
  description: >
    Infantogram/skeletal survey shows a generalized increase in bone density of
    all bones with marked sclerosis of the skull base and long bones, plus
    periosteal new bone formation.
  phenotype_term:
    preferred_term: Generalized osteosclerosis
    term:
      id: HP:0005789
      label: Generalized osteosclerosis
  diagnostic: true
  evidence:
  - reference: PMID:24959018
    reference_title: "Raine syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Infantogram of the baby showed generalized osteosclerosis"
    explanation: Radiographic documentation of generalized osteosclerosis.
- name: Intracranial calcification on CT
  modality: CT
  description: >
    Brain CT shows hyperdense calcification in the periventricular region,
    corpus callosum and basal ganglia, characteristically bilateral.
  phenotype_term:
    preferred_term: Cerebral calcification
    term:
      id: HP:0002514
      label: Cerebral calcification
  diagnostic: true
  evidence:
  - reference: PMID:24959018
    reference_title: "Raine syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Computed tomography scan of the brain showed diffuse hyperdense areas of calcification in periventricular region, corpus callosum and basal ganglia on both sides"
    explanation: CT documentation of the characteristic intracranial calcification distribution.
genetic:
- name: FAM20C
  gene_term:
    preferred_term: FAM20C
    term:
      id: hgnc:22140
      label: FAM20C
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  inheritance:
  - name: Autosomal recessive
    inheritance_term:
      preferred_term: Autosomal recessive inheritance
      term:
        id: HP:0000007
        label: Autosomal recessive inheritance
    evidence:
    - reference: PMID:19250384
      reference_title: Mutations in FAM20C also identified in non-lethal osteosclerotic bone dysplasia.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Mutations in FAM20C, consistent with autosomal recessive inheritance, were identified in both cases."
      explanation: Confirms autosomal recessive segregation of FAM20C variants.
  notes: >
    Biallelic pathogenic variants in FAM20C at 7p22.3 cause Raine syndrome. The
    gene spans ~107 kb, consists of 10 exons and encodes a 584-amino-acid Golgi
    serine/threonine kinase whose critical kinase domain lies in the C-terminus
    (approximately residues 354-565). Reported alleles include missense
    substitutions at evolutionarily conserved residues, splice-site changes,
    nonsense variants, a synonymous splice-disrupting variant, and whole-gene
    deletions (including a 487-kb 7p22.3 deletion and a chromosome 7
    uniparental isodisomy with 7p telomeric microdeletion). Complete
    loss-of-function alleles are associated with the lethal neonatal
    presentation, while hypomorphic alleles retaining residual kinase activity
    or partial function underlie the non-lethal form; a nonsense variant in the
    terminal exon (c.1680C>A, p.Cys560Ter) has been associated with an extended
    lifespan. Genotype-phenotype correlation remains imperfect, with marked
    intrafamilial variability and discordant phenotypes reported for identical
    genotypes.
  evidence:
  - reference: PMID:17924334
    reference_title: "Mutations in FAM20C are associated with lethal osteosclerotic bone dysplasia (Raine syndrome), highlighting a crucial molecule in bone development."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sequence analysis of FAM20C, located within the deleted region, in six additional affected subjects revealed four homozygous mutations and two compound heterozygotes."
    explanation: Original identification of FAM20C as the Raine syndrome disease gene.
  - reference: PMID:40794899
    reference_title: "A synonymous single nucleotide variant on the FAM20C gene causes non-lethal Raine syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Biallelic mutations in the FAM20C gene, which encodes a Golgi serine/threonine protein kinase that phosphorylates secretory pathway proteins, are responsible for RNS."
    explanation: Confirms biallelic FAM20C variants as the cause of Raine syndrome.
  - reference: PMID:33676444
    reference_title: "Recurrent variant c.1680C>A in FAM20C gene and genotype-phenotype correlation in a patient with Raine syndrome: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "FAM20C gene, located on chromosome 7p22.3, spanning ~ 107 kb consists of 10 exons and encodes a protein of 584 amino acids in length. A critical kinase domain resides in its C-terminal, encompassing amino acids 354 to 565"
    explanation: Gene structure and kinase-domain location.
  - reference: PMID:33676444
    reference_title: "Recurrent variant c.1680C>A in FAM20C gene and genotype-phenotype correlation in a patient with Raine syndrome: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the position of a nonsense variant in the terminal exon of FAM20C gene, could have had a partial effect on the protein function, thereby resulting in a relatively milder phenotype and extended lifespan."
    explanation: Supports the hypomorphic-allele basis of the extended-lifespan phenotype.
  - reference: PMID:34360805
    reference_title: "FAM20C Overview: Classic and Novel Targets, Pathogenic Variants and Raine Syndrome Phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "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."
    explanation: Reviews the lethal versus non-lethal FAM20C variant-phenotype spectrum.
  - reference: PMID:24039075
    reference_title: "Hereditary deletion of the entire FAM20C gene in a patient with Raine syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Raine cases due to whole gene deletion do not seem to have a major difference in the phenotype over those caused by various mutations."
    explanation: Whole-gene deletion produces a phenotype comparable to point variants, consistent with loss of function.
biochemical:
- name: Elevated intact FGF23
  notes: >
    Circulating full-length, biologically active FGF23 is increased owing to
    loss of FAM20C-dependent Ser180 phosphorylation and reduced DMP1-mediated
    suppression, driving renal phosphate wasting.
  presence: INCREASED
  evidence:
  - reference: PMID:24706917
    reference_title: "Dynamic regulation of FGF23 by Fam20C phosphorylation, GalNAc-T3 glycosylation, and furin proteolysis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "humans with FAM20C mutations and Fam20C KO mice develop hypophosphatemia due to an increase in full-length, biologically active FGF23"
    explanation: >
      Background statement summarising prior human and mouse work rather than this
      paper's own data, and it mixes species in one sentence - hence OTHER.
  - reference: PMID:31471673
    reference_title: Non-lethal Raine Syndrome in a Middle-Aged Woman Caused by a Novel FAM20C Mutation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "hypophosphatemia due to renal phosphate wasting"
    explanation: Human-only evidence for the renal phosphate-wasting mechanism.
- name: Low serum phosphate
  notes: >
    Hypophosphatemia from FGF23-mediated renal phosphate wasting, prominent in
    the non-lethal form.
  presence: DECREASED
  evidence:
  - reference: PMID:31471673
    reference_title: "Non-lethal Raine Syndrome in a Middle-Aged Woman Caused by a Novel FAM20C Mutation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "pectus excavatum, and hypophosphatemia due to renal phosphate wasting"
    explanation: Biochemical documentation of hypophosphatemia with renal phosphate wasting.
diagnosis:
- name: Molecular genetic testing of FAM20C
  description: >
    Sequencing of FAM20C confirms the clinical diagnosis. Copy-number analysis
    must accompany sequencing because whole-gene and multi-exon deletions
    (including a 487-kb 7p22.3 deletion and a chromosome 7 uniparental
    isodisomy with 7p telomeric microdeletion) are established causes; a
    sequencing-only workflow that finds a single heterozygous allele can miss
    the second hit.
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: NCIT:C19770
      label: Molecular Analysis
  evidence:
  - reference: PMID:25019372
    reference_title: "Raine syndrome: an overview."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "molecular testing of FAM20C can confirm this"
    explanation: Establishes FAM20C molecular testing as the confirmatory test.
  - reference: PMID:24039075
    reference_title: "Hereditary deletion of the entire FAM20C gene in a patient with Raine syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report on a child who is homozygous for a 487-kb deletion in 7p22.3 that contains FAM20C."
    explanation: Whole-gene deletion as a disease mechanism is the rationale for adding copy-number analysis.
- name: Skeletal radiography
  description: >
    Skeletal survey / infantogram demonstrating generalized osteosclerosis with
    periosteal new bone formation, most marked at the skull base and long bones.
  diagnosis_term:
    preferred_term: radiograph imaging procedure
    term:
      id: NCIT:C38101
      label: X-Ray Imaging
  evidence:
  - reference: PMID:24959018
    reference_title: Raine syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Infantogram of the baby showed generalized osteosclerosis"
    explanation: Radiography is the modality that demonstrates the cardinal skeletal finding.
- name: Prenatal ultrasound and fetal MRI
  description: >
    Raine syndrome can be identified prenatally; fetal phenotyping by ultrasound
    and MRI has demonstrated the characteristic craniofacial and CNS features,
    allowing delivery to be planned with neonatal intensive care available.
  diagnosis_term:
    preferred_term: prenatal genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:38163266
    reference_title: "Raine syndrome: Prenatally identified severe craniofacial phenotype with multisuture synostosis and brain abnormalities associated with variants in FAM20C."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Fetal phenotyping was based on ultrasound and MRI."
    explanation: Documents prenatal ultrasound and fetal MRI as the modalities used for antenatal identification.
- name: Clinical and radiographic diagnosis with molecular confirmation
  description: >
    The characteristic facial appearance together with radiological findings
    (generalized osteosclerosis with periosteal bone formation and intracranial
    calcification) permits a clinical diagnosis; molecular testing of FAM20C
    confirms it. Prenatal identification is possible by ultrasound and fetal
    MRI.
  evidence:
  - reference: PMID:25019372
    reference_title: "Raine syndrome: an overview."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Facial appearance and radiological findings allow the clinical diagnosis, and molecular testing of FAM20C can confirm this."
    explanation: States the diagnostic pathway for Raine syndrome.
differential_diagnoses:
- name: Desmosterolosis
  description: >
    Desmosterolosis may resemble Raine syndrome clinically and should be
    considered in the differential diagnosis.
  evidence:
  - reference: PMID:25019372
    reference_title: "Raine syndrome: an overview."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Desmosterolosis and congenital cytomegalovirus infection may resemble Raine syndrome."
    explanation: Named as a phenocopy in the disease overview.
  - reference: PMID:9450875
    reference_title: Clinical phenotype of desmosterolosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A phenotypic overlap of this case with Raine syndrome was noted; however, desmosterol accumulation was not found on postmortem tissue samples from a previously reported case of this disorder."
    explanation: Primary report documenting the desmosterolosis-Raine syndrome phenotypic overlap and the biochemical test that separates them.
- name: Congenital cytomegalovirus infection
  description: >
    Congenital CMV infection can mimic Raine syndrome, particularly the
    intracranial calcification; CMV serology was negative in reported Raine
    syndrome cases where it was tested.
  evidence:
  - reference: PMID:25019372
    reference_title: "Raine syndrome: an overview."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Desmosterolosis and congenital cytomegalovirus infection may resemble Raine syndrome."
    explanation: Named as a phenocopy in the disease overview.
- name: FAM20A-related enamel-renal syndrome
  description: >
    FAM20A is the pseudokinase that allosterically activates FAM20C, and
    loss-of-function alleles cause amelogenesis imperfecta with gingival
    fibromatosis and nephrocalcinosis. It is the most instructive differential
    for the oral phenotype of non-lethal Raine syndrome (hypoplastic AI plus
    gingival fibrosis) but lacks osteosclerosis, periosteal bone formation and
    intracranial calcification.
  distinguishing_features:
  - FAM20A disease has no osteosclerosis, periosteal bone formation or intracranial calcification
  - FAM20A disease characteristically has nephrocalcinosis
  evidence:
  - reference: PMID:33759783
    reference_title: The ABCs of the atypical Fam20 secretory pathway kinases.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Loss-of-function genetic alterations in the Fam20 family lead to human diseases such as amelogenesis imperfecta, nephrocalcinosis, lethal and nonlethal forms of Raine syndrome with major skeletal defects, and altered phosphate homeostasis."
    explanation: Places the FAM20A and FAM20C disease phenotypes side by side within one gene family.
  - reference: PMID:33759783
    reference_title: The ABCs of the atypical Fam20 secretory pathway kinases.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "structural studies revealed that related member Fam20A allosterically activates Fam20C by forming a heterodimeric/tetrameric complex"
    explanation: Explains the mechanistic basis for the phenotypic overlap between FAM20A and FAM20C disease.
- name: Osteopetrosis
  description: >
    Osteopetrosis and other sclerosing bone dysplasias share generalized
    increased bone density but lack the periosteal new bone formation
    characteristic of Raine syndrome.
  distinguishing_features:
  - Periosteal bone formation is present in Raine syndrome and absent in osteopetrosis
  evidence:
  - reference: PMID:33676444
    reference_title: "Recurrent variant c.1680C>A in FAM20C gene and genotype-phenotype correlation in a patient with Raine syndrome: a case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Periosteal bone formation is also a characteristic feature of this disorder differentiating it from osteopetrosis and other known lethal and nonlethal osteosclerotic bone dysplasias."
    explanation: Names the radiographic feature distinguishing Raine syndrome from osteopetrosis.
treatments:
- name: Neonatal intensive care and airway management
  description: >
    When Raine syndrome is suspected prenatally, delivery should be planned
    with immediate neonatal intensive care availability because significant
    respiratory distress is usually present from birth; airway management for
    choanal atresia/stenosis is the immediate priority. Care remains supportive
    — there is no disease-modifying therapy.
  action_category: THERAPEUTIC
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: neonatal respiratory support and airway management
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Neonatal respiratory distress
    term:
      id: HP:0002643
      label: Neonatal respiratory distress
  evidence:
  - reference: PMID:25019372
    reference_title: "Raine syndrome: an overview."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "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."
    explanation: Directly supports planned neonatal intensive care as management.
- name: Phosphate salts and alfacalcidol for hypophosphatemic rickets
  description: >
    Conventional therapy for hypophosphatemic rickets with oral phosphate salts
    and the active vitamin D analogue alfacalcidol has been used in non-lethal
    Raine syndrome, but the rickets is reported as scarcely responsive to this
    regimen.
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: oral phosphate salts
      term:
        id: CHEBI:37853
        label: phosphate salt
    - preferred_term: alfacalcidol
      term:
        id: CHEBI:31186
        label: alfacalcidol
  target_phenotypes:
  - preferred_term: Hypophosphatemic rickets
    term:
      id: HP:0004912
      label: Hypophosphatemic rickets
  target_mechanisms:
  - target: Dysregulated FGF23 and Renal Phosphate Wasting
    description: >
      Aims to replace the phosphate lost through FGF23-driven renal wasting and
      support mineralization.
    evidence:
    - reference: PMID:32299476
      reference_title: Natural history of non-lethal Raine syndrome during childhood.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Persistent hypophosphatemic rickets was the most striking endocrinological manifestation, which was scarcely responsive to therapy with phosphate salts and alfacalcidol."
      explanation: Identifies the FGF23-driven phosphate-wasting mechanism as the therapeutic target, with limited response.
  notes: >
    Preclinical only: a high-phosphate diet improved skeletal development and
    rescued growth-plate defects in Fam20c-deficient mice (PMID:32101876),
    supporting hypophosphatemia as a partially reversible driver of the skeletal
    phenotype, but this has not been established as a human therapy.
  evidence:
  - reference: PMID:32299476
    reference_title: "Natural history of non-lethal Raine syndrome during childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Persistent hypophosphatemic rickets was the most striking endocrinological manifestation, which was scarcely responsive to therapy with phosphate salts and alfacalcidol."
    explanation: Documents the treatment used and its limited efficacy in non-lethal Raine syndrome.
  - reference: PMID:32101876
    reference_title: "High-Phosphate Diet Improved the Skeletal Development of Fam20c-Deficient Mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Plain X-ray radiography and micro-CT radiography analyses showed that the hPi diet improved the shape and mineral density of the Fam20c-deficient femurs/tibiae, and rescued the growth plate defects in the long bone."
    explanation: Preclinical rationale for phosphate repletion; mouse data only, not established human therapy.
- name: Restorative and oral surgical dental management
  description: >
    Extensive restorative and oral surgical intervention is required for the
    dental sequelae of non-lethal Raine syndrome, including hypoplastic
    amelogenesis imperfecta and spontaneous recurrent abscesses on non-carious
    teeth.
  action_category: THERAPEUTIC
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: surgical procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  target_phenotypes:
  - preferred_term: Amelogenesis imperfecta
    term:
      id: HP:0000705
      label: Amelogenesis imperfecta
  evidence:
  - reference: PMID:33505751
    reference_title: "Hypophosphataemic Rickets Secondary to Raine Syndrome: A Review of the Literature and Case Reports of Three Paediatric Patients' Dental Management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This article presents the dental manifestations and extensive restorative and oral surgical intervention of three siblings with hypophosphataemic rickets secondary to Raine Syndrome treated at Great Ormond Street Hospital for Children, a tertiary referral hospital."
    explanation: Describes the restorative and surgical dental management used for these patients.
- name: Genetic counseling
  description: >
    Autosomal recessive inheritance with a 25% recurrence risk for siblings;
    consanguinity is common. Carrier testing and prenatal or preimplantation
    diagnosis are possible once the familial FAM20C variants are known.
  action_category: COUNSELING_INFORMATIONAL
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:24039075
    reference_title: "Hereditary deletion of the entire FAM20C gene in a patient with Raine syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We report on a child who is homozygous for a 487-kb deletion in 7p22.3 that contains FAM20C. Both parents were heterozygous for the deletion."
    explanation: Carrier status of both parents underpins recurrence-risk counseling.
animal_models:
- species: Mus musculus
  genotype: Fam20c conditional knockout (Sox2-Cre global; 3.6 kb Col1a1-Cre mineralized tissue)
  category: KNOCKOUT
  genes:
  - preferred_term: FAM20C
    term:
      id: hgnc:22140
      label: FAM20C
  description: >
    Global and mineralized-tissue-specific Fam20c knockout mice develop
    hypophosphatemic rickets with markedly elevated FGF23 rather than
    osteosclerosis — a partial, not faithful, model of the human disease.
  evidence:
  - reference: PMID:22615579
    reference_title: "Inactivation of a novel FGF23 regulator, FAM20C, leads to hypophosphatemic rickets in mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "both the global and mineralized tissue-specific cKO mice developed hypophosphatemic rickets (but not osteosclerosis)"
    explanation: Establishes the mouse knockout as a model of the hypophosphatemic-rickets arm only.
  - reference: PMID:32101876
    reference_title: "High-Phosphate Diet Improved the Skeletal Development of Fam20c-Deficient Mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "These results suggested that the hPi diet significantly improved the skeletal development of the Fam20c-deficient mice, implying that hypophosphatemia partially contributed to the skeletal defects in Fam20c-deficient subjects."
    explanation: Dietary phosphate rescue in the same model shows hypophosphatemia is a causal, partially reversible contributor to the skeletal phenotype.
- species: Mus musculus
  genotype: Fam20c D446N knock-in (conditional Col1a1-Cre and conventional Hprt-Cre)
  category: KNOCKIN
  genes:
  - preferred_term: FAM20C
    term:
      id: hgnc:22140
      label: FAM20C
  description: >
    Knock-in of the non-lethal Raine syndrome D446N allele produces
    hypophosphatemic rickets in most mice with elevated Fgf23 and decreased
    Dmp1; a minority of conventional knock-ins die before weaning with
    osteosclerotic radiography, partially recapitulating the lethal human
    phenotype.
  evidence:
  - reference: PMID:39748245
    reference_title: "Mutant Fam20c knock-in mice recapitulate both lethal and non-lethal human Raine Syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Our results suggested that hypophosphatemia rickets was the predominant phenotype in both conditional and conventional Fam20c deficient mice, while the lethal osteosclerotic phenotype occasionally took place in the conventional Fam20c mutant mice."
    explanation: Documents partial recapitulation of both human subtypes in the knock-in model.
- species: Mus musculus
  genotype: Fam20c brain-specific knockout (Nestin-Cre)
  category: KNOCKOUT
  genes:
  - preferred_term: FAM20C
    term:
      id: hgnc:22140
      label: FAM20C
  description: >
    Brain-specific deletion produces cerebral calcification without skeletal or
    dental defects, isolating the CNS calcification mechanism.
  evidence:
  - reference: PMID:36914045
    reference_title: "Intracranial calcification in Fam20c-deficient mice recapitulates human Raine syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "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"
    explanation: Isolates the brain-intrinsic contribution to intracranial calcification.
- species: Canis lupus familiaris
  genotype: FAM20C missense variant (dental hypomineralization)
  category: SPONTANEOUS
  genes:
  - preferred_term: FAM20C
    term:
      id: hgnc:22140
      label: FAM20C
  description: >
    A naturally occurring canine FAM20C missense variant causes dental
    hypomineralization, providing a spontaneous large-animal model relevant to
    the dental arm of Raine syndrome.
  evidence:
  - reference: PMID:27187611
    reference_title: "Molecular Characterization of Three Canine Models of Human Rare Bone Diseases: Caffey, van den Ende-Gupta, and Raine Syndromes."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "to investigate the clinico-pathological features and genetic causes of three developmental syndromes in dogs, including craniomandibular osteopathy (CMO), a previously undescribed skeletal syndrome, and dental hypomineralization, for which we identified pathogenic variants in the canine SLC37A2 (truncating splicing enhancer variant), SCARF2 (truncating 2-bp deletion) and FAM20C (missense variant) genes, respectively."
    explanation: Identifies a spontaneous canine FAM20C model of dental hypomineralization.
discussions:
- discussion_id: raine_osteosclerosis_vs_osteomalacia_model_mismatch
  kind: HUMAN_MODEL_MISMATCH
  prompt: >
    Why does Fam20c loss in mice produce hypophosphatemic rickets rather than
    the generalized osteosclerosis that defines human Raine syndrome, and what
    does that imply about the origin of the human sclerotic phenotype?
  rationale: >
    Global and tissue-specific Fam20c knockout mice, and transgenic mice
    expressing lethal (G374R) and non-lethal (D446N) Raine syndrome alleles,
    consistently develop hypophosphatemic rickets or osteomalacia without
    osteosclerosis. Only occasional conventional knock-in mice show an
    osteosclerotic radiographic appearance, and micro-CT of those bones shows
    reduced mineral density and increased porosity. Human autopsy histology
    likewise shows severe osteomalacia rather than true hypermineralization.
    This raises the possibility that human "osteosclerosis" is a radiographic
    semblance superimposed on an underlying osteomalacic/rachitic process,
    driven by extraskeletal systems (or FAM20C substrates outside bone) not
    captured by the mouse models.
  attaches_to:
  - pathophysiology#Abnormal Bone Matrix Mineralization
  proposed_experiments:
  - experiment_id: raine_bse_histomorphometry
    name: Quantitative bone mineral density distribution in human Raine syndrome bone
    description: >
      Quantitative backscattered-electron imaging and static/dynamic
      histomorphometry of non-decalcified human Raine syndrome bone, compared
      directly against the radiographic density of the same specimens, to test
      whether radiographic "osteosclerosis" reflects true hypermineralization or
      an osteomalacic matrix with altered geometry.
    supporting_outcome:
    - Radiographic osteosclerosis overlies an undermineralized osteomalacic matrix
    refuting_outcome:
    - Raine syndrome bone is genuinely hypermineralized, matching the radiographic appearance
  - experiment_id: raine_extraskeletal_rescue
    name: Tissue-restricted Fam20c rescue outside the skeleton
    description: >
      Re-express Fam20c in candidate extraskeletal compartments (kidney, liver,
      brain, vasculature) on a global Fam20c-null background and assay whether
      an osteosclerotic skeletal phenotype emerges or is prevented, testing the
      hypothesis that the human sclerotic phenotype is driven by non-skeletal
      FAM20C substrates.
    supporting_outcome:
    - Osteosclerosis in Raine syndrome depends on loss of FAM20C activity outside bone
    refuting_outcome:
    - The skeletal phenotype is entirely cell-autonomous to bone
  evidence:
  - reference: PMID:37698039
    reference_title: "Mutations of family with sequence similarity 20-member C gene causing lethal and nonlethal Raine syndrome causes hypophosphatemia rickets."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "transgenic mice expressing the mutant Fam20c found in the lethal (KO;G374R) and nonlethal (KO;D446N) Raine syndrome exhibited osteomalacia without osteosclerotic features."
    explanation: Documents the mouse-human mismatch for the defining osteosclerotic phenotype.
  - reference: PMID:36572689
    reference_title: "Altered sulfation status of FAM20C-dependent chondroitin sulfate is associated with osteosclerotic bone dysplasia."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Fam20c deficiency in mice does not recapitulate the human disorder, so the underlying pathoetiological mechanisms remain poorly understood."
    explanation: States the model-human mismatch explicitly.
notes: >
  No GeneReviews chapter exists for Raine syndrome or FAM20C (PubMed searches
  for "Raine syndrome AND GeneReviews" and "FAM20C AND GeneReviews" return no
  results, checked 2026-07-31), so the phenotype baseline is drawn from the
  disease overview (PMID:25019372), the FAM20C/Raine syndrome review
  (PMID:34360805), and the non-lethal natural-history cohort (PMID:32299476).
  Nomenclature note: Whyte and colleagues showed that Raine syndrome
  (MIM #259775) and congenital sclerosing osteomalacia with cerebral
  calcification (MIM 259660) are the same FAM20C-related entity, which is why
  MONDO:0009821 carries both OMIM xrefs.
references:
- reference: PMID:25019372
  title: "Raine syndrome: an overview."
- reference: PMID:34360805
  title: "FAM20C Overview: Classic and Novel Targets, Pathogenic Variants and Raine Syndrome Phenotypes."
- reference: PMID:32299476
  title: Natural history of non-lethal Raine syndrome during childhood.

📚

References & Deep Research

References

3

PMID:25019372

Raine syndrome: an overview.

No top-level findings curated for this source.

PMID:34360805

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

No top-level findings curated for this source.

PMID:32299476

Natural history of non-lethal Raine syndrome during childhood.

No top-level findings curated for this source.

Deep Research

1

Falcon ▸

Raine Syndrome: Disease Characteristics Research Report

Edison Scientific Literature 25 citations 2026-07-31T00:49:53.288411

Raine Syndrome: Disease Characteristics Research Report

Executive summary

Raine syndrome (RNS) is an ultra-rare, autosomal-recessive skeletal dysplasia caused by biallelic loss-of-function variants in FAM20C, which encodes a Golgi-associated kinase responsible for phosphorylating many secreted proteins. Its spectrum extends from a severe congenital form—characterized by generalized osteosclerosis, distinctive craniofacial abnormalities, intracranial calcification, pulmonary hypoplasia, and death in early infancy—to nonlethal disease with hypophosphatemic rickets/osteomalacia, neurological disability, hearing or visual impairment, and major dental/gingival disease. A 2021 literature synthesis counted 70 reported patients: 41 lethal and 29 nonlethal; prevalence remains estimated at less than 1 per million. These figures reflect published cases rather than population-based surveillance and are therefore vulnerable to ascertainment bias. (costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 1-2)

Recent work has expanded the disease beyond a simple osteosclerotic dysplasia. A 2023 computational study proposed brain-relevant FAM20C substrates involving cholesterol/lipoprotein biology and axodendritic transport; a 2023 mouse study reproduced intracranial calcification; and a 2024 human gingival proteomics study identified a TGFβ–SMAD–YAP/TAZ profibrotic loop in affected gingiva. (palmalara2023potentialroleof pages 1-2, costa2024gingivalproteomicsreveals pages 2-3, costa2024gingivalproteomicsreveals pages 1-2)

domain	key evidence/finding	suggested ontology identifiers
Disease identifiers	Raine syndrome is an ultra-rare osteosclerotic skeletal dysplasia caused by biallelic FAM20C loss-of-function; legacy disease identifiers include OMIM 259775 and the historical descriptor “congenital sclerosing osteomalacia with cerebral calcification” (OMIM 259660). Open Targets links FAM20C to MONDO_0009821 lethal osteosclerotic bone dysplasia; mapping between MONDO labels and Raine syndrome nomenclature should be curated carefully. Prevalence reported as <1/1,000,000. (OpenTargets Search: Raine syndrome-FAM20C, costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 1-2)	MONDO_0009821; OMIM:259775; OMIM:259660; MeSH/Orphanet/ICD term-only suggestions
Gene / molecular basis	Causal gene: FAM20C (Golgi-associated secretory pathway kinase). Human disease mechanism is predominantly germline autosomal recessive loss of function. Reported pathogenic classes include whole-gene deletions, microdeletions, missense, nonsense, splice-site, and frameshift/truncating variants; 2024 review context summarized 42 variants total (22 lethal, 20 nonlethal). Residual kinase activity is thought to correlate with nonlethal survival, but genotype-phenotype prediction remains imperfect. (costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 16-17, costa2024gingivalproteomicsreveals pages 2-3)	HGNC:FAM20C term-only suggestion; SO:missense_variant / nonsense_variant / splice_donor_variant / frameshift_variant / deletion term-only suggestions
Inheritance / population	Inheritance is autosomal recessive. Published review-level aggregation identified 70 total cases through 2021 (41 lethal, 29 nonlethal), indicating extreme rarity and likely ascertainment bias. No robust carrier-frequency or incidence estimate was identified in the retrieved evidence. (costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 1-2)	HP:Autosomal recessive inheritance (term-only suggestion); epidemiology ontology term-only suggestions
Core phenotype (skeletal / craniofacial)	Core recurrent manifestations include generalized osteosclerosis, periosteal bone formation, flat facial profile, hypoplastic nose, midface hypoplasia, prominent eyes/exophthalmos, choanal atresia/stenosis, and severe respiratory compromise in lethal neonatal disease. Nonlethal cases may evolve from osteosclerosis toward osteomalacia/rickets-like features with variable craniofacial persistence. (palmalara2023potentialroleof pages 1-2, costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 1-2)	HPO term-only suggestions: osteosclerosis; periosteal bone thickening; flat facies; hypoplastic nose; midface retrusion; exophthalmos; choanal atresia/choanal stenosis; respiratory insufficiency
Core phenotype (neurologic / imaging)	Intracranial/intracerebral calcifications are a hallmark; neurological features can include developmental delay, intellectual disability, seizures, structural brain defects, and in prenatal imaging an echogenic brain or enlarged choroid plexus. 2023 mouse work further supports intracranial calcification as a disease-relevant feature. (palmalara2023potentialroleof pages 1-2, palmalara2021fam20coverviewclassic pages 1-2)	HPO term-only suggestions: intracranial calcification; cerebral calcification; developmental delay; intellectual disability; seizures; abnormality of the choroid plexus
Core phenotype (oral / dental / gingival)	Nonlethal disease frequently includes hypoplastic amelogenesis imperfecta, dentin defects, gingival hyperplasia/overgrowth, fibrosis, and ectopic gingival calcifications. The 2024 proteomics study documented fibrosis and pathological gingival calcifications in two unrelated patients with distinct nonlethal variants. (costa2024gingivalproteomicsreveals pages 1-2, costa2024gingivalproteomicsreveals pages 2-3)	HPO term-only suggestions: amelogenesis imperfecta; abnormal dentin morphology; gingival overgrowth; gingival fibrosis; ectopic calcification
Laboratory abnormalities	Nonlethal Raine syndrome is repeatedly associated with hypophosphatemia and disturbed phosphatemia regulation; mechanistic literature links FAM20C deficiency to abnormal FGF23 handling and phosphate wasting. Exact laboratory ranges were not available in retrieved context. (palmalara2023potentialroleof pages 1-2, costa2024gingivalproteomicsreveals pages 21-22, zhang2020highphosphatedietimproved pages 11-12, costa2024gingivalproteomicsreveals pages 1-2)	HPO term-only suggestions: hypophosphatemia; increased circulating FGF23; renal phosphate wasting
Mechanism / pathophysiology	FAM20C is a Golgi kinase that phosphorylates secreted phosphoproteins, especially proteins involved in biomineralization. Disease mechanism: FAM20C loss impairs phosphorylation/localization/activity of secreted substrates, disrupting SIBLING proteins, FGF23 regulation, extracellular matrix organization, and mineralization in bone/teeth; 2024 work additionally implicates TGFβ/SMAD and YAP/TAZ signaling in gingival fibrosis. (palmalara2023potentialroleof pages 1-2, costa2024gingivalproteomicsreveals pages 1-2, costa2024gingivalproteomicsreveals pages 2-3)	GO term-only suggestions: protein phosphorylation; biomineral tissue development; extracellular matrix organization; regulation of phosphate ion homeostasis; TGF-beta receptor signaling pathway; SMAD protein signal transduction; Hippo signaling/YAP-TAZ-related transcription
Anatomy affected	Primary structures: craniofacial skeleton, long bones, teeth, gingiva, and brain/intracranial tissues; secondary involvement includes airways/choanae and lungs via respiratory compromise/pulmonary hypoplasia in lethal neonatal disease. (palmalara2023potentialroleof pages 1-2, costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 1-2)	UBERON term-only suggestions: craniofacial skeleton; long bone; tooth; gingiva; brain; choroid plexus; choana; lung
Cell / tissue types	Disease-relevant cell populations inferred from human and model evidence include osteoblast-lineage cells, odontoblasts, ameloblasts, gingival fibroblasts, and likely brain-resident cells affected by abnormal phosphoproteome/mineralization. The 2024 human study specifically analyzed primary gingival fibroblasts. (costa2024gingivalproteomicsreveals pages 2-3, costa2024gingivalproteomicsreveals pages 1-2, palmalara2023potentialroleof pages 1-2)	CL term-only suggestions: osteoblast; odontoblast; ameloblast; fibroblast; gingival fibroblast; neuron term-only suggestion
Subcellular localization	Normal FAM20C is Golgi-localized within the secretory pathway; disease-associated dysfunction includes altered localization and loss of effective Golgi association. In gingival fibroblasts from affected individuals, 2024 data showed increased ER colocalization and reduced cis-Golgi association. (costa2024gingivalproteomicsreveals pages 2-3, palmalara2023potentialroleof pages 1-2)	GO Cellular Component term-only suggestions: Golgi apparatus; Golgi lumen; endoplasmic reticulum; extracellular region
Diagnostics	Diagnosis is based on clinical-radiologic suspicion plus molecular confirmation of biallelic FAM20C variants. Useful findings include prenatal ultrasound recognition of characteristic facies and intracranial calcification, postnatal skeletal imaging showing osteosclerosis, brain imaging for calcifications, and biochemical assessment of phosphate/FGF23 axis where survival permits. No standardized disease-specific diagnostic criteria were identified in the retrieved evidence. (palmalara2021fam20coverviewclassic pages 1-2)	MAXO term-only suggestions: molecular genetic testing; exome sequencing; genome sequencing; targeted gene panel; prenatal ultrasound; skeletal radiography; cranial CT/MRI; serum phosphate measurement
Treatment / supportive care	No approved disease-modifying therapy specific to Raine syndrome was identified. Management is supportive and multidisciplinary: neonatal airway/respiratory support in lethal presentations; management of hypophosphatemia/rickets-like disease in survivors; dental and periodontal care for amelogenesis imperfecta/gingival disease. Experimental mouse data suggest high-phosphate diet can improve skeletal development, but this is preclinical and not an established human therapy. (zhang2020highphosphatedietimproved pages 11-12, costa2024gingivalproteomicsreveals pages 1-2)	MAXO term-only suggestions: respiratory support; phosphate supplementation; active vitamin D analogue therapy term-only suggestion; dental surveillance; periodontal management; nutritional management; multidisciplinary care
Prognosis / course	Prognosis is bimodal: classic lethal disease often causes death in the first weeks of life, largely due to pulmonary hypoplasia/respiratory failure; nonlethal disease shows variable expressivity with childhood-to-adult survival and chronic skeletal, neurologic, hearing/vision, and dental morbidity. Long-term survival statistics were not available. (costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 1-2, costa2024gingivalproteomicsreveals pages 2-3)	HPO term-only suggestions: pulmonary hypoplasia; respiratory failure; variable expressivity
Model organisms / experimental systems	Mouse Fam20c-deficient models recapitulate key features including abnormal mineralization, hypophosphatemic rickets/osteomalacia-like changes, dental defects, and intracranial calcification (2023). Human mechanistic evidence also includes 2024 gingival proteomics, primary fibroblast studies, siRNA knockdown, and prior in vitro kinase assays. (palmalara2023potentialroleof pages 1-2, zhang2020highphosphatedietimproved pages 11-12, costa2024gingivalproteomicsreveals pages 2-3, costa2024gingivalproteomicsreveals pages 1-2)	NCBITaxon term-only suggestion: Mus musculus; GO/CL term-only suggestions as above
Evidence limitations	Much evidence comes from case reports, small families, reviews, mouse studies, and one 2024 two-patient omics study. Many exact ontology IDs, laboratory ranges, penetrance estimates, founder effects, and standardized treatment outcomes were not available in retrieved context; phenotype frequencies are incompletely quantified and likely affected by publication bias. (costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 1-2, costa2024gingivalproteomicsreveals pages 2-3)	Evidence Ontology term-only suggestions: case report; review; animal model; in vitro experiment; proteomics study

Table: This compact table summarizes the main knowledge-base elements for Raine syndrome, including identifiers, core phenotypes, mechanisms, anatomy, diagnostics, management, and evidence gaps. It is useful as a structured seed for ontology mapping and curation.

1. Disease information

Definition and classification

Raine syndrome is a Mendelian, autosomal-recessive disorder of secretory-pathway protein phosphorylation, biomineralization, and phosphate homeostasis. It is conventionally classified among osteosclerotic bone dysplasias, although surviving patients can develop hypophosphatemic rickets or osteomalacia alongside radiographic sclerosis. (palmalara2023potentialroleof pages 1-2, costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 1-2)

Principal identifiers and names

MONDO: MONDO:0009821, labeled “lethal osteosclerotic bone dysplasia” in the retrieved Open Targets mapping.
OMIM: 259775, Raine syndrome; 259660 is the historical entry “congenital sclerosing osteomalacia with cerebral calcification.”
Gene-associated name: FAM20C-related osteosclerotic dysplasia.
Synonyms: Raine syndrome; lethal osteosclerotic bone dysplasia; osteosclerotic bone dysplasia, Raine type; congenital sclerosing osteomalacia with cerebral calcification; lethal and nonlethal Raine syndrome.
A dedicated, disease-specific ICD-10 or ICD-11 code was not established in the retrieved material; clinically, broader congenital osteochondrodysplasia codes may be used. MeSH and SNOMED CT mappings should be verified directly before production use. (OpenTargets Search: Raine syndrome-FAM20C, palmalara2023potentialroleof pages 26-27, palmalara2021fam20coverviewclassic pages 1-2)

The evidence base is predominantly aggregated disease-level literature assembled from individual case reports and small families, not EHR-derived population data. The 2024 mechanistic study used tissue and primary fibroblasts from only two affected individuals. (costa2024gingivalproteomicsreveals pages 2-3, palmalara2021fam20coverviewclassic pages 1-2)

2. Etiology, risk, and protective factors

Causal factor

The primary cause is germline biallelic loss of FAM20C function. FAM20C is a serine/threonine kinase located mainly in the Golgi/secretory pathway and recognizes secreted-protein motifs including S-X-E/pS. Loss of kinase activity, defective intracellular localization, altered secretion, or protein truncation impairs extracellular phosphoprotein regulation. (palmalara2023potentialroleof pages 1-2, costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 16-17)

Reported variant classes include whole-gene and multiexon deletions, frameshift, nonsense, splice-site, and missense variants. A 2024 summary listed 42 disease-associated variants—22 associated with lethal and 20 with nonlethal disease. Variants abolishing protein or kinase activity tend to produce lethal disease, whereas residual activity is more often compatible with survival; this is a trend rather than a deterministic clinical rule. (costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 16-17)

Risk factors

Genetic: two pathogenic/likely pathogenic alleles in trans; parental consanguinity raises the probability of homozygosity. Each pregnancy of two confirmed carriers has the standard autosomal-recessive risks: 25% affected, 50% carrier, and 25% unaffected/noncarrier.
Family history: an affected sibling or known parental carrier status materially increases prior probability.
Sex, age, and ancestry: no demonstrated sex-specific biological risk or reliable ethnicity-specific prevalence was found.
Environment, lifestyle, toxins, occupation, or infection: no evidence that any of these causes Raine syndrome.

No validated protective FAM20C allele, modifier gene, lifestyle factor, or gene–environment interaction has been established. Dietary phosphate modified skeletal severity in a mouse model, but that is modification of downstream physiology—not prevention of the genetic disorder. (zhang2020highphosphatedietimproved pages 11-12)

3. Phenotypes

Because published series are small and enriched for severe cases, robust percentages are unavailable for most manifestations. “Common” below means recurrent in reports/reviews, not a population-derived frequency.

Congenital skeletal and craniofacial phenotype

Generalized osteosclerosis—congenital, often severe in lethal disease; suggested HPO: Osteosclerosis.
Periosteal bone formation/thickening; HPO term suggestion: Abnormal periosteum morphology.
Flat facial profile, midface hypoplasia, hypoplastic/depressed nasal bridge, prominent eyes or exophthalmos, low-set ears, microcephaly, and cleft palate; congenital and variably persistent.
Choanal stenosis/atresia, which can compound neonatal respiratory compromise.
Craniosynostosis/multisuture synostosis has been documented prenatally in recent severe presentations.
Long-bone and growth-plate abnormalities can evolve into rickets/osteomalacia in survivors. (palmalara2023potentialroleof pages 1-2, costa2024gingivalproteomicsreveals pages 21-22, palmalara2021fam20coverviewclassic pages 1-2)

Suggested HPO terms include Midface retrusion, Hypoplastic nose, Depressed nasal bridge, Exophthalmos, Low-set ears, Microcephaly, Cleft palate, Choanal atresia, Craniosynostosis, Rickets, and Osteomalacia.

Neurological and neuroimaging phenotype

Intracranial or intracerebral calcification is a hallmark and may be visible prenatally. Other reported findings include enlarged choroid plexuses, echogenic fetal brain, ventricular abnormalities, structural brain malformations, developmental delay, intellectual disability, and seizures. Severity ranges from imaging abnormalities without fully defined functional effect to substantial lifelong neurodevelopmental disability. (palmalara2023potentialroleof pages 1-2, palmalara2021fam20coverviewclassic pages 1-2)

Suggested HPO terms: Intracranial calcification, Cerebral calcification, Structural brain anomaly, Global developmental delay, Intellectual disability, Seizure, and Abnormality of the choroid plexus.

Respiratory phenotype

Pulmonary hypoplasia and respiratory insufficiency are major determinants of neonatal lethality; craniofacial airway obstruction can contribute. Most classic lethal cases die during the first weeks of life. Suggested HPO: Pulmonary hypoplasia, Respiratory insufficiency, Neonatal respiratory distress. (palmalara2021fam20coverviewclassic pages 1-2)

Dental and gingival phenotype

Survivors commonly have hypoplastic amelogenesis imperfecta, abnormal dentin, delayed or abnormal tooth development, gingival overgrowth/fibrosis, and gingival or other ectopic calcifications. These impair mastication, oral hygiene, appearance, speech, and periodontal health and can require repeated dental care. In two 2024 cases, one patient also had visual impairment and the other hearing impairment. (costa2024gingivalproteomicsreveals pages 2-3, costa2024gingivalproteomicsreveals pages 1-2)

Suggested HPO: Amelogenesis imperfecta, Abnormal dentin morphology, Gingival overgrowth, Gingival fibrosis, Ectopic calcification, Visual impairment, and Hearing impairment.

Laboratory abnormalities

Nonlethal disease is associated with hypophosphatemia, FGF23 dysregulation, renal phosphate wasting, and rickets/osteomalacia physiology. Appropriate measurements include fasting serum phosphate interpreted against age-specific ranges, calcium, alkaline phosphatase, PTH, creatinine, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, intact and/or C-terminal FGF23, urine phosphate, tubular maximum phosphate reabsorption/GFR, and renal ultrasound for nephrocalcinosis. Exact disease-specific reference ranges or sensitivities have not been established. (palmalara2023potentialroleof pages 1-2, costa2024gingivalproteomicsreveals pages 21-22, zhang2020highphosphatedietimproved pages 11-12)

No validated Raine-specific quality-of-life instrument or EQ-5D/SF-36 dataset was found.

4. Genetic and molecular information

Causal gene: FAM20C, encoding FAM20C Golgi-associated secretory-pathway kinase; Ensembl target ENSG00000177706. The variants are constitutional/germline, not somatic drivers. (OpenTargets Search: Raine syndrome-FAM20C)

The pathogenic mechanism is predominantly loss of function through absent protein, truncation/nonsense-mediated decay, catalytic impairment, mislocalization, or defective secretion. Among 22 exclusively lethal variants summarized in a 2021 review, absent/nonsense/truncated forms were the largest category, including homozygous whole-gene deletions and a reported approximately 487-kb 7p22 deletion. (palmalara2021fam20coverviewclassic pages 16-17)

The 2024 gingival study examined two nonlethal genotypes: p.Pro496Leu, predicted to disrupt the activation loop, and a splice-associated p.Trp202Cysfs* product yielding a 239-amino-acid truncated protein. Variant interpretation should nevertheless use current ACMG/AMP criteria, segregation, population frequency, phenotype match, and functional evidence rather than the publication’s phenotype alone. (costa2024gingivalproteomicsreveals pages 2-3)

Pathogenic alleles are expected to be individually rare or absent from large population databases, but no comprehensive gnomAD allele-frequency table was retrieved. No validated modifier genes, protective alleles, disease-specific methylation signature, repeat expansion, recurrent aneuploidy, or somatic mosaic mechanism is established. Large deletions encompassing FAM20C can cause disease, so copy-number analysis is necessary when sequencing detects only one allele. (palmalara2021fam20coverviewclassic pages 16-17)

5. Environmental information

Raine syndrome is not known to be caused or triggered by toxins, radiation, pollution, smoking, alcohol, diet, exercise, occupational exposure, bacteria, viruses, fungi, or parasites. Environment can influence complications—for example, phosphate intake, dental hygiene, respiratory infection burden, and access to specialist care—but evidence for disease-specific gene–environment interaction is absent. There is no zoonotic or transmissible component.

6. Mechanism and pathophysiology

Causal chain

Upstream genetic defect: biallelic FAM20C loss-of-function.
Subcellular defect: reduced Golgi/secretory-pathway kinase activity, with some variants causing ER retention or altered localization.
Substrate defect: hypophosphorylation of secreted phosphoproteins, including SIBLING-family biomineralization proteins and proteins involved in FGF23 processing.
Systemic consequences: disordered extracellular-matrix mineralization and abnormal FGF23/phosphate homeostasis.
Tissue outcomes: osteosclerosis and periosteal abnormalities prenatally, followed in survivors by renal-phosphate-wasting hypophosphatemia, rickets/osteomalacia, dental mineralization defects, ectopic calcification, and neurological abnormalities.
Clinical outcomes: craniofacial dysplasia, respiratory failure in severe neonatal disease, chronic skeletal/dental disability, and variable neurodevelopmental impairment. (palmalara2023potentialroleof pages 1-2, costa2024gingivalproteomicsreveals pages 1-2, zhang2020highphosphatedietimproved pages 11-12)

FAM20C phosphorylates more than 90–100 secreted or body-fluid proteins, supporting a multisystem phosphoproteinopathy rather than a bone-exclusive disorder. Suggested GO annotations include protein phosphorylation, extracellular matrix organization, biomineral tissue development, regulation of phosphate ion homeostasis, skeletal system development, and tooth mineralization. Relevant compartments are Golgi apparatus, Golgi lumen, endoplasmic reticulum, secretory vesicle, and extracellular region. (palmalara2023potentialroleof pages 1-2, palmalara2021fam20coverviewclassic pages 1-2)

2024 human proteomics development

Costa et al. used gingival tissue, primary gingival fibroblasts, label-free LC-MS/MS proteomics, immunomorphology, biochemistry, and siRNA in two unrelated patients. They found excessive/disorganized ECM, fibrosis, pathological calcification, and increased POSTN, SPARC, and VIM. TGFβ/SMAD signaling and YAP/TAZ cofactors were activated; FAM20C knockdown supported a self-reinforcing profibrotic loop. Mutant fibroblasts showed enhanced ER colocalization and loss of normal cis-Golgi association. This is direct human tissue and cell evidence, but sample size was two. (costa2024gingivalproteomicsreveals pages 2-3, costa2024gingivalproteomicsreveals pages 1-2)

The authors’ abstract states: “They furthermore uncover the contribution of increased TGFβ–YAP/TAZ signaling in the pathogenesis of the gingival fibrosis.” [Scientific Reports, 12 April 2024; DOI: https://doi.org/10.1038/s41598-024-59713-0]. (costa2024gingivalproteomicsreveals pages 1-2)

Brain mechanisms

The 2023 computational analysis linked highly expressed brain targets/interactors to cholesterol and lipoprotein processes, axodendritic transport, and neuronal compartments. These are hypothesis-generating associations, not proof that any individual substrate causes seizures or intellectual disability. Suggested GO terms include axon transport, dendrite development, and cholesterol metabolic process; suggested CL terms include neuron, astrocyte, and choroid plexus epithelial cell, although direct cell-specific causality remains unproven. [Published 17 May 2023; DOI: https://doi.org/10.3390/ijms24108904]. (palmalara2023potentialroleof pages 1-2)

No disease-specific single-cell, spatial transcriptomic, lipidomic, metabolomic, CRISPR-screen, or integrated multi-omic human study was identified.

7. Anatomical structures affected

Primary sites are the craniofacial skeleton, skull sutures, long bones and growth plates, teeth, dentin, enamel, gingiva/periodontium, and brain/intracranial tissues. The choanae, upper airway, lungs, eyes, ears, and kidneys may be involved directly or through complications. Disease is usually systemic and bilateral rather than consistently lateralized. (palmalara2023potentialroleof pages 1-2, costa2024gingivalproteomicsreveals pages 2-3, palmalara2021fam20coverviewclassic pages 1-2)

Suggested UBERON terms: craniofacial skeleton, calvaria, cranial suture, long bone, growth plate cartilage, tooth, enamel, dentin, gingiva, periodontal ligament, brain, choroid plexus, choana, lung, and kidney. Suggested CL terms: osteoblast, osteocyte, chondrocyte, odontoblast, ameloblast, gingival fibroblast, and neuron. The best directly demonstrated human cell type in recent work is the gingival fibroblast. (costa2024gingivalproteomicsreveals pages 2-3, costa2024gingivalproteomicsreveals pages 1-2)

8. Temporal development

The severe phenotype begins prenatally. Ultrasound may reveal a flat profile, hypoplastic nose, prominent eyes, echogenic brain, enlarged choroid plexus, ventricular changes, intracranial calcification, and craniosynostosis. Neonatal disease can progress rapidly to respiratory death. (palmalara2021fam20coverviewclassic pages 1-2)

Nonlethal disease is congenital but chronic and variably progressive. Skeletal findings can shift from early osteosclerosis to hypophosphatemic rickets/osteomalacia; dental and gingival abnormalities emerge with tooth development, while developmental disability or seizures may become apparent in childhood. Adult survival—including middle-aged and elderly patients—has been reported, but no formal stages, remission pattern, median survival, or validated longitudinal progression rate exists. (costa2024gingivalproteomicsreveals pages 1-2, costa2024gingivalproteomicsreveals pages 21-22)

Critical clinical windows are prenatal recognition, immediate neonatal airway assessment, childhood growth and phosphate monitoring, tooth eruption, and ongoing neurological surveillance. There is no evidence of spontaneous molecular remission.

9. Inheritance and population

Inheritance is autosomal recessive. Penetrance for individuals with two severe pathogenic alleles appears high, but allele-specific penetrance has not been quantified. Expressivity is markedly variable. Anticipation is not expected; no repeat-expansion mechanism exists. Germline mosaicism is theoretically possible but not established as a recurrent feature. (costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 1-2)

The estimated prevalence is <1 per 1,000,000. A 2021 review found 70 published patients—41 lethal and 29 nonlethal—while a 2024 paper summarized 42 variants. Neither statistic represents incidence or a complete global registry. Consanguinity is recurrent in autosomal-recessive case literature, but no population-specific founder allele, carrier frequency, geographic hotspot, sex ratio, or robust incidence estimate was identified. (costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 1-2)

10. Diagnostics

Recommended approach

Clinical recognition: congenital craniofacial phenotype, osteosclerosis, intracranial calcification, choanal obstruction, neonatal respiratory compromise, or—later—hypophosphatemia with osteosclerosis plus enamel/dentin and gingival abnormalities.
Imaging: prenatal ultrasound; fetal MRI where available; postnatal skeletal survey/radiographs; low-dose cranial CT when calcification detection is essential; brain MRI for anatomy; renal ultrasound for nephrocalcinosis.
Biochemistry: phosphate/FGF23 and mineral metabolism panel as described above.
Molecular confirmation: sequencing and deletion/duplication analysis of FAM20C. A skeletal-dysplasia, craniosynostosis, hypophosphatemia, or amelogenesis-imperfecta panel is reasonable. WES/WGS is appropriate when the phenotype is atypical or panel testing is negative.
Family studies: parental segregation, carrier testing, and testing of at-risk siblings. (palmalara2023potentialroleof pages 26-27, palmalara2021fam20coverviewclassic pages 1-2, costa2024gingivalproteomicsreveals pages 2-3)

Sanger single-gene testing is useful for a known familial variant. CMA can detect larger 7p22 deletions but may miss sequence variants; karyotyping and FISH are not first-line unless a structural rearrangement is suspected. Mitochondrial, repeat-expansion, liquid-biopsy, proteomic, and methylation testing are not established diagnostic methods. No validated clinical scoring criteria or biochemical biomarker with known sensitivity/specificity exists.

Differential diagnosis

Important alternatives include other osteosclerosing dysplasias and craniotubular disorders, osteopetrosis, pyknodysostosis, dysosteosclerosis, infantile hypophosphatasia, congenital infections and interferonopathies causing intracranial calcification, primary familial brain calcification, hypophosphatemic rickets syndromes, and enamel-renal syndrome due to FAM20A. The combination of biallelic FAM20C variants with osteosclerosis, cerebral calcification, craniofacial dysplasia, and dental/phosphate abnormalities is distinguishing.

Suggested MAXO actions: molecular genetic testing, exome sequencing, genome sequencing, deletion/duplication analysis, prenatal ultrasound, fetal MRI, skeletal radiography, cranial CT, brain MRI, and serum phosphate measurement.

11. Outcome and prognosis

The classic form often causes death within the first weeks from pulmonary hypoplasia and respiratory failure. No reliable 5- or 10-year survival estimate exists. Survivors may live into adulthood but can experience chronic rickets/osteomalacia, impaired growth or mobility, bone pain, neurodevelopmental disability, seizures, sensory impairment, and extensive dental/periodontal morbidity. (palmalara2021fam20coverviewclassic pages 1-2, costa2024gingivalproteomicsreveals pages 2-3)

Likely adverse prognostic indicators are severe prenatal osteosclerosis, pulmonary hypoplasia, major airway obstruction, multisuture craniosynostosis, extensive brain abnormalities, and variants leaving little or no kinase activity. Residual function is generally associated with nonlethal disease, but individual prognosis should not be inferred from variant class alone. No validated prognostic biomarker or disease-specific patient-reported outcome measure exists. (costa2024gingivalproteomicsreveals pages 1-2, palmalara2021fam20coverviewclassic pages 16-17)

12. Treatment and current applications

There is no approved curative or FAM20C-directed therapy, published treatment algorithm, or disease-specific pharmacogenomic guideline.

Neonatal care: airway stabilization, respiratory support, management of choanal obstruction, feeding support, and palliative-care involvement when disease is lethal.
Metabolic bone care: individualized phosphate and active-vitamin-D management may be considered for FGF23-mediated hypophosphatemia, with close monitoring of calcium, PTH, urine calcium, renal function, and nephrocalcinosis. Human response rates specific to Raine syndrome are unavailable.
Dental/periodontal care: preventive dentistry, restoration/prosthodontics as appropriate, treatment of gingival overgrowth and periodontitis, and multidisciplinary management of amelogenesis imperfecta.
Developmental care: physical, occupational, speech/feeding, hearing, vision, and neurological services.
Surgery: individualized correction of choanal atresia, craniosynostosis, cleft palate, or severe orthopedic deformity; disease-specific outcome series are absent.

Suggested MAXO terms include respiratory support, assisted ventilation, phosphate supplementation, active vitamin D therapy, dental surveillance, periodontal treatment, physical therapy, occupational therapy, speech therapy, hearing assessment, vision assessment, and genetic counseling.

In Fam20c-deficient mice, a high-phosphate diet improved long-bone shape and mineral density and nearly normalized growth-plate widening. The abstract concludes: “These results suggested that the hPi diet significantly improved the skeletal development of the Fam20c-deficient mice, implying that hypophosphatemia partially contributed to the skeletal defects.” This is preclinical evidence and does not establish safety or efficacy in humans. [Published February 2020; DOI: https://doi.org/10.1159/000506005]. (zhang2020highphosphatedietimproved pages 11-12)

A ClinicalTrials.gov search found no trial whose condition was genuinely Raine syndrome; records using “RNS” for neuromodulation were acronym collisions. Gene replacement, CRISPR editing, RNA therapies, cell therapies, immunotherapy, and anti-FGF23 therapy remain unvalidated for this disease.

13. Prevention

The genotype cannot be prevented by lifestyle or vaccination. Evidence-based prevention is reproductive and complication-directed:

carrier and cascade testing after a molecular diagnosis;
genetic counseling with 25% recurrence-risk discussion for carrier couples;
targeted prenatal diagnosis by chorionic-villus sampling or amniocentesis;
preimplantation genetic testing for a known familial variant;
detailed prenatal imaging in at-risk pregnancies;
early respiratory, phosphate, renal, dental, hearing, vision, and developmental surveillance;
tertiary prevention of rickets, nephrocalcinosis, dental infection, periodontal disease, contractures, and developmental complications.

Population newborn biochemical screening is not available. Expanded genomic screening could detect FAM20C variants, but interpretation, prevalence, and clinical utility have not been established.

14. Other species and natural disease

No well-established naturally occurring veterinary analogue or zoonotic form was identified. FAM20C orthologues are evolutionarily conserved across vertebrates, and related secretory-pathway kinase activity also exists in Drosophila. Comparative data support conservation of extracellular phosphoprotein and biomineralization biology, but experimental models should not be described as naturally transmitted disease. Suggested taxonomy terms include Homo sapiens and Mus musculus; the exact NCBI Gene identifiers should be verified in NCBI Gene before database ingestion.

15. Model organisms and experimental systems

Mouse: global or conditional Fam20c deficiency reproduces hypophosphatemia, elevated FGF23, rickets/osteomalacia-like skeletal defects, abnormal dentin/enamel, and intracranial calcification. The 2023 study specifically showed that intracranial calcification in Fam20c-deficient mice recapitulates a defining human feature. [Neuroscience Letters, April 2023; DOI: https://doi.org/10.1016/j.neulet.2023.137176]. These models are useful for phosphate physiology, mineralized tissues, brain calcification, and preclinical dietary interventions, but they do not capture the full human lethal craniofacial/respiratory spectrum. (palmalara2023potentialroleof pages 1-2, zhang2020highphosphatedietimproved pages 11-12)

Human cell systems: primary gingival fibroblasts and siRNA-mediated FAM20C knockdown model ECM disorganization and the TGFβ–YAP/TAZ fibrotic loop. Their strength is direct patient relevance; limitations include only two genotypes and one tissue lineage. (costa2024gingivalproteomicsreveals pages 2-3, costa2024gingivalproteomicsreveals pages 1-2)

In-vitro kinase systems: recombinant FAM20C experiments establish phosphorylation of secreted biomineralization proteins and show that disease-associated substitutions impair localization or kinase activity. This supplies biochemical causality but cannot alone predict organismal severity. The foundational abstract states: “Our results identify FAM20C as a kinase for secreted phosphoproteins and establish a biochemical basis for Raine syndrome.” [Published 13 August 2012; DOI: https://doi.org/10.1371/journal.pone.0042988]. (palmalara2023potentialroleof pages 1-2)

Evidence appraisal and knowledge gaps

The strongest conclusions are the biallelic FAM20C etiology, autosomal-recessive inheritance, core skeletal/craniofacial/calcification phenotype, and secretory-pathway kinase mechanism. Major limitations are extreme rarity, case-report ascertainment, inconsistent laboratory reporting, incomplete functional characterization of variants, and the absence of registries, controlled treatment trials, standardized diagnostic criteria, longitudinal quality-of-life data, or validated prognostic models. The 2023–2024 studies materially advance mechanism but do not yet change standard clinical care. (costa2024gingivalproteomicsreveals pages 1-2, costa2024gingivalproteomicsreveals pages 2-3, palmalara2023potentialroleof pages 1-2)

Key recent and foundational sources

Costa et al. Gingival proteomics reveals the role of TGF beta and YAP/TAZ signaling in Raine syndrome fibrosis. Scientific Reports. Published April 2024. https://doi.org/10.1038/s41598-024-59713-0. (costa2024gingivalproteomicsreveals pages 2-3, costa2024gingivalproteomicsreveals pages 1-2)
Zhang et al. Intracranial calcification in Fam20c-deficient mice recapitulates human Raine syndrome. Neuroscience Letters. Published April 2023. https://doi.org/10.1016/j.neulet.2023.137176. (palmalara2023potentialroleof pages 1-2)
Palma-Lara et al. Potential Role of Protein Kinase FAM20C on the Brain in Raine Syndrome, an In Silico Analysis. International Journal of Molecular Sciences. Published 17 May 2023. https://doi.org/10.3390/ijms24108904. (palmalara2023potentialroleof pages 1-2)
Palma-Lara et al. FAM20C Overview: Classic and Novel Targets, Pathogenic Variants and Raine Syndrome Phenotypes. International Journal of Molecular Sciences. Published July 2021. https://doi.org/10.3390/ijms22158039. (palmalara2021fam20coverviewclassic pages 16-17, palmalara2021fam20coverviewclassic pages 1-2)
Ishikawa et al. The Raine Syndrome Protein FAM20C Is a Golgi Kinase That Phosphorylates Bio-Mineralization Proteins. PLOS ONE. Published 13 August 2012. https://doi.org/10.1371/journal.pone.0042988. (palmalara2023potentialroleof pages 1-2)

PMIDs were not exposed in the retrieved records for these papers; DOIs and publication dates are therefore supplied rather than risking incorrect PMID assignment.

References

(costa2024gingivalproteomicsreveals pages 1-2): Cláudio Rodrigues Rezende Costa, Rym Chalgoumi, Amina Baker, Clément Guillou, Paulo Marcio Yamaguti, Victor Simancas Escorcia, Lilia Abbad, Bruna Rabelo Amorin, Caroline Lourenço de Lima, Vidjea Cannaya, Mourad Benassarou, Ariane Berdal, Christos Chatziantoniou, Olivier Cases, Pascal Cosette, Renata Kozyraki, and Ana Carolina Acevedo. Gingival proteomics reveals the role of tgf beta and yap/taz signaling in raine syndrome fibrosis. Scientific Reports, Apr 2024. URL: https://doi.org/10.1038/s41598-024-59713-0, doi:10.1038/s41598-024-59713-0. This article has 5 citations and is from a peer-reviewed journal.
(palmalara2021fam20coverviewclassic pages 1-2): Icela Palma-Lara, Monserrat Pérez-Ramírez, Patricia García Alonso-Themann, Ana María Espinosa-García, Ricardo Godinez-Aguilar, José Bonilla-Delgado, Adolfo López-Ornelas, Georgina Victoria-Acosta, María Guadalupe Olguín-García, José Moreno, and Carmen Palacios-Reyes. Fam20c overview: classic and novel targets, pathogenic variants and raine syndrome phenotypes. International Journal of Molecular Sciences, 22:8039, Jul 2021. URL: https://doi.org/10.3390/ijms22158039, doi:10.3390/ijms22158039. This article has 35 citations.
(palmalara2023potentialroleof pages 1-2): Icela Palma-Lara, Patricia García Alonso-Themann, Javier Pérez-Durán, Ricardo Godínez-Aguilar, José Bonilla-Delgado, Damián Gómez-Archila, Ana María Espinosa-García, Manuel Nolasco-Quiroga, Georgina Victoria-Acosta, Adolfo López-Ornelas, Juan Carlos Serrano-Bello, María Guadalupe Olguín-García, and Carmen Palacios-Reyes. Potential role of protein kinase fam20c on the brain in raine syndrome, an in silico analysis. International Journal of Molecular Sciences, 24:8904, May 2023. URL: https://doi.org/10.3390/ijms24108904, doi:10.3390/ijms24108904. This article has 3 citations.
(costa2024gingivalproteomicsreveals pages 2-3): Cláudio Rodrigues Rezende Costa, Rym Chalgoumi, Amina Baker, Clément Guillou, Paulo Marcio Yamaguti, Victor Simancas Escorcia, Lilia Abbad, Bruna Rabelo Amorin, Caroline Lourenço de Lima, Vidjea Cannaya, Mourad Benassarou, Ariane Berdal, Christos Chatziantoniou, Olivier Cases, Pascal Cosette, Renata Kozyraki, and Ana Carolina Acevedo. Gingival proteomics reveals the role of tgf beta and yap/taz signaling in raine syndrome fibrosis. Scientific Reports, Apr 2024. URL: https://doi.org/10.1038/s41598-024-59713-0, doi:10.1038/s41598-024-59713-0. This article has 5 citations and is from a peer-reviewed journal.
(OpenTargets Search: Raine syndrome-FAM20C): Open Targets Query (Raine syndrome-FAM20C, 1 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(palmalara2021fam20coverviewclassic pages 16-17): Icela Palma-Lara, Monserrat Pérez-Ramírez, Patricia García Alonso-Themann, Ana María Espinosa-García, Ricardo Godinez-Aguilar, José Bonilla-Delgado, Adolfo López-Ornelas, Georgina Victoria-Acosta, María Guadalupe Olguín-García, José Moreno, and Carmen Palacios-Reyes. Fam20c overview: classic and novel targets, pathogenic variants and raine syndrome phenotypes. International Journal of Molecular Sciences, 22:8039, Jul 2021. URL: https://doi.org/10.3390/ijms22158039, doi:10.3390/ijms22158039. This article has 35 citations.
(costa2024gingivalproteomicsreveals pages 21-22): Cláudio Rodrigues Rezende Costa, Rym Chalgoumi, Amina Baker, Clément Guillou, Paulo Marcio Yamaguti, Victor Simancas Escorcia, Lilia Abbad, Bruna Rabelo Amorin, Caroline Lourenço de Lima, Vidjea Cannaya, Mourad Benassarou, Ariane Berdal, Christos Chatziantoniou, Olivier Cases, Pascal Cosette, Renata Kozyraki, and Ana Carolina Acevedo. Gingival proteomics reveals the role of tgf beta and yap/taz signaling in raine syndrome fibrosis. Scientific Reports, Apr 2024. URL: https://doi.org/10.1038/s41598-024-59713-0, doi:10.1038/s41598-024-59713-0. This article has 5 citations and is from a peer-reviewed journal.
(zhang2020highphosphatedietimproved pages 11-12): Hua Zhang, Lili Li, Matthew J. Kesterke, Yongbo Lu, and Chunlin Qin. High-phosphate diet improved the skeletal development of fam20c-deficient mice. Cells Tissues Organs, 208:25-36, Feb 2020. URL: https://doi.org/10.1159/000506005, doi:10.1159/000506005. This article has 8 citations and is from a peer-reviewed journal.
(palmalara2023potentialroleof pages 26-27): Icela Palma-Lara, Patricia García Alonso-Themann, Javier Pérez-Durán, Ricardo Godínez-Aguilar, José Bonilla-Delgado, Damián Gómez-Archila, Ana María Espinosa-García, Manuel Nolasco-Quiroga, Georgina Victoria-Acosta, Adolfo López-Ornelas, Juan Carlos Serrano-Bello, María Guadalupe Olguín-García, and Carmen Palacios-Reyes. Potential role of protein kinase fam20c on the brain in raine syndrome, an in silico analysis. International Journal of Molecular Sciences, 24:8904, May 2023. URL: https://doi.org/10.3390/ijms24108904, doi:10.3390/ijms24108904. This article has 3 citations.

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Raine Syndrome: Disease Characteristics Research Report

Executive summary

1. Disease information

Definition and classification

2. Etiology, risk, and protective factors

Causal factor

Risk factors

3. Phenotypes

Congenital skeletal and craniofacial phenotype

Neurological and neuroimaging phenotype

Respiratory phenotype

Dental and gingival phenotype

Laboratory abnormalities

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6. Mechanism and pathophysiology

Causal chain

2024 human proteomics development

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8. Temporal development

9. Inheritance and population

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