Keutel syndrome is an autosomal recessive disorder of abnormal cartilage calcification with peripheral pulmonary artery stenosis and midface hypoplasia, caused by biallelic loss-of-function variants in MGP, which encodes matrix Gla protein. Its mechanism runs in the opposite direction from most skeletal dysplasias: nothing fails to mineralize, something fails to *stop* mineralizing. Matrix Gla protein is a small extracellular matrix protein secreted by chondrocytes and vascular smooth muscle cells - precisely the two cell types that are supposed to build an uncalcified matrix - and its glutamate residues are gamma-carboxylated by a vitamin-K-dependent carboxylase, which is what gives the mature protein its high affinity for calcium, phosphate, and hydroxyapatite. Losing it removes an active brake, and the tissues that most need that brake calcify: laryngeal, tracheobronchial, costal, nasal, and auricular cartilage, and in some patients the arteries. The gene was reached by homozygosity mapping and picked out of the linked interval on the strength of a mouse phenotype - Mgp-null mice, which calcify their arteries fatally and their cartilages progressively, had already established that extracellular matrix calcification must be actively inhibited in soft tissue rather than merely not induced. Keutel syndrome sits in the chondrodysplasia punctata group of the skeletal nosology, and it earns the placement: about three quarters of patients have brachytelephalangism with punctate epiphyses, and the review literature records that the syndrome's core features overlap chondrodysplasia punctata closely enough that cases have been misdiagnosed as Conradi's disease. The prognosis is generally good and depends mainly on the pulmonary complications, but no disease-modifying therapy exists and the mechanism by which MGP prevents abnormal calcification remains poorly understood.
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Conditions with similar clinical presentations that must be differentiated from Keutel Syndrome:
name: Keutel Syndrome
creation_date: "2026-08-27T00:00:00Z"
category: Mendelian
description: >-
Keutel syndrome is an autosomal recessive disorder of abnormal cartilage calcification
with peripheral pulmonary artery stenosis and midface hypoplasia, caused by biallelic
loss-of-function variants in MGP, which encodes matrix Gla protein. Its mechanism runs
in the opposite direction from most skeletal dysplasias: nothing fails to mineralize,
something fails to *stop* mineralizing. Matrix Gla protein is a small extracellular
matrix protein secreted by chondrocytes and vascular smooth muscle cells - precisely
the two cell types that are supposed to build an uncalcified matrix - and its glutamate
residues are gamma-carboxylated by a vitamin-K-dependent carboxylase, which is what
gives the mature protein its high affinity for calcium, phosphate, and hydroxyapatite.
Losing it removes an active brake, and the tissues that most need that brake calcify:
laryngeal, tracheobronchial, costal, nasal, and auricular cartilage, and in some
patients the arteries. The gene was reached by homozygosity mapping and picked out of
the linked interval on the strength of a mouse phenotype - Mgp-null mice, which
calcify their arteries fatally and their cartilages progressively, had already
established that extracellular matrix calcification must be actively inhibited in soft
tissue rather than merely not induced. Keutel syndrome sits in the chondrodysplasia
punctata group of the skeletal nosology, and it earns the placement: about three
quarters of patients have brachytelephalangism with punctate epiphyses, and the review
literature records that the syndrome's core features overlap chondrodysplasia punctata
closely enough that cases have been misdiagnosed as Conradi's disease. The prognosis is
generally good and depends mainly on the pulmonary complications, but no
disease-modifying therapy exists and the mechanism by which MGP prevents abnormal
calcification remains poorly understood.
synonyms:
- KTLS
- Pulmonic stenosis, brachytelephalangism, and calcification of cartilages
- Pulmonic stenosis-brachytelephalangism-calcification of cartilages syndrome
disease_term:
preferred_term: Keutel syndrome
term:
id: MONDO:0009495
label: Keutel syndrome
parents:
- Chondrodysplasia Punctata
- Congenital Limb Malformation
classifications:
harrisons_chapter:
- classification_value: GENETICS_ENVIRONMENT_DISEASE
notes: >-
An autosomal recessive Mendelian multisystem disorder diagnosed by genetic testing.
- classification_value: CARDIOVASCULAR
notes: >-
The manifestation that determines prognosis is cardiovascular - multiple peripheral
pulmonary artery stenoses, with pulmonary hypertension and right-heart consequences -
and it is often what brings the patient to attention, in one reported case an
incidentally auscultated murmur.
isds_skeletal_category:
- classification_value: chondrodysplasia_punctata
notes: >-
ISDS Nosology of Genetic Skeletal Disorders, 2023 revision (Unger et al.,
PMID:36779427), group 23 "Chondrodysplasia punctata (CDP) group", row
NOS 23-0040 "Keutel syndrome, MGP-related" (MIM 245150). Carried forward from the
2019 revision (Mortier et al., PMID:31633310), where the group was numbered 21.
The placement is worth a note because Keutel syndrome is the group's mechanistic
inverse - the other members fail to mineralize cartilage correctly, whereas here an
inhibitor of mineralization is lost - and because its dominant clinical problem is
cardiovascular rather than skeletal. It nonetheless belongs: brachytelephalangism
with punctate epiphyses is present in about three quarters of genotyped patients,
and the clinical overlap with chondrodysplasia punctata is close enough to have
caused documented misdiagnosis. Note also that MGP is vitamin-K-dependent, which
places Keutel syndrome and CDPX1 - the group's other brachytelephalangic entity, and
one whose enzyme is warfarin-sensitive with vitamin-K-deficiency phenocopies - on a
shared thematic axis the nosology does not itself draw.
mappings:
mondo_mappings:
- term:
id: MONDO:0009495
label: Keutel syndrome
mapping_predicate: skos:exactMatch
mapping_source: MONDO
mapping_justification: >-
The dismech entry and the MONDO class denote the same entity: MGP-related Keutel
syndrome.
references:
- reference: PMID:9916809
title: "Mutations in the gene encoding the human matrix Gla protein cause Keutel syndrome."
- reference: PMID:33996798
title: "Keutel Syndrome, a Review of 50 Years of Literature."
- reference: PMID:9052783
title: "Spontaneous calcification of arteries and cartilage in mice lacking matrix GLA protein."
- reference: PMID:37252084
title: "Tracheobronchial Tree Ossification in a 5-Year-Old Boy with Keutel Syndrome: A Case Report."
prevalence:
- population: Worldwide
measure_type: POINT_PREVALENCE
prevalence_class: BELOW_1_IN_1000000
rate_per_100000: 0.1
notes: >-
Estimated at 1 in 1,000,000 in the 50-year review. The review itself argues the figure
is probably an underestimate, since mild and intrafamilially variable cases may go
undetected and since the core features overlap other disorders well enough to cause
misdiagnosis.
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
It is an extremely rare autosomal recessive disorder (estimated prevalence of 1 in
1,000,000), which is usually diagnosed during childhood, although it can remain
undetected until adulthood.
explanation: Gives the prevalence estimate and the age at diagnosis.
- population: Reported cases in the literature to 2021
measure_type: CASES_IN_LITERATURE
prevalence_class: ULTRA_RARE
notes: >-
Forty-two reported cases, half of them in the Turkish population - an ascertainment
concentration that follows from the disorder's recessive inheritance and the role of
consanguinity.
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Forty-two cases have been reported so far, with half in Turkish population (Table 1)."
explanation: Gives the cumulative case count and its geographic concentration.
progression:
- phase: Infancy - recurrent otitis media and unremarkable examination
notes: >-
Many patients are normal at birth. Recurrent otitis media in infancy is a common early
thread, and it feeds into the hearing loss that becomes a persistent problem.
evidence:
- reference: PMID:37252084
reference_title: "Tracheobronchial Tree Ossification in a 5-Year-Old Boy with Keutel Syndrome: A Case Report."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
He had no obvious abnormalities at birth but suffered from recurrent episodes of
infectious otitis media during infancy.
explanation: Documents a normal newborn examination followed by recurrent otitis media.
- phase: Childhood - diagnosis, usually via the facial or cardiac findings
notes: >-
Diagnosis is usually made in childhood. In practice it is triggered either by the
facial appearance and brachytelephalangism or by a heart murmur, since peripheral
pulmonary artery stenosis is present in almost all patients and can be found
incidentally.
evidence:
- reference: PMID:37252084
reference_title: "Tracheobronchial Tree Ossification in a 5-Year-Old Boy with Keutel Syndrome: A Case Report."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Finally, at the age of 5 years, after an accidental auscultation of a systolic
murmur, he was referred to our center for further investigation.
explanation: Documents a diagnosis reached through incidental cardiac auscultation.
- phase: Long-term - good prognosis, determined by pulmonary complications
notes: >-
Unlike most entries in its nosology group, Keutel syndrome is not lethal and most
patients do well. What sets life expectancy is the severity of the pulmonary
complications, which is why surveillance is directed at the pulmonary arteries, the
airway, and hearing rather than at the skeleton.
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The prognosis of KS is good in most patients and their life expectancy mostly depends
on the severity of the pulmonary complications.
explanation: States the prognosis and what determines it.
pathophysiology:
- name: Matrix Gla Protein Loss of Function
biological_scale: MOLECULAR
description: >-
Biallelic MGP variants produce a non-functional matrix Gla protein. MGP is a 10-kD
extracellular matrix protein of the Gla family - the family that also contains
osteocalcin and the vitamin-K-dependent coagulation factors - whose glutamate residues
are gamma-carboxylated using vitamin K as cofactor. It is the gamma-carboxyglutamate
residues that give the mature protein its high affinity for calcium, phosphate, and
hydroxyapatite, so a protein that is not properly made or not properly carboxylated
cannot bind the mineral it is meant to control.
genetic_context:
functional_impact_category: LOSS_OF_FUNCTION
variant_origin: GERMLINE
zygosity: HOMOZYGOUS
gene:
preferred_term: MGP
term:
id: hgnc:7060
label: MGP
description: >-
Biallelic germline loss-of-function variants. The three variants in the original
mapping study - a single-base deletion, a splice-acceptor change, and a missense
change - all predict a non-functional protein, and parental consanguinity is common.
biological_processes:
- preferred_term: peptidyl-glutamic acid carboxylation
term:
id: GO:0017187
label: peptidyl-glutamic acid carboxylation
- preferred_term: negative regulation of biomineral tissue development
modifier: LOSS_OF_FUNCTION
term:
id: GO:0070168
label: negative regulation of biomineral tissue development
evidence:
- reference: PMID:9916809
reference_title: "Mutations in the gene encoding the human matrix Gla protein cause Keutel syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Mutational analysis of MGP in three unrelated probands identified three different
mutations: c.69delG, IVS1-2A-->G and c.113T-->A. All three mutations predict a
non-functional MGP.
explanation: Establishes loss of function of MGP as the molecular lesion in three unrelated families.
- reference: PMID:9916809
reference_title: "Mutations in the gene encoding the human matrix Gla protein cause Keutel syndrome."
supports: SUPPORT
evidence_source: OTHER
snippet: >-
All members of this family have glutamic acid residues modified to gamma-carboxyglutamic
acids (Gla) by a specific gamma-carboxylase using vitamin K as a cofactor.
explanation: >-
States the vitamin-K-dependent post-translational modification that the protein's
mineral-binding capacity depends on.
downstream:
- target: Loss of Active Inhibition of Extracellular Matrix Calcification
description: >-
Without a functional mineral-binding Gla protein in the matrix, the brake on
calcification is removed in the tissues that express it.
causal_link_type: DIRECT
evidence:
- reference: PMID:9916809
reference_title: "Mutations in the gene encoding the human matrix Gla protein cause Keutel syndrome."
supports: SUPPORT
evidence_source: OTHER
snippet: >-
The modified glutamic acid residues of Gla proteins confer a high affinity for
mineral ions such as calcium, phosphate and hydroxyapatite crystals, the mineral
components of the skeletal ECM.
explanation: >-
Explains the physical basis for the protein's action on mineral, and hence for what
is lost.
- name: Loss of Active Inhibition of Extracellular Matrix Calcification
biological_scale: TISSUE
description: >-
The central mechanistic claim of this disorder, and the one that generalized beyond
it: extracellular matrix calcification in soft tissue is actively inhibited, not
merely not induced. MGP is expressed by the two cell types that build an uncalcified
matrix - vascular smooth muscle cells and chondrocytes - and those are exactly the
tissues that mineralize when it is lost.
cell_types:
- preferred_term: chondrocyte
term:
id: CL:0000138
label: chondrocyte
- preferred_term: vascular smooth muscle cell
term:
id: CL:0000359
label: vascular associated smooth muscle cell
biological_processes:
- preferred_term: biomineral tissue development
modifier: INCREASED
term:
id: GO:0031214
label: biomineral tissue development
- preferred_term: extracellular matrix organization
modifier: ABNORMAL
term:
id: GO:0030198
label: extracellular matrix organization
evidence:
- reference: PMID:9052783
reference_title: "Spontaneous calcification of arteries and cartilage in mice lacking matrix GLA protein."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
These results indicate that ECM calcification must be actively inhibited in soft
tissues.
explanation: >-
States the general principle that the knockout phenotype established, and which this
disorder is the human instance of.
- reference: PMID:9052783
reference_title: "Spontaneous calcification of arteries and cartilage in mice lacking matrix GLA protein."
supports: SUPPORT
evidence_source: OTHER
snippet: >-
A candidate molecule is matrix GLA protein (Mgp), a mineral-binding ECM protein
synthesized by vascular smooth-muscle cells and chondrocytes, two cell types that
produce an uncalcified ECM.
explanation: >-
Identifies the expressing cell types and, in doing so, predicts which tissues are at
risk.
downstream:
- target: Abnormal Cartilage Calcification
description: >-
Cartilage that should stay uncalcified mineralizes - larynx, tracheobronchial tree,
ears, nose, and ribs.
causal_link_type: DIRECT
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
abnormal cartilage calcification in the larynx, the respiratory tract, the ears,
the nose and the ribs
explanation: Enumerates the cartilages that calcify in patients.
- target: Peripheral Pulmonary Artery Stenosis
description: >-
The vascular arm of the same lesion. Multiple peripheral pulmonary artery stenoses
are found in almost all patients and are the finding that governs prognosis.
causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
intermediate_mechanisms:
- Loss of MGP-mediated inhibition of mineralization in vascular smooth muscle, with mural calcification and segmental narrowing of the peripheral pulmonary arteries.
evidence:
- reference: PMID:37252084
reference_title: "Tracheobronchial Tree Ossification in a 5-Year-Old Boy with Keutel Syndrome: A Case Report."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Computed tomography angiography confirmed calcification and segmental stenosis in
the peripheral pulmonary arteries.
explanation: >-
Imaging shows calcification and stenosis together in the same vessels, which is the
observation that links the vascular narrowing to the calcification mechanism.
- target: Midface Hypoplasia
description: >-
Underdevelopment of the midface, with depressed nasal bridge, hypoplastic nasal alae,
and sloping forehead. Nasal cartilage is among the cartilages affected, so the
craniofacial phenotype is plausibly the same lesion in a different site, though the
developmental route is not established.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
- target: Depressed Nasal Bridge
description: The nasal component of the midfacial underdevelopment.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
- target: Sloping Forehead
description: The frontal component of the same craniofacial pattern.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
- target: Brachytelephalangism
description: >-
Shortening and broadening of the first to fourth distal phalanges with punctate
epiphyses, characteristically sparing the fifth. This is the feature that places the
disorder in the chondrodysplasia punctata group.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
- target: Epiphyseal Stippling
description: >-
Punctate epiphyses in the shortened distal phalanges - the chondrodysplasia punctata
finding itself.
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
- name: Abnormal Cartilage Calcification
biological_scale: TISSUE
description: >-
Pathological mineralization of cartilage across multiple sites. In the airway it
progresses to frank ossification of the tracheobronchial tree, and in the ear
cartilage, biopsies have shown direct ossification without preceding tissue reaction -
which is the histological reading of a lost inhibitor rather than an inflammatory or
reactive process.
biological_processes:
- preferred_term: cartilage development
modifier: ABNORMAL
term:
id: GO:0051216
label: cartilage development
evidence:
- reference: PMID:37252084
reference_title: "Tracheobronchial Tree Ossification in a 5-Year-Old Boy with Keutel Syndrome: A Case Report."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Biopsies of ear cartilages have shown direct ossification without any tissue reaction
or calcification, resulting in neurosensory and conductive hearing loss.
explanation: >-
The histological pattern - direct ossification with no tissue reaction - and its link
to the hearing loss.
downstream:
- target: Tracheal Calcification
causal_link_type: DIRECT
description: Calcification and ossification of the tracheobronchial cartilage, visible on chest radiography.
- target: Calcification of the Auricular Cartilage
causal_link_type: DIRECT
description: >-
Direct ossification of the ear cartilage, the site whose histology was examined.
- target: Mixed Hearing Impairment
causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
intermediate_mechanisms:
- Direct ossification of auricular and middle-ear cartilage, giving both conductive and sensorineural components.
description: >-
Hearing loss, mild to severe, unilateral or bilateral, and mixed in character - the
conductive element following the ossified cartilage directly.
- name: Peripheral Pulmonary Artery Stenosis
biological_scale: ORGANISM
description: >-
Multiple stenoses of the peripheral pulmonary arteries, present in almost all patients.
They raise right ventricular afterload and can lead to pulmonary hypertension,
tricuspid regurgitation, and right ventricular hypertrophy and dysfunction. This node,
not the skeletal phenotype, determines the patient's prognosis.
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Additional symptoms found in almost all patients include multiple peripheral pulmonary
artery stenoses
explanation: Establishes the near-universal presence of the pulmonary artery stenoses.
downstream:
- target: Pulmonary Arterial Hypertension
causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
intermediate_mechanisms:
- Fixed obstruction to pulmonary arterial flow with elevated pulmonary vascular resistance.
description: >-
Pulmonary hypertension with right-heart consequences follows from the fixed
obstruction.
evidence:
- reference: PMID:37252084
reference_title: "Tracheobronchial Tree Ossification in a 5-Year-Old Boy with Keutel Syndrome: A Case Report."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Transthoracic echocardiography illustrated peripheral pulmonary artery stenosis,
moderate tricuspid regurgitation, and pulmonary hypertension.
explanation: Documents the stenoses together with pulmonary hypertension in one patient.
phenotypes:
- name: Abnormal Cartilage Calcification
category: Skeletal
description: >-
Calcification of the laryngeal, tracheobronchial, auricular, nasal, and costal
cartilages - the most characteristic finding of the syndrome.
phenotype_term:
preferred_term: Calcification of cartilage
term:
id: HP:0100593
label: Calcification of cartilage
evidence:
- reference: PMID:9916809
reference_title: "Mutations in the gene encoding the human matrix Gla protein cause Keutel syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Keutel syndrome (KS, MIM 245150) is an autosomal recessive disorder characterized by
abnormal cartilage calcification, peripheral pulmonary stenosis and midfacial
hypoplasia.
explanation: Names abnormal cartilage calcification as one of the three defining features.
- name: Tracheal Calcification
category: Respiratory
description: >-
Calcification progressing to ossification of the tracheobronchial tree, visible on
plain chest radiography.
phenotype_term:
preferred_term: Tracheal calcification
term:
id: HP:0002787
label: Tracheal calcification
evidence:
- reference: PMID:37252084
reference_title: "Tracheobronchial Tree Ossification in a 5-Year-Old Boy with Keutel Syndrome: A Case Report."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Chest radiography showed tracheobronchial tree calcification."
explanation: Documents the radiographic finding.
- name: Calcification of the Auricular Cartilage
category: Otologic
description: >-
Calcification and direct ossification of the ear cartilage. It is named separately from
the generic cartilage calcification because it is the site whose histology was actually
examined - biopsies show ossification with no preceding tissue reaction - and because it
is the anatomic basis of the conductive component of the hearing loss.
phenotype_term:
preferred_term: Calcification of the auricular cartilage
term:
id: HP:0005103
label: Calcification of the auricular cartilage
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
abnormal cartilage calcification in the larynx, the respiratory tract, the ears, the
nose and the ribs
explanation: Names the ears among the sites of abnormal cartilage calcification.
- reference: PMID:37252084
reference_title: "Tracheobronchial Tree Ossification in a 5-Year-Old Boy with Keutel Syndrome: A Case Report."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Biopsies of ear cartilages have shown direct ossification without any tissue reaction
or calcification, resulting in neurosensory and conductive hearing loss.
explanation: >-
Gives the histology of the ear-cartilage lesion and links it to the hearing loss.
- name: Peripheral Pulmonary Artery Stenosis
category: Cardiovascular
description: >-
Multiple stenoses of the peripheral pulmonary arteries, present in almost all patients
and the determinant of prognosis.
phenotype_term:
preferred_term: Peripheral pulmonary artery stenosis
term:
id: HP:0004969
label: Peripheral pulmonary artery stenosis
evidence:
- reference: PMID:9916809
reference_title: "Mutations in the gene encoding the human matrix Gla protein cause Keutel syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "abnormal cartilage calcification, peripheral pulmonary stenosis and midfacial hypoplasia"
explanation: Names peripheral pulmonary stenosis as a defining feature.
- name: Pulmonary Arterial Hypertension
category: Cardiovascular
description: Pulmonary hypertension arising from the fixed peripheral pulmonary arterial obstruction.
phenotype_term:
preferred_term: Pulmonary arterial hypertension
term:
id: HP:0002092
label: Pulmonary arterial hypertension
evidence:
- reference: PMID:37252084
reference_title: "Tracheobronchial Tree Ossification in a 5-Year-Old Boy with Keutel Syndrome: A Case Report."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Transthoracic echocardiography illustrated peripheral pulmonary artery stenosis,
moderate tricuspid regurgitation, and pulmonary hypertension.
explanation: Documents pulmonary hypertension in a patient with the stenoses.
- name: Midface Hypoplasia
category: Craniofacial
description: >-
Midfacial underdevelopment with depressed nasal bridge, hypoplastic nasal alae, sloping
forehead, and receding chin.
phenotype_term:
preferred_term: Midface retrusion
term:
id: HP:0011800
label: Midface retrusion
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
dysmorphic facial abnormalities including sloping forehead, midface hypoplasia,
depressed nasal bridge and hypoplastic alae nasi, receding chin and sometimes short
palate
explanation: Enumerates the craniofacial findings.
- name: Depressed Nasal Bridge
category: Craniofacial
description: Depressed nasal bridge with hypoplastic nasal alae, part of the midfacial pattern.
phenotype_term:
preferred_term: Depressed nasal bridge
term:
id: HP:0005280
label: Depressed nasal bridge
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "depressed nasal bridge and hypoplastic alae nasi"
explanation: Names the depressed nasal bridge among the consistent facial findings.
- name: Sloping Forehead
category: Craniofacial
description: Sloping forehead, listed among the consistent dysmorphic features.
phenotype_term:
preferred_term: Sloping forehead
term:
id: HP:0000340
label: Sloping forehead
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "dysmorphic facial abnormalities including sloping forehead, midface hypoplasia"
explanation: Names the sloping forehead as a consistent facial finding.
- name: Brachytelephalangism
category: Skeletal
description: >-
Shortening and broadening of the first to fourth distal phalanges with punctate
epiphyses, characteristically sparing the fifth phalanx, in about three quarters of
patients. This is the feature that ties the syndrome to the chondrodysplasia punctata
group.
phenotype_term:
preferred_term: Shortening of all distal phalanges of the fingers
term:
id: HP:0006118
label: Shortening of all distal phalanges of the fingers
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
brachytelephalangism that, in around 75% of the cases, is characterized by shortening
and broadening of the first to fourth distal phalanges (punctate epiphyses), with
sparing of the fifth phalange
explanation: >-
Gives the frequency, the digit pattern, and - importantly for the nosology placement -
records punctate epiphyses.
- name: Epiphyseal Stippling
category: Skeletal
description: >-
Punctate epiphyses accompanying the brachytelephalangism. This is the specific finding
that connects Keutel syndrome to the chondrodysplasia punctata group and makes the ISDS
placement more than an administrative one.
phenotype_term:
preferred_term: Epiphyseal stippling
term:
id: HP:0010655
label: Epiphyseal stippling
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
brachytelephalangism that, in around 75% of the cases, is characterized by shortening
and broadening of the first to fourth distal phalanges (punctate epiphyses), with
sparing of the fifth phalange
explanation: >-
The review describes the brachytelephalangism as involving punctate epiphyses, in
around 75% of genotyped cases.
- name: Mixed Hearing Impairment
category: Otologic
description: >-
Mild to severe, unilateral or bilateral hearing loss with both sensorineural and
conductive components, the conductive element following ossification of the ear
cartilage.
phenotype_term:
preferred_term: Mixed hearing impairment
term:
id: HP:0000410
label: Mixed hearing impairment
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
mild to severe unilateral or bilateral sensorineural, mixed hearing loss
explanation: States the hearing loss and its mixed character.
- name: Recurrent Otitis Media
category: Otologic
description: >-
Recurrent middle-ear infection, often beginning in infancy and preceding the diagnosis.
phenotype_term:
preferred_term: Recurrent otitis media
term:
id: HP:0000403
label: Recurrent otitis media
evidence:
- reference: PMID:37252084
reference_title: "Tracheobronchial Tree Ossification in a 5-Year-Old Boy with Keutel Syndrome: A Case Report."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
He had no obvious abnormalities at birth but suffered from recurrent episodes of
infectious otitis media during infancy.
explanation: Documents recurrent otitis media in infancy.
- name: Global Developmental Delay
category: Neurologic
description: >-
Intellectual function ranges from borderline to mild developmental delay; the disorder
is not associated with severe intellectual disability.
phenotype_term:
preferred_term: Global developmental delay
term:
id: HP:0001263
label: Global developmental delay
severity: MILD
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
intellectual disability that ranges from borderline intelligence to mild developmental
delay, short stature, and respiratory conditions including dyspnea, wheezing, cough,
and infections
explanation: States the range of intellectual involvement.
- name: Short Stature
category: Growth
description: Short stature is reported among the additional features found in almost all patients.
phenotype_term:
preferred_term: Short stature
term:
id: HP:0004322
label: Short stature
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "mild developmental delay, short stature, and respiratory conditions"
explanation: Lists short stature among the additional features.
genetic:
- name: MGP
relationship_type: CAUSATIVE
presence: Present
gene_term:
preferred_term: MGP
term:
id: hgnc:7060
label: MGP
notes: >-
MGP at 12p12.3-13.1, found by homozygosity mapping. It was selected from the linked
interval on two grounds - its map position and the known function of its protein - and
the Mgp-null mouse phenotype published two years earlier was what made that function
a compelling prediction.
evidence:
- reference: PMID:9916809
reference_title: "Mutations in the gene encoding the human matrix Gla protein cause Keutel syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
A genome search using homozygosity mapping provided evidence of linkage to chromosome
12p12.3-13.1 (maximum multipoint lod score, 4.06).
explanation: Establishes the locus by linkage.
- reference: PMID:9916809
reference_title: "Mutations in the gene encoding the human matrix Gla protein cause Keutel syndrome."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Our data indicate that mutations in MGP are responsible for KS and confirm its role in
the regulation of extracellular matrix calcification.
explanation: States the gene assignment and its mechanistic interpretation.
inheritance:
- name: Autosomal recessive inheritance
inheritance_term:
preferred_term: autosomal recessive inheritance
term:
id: HP:0000007
label: Autosomal recessive inheritance
description: >-
Biallelic variants are required and parental consanguinity is common, which is why
homozygosity mapping succeeded and why reported cases cluster geographically.
Intrafamilial phenotypic variability has been reported, so a mildly affected sibling
may go unrecognized.
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Although parental consanguinity is prevalent in KS, pregnancy is normal (except for
one reported case of repeated miscarriages) and blood parameters, including calcium
and phosphate serum levels, are usually unremarkable.
explanation: >-
States the prevalence of consanguinity, and separately the important negative that
serum calcium and phosphate are normal.
biochemical:
- name: Serum calcium and phosphate
notes: >-
A diagnostically important *negative*. Serum calcium and phosphate are usually
unremarkable, so this is not a disorder of mineral homeostasis - the lesion is local
control of where mineral is allowed to deposit, not how much of it circulates. A normal
mineral panel therefore does not argue against the diagnosis.
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
blood parameters, including calcium and phosphate serum levels, are usually
unremarkable
explanation: States that circulating mineral levels are normal.
diagnosis:
- name: Clinical suspicion confirmed by MGP genetic testing
description: >-
The syndrome is suspected on the combination of midface hypoplasia, cartilage
calcification, brachytelephalangism, and peripheral pulmonary stenosis, and confirmed by
finding a homozygous MGP variant.
diagnosis_term:
preferred_term: molecular genetic testing
term:
id: NCIT:C15709
label: Genetic Testing
evidence:
- reference: PMID:37252084
reference_title: "Tracheobronchial Tree Ossification in a 5-Year-Old Boy with Keutel Syndrome: A Case Report."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
KS is clinically suspected and diagnosed by genetic testing as being due to a
homozygous mutation in the matrix Gla protein (MGP) gene
explanation: States the diagnostic route.
treatments:
- name: Symptomatic management of hypertension and respiratory complications
description: >-
No disease-modifying therapy exists. Available treatment is symptomatic, directed at
the hypertension and the respiratory complications - which the 50-year review
explicitly identifies as a consequence of the mechanism not being understood well
enough to target.
therapeutic_modality: OTHER
treatment_term:
preferred_term: supportive care
term:
id: NCIT:C15747
label: Supportive Care
target_phenotypes:
- preferred_term: pulmonary arterial hypertension
term:
id: HP:0002092
label: Pulmonary arterial hypertension
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Indeed, at present, only symptomatic treatments are available to treat hypertension
and respiratory complications occurring in the KS patients.
explanation: States that only symptomatic treatment is available and what it targets.
- name: Cardiac, airway, and audiologic surveillance
description: >-
Because the pulmonary arterial and airway lesions can progress and set the prognosis,
follow-up attends to upper respiratory tract symptoms, hearing, and the development of
tracheal and pulmonary artery stenosis.
therapeutic_modality: BEHAVIORAL
treatment_term:
preferred_term: supportive care
term:
id: NCIT:C15747
label: Supportive Care
target_phenotypes:
- preferred_term: peripheral pulmonary artery stenosis
term:
id: HP:0004969
label: Peripheral pulmonary artery stenosis
evidence:
- reference: PMID:37252084
reference_title: "Tracheobronchial Tree Ossification in a 5-Year-Old Boy with Keutel Syndrome: A Case Report."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
During the follow-up of these patients and examinations, we should pay attention to
their symptoms related to upper respiratory tract infections, the extent of hearing,
and the possibility of tracheal and pulmonary artery stenosis development.
explanation: States the recommended surveillance targets.
animal_models:
- name: Mgp-null mouse
species: Mouse
genotype: Mgp knockout, homozygous null
publication: PMID:9052783
description: >-
The knockout that established the mechanism before the human gene was known, and which
is described in the review literature as a faithful model of the human syndrome. Null
mice develop to term and then die within two months of arterial calcification leading
to blood-vessel rupture, with inappropriate calcification of cartilage including the
growth plate.
modeled_mechanisms:
- target: Loss of Active Inhibition of Extracellular Matrix Calcification
relationship: RECAPITULATES
fidelity: HIGH
description: >-
The knockout demonstrated that MGP loss is sufficient for spontaneous calcification of
both arteries and cartilage, which is the mechanism the human disorder instantiates.
Its explanatory role was not merely confirmatory: the mouse phenotype is what made MGP
the compelling candidate in the human linkage interval.
limitations: >-
The mouse phenotype is considerably more severe on the vascular side than the human
disorder - null mice die within two months of vessel rupture, whereas Keutel patients
generally have a good prognosis - so the model overstates the vascular lethality even
while capturing the mechanism.
readouts:
- name: Spontaneous arterial calcification with vessel rupture
target: Loss of Active Inhibition of Extracellular Matrix Calcification
direction: INCREASED
interpretation: Mineralization of an arterial matrix that is normally kept uncalcified.
evidence:
- reference: PMID:9052783
reference_title: "Spontaneous calcification of arteries and cartilage in mice lacking matrix GLA protein."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Mice that lack Mgp develop to term but die within two months as a result of
arterial calcification which leads to blood-vessel rupture.
explanation: Reports the vascular calcification phenotype and its lethality.
- name: Inappropriate cartilage calcification including the growth plate
target: Loss of Active Inhibition of Extracellular Matrix Calcification
direction: INCREASED
interpretation: >-
The cartilage arm of the same lesion, and the direct counterpart of the human
cartilage calcification.
evidence:
- reference: PMID:9052783
reference_title: "Spontaneous calcification of arteries and cartilage in mice lacking matrix GLA protein."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Mgp-deficient mice additionally exhibit inappropriate calcification of various
cartilages, including the growth plate, which eventually leads to short stature,
osteopenia and fractures.
explanation: Reports the cartilage calcification and its skeletal consequences.
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
While studies on Mgp -/- mouse, a faithful model of KS, show that pathologic mineral
deposition (ectopic calcification) in cartilaginous and vascular tissues is the
primary cause underlying many of these abnormalities, the mechanisms explaining how
MGP prevents abnormal calcification remain poorly understood.
explanation: >-
The review calls the knockout a faithful model of the human syndrome, and in the same
sentence marks the limit of what it has explained.
differential_diagnoses:
- name: Chondrodysplasia punctata, including Conradi's disease
disease_term:
preferred_term: chondrodysplasia punctata
term:
id: MONDO:0019701
label: chondrodysplasia punctata
description: >-
Not a theoretical differential: the review literature records that the shared features -
midface hypoplasia, abnormal cartilage calcification, brachytelephalangism, peripheral
pulmonary stenosis - have caused Keutel syndrome to be misdiagnosed as chondrodysplasia
punctata. Since the ISDS nosology places Keutel syndrome inside the CDP group, this is
a differential within a family rather than across families.
distinguishing_features:
- Keutel syndrome has multiple peripheral pulmonary artery stenoses in almost all patients; these are not a feature of the other CDPs
- Keutel syndrome calcifies cartilage that should never mineralize (larynx, trachea, ears, nose) rather than showing transient epiphyseal stippling that resolves
- Keutel syndrome is autosomal recessive with normal serum calcium and phosphate and no diagnostic sterol or plasmalogen abnormality
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
are also observed in other disorders (for example, chondrodysplasia punctata or
Conradi's disease), leading to the misdiagnosis of some forms of KS into another
disease (Say et al., 1973)
explanation: Documents actual misdiagnosis as chondrodysplasia punctata.
discussions:
- discussion_id: mgp_inhibition_mechanism
kind: KNOWLEDGE_GAP
status: OPEN
attaches_to:
- pathophysiology#Loss of Active Inhibition of Extracellular Matrix Calcification
- treatments#Symptomatic management of hypertension and respiratory complications
prompt: >-
By what molecular mechanism does matrix Gla protein prevent calcification of cartilage
and vascular matrix?
rationale: >-
That MGP is a calcification inhibitor is established from both directions - the null
mouse calcifies spontaneously, and the human loss-of-function disorder reproduces it -
and the physical basis is at least sketched, since gamma-carboxyglutamate residues bind
calcium, phosphate, and hydroxyapatite. What is not established is how that binding
translates into inhibition: whether MGP sequesters mineral ions, caps nascent
hydroxyapatite crystals, antagonizes BMP signalling in the matrix, or acts by some
combination. The review that marks the syndrome's fiftieth year states the gap plainly
and draws the practical consequence - it is why there is no cure and why treatment is
symptomatic. This is an unusually well-posed gap: the disorder, the knockout, and the
protein's chemistry are all in hand, and what is missing is the step between them.
evidence:
- reference: PMID:33996798
reference_title: "Keutel Syndrome, a Review of 50 Years of Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
the mechanisms explaining how MGP prevents abnormal calcification remain poorly
understood. This has negative implication for the development of a cure for KS.
explanation: States the gap and links it directly to the absence of a therapy.
- discussion_id: vitamin_k_dependence_therapeutic_angle
kind: KNOWLEDGE_GAP
status: OPEN
attaches_to:
- pathophysiology#Matrix Gla Protein Loss of Function
prompt: >-
Does the vitamin-K dependence of MGP carboxylation offer any therapeutic leverage in
patients whose MGP variants leave a partially functional protein?
rationale: >-
MGP requires vitamin-K-dependent gamma-carboxylation to bind mineral, so its activity
has a cofactor-dependent step that a null allele destroys but a hypomorphic one might
only limit. The reported MGP variants include a missense change alongside frameshift and
splice alleles, and intrafamilial phenotypic variability has been described - both
consistent with a range of residual function. Whether vitamin K status modifies the
phenotype in such patients has not, as far as this entry's sources go, been tested. The
question is worth recording because it is one of the few angles on a disorder for which
only symptomatic treatment exists, and because the same vitamin-K axis connects this
entry to CDPX1, the other brachytelephalangic entity in the same nosology group, whose
enzyme is warfarin-sensitive and which has vitamin-K-deficiency phenocopies.
evidence:
- reference: PMID:9916809
reference_title: "Mutations in the gene encoding the human matrix Gla protein cause Keutel syndrome."
supports: SUPPORT
evidence_source: OTHER
snippet: >-
All members of this family have glutamic acid residues modified to gamma-carboxyglutamic
acids (Gla) by a specific gamma-carboxylase using vitamin K as a cofactor.
explanation: >-
Establishes the vitamin-K-dependent step on which the question turns. Note this
supports the biochemistry only; no source cited here tests a vitamin-K intervention in
patients.
notes: >-
Curated as its own dismech entry because the ISDS 2023 nosology lists it as its own row
(NOS 23-0040). It is the least typical member of its group - the mechanism is loss of an
inhibitor of mineralization rather than a defect in a biosynthetic pathway, and the
clinically dominant feature is cardiovascular - but the placement is sound: three quarters
of genotyped patients have brachytelephalangism with punctate epiphyses, and the syndrome
has been misdiagnosed as chondrodysplasia punctata in practice. A member of the
Chondrodysplasia_Punctata grouping.