Monilethrix is a rare autosomal dominant hair shaft dysplasia caused by heterozygous variants in the hair-cortex ("hard") keratins KRT81, KRT83 and KRT86. It is the hair-follicle instance of the keratinopathy mechanism: a dominant-negative variant in a keratin filament-assembly domain collapses the keratin network, but because these keratins are expressed in the hair shaft cortex rather than in epidermis, the fragile structure produced is a hair rather than a skin layer. The shaft develops a regular periodic narrowing that gives it a beaded, necklace-like appearance - the name is from Latin monile, necklace, and Greek thrix, hair - and fractures at the internodes, so hair breaks close to the scalp and patchy dystrophic alopecia results. Follicular hyperkeratosis on the nape and extensor surfaces is a frequent associated finding. A recessive form caused by DSG4 variants exists and reaches the same hair-shaft phenotype through desmosomal rather than keratin failure.
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name: Monilethrix
creation_date: "2026-08-22T00:00:00Z"
description: >-
Monilethrix is a rare autosomal dominant hair shaft dysplasia caused by
heterozygous variants in the hair-cortex ("hard") keratins KRT81, KRT83 and
KRT86. It is the hair-follicle instance of the keratinopathy mechanism:
a dominant-negative variant in a keratin filament-assembly domain collapses
the keratin network, but because these keratins are expressed in the hair
shaft cortex rather than in epidermis, the fragile structure produced is a
hair rather than a skin layer. The shaft develops a regular periodic
narrowing that gives it a beaded, necklace-like appearance - the name is from
Latin monile, necklace, and Greek thrix, hair - and fractures at the
internodes, so hair breaks close to the scalp and patchy dystrophic alopecia
results. Follicular hyperkeratosis on the nape and extensor surfaces is a
frequent associated finding. A recessive form caused by DSG4 variants exists
and reaches the same hair-shaft phenotype through desmosomal rather than
keratin failure.
category: Genetic
parents:
- Genodermatosis
disease_term:
preferred_term: monilethrix
term:
id: MONDO:0008009
label: monilethrix
classifications:
harrisons_chapter:
- classification_value: DERMATOLOGY
- classification_value: GENETICS_ENVIRONMENT_DISEASE
references:
- reference: PMID:25557232
title: Novel KRT83 and KRT86 mutations associated with monilethrix.
found_in:
- Monilethrix-deep-research-asta.md
findings:
- statement: "Autosomal dominant hard-keratin aetiology (KRT81, KRT83, KRT86), relative gene contribution, and the associated follicular hyperkeratosis."
- reference: PMID:30969635
title: Monilethrix.
found_in:
- Monilethrix-deep-research-asta.md
findings:
- statement: "Periodic shaft narrowing producing the beaded appearance, and patchy dystrophic alopecia as the clinical endpoint."
- reference: PMID:30201151
title: Trichoscopy in Hair Shaft Disorders.
found_in:
- Monilethrix-deep-research-asta.md
findings:
- statement: "Trichoscopic diagnosis: uniform elliptical nodosities with intermittent constrictions, replacing light microscopy."
inheritance:
- name: Autosomal Dominant
description: >-
The keratin-associated form is autosomal dominant with variable penetrance.
Because mild cases may go unrecognized, the disorder is thought to be
underreported rather than as rare as case counts suggest.
inheritance_term:
preferred_term: Autosomal dominant inheritance
term:
id: HP:0000006
label: Autosomal dominant inheritance
evidence:
- reference: PMID:25557232
reference_title: "Novel KRT83 and KRT86 mutations associated with monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Monilethrix is an autosomal dominant hair disorder caused by mutations in the hard keratins KRT81, KRT83 and KRT86.
explanation: >-
States the mode of inheritance and names the three causal hair keratins.
- reference: PMID:23723505
reference_title: "Monilethrix: a rare hereditary condition."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Monilethrix is a rare hereditary condition generally considered to be an autosomal-dominant disorder with variable penetrance.
explanation: >-
Independently confirms dominant inheritance and records the variable
penetrance.
pathophysiology:
- name: Dominant-Negative Hair Cortex Keratin Variant
conforms_to: "keratin_intermediate_filament_fragility#Dominant-Negative Keratin Variant in a Filament Assembly Domain"
biological_scale: MOLECULAR
description: >-
A heterozygous variant in one of the hair-cortex keratins KRT81, KRT83 or
KRT86 alters a residue required for keratin filament assembly. KRT81 and
KRT86 variants are the most commonly reported. These are the same class of
filament-assembly lesion that produces epidermolysis bullosa simplex and
pachyonychia congenita in other keratin pairs; what differs is the tissue in
which the affected pair is expressed.
cell_types:
- preferred_term: hair follicle cell
term:
id: CL:0002559
label: hair follicle cell
molecular_functions:
- preferred_term: structural constituent of cytoskeleton
term:
id: GO:0005200
label: structural constituent of cytoskeleton
modifier: LOSS_OF_FUNCTION
cellular_components:
- preferred_term: keratin filament
term:
id: GO:0045095
label: keratin filament
locations:
- preferred_term: hair follicle
term:
id: UBERON:0002073
label: hair follicle
downstream:
- target: Cortical Keratin Network Collapse
description: >-
The variant chain is incorporated into the cortical keratin network and
disrupts its assembly.
evidence:
- reference: PMID:25557232
reference_title: "Novel KRT83 and KRT86 mutations associated with monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Monilethrix is an autosomal dominant hair disorder caused by mutations in the hard keratins KRT81, KRT83 and KRT86.
explanation: >-
Establishes hair-cortex keratin variants as the causal lesion.
- reference: PMID:25557232
reference_title: "Novel KRT83 and KRT86 mutations associated with monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Mutations in KRT81 and KRT86 are the most common.
explanation: >-
Records the relative contribution of the three causal keratin genes.
- name: Cortical Keratin Network Collapse
conforms_to: "keratin_intermediate_filament_fragility#Keratin Filament Network Collapse and Aggregation"
biological_scale: CELLULAR
description: >-
The mutant hard-keratin chain is incorporated into the obligate
type-I/type-II heterodimer of the hair cortex, so filament assembly is
disrupted throughout the network rather than in the mutant protein alone.
This is the dominant-negative step, and it is what makes a single variant
allele sufficient.
cell_types:
- preferred_term: hair follicle cell
term:
id: CL:0002559
label: hair follicle cell
biological_processes:
- preferred_term: intermediate filament organization
term:
id: GO:0045109
label: intermediate filament organization
modifier: ABNORMAL
cellular_components:
- preferred_term: keratin filament
term:
id: GO:0045095
label: keratin filament
downstream:
- target: Defective Keratin Assembly in the Hair Shaft Cortex
description: >-
A disrupted network cannot build a mechanically sound cortex.
evidence:
- reference: PMID:25557232
reference_title: "Novel KRT83 and KRT86 mutations associated with monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Monilethrix is an autosomal dominant hair disorder caused by mutations in the hard keratins KRT81, KRT83 and KRT86.
explanation: >-
Establishes that the causal proteins are hard keratins, which assemble as
obligate heterodimers and so admit the dominant-negative mechanism this
node asserts.
notes: >-
Dominant-negative incorporation is inferred here from the autosomal dominant
inheritance of missense alleles in obligate-heterodimer keratins, by analogy
with the well-demonstrated epidermal keratinopathies. The cited source is
not offered as a direct demonstration of network collapse in hair cortex.
- name: Defective Keratin Assembly in the Hair Shaft Cortex
conforms_to: "keratin_intermediate_filament_fragility#Loss of Keratinocyte Mechanical Resilience"
biological_scale: CELLULAR
description: >-
The cortical keratin network of the developing hair shaft is assembled
abnormally, so the shaft loses the mechanical resilience that its densely
packed keratin filaments normally provide. Unlike the epidermal
keratinopathies, the affected cells are not lysed in a living tissue plane -
the hair shaft is already a dead, keratinized structure - so the mechanical
failure presents as fracture of a structure rather than as cytolysis and
blistering.
cell_types:
- preferred_term: hair follicle cell
term:
id: CL:0002559
label: hair follicle cell
biological_processes:
- preferred_term: intermediate filament organization
term:
id: GO:0045109
label: intermediate filament organization
modifier: ABNORMAL
- preferred_term: keratinization
term:
id: GO:0031424
label: keratinization
modifier: ABNORMAL
locations:
- preferred_term: hair follicle
term:
id: UBERON:0002073
label: hair follicle
downstream:
- target: Periodic Shaft Narrowing and Hair Fragility
description: >-
A mechanically incompetent cortex yields a shaft that thins periodically
and fractures at the thinned points.
evidence:
- reference: PMID:25557232
reference_title: "Novel KRT83 and KRT86 mutations associated with monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The affected hairs are fragile and break easily
explanation: >-
Documents the loss of mechanical resilience in the affected structure. The
quote is deliberately truncated before the source's phrase "leading to
scarring alopecia": monilethrix alopecia is NON-scarring, because the hair
fractures above a preserved follicle, and quoting that clause would have
the entry cite a claim its own phenotype description refutes.
notes: >-
Conformance here is declared against the keratin module's central effector,
but the module's node is written for keratinocytes and its effector node
speaks of cytolysis. Monilethrix reaches mechanical failure without
cytolysis because the failing structure is already dead and keratinized.
That is a genuine partial mismatch and is recorded rather than papered over:
the entry conforms to the module's trigger and resilience nodes and
deliberately does NOT conform to its cytolysis node.
- name: Periodic Shaft Narrowing and Hair Fragility
biological_scale: TISSUE
description: >-
The hair shaft develops regular, periodic constrictions alternating with
normal-calibre nodes, giving the beaded or necklace-like appearance on
microscopy that is diagnostic. The internodal constrictions are the
mechanically weak points, and the shaft fractures there.
locations:
- preferred_term: hair follicle
term:
id: UBERON:0002073
label: hair follicle
downstream:
- target: Patchy Dystrophic Alopecia
description: >-
Hair that fractures close to the scalp cannot achieve length, so alopecia
results despite normal follicular density.
- target: Follicular Hyperkeratosis
description: >-
The same follicles show keratotic plugging, a claim about follicular
keratinization rather than about shaft fracture and therefore modelled
separately.
evidence:
- reference: PMID:30969635
reference_title: "Monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
it is characterized by a regular, periodic thinning of the hair shaft, leading to a characteristic beaded appearance of the hair
explanation: >-
Documents the periodic shaft narrowing that defines this node and gives
the disorder its name.
- name: Patchy Dystrophic Alopecia
biological_scale: ORGANISM
description: >-
Hair that breaks before it can grow long, producing patchy alopecia most
marked at sites of friction such as the occiput. The alopecia is
non-scarring: the shaft fractures above a preserved follicle, so follicular
density is normal and regrowth occurs whenever a shaft survives. Severity
ranges from near-complete alopecia to changes mild enough to be missed.
biological_processes:
- preferred_term: keratinization
term:
id: GO:0031424
label: keratinization
modifier: ABNORMAL
locations:
- preferred_term: skin
term:
id: UBERON:0002097
label: skin of body
evidence:
- reference: PMID:30969635
reference_title: "Monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
monilethrix is a rare structural hair shaft disorder characterized by hair fragility and resulting in patchy dystrophic alopecia
explanation: >-
Documents the alopecia endpoint and attributes it to shaft fragility
rather than to follicular loss.
- name: Follicular Hyperkeratosis
biological_scale: TISSUE
description: >-
Keratotic follicular papules, characteristically on the nape of the neck and
the extensor surfaces of the limbs. This is a follicular keratinization
abnormality rather than a consequence of shaft fracture, and it is present
in many but not all affected individuals.
biological_processes:
- preferred_term: keratinization
term:
id: GO:0031424
label: keratinization
modifier: INCREASED
locations:
- preferred_term: hair follicle
term:
id: UBERON:0002073
label: hair follicle
evidence:
- reference: PMID:25557232
reference_title: "Novel KRT83 and KRT86 mutations associated with monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Follicular hyperkeratosis in the neck and on extensor sides of extremities is a frequently associated finding.
explanation: >-
Documents the associated follicular hyperkeratosis and its characteristic
distribution.
phenotypes:
- category: Dermatologic
name: Beaded Fragile Hair
frequency: Very frequent
description: >-
Hair with regular periodic shaft narrowing giving a beaded appearance, which
is fragile and fractures at the internodal constrictions.
phenotype_term:
preferred_term: Brittle hair
term:
id: HP:0002299
label: Brittle hair
evidence:
- reference: PMID:25557232
reference_title: "Novel KRT83 and KRT86 mutations associated with monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The affected hairs are fragile and break easily
explanation: >-
Documents hair fragility and easy breakage as the defining feature. Quote
truncated before the source's "scarring alopecia" clause, which is a
clinical error in that letter - monilethrix alopecia is non-scarring.
- category: Dermatologic
name: Patchy Dystrophic Alopecia
frequency: Very frequent
description: >-
Patchy alopecia resulting from hair fracture rather than from loss of
follicles, typically worst at sites of mechanical friction.
phenotype_term:
preferred_term: Alopecia
term:
id: HP:0001596
label: Alopecia
evidence:
- reference: PMID:30969635
reference_title: "Monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
monilethrix is a rare structural hair shaft disorder characterized by hair fragility and resulting in patchy dystrophic alopecia
explanation: >-
Documents patchy dystrophic alopecia as the clinical consequence.
- category: Dermatologic
name: Follicular Hyperkeratosis
frequency: Frequent
description: >-
Keratotic follicular papules, characteristically on the nape of the neck and
the extensor surfaces of the limbs.
phenotype_term:
preferred_term: Follicular hyperkeratosis
term:
id: HP:0007502
label: Follicular hyperkeratosis
evidence:
- reference: PMID:25557232
reference_title: "Novel KRT83 and KRT86 mutations associated with monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Follicular hyperkeratosis in the neck and on extensor sides of extremities is a frequently associated finding.
explanation: >-
Documents the finding and its stated frequency, which is the basis for the
frequency band recorded here.
diagnosis:
- name: Trichoscopy
diagnosis_term:
preferred_term: dermoscopy
term:
id: NCIT:C116478
label: Dermoscopy
description: >-
Trichoscopy is the diagnostic test of choice and is close to pathognomonic:
it shows uniform elliptical nodosities separated by regular constrictions
along the shaft. It has largely replaced light microscopy, which requires
plucking multiple hairs, and it can be done at the bedside on hair in situ.
results: >-
Uniform elliptical nodosities with intermittent constrictions.
evidence:
- reference: PMID:30201151
reference_title: "Trichoscopy in Hair Shaft Disorders."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
In monilethrix, trichoscopy shows uniform elliptical nodosities with intermittent constrictions.
explanation: >-
States the monilethrix trichoscopic finding directly.
- reference: PMID:30201151
reference_title: "Trichoscopy in Hair Shaft Disorders."
supports: SUPPORT
evidence_source: OTHER
snippet: >-
Trichoscopy allows analyzing the structure and size of growing hair shafts in their natural environment in children and adults. The method replaces light microscopy, which requires pulling of multiple hairs for investigation.
explanation: >-
Supports trichoscopy as the preferred modality over light microscopy,
which is the practical reason it is listed first here.
genetic:
- name: KRT86
notes: >-
KRT86 encodes a type II hair-cortex keratin. Along with KRT81 it accounts
for most reported monilethrix, and novel variants continue to be described.
gene_term:
preferred_term: KRT86
term:
id: hgnc:6463
label: KRT86
relationship_type: CAUSATIVE
evidence:
- reference: PMID:25557232
reference_title: "Novel KRT83 and KRT86 mutations associated with monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
In the French and Dutch patients, we found novel KRT86 and KRT83 mutations. Our findings expand the mutational spectrum associated with monilethrix.
explanation: >-
Reports novel causal KRT86 variants in independent kindreds.
- name: KRT81
notes: >-
KRT81 encodes a type II hair-cortex keratin and is, with KRT86, one of the
two most commonly implicated genes.
gene_term:
preferred_term: KRT81
term:
id: hgnc:6458
label: KRT81
relationship_type: CAUSATIVE
evidence:
- reference: PMID:25557232
reference_title: "Novel KRT83 and KRT86 mutations associated with monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Mutations in KRT81 and KRT86 are the most common.
explanation: >-
Establishes KRT81 as one of the two most frequent causal genes.
- name: KRT83
notes: >-
KRT83 encodes a type II hair-cortex keratin and is the least commonly
implicated of the three.
gene_term:
preferred_term: KRT83
term:
id: hgnc:6460
label: KRT83
relationship_type: CAUSATIVE
evidence:
- reference: PMID:25557232
reference_title: "Novel KRT83 and KRT86 mutations associated with monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
In the French and Dutch patients, we found novel KRT86 and KRT83 mutations. Our findings expand the mutational spectrum associated with monilethrix.
explanation: >-
Reports novel causal KRT83 variants.
- name: DSG4
notes: >-
DSG4 (desmoglein 4) causes a recessive form of monilethrix that reaches the
same beaded-hair phenotype through desmosomal rather than keratin failure.
It is recorded here for completeness of the genetic spectrum; this entry's
pathophysiology models the dominant keratin-associated disease only, and the
DSG4 route belongs mechanistically with `desmosomal_adhesion_failure`.
gene_term:
preferred_term: DSG4
term:
id: hgnc:21307
label: DSG4
relationship_type: CAUSATIVE
evidence:
- reference: PMID:30969635
reference_title: "Monilethrix."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Monilethrix typically transmits in an autosomal dominant mode
explanation: >-
Supports only that dominant transmission is the typical mode, which is the
contrast against which the recessive DSG4 form is recorded. This entry
does not cite direct evidence for DSG4 causation, and the gene is listed
for spectrum completeness rather than as a curated mechanism.
treatments:
- name: Supportive Hair Care and Trauma Avoidance
description: >-
No specific therapy corrects the keratin defect. Because breakage is
mechanical, gentle hair care and avoidance of physical and chemical trauma
are the mainstay. Oral acitretin, topical and oral minoxidil, and oral
N-acetylcysteine have all been reported, but only at case-report and small
case-series level with inconsistent and often non-sustained benefit, so
none is curated here as an effective treatment. They are named rather than
silently omitted so a later curator can see what was considered.
therapeutic_modality: BEHAVIORAL
treatment_term:
preferred_term: Supportive care
term:
id: NCIT:C15747
label: Supportive Care
evidence:
- reference: PMID:23723505
reference_title: "Monilethrix: a rare hereditary condition."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Monilethrix remains as a therapeutic challenge for dermatologists.
explanation: >-
Supports the absence of an established effective therapy, which is the
rationale for a supportive approach.
- name: Genetic Counseling
description: >-
Counseling for autosomal dominant inheritance with variable penetrance,
noting that mildly affected relatives may be unaware they are affected.
treatment_term:
preferred_term: Genetic counseling
term:
id: NCIT:C15240
label: Genetic Counseling
notes: >-
Monilethrix is the hair-cortex conformer of
`keratin_intermediate_filament_fragility`. The module names KRT81/KRT83/KRT86
as a substitutable trigger; this entry supplies the worked example.
Two things about the conformance are deliberately partial and should not be
"tidied". First, the module's effector node is cytolysis, and monilethrix does
not lyse cells - the hair shaft is already dead and keratinized when it fails
- so the entry conforms at the trigger and resilience nodes only. Second, a
recessive DSG4-associated form of monilethrix exists that reaches the same
beaded-hair phenotype through desmoglein-4 rather than keratin failure; that
route belongs mechanistically with `desmosomal_adhesion_failure` and is not
curated in this entry's pathophysiology, which models the dominant
keratin-associated disease only.
One cited report describes a Venezuelan kindred with digenic changes - a
KRT86 variant with a KRT81 variant of unknown significance. This entry does
not curate digenic inheritance, because a variant of unknown significance is
not evidence of a second required locus.
Three pharmacological options reported for monilethrix are deliberately not
curated as treatments: oral acitretin, minoxidil (topical and oral), and oral
N-acetylcysteine. Each rests on case reports or small series with
inconsistent, frequently non-sustained response - one cited report describes
slight improvement on N-acetylcysteine at two months that did not progress -
which is below the bar this knowledge base applies to a treatment claim. They
are named in the supportive-care description so the omission reads as a
judgement rather than an oversight.
This report is retrieval-only and is generated directly from Asta results.
search_papers_by_relevance with snippet_search.Checked with linkml-reference-validator 0.2.1.
| Outcome | Count |
|---|---|
| References checked | 37 |
| Resolved | 37 |
| Unresolved (possible confabulation) | 0 |
| Unverifiable | 0 |
| References weighed for topical relevance | 37 |
| On topic | 17 |
| Off topic | 0 |
All extracted references resolved successfully.