Xeroderma Pigmentosum

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Inheritance

1

Autosomal recessive inheritance HP:0000007

Xeroderma pigmentosum is inherited in an autosomal recessive manner and is established by biallelic pathogenic variants in XP-related DNA repair genes.

Autosomal recessive inheritance

Show evidence (1 reference)

PMID:20301571 SUPPORT Other

"XP is inherited in an autosomal recessive manner. If both parents are known to be heterozygous for an XP-related pathogenic variant, each sib of an affected individual has at conception a 25% chance of being affected."

GeneReviews explicitly states autosomal recessive inheritance and recurrence risk.

◆

Subtypes

8

xeroderma pigmentosum complementation group A MONDO:0010210

XPA link

XP-A is caused by biallelic XPA pathogenic variants and is one of the XP subtypes with prominent neurologic disease.

Show evidence (1 reference)

DOI:10.1093/brain/awad266 SUPPORT Human Clinical

"XP results from biallelic mutations in any of eight genes involved in DNA repair systems, thus defining eight different genotypes (XPA, XPB, XPC, XPD, XPE, XPF, XPG and XP variant or XPV)."

This abstract supports XP-A as one of the canonical xeroderma pigmentosum complementation groups.

xeroderma pigmentosum complementation group B MONDO:0012531

ERCC3 link

XP-B is caused by biallelic ERCC3 pathogenic variants.

Show evidence (1 reference)

DOI:10.1093/brain/awad266 SUPPORT Human Clinical

"XP results from biallelic mutations in any of eight genes involved in DNA repair systems, thus defining eight different genotypes (XPA, XPB, XPC, XPD, XPE, XPF, XPG and XP variant or XPV)."

This abstract supports XP-B as one of the canonical xeroderma pigmentosum complementation groups.

xeroderma pigmentosum complementation group C MONDO:0010211

XPC link

XP-C is caused by biallelic XPC pathogenic variants and is often dominated by cutaneous and ocular disease.

Show evidence (1 reference)

DOI:10.1093/brain/awad266 SUPPORT Human Clinical

"XP results from biallelic mutations in any of eight genes involved in DNA repair systems, thus defining eight different genotypes (XPA, XPB, XPC, XPD, XPE, XPF, XPG and XP variant or XPV)."

This abstract supports XP-C as one of the canonical xeroderma pigmentosum complementation groups.

xeroderma pigmentosum complementation group D MONDO:0010212

ERCC2 link

XP-D is caused by biallelic ERCC2 pathogenic variants and is enriched for progressive neurologic involvement.

Show evidence (1 reference)

DOI:10.1093/brain/awad266 SUPPORT Human Clinical

"XP results from biallelic mutations in any of eight genes involved in DNA repair systems, thus defining eight different genotypes (XPA, XPB, XPC, XPD, XPE, XPF, XPG and XP variant or XPV)."

This abstract supports XP-D as one of the canonical xeroderma pigmentosum complementation groups.

xeroderma pigmentosum complementation group E MONDO:0010213

DDB2 link

XP-E is caused by biallelic DDB2 pathogenic variants.

Show evidence (1 reference)

DOI:10.1093/brain/awad266 SUPPORT Human Clinical

"XP results from biallelic mutations in any of eight genes involved in DNA repair systems, thus defining eight different genotypes (XPA, XPB, XPC, XPD, XPE, XPF, XPG and XP variant or XPV)."

This abstract supports XP-E as one of the canonical xeroderma pigmentosum complementation groups.

xeroderma pigmentosum complementation group F MONDO:0010215

ERCC4 link

XP-F is caused by biallelic ERCC4 pathogenic variants, including deep intronic founder alleles described in Japan.

Show evidence (1 reference)

DOI:10.1093/brain/awad266 SUPPORT Human Clinical

"XP results from biallelic mutations in any of eight genes involved in DNA repair systems, thus defining eight different genotypes (XPA, XPB, XPC, XPD, XPE, XPF, XPG and XP variant or XPV)."

This abstract supports XP-F as one of the canonical xeroderma pigmentosum complementation groups.

xeroderma pigmentosum complementation group G MONDO:0010216

ERCC5 link

XP-G is caused by biallelic ERCC5 pathogenic variants and is one of the subtypes enriched for neurologic disability; ERCC5 variants can also produce xeroderma pigmentosum-Cockayne syndrome overlap phenotypes.

Show evidence (2 references)

DOI:10.1093/brain/awad266 SUPPORT Human Clinical

"XP results from biallelic mutations in any of eight genes involved in DNA repair systems, thus defining eight different genotypes (XPA, XPB, XPC, XPD, XPE, XPF, XPG and XP variant or XPV)."

This abstract supports XP-G as one of the canonical xeroderma pigmentosum complementation groups.

PMID:37848274 SUPPORT Human Clinical

"Xeroderma pigmentosum-Cockayne syndrome complex (XP-CS) is exceedingly rare, with 43 cases described over the past five decades; 21 of these cases exhibited mutations in the ERCC5 endonuclease associated with xeroderma pigmentosum, group G."

This case report supports ERCC5-associated XP-G as a known source of XP-Cockayne overlap phenotypes.

xeroderma pigmentosum variant MONDO:0010214

POLH link

XP-V is caused by biallelic POLH pathogenic variants and reflects a defect in error-free translesion synthesis.

Show evidence (1 reference)

DOI:10.1093/brain/awad266 SUPPORT Human Clinical

"XP results from biallelic mutations in any of eight genes involved in DNA repair systems, thus defining eight different genotypes (XPA, XPB, XPC, XPD, XPE, XPF, XPG and XP variant or XPV)."

This abstract supports XP-V as one of the canonical xeroderma pigmentosum complementation groups.

⚙

Pathophysiology

6

UV-induced DNA photoproduct formation

Ultraviolet exposure creates DNA damage that XP cells cannot adequately process, making sunlight the dominant upstream trigger for disease biology in skin and ocular tissues.

keratinocyte link melanocyte link

response to UV link ⚠ ABNORMAL

Downstream

Impaired nucleotide-excision repair UV photoproducts persist because the canonical XP repair network is defective.

Show evidence (1 reference)

PMID:35520754 SUPPORT Other

"Xeroderma pigmentosum is a condition of abnormal DNA repair of ultraviolet radiation-induced and oxidative DNA damage, which leads to increased skin cancer susceptibility."

The review supports UV-induced DNA damage as the initiating lesion in XP.

Impaired nucleotide-excision repair

Biallelic pathogenic variants in core XP genes compromise nucleotide-excision repair and prevent efficient removal of ultraviolet-induced bulky DNA lesions.

XPA link XPC link ERCC2 link ERCC3 link DDB2 link ERCC4 link ERCC5 link

nucleotide-excision repair link ⚠ ABNORMAL

Downstream

Defective error-free translesion synthesis in XP-V POLH deficiency creates an alternative route to XP through failed lesion bypass during replication.

UV-signature mutagenesis and tumor mutation burden Persistent DNA lesions increase the mutational load in sun-exposed tissues.

Show evidence (1 reference)

DOI:10.1038/s41467-023-38311-0 SUPPORT Human Clinical

"Xeroderma pigmentosum (XP) is a genetic disorder caused by mutations in genes of the Nucleotide Excision Repair (NER) pathway (groups A-G) or in Translesion Synthesis DNA polymerase η (V)."

The Nature Communications abstract directly supports NER deficiency as the core XP mechanism.

Defective error-free translesion synthesis in XP-V

In XP-V, POLH deficiency impairs error-free translesion synthesis across UV photolesions, generating a distinct route to mutagenesis despite an intact excision machinery.

POLH link

translesion synthesis link ↓ DECREASED

Downstream

UV-signature mutagenesis and tumor mutation burden Failed lesion bypass contributes to the distinctive mutational spectra of XP-V tumors.

Show evidence (1 reference)

DOI:10.1038/s41467-023-38311-0 SUPPORT Human Clinical

"Mutational profile in XP-V tumors and experiments with POLH knockout cell line reveal the role of polymerase η in the error-free bypass of (i) rare TpG and TpA DNA lesions, (ii) 3' nucleotides in pyrimidine dimers, and (iii) TpT photodimers."

The tumor-genomics paper supports XP-V as a lesion-bypass defect centered on POLH.

UV-signature mutagenesis and tumor mutation burden

Persistent unrepaired or inaccurately bypassed UV lesions produce the high mutational burden and UV-signature mutations that underlie XP skin-cancer susceptibility.

keratinocyte link melanocyte link

Downstream

Cutaneous carcinogenesis Extreme UV-driven mutagenesis promotes early basal cell carcinoma, squamous cell carcinoma, and melanoma.

Show evidence (1 reference)

DOI:10.1038/s41467-023-38311-0 SUPPORT Human Clinical

"XP is associated with an increased skin cancer risk, reaching, for some groups, several thousand-fold compared to the general population."

The 2023 tumor-genomics study links defective repair to extreme mutagenic cancer risk.

Cutaneous carcinogenesis

XP dramatically accelerates development of sunlight-induced basal cell carcinoma, squamous cell carcinoma, and melanoma, often beginning in the first decade of life.

Downstream

Progressive neurologic vulnerability In susceptible genotypes, DNA repair failure also contributes to neuronal damage and disability.

Show evidence (1 reference)

PMID:20301571 SUPPORT Other

"Greatly increased risk of sunlight-induced cutaneous neoplasms (basal cell carcinoma, squamous cell carcinoma, melanoma) within the first decade of life."

GeneReviews directly supports early carcinogenesis as a core downstream consequence of XP.

Progressive neurologic vulnerability

In neurologically affected XP genotypes, neural cells show impaired DNA repair and heightened apoptosis, providing a mechanistic route to ataxia, hearing loss, and cognitive decline.

neuron link

apoptotic process link ↑ INCREASED

Show evidence (1 reference)

PMID:26874523 SUPPORT In Vitro

"Mutation of XPA in either neural stem cells (NSCs) or neurons resulted in severe DNA damage repair defects, and these neural cells with mutant XPA were hyper-sensitive to DNA damage-induced apoptosis."

Patient-derived neural-cell models support a repair-defect to apoptosis mechanism for XP neurodegeneration.

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Pathograph

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Phenotypes

13

Ear 1

Sensorineural hearing impairment Sensorineural hearing impairment (HP:0000407)

Show evidence (1 reference)

PMID:20301571 SUPPORT Other

"Approximately 25% of affected individuals have neurologic manifestations (acquired microcephaly, diminished or absent deep tendon stretch reflexes, progressive sensorineural hearing loss, progressive cognitive impairment, and ataxia)."

GeneReviews directly lists progressive sensorineural hearing loss among core XP neurologic features.

Eye 1

Photophobia Photophobia (HP:0000613)

Show evidence (1 reference)

PMID:28554534 SUPPORT Human Clinical

"Ninety-three percent of XP patients in our cohort had ocular involvement, with 65% describing photophobia."

The UK ophthalmology cohort quantifies photophobia as a common XP manifestation.

Integument 4

Photosensitivity Cutaneous photosensitivity (HP:0000992)

Show evidence (1 reference)

PMID:20301571 SUPPORT Other

"Acute sun sensitivity (severe sunburn with blistering, persistent erythema on minimal sun exposure)."

GeneReviews directly supports severe photosensitivity as a defining XP phenotype.

Freckling in sun-exposed skin Freckling (HP:0001480)

Show evidence (1 reference)

PMID:20301571 SUPPORT Other

"marked freckle-like pigmentation of the face before age two years"

GeneReviews directly supports early pigmentary change as a hallmark XP phenotype.

Basal cell carcinoma Basal cell carcinoma (HP:0002671)

Show evidence (1 reference)

PMID:20301571 SUPPORT Other

"Greatly increased risk of sunlight-induced cutaneous neoplasms (basal cell carcinoma, squamous cell carcinoma, melanoma) within the first decade of life."

GeneReviews directly lists basal cell carcinoma as a characteristic early XP malignancy.

Squamous cell carcinoma of the skin Squamous cell carcinoma of the skin (HP:0006739)

Show evidence (1 reference)

PMID:20301571 SUPPORT Other

"Greatly increased risk of sunlight-induced cutaneous neoplasms (basal cell carcinoma, squamous cell carcinoma, melanoma) within the first decade of life."

GeneReviews directly lists cutaneous squamous cell carcinoma as a characteristic XP malignancy.

Nervous System 4

Peripheral neuropathy Peripheral neuropathy (HP:0009830)

Show evidence (1 reference)

DOI:10.1093/brain/awad266 SUPPORT Human Clinical

"Cerebellar and global brain atrophy, axonal sensory and sensorimotor neuropathies, and sensorineural hearing loss were common findings in patients."

The prospective cohort directly supports peripheral neuropathy as a common neurologic manifestation in XP.

Dystonia Dystonia (HP:0001332)

Show evidence (1 reference)

DOI:10.1093/brain/awad266 SUPPORT Human Clinical

"Hyporeflexia, hypopallesthaesia, upper motor neuron signs, chorea, dystonia, oculomotor signs and cognitive impairment were frequent findings in XPA, XPD and XPG."

The prospective cohort identifies dystonia as a frequent neurologic sign in XPA, XPD, and XPG disease.

Cognitive impairment Cognitive impairment (HP:0100543)

Show evidence (1 reference)

PMID:20301571 SUPPORT Other

"Approximately 25% of affected individuals have neurologic manifestations (acquired microcephaly, diminished or absent deep tendon stretch reflexes, progressive sensorineural hearing loss, progressive cognitive impairment, and ataxia)."

GeneReviews directly supports progressive cognitive impairment in XP.

Progressive cerebellar ataxia Progressive cerebellar ataxia (HP:0002073)

Show evidence (1 reference)

DOI:10.1093/brain/awad266 SUPPORT Human Clinical

"SARA total scores significantly increased over time in XPD (0.91 points/year, 95% confidence interval: 0.61, 1.21) and XPA (0.63 points/year, 95% confidence interval: 0.38, 0.89)."

The prospective cohort quantifies progressive ataxia in XPA and XPD.

Other 3

Ocular involvement

Show evidence (1 reference)

PMID:28554534 SUPPORT Human Clinical

"Ninety-three percent of XP patients in our cohort had ocular involvement, with 65% describing photophobia. The most common abnormalities were in the periocular skin and ocular surface, including interpalpebral conjunctival melanosis (44%) and conjunctival injection (43%). Eleven percent of..."

The UK cohort establishes ocular involvement as a highly prevalent clinical domain in XP.

Cutaneous melanoma Melanoma (HP:0002861)

Show evidence (1 reference)

PMID:20301571 SUPPORT Other

"Greatly increased risk of sunlight-induced cutaneous neoplasms (basal cell carcinoma, squamous cell carcinoma, melanoma) within the first decade of life."

GeneReviews directly lists melanoma as part of the classic XP cancer spectrum.

Hyporeflexia Hyporeflexia (HP:0001265)

Show evidence (1 reference)

DOI:10.1093/brain/awad266 SUPPORT Human Clinical

"Hyporeflexia, hypopallesthaesia, upper motor neuron signs, chorea, dystonia, oculomotor signs and cognitive impairment were frequent findings in XPA, XPD and XPG."

The prospective cohort identifies hyporeflexia as a frequent neurologic sign in the neurodegenerative XP genotypes.

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Genetic Associations

4

Core nucleotide-excision repair genes (Causative)

Show evidence (1 reference)

DOI:10.1093/brain/awad266 SUPPORT Human Clinical

"XP results from biallelic mutations in any of eight genes involved in DNA repair systems, thus defining eight different genotypes (XPA, XPB, XPC, XPD, XPE, XPF, XPG and XP variant or XPV)."

The cohort abstract establishes the canonical complementation-group architecture of XP.

POLH pathogenic variants (Causative)

Show evidence (1 reference)

DOI:10.1038/s41467-023-38311-0 SUPPORT Human Clinical

"Xeroderma pigmentosum (XP) is a genetic disorder caused by mutations in genes of the Nucleotide Excision Repair (NER) pathway (groups A-G) or in Translesion Synthesis DNA polymerase η (V)."

The Nature Communications abstract directly supports POLH as the causative gene for XP-V.

XPA genotype-severity correlations (Modifier of neurologic severity)

Show evidence (1 reference)

DOI:10.1371/journal.pgen.1011265 SUPPORT Human Clinical

"Our findings revealed correlations between disease severity, DNA repair capacity, and XPA variant type and location."

The 2024 XPA natural-history study supports genotype-based prognostic stratification within XP-A.

ERCC4 deep intronic founder variants (Causative)

Show evidence (1 reference)

DOI:10.1073/pnas.2217423120 SUPPORT Human Clinical

"The first variant, located in intron 1, is a Japanese founder mutation, which additionally accounts for ~10% of the entire Japanese XP cases."

The PNAS abstract supports a clinically important non-coding ERCC4 founder mechanism in XP-F.

💊

Treatments

5

Rigorous ultraviolet avoidance

Lifelong photoprotection with strict sun avoidance, protective clothing, sunscreen, and UV reduction is the core management strategy in XP.

Show evidence (1 reference)

PMID:35520754 SUPPORT Other

"Strict and consistent sun avoidance and protection and early detection and treatment of premalignant and malignant skin lesions are the mainstays of management."

The updated review directly supports rigorous UV avoidance and protection as standard of care.

Dermatologic and ophthalmologic surveillance

Action: supportive care MAXO:0000950

Regular skin examinations, eye examinations, neurologic follow-up, and audiograms are recommended to detect premalignant lesions, ocular injury, and progressive neurologic complications early.

Show evidence (1 reference)

PMID:20301571 SUPPORT Other

"Surveillance: Skin examinations by a physician every three to 12 months; eye exams for signs of UV exposure and damage every six months; routine eye and neurologic examinations for progressive neurologic abnormalities every 12 months; audiograms every six to12 months."

GeneReviews provides explicit surveillance intervals for multidisciplinary XP follow-up.

Local treatment of premalignant and malignant skin lesions

Actinic keratoses and skin cancers are managed with local therapies such as cryotherapy, topical field therapy, curettage, Mohs surgery, or surgical excision depending on lesion burden and recurrence risk.

Show evidence (1 reference)

PMID:20301571 SUPPORT Other

"Premalignant skin lesions such as actinic keratoses can be treated by freezing with liquid nitrogen; larger areas can be treated with field treatments such as topical 5-fluorouracil or imiquimod preparations. Rarely, therapeutic dermatome shaving or dermabrasion has been used; skin neoplasms can..."

GeneReviews directly supports lesion-directed dermatologic management in XP.

Oral isotretinoin chemoprevention

High-dose oral isotretinoin can reduce new skin-cancer formation in selected high-risk XP patients, but toxicity limits long-term use.

Show evidence (1 reference)

PMID:3287161 SUPPORT Human Clinical

"During two years of treatment with isotretinoin, there were 25 tumors (mean, 5; range, 3 to 9), with an average reduction in skin cancers of 63 percent (P = 0.019)."

The prospective study provides direct chemoprevention evidence for isotretinoin in XP.

Genetic counseling

Action: genetic counseling MAXO:0000079

Genetic counseling supports recurrence-risk assessment, testing of at-risk relatives, and reproductive planning in affected families.

Show evidence (1 reference)

PMID:20301571 SUPPORT Other

"Once the XP-related pathogenic variants have been identified in an affected family member, prenatal testing for a pregnancy at increased risk and preimplantation genetic testing for XP are possible."

GeneReviews supports family counseling and cascade testing implications for XP.

🌍

Environmental Factors

1

Ultraviolet radiation exposure

Ultraviolet radiation is the dominant environmental exposure that drives DNA damage, clinical photosensitivity, and carcinogenesis in xeroderma pigmentosum.

Show evidence (1 reference)

PMID:35520754 SUPPORT Other

"Early recognition of xeroderma pigmentosum is important to minimize the complications arising from the harmful effects of exposure to ultraviolet radiation."

The updated review identifies UV radiation exposure as the main harmful external driver of disease complications.

🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Xeroderma Pigmentosum:

Cockayne syndrome MONDO:0016006

Overlapping Features Cockayne syndrome can overlap clinically with xeroderma pigmentosum through ultraviolet sensitivity and neurologic dysfunction, particularly in patients with severe neurodegeneration out of proportion to cutaneous cancer burden.

Distinguishing Features

Recovery of RNA synthesis after UV exposure is abnormal in Cockayne syndrome, whereas classic XP is defined by a DNA excision-repair defect or XP-variant replication defect.
Severe neurologic disease with relatively mild cutaneous abnormalities should raise concern for Cockayne syndrome or an overlap phenotype rather than classic XP alone.

Show evidence (1 reference)

PMID:1372469 SUPPORT Human Clinical

"Rather, a failure of RNA synthesis to recover to normal levels after UV exposure was observed, a biochemical abnormality seen in Cockayne syndrome (CS), one of the premature-aging syndromes with clinical UV sensitivity."

This abstract directly supports Cockayne syndrome as a biochemical and clinical differential for XP-like photosensitive neurologic disease.

Trichothiodystrophy Not Yet Curated MONDO:0018053

Overlapping Features Trichothiodystrophy caused by ERCC2 variants overlaps with XP because both disorders involve DNA-repair genes and photosensitivity-associated neurodevelopmental disease, but TTD has a distinct syndromic presentation.

Distinguishing Features

Classic TTD findings and progressive hypomyelination can distinguish ERCC2-related TTD from XP.
Clinical and paraclinical evaluation can separate TTD from Cockayne syndrome and XP even when the causal gene overlaps.

Show evidence (1 reference)

PMID:39976384 SUPPORT Human Clinical

"Clinical and paraclinical findings enabled differentiation of TTD from Cockayne syndrome and XP."

This abstract directly supports trichothiodystrophy as an ERCC2-related differential diagnosis that can be separated from XP clinically.

🔬

Clinical Trials

4

NCT00002811 PHASE_III

Phase III randomized trial of T4N5 liposome lotion versus placebo to reduce actinic keratoses and other sun-induced skin damage in XP.

Show evidence (1 reference)

clinicaltrials:NCT00002811 SUPPORT Other

"Randomized double-blinded phase III trial to compare treatment using T4N5 liposome lotion with treatment using placebo in reducing actinic keratoses and other sun-induced skin damage in patients with xeroderma pigmentosum."

The ClinicalTrials.gov record directly supports the T4N5 chemoprevention trial.

NCT03445052 NOT_APPLICABLE

XPAND is a randomized controlled trial testing a personalized adherence intervention to improve photoprotection behavior and reduce UVR reaching the face in adults with XP.

Show evidence (1 reference)

clinicaltrials:NCT03445052 SUPPORT Other

"This research will test whether an intervention designed to enhance photoprotection activities is successful. It will use a randomised controlled trial design to compare the amount of UVR reaching the face."

The trial record supports behavioral photoprotection as an active interventional research area in XP.

NCT05159752 PHASE_II

Open-label phase IIa afamelanotide study in XP-C designed to assess safety, UV-provoked DNA damage, and reparative endpoints.

Show evidence (1 reference)

clinicaltrials:NCT05159752 SUPPORT Other

"The CUV156 study will evaluate the safety of afamelanotide in XP-C patients, as well as the drug's ability to assist reparative processes following ultraviolet (UV) provoked DNA damage of the skin."

The record supports afamelanotide as an active investigational therapy in XP-C.

NCT05370235 PHASE_II

Open-label phase IIa afamelanotide study in XP-C and XP-V assessing safety, UV-provoked DNA damage, and repair-related endpoints.

Show evidence (1 reference)

clinicaltrials:NCT05370235 SUPPORT Other

"The CUV152 study will evaluate the safety of afamelanotide in XP-C and XP-V patients, as well as the drug's ability to assist reparative processes following ultraviolet (UV) provoked DNA damage of the skin."

The record supports ongoing genotype-targeted afamelanotide trials in XP.

{ }

Source YAML

click to show

name: Xeroderma Pigmentosum
creation_date: "2026-05-13T00:00:00Z"
updated_date: "2026-05-13T16:40:00Z"
description: >-
  Xeroderma pigmentosum is a rare autosomal recessive DNA repair disorder caused
  by biallelic pathogenic variants in nucleotide-excision repair genes or POLH,
  leading to extreme ultraviolet sensitivity, early pigmentary change, marked
  skin-cancer susceptibility, ocular surface disease, and genotype-enriched
  progressive neurodegeneration.
category: Mendelian
parents:
- hereditary disease
- Cancer Predisposition Syndrome
synonyms:
- XP
has_subtypes:
- name: XP-A
  display_name: xeroderma pigmentosum complementation group A
  subtype_term:
    preferred_term: xeroderma pigmentosum group A
    term:
      id: MONDO:0010210
      label: xeroderma pigmentosum group A
  description: >-
    XP-A is caused by biallelic XPA pathogenic variants and is one of the XP
    subtypes with prominent neurologic disease.
  genes:
  - preferred_term: XPA
    term:
      id: hgnc:12814
      label: XPA
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      XP results from biallelic mutations in any of eight genes involved in DNA
      repair systems, thus defining eight different genotypes (XPA, XPB, XPC,
      XPD, XPE, XPF, XPG and XP variant or XPV).
    explanation: This abstract supports XP-A as one of the canonical xeroderma pigmentosum complementation groups.
- name: XP-B
  display_name: xeroderma pigmentosum complementation group B
  subtype_term:
    preferred_term: xeroderma pigmentosum group B
    term:
      id: MONDO:0012531
      label: xeroderma pigmentosum group B
  description: >-
    XP-B is caused by biallelic ERCC3 pathogenic variants.
  genes:
  - preferred_term: ERCC3
    term:
      id: hgnc:3435
      label: ERCC3
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      XP results from biallelic mutations in any of eight genes involved in DNA
      repair systems, thus defining eight different genotypes (XPA, XPB, XPC,
      XPD, XPE, XPF, XPG and XP variant or XPV).
    explanation: This abstract supports XP-B as one of the canonical xeroderma pigmentosum complementation groups.
- name: XP-C
  display_name: xeroderma pigmentosum complementation group C
  subtype_term:
    preferred_term: xeroderma pigmentosum group C
    term:
      id: MONDO:0010211
      label: xeroderma pigmentosum group C
  description: >-
    XP-C is caused by biallelic XPC pathogenic variants and is often dominated
    by cutaneous and ocular disease.
  genes:
  - preferred_term: XPC
    term:
      id: hgnc:12816
      label: XPC
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      XP results from biallelic mutations in any of eight genes involved in DNA
      repair systems, thus defining eight different genotypes (XPA, XPB, XPC,
      XPD, XPE, XPF, XPG and XP variant or XPV).
    explanation: This abstract supports XP-C as one of the canonical xeroderma pigmentosum complementation groups.
- name: XP-D
  display_name: xeroderma pigmentosum complementation group D
  subtype_term:
    preferred_term: xeroderma pigmentosum group D
    term:
      id: MONDO:0010212
      label: xeroderma pigmentosum group D
  description: >-
    XP-D is caused by biallelic ERCC2 pathogenic variants and is enriched for
    progressive neurologic involvement.
  genes:
  - preferred_term: ERCC2
    term:
      id: hgnc:3434
      label: ERCC2
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      XP results from biallelic mutations in any of eight genes involved in DNA
      repair systems, thus defining eight different genotypes (XPA, XPB, XPC,
      XPD, XPE, XPF, XPG and XP variant or XPV).
    explanation: This abstract supports XP-D as one of the canonical xeroderma pigmentosum complementation groups.
- name: XP-E
  display_name: xeroderma pigmentosum complementation group E
  subtype_term:
    preferred_term: xeroderma pigmentosum group E
    term:
      id: MONDO:0010213
      label: xeroderma pigmentosum group E
  description: >-
    XP-E is caused by biallelic DDB2 pathogenic variants.
  genes:
  - preferred_term: DDB2
    term:
      id: hgnc:2718
      label: DDB2
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      XP results from biallelic mutations in any of eight genes involved in DNA
      repair systems, thus defining eight different genotypes (XPA, XPB, XPC,
      XPD, XPE, XPF, XPG and XP variant or XPV).
    explanation: This abstract supports XP-E as one of the canonical xeroderma pigmentosum complementation groups.
- name: XP-F
  display_name: xeroderma pigmentosum complementation group F
  subtype_term:
    preferred_term: xeroderma pigmentosum group F
    term:
      id: MONDO:0010215
      label: xeroderma pigmentosum group F
  description: >-
    XP-F is caused by biallelic ERCC4 pathogenic variants, including deep
    intronic founder alleles described in Japan.
  genes:
  - preferred_term: ERCC4
    term:
      id: hgnc:3436
      label: ERCC4
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      XP results from biallelic mutations in any of eight genes involved in DNA
      repair systems, thus defining eight different genotypes (XPA, XPB, XPC,
      XPD, XPE, XPF, XPG and XP variant or XPV).
    explanation: This abstract supports XP-F as one of the canonical xeroderma pigmentosum complementation groups.
- name: XP-G
  display_name: xeroderma pigmentosum complementation group G
  subtype_term:
    preferred_term: xeroderma pigmentosum group G
    term:
      id: MONDO:0010216
      label: xeroderma pigmentosum group G
  description: >-
    XP-G is caused by biallelic ERCC5 pathogenic variants and is one of the
    subtypes enriched for neurologic disability; ERCC5 variants can also produce
    xeroderma pigmentosum-Cockayne syndrome overlap phenotypes.
  genes:
  - preferred_term: ERCC5
    term:
      id: hgnc:3437
      label: ERCC5
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      XP results from biallelic mutations in any of eight genes involved in DNA
      repair systems, thus defining eight different genotypes (XPA, XPB, XPC,
      XPD, XPE, XPF, XPG and XP variant or XPV).
    explanation: This abstract supports XP-G as one of the canonical xeroderma pigmentosum complementation groups.
  - reference: PMID:37848274
    reference_title: Characterisation of a novel missense mutation in the ERCC5 gene leading to group G xeroderma pigmentosum/Cockayne syndrome overlap.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Xeroderma pigmentosum-Cockayne syndrome complex (XP-CS) is exceedingly
      rare, with 43 cases described over the past five decades; 21 of these
      cases exhibited mutations in the ERCC5 endonuclease associated with
      xeroderma pigmentosum, group G.
    explanation: This case report supports ERCC5-associated XP-G as a known source of XP-Cockayne overlap phenotypes.
- name: XP-V
  display_name: xeroderma pigmentosum variant
  subtype_term:
    preferred_term: xeroderma pigmentosum variant type
    term:
      id: MONDO:0010214
      label: xeroderma pigmentosum variant type
  description: >-
    XP-V is caused by biallelic POLH pathogenic variants and reflects a defect
    in error-free translesion synthesis.
  genes:
  - preferred_term: POLH
    term:
      id: hgnc:9181
      label: POLH
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      XP results from biallelic mutations in any of eight genes involved in DNA
      repair systems, thus defining eight different genotypes (XPA, XPB, XPC,
      XPD, XPE, XPF, XPG and XP variant or XPV).
    explanation: This abstract supports XP-V as one of the canonical xeroderma pigmentosum complementation groups.
disease_term:
  preferred_term: xeroderma pigmentosum
  term:
    id: MONDO:0019600
    label: xeroderma pigmentosum
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Xeroderma pigmentosum is inherited in an autosomal recessive manner and is
    established by biallelic pathogenic variants in XP-related DNA repair genes.
  evidence:
  - reference: PMID:20301571
    reference_title: Xeroderma Pigmentosum.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      XP is inherited in an autosomal recessive manner. If both parents are
      known to be heterozygous for an XP-related pathogenic variant, each sib
      of an affected individual has at conception a 25% chance of being
      affected.
    explanation: GeneReviews explicitly states autosomal recessive inheritance and recurrence risk.
prevalence:
- population: Worldwide
  notes: >-
    The worldwide prevalence of xeroderma pigmentosum is roughly 1 to 4 per
    million, with much higher incidence in founder populations.
  evidence:
  - reference: DOI:10.1073/pnas.2217423120
    reference_title: "Deep intronic founder mutations identified in the ERCC4/XPF gene are potential therapeutic targets for a high-frequency form of xeroderma pigmentosum"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The worldwide prevalence of XP is ~1 to 4 in million, with higher
      incidence in some countries and regions including Japan (1 in 22,000) and
      North Africa due to founder mutations and a high degree of consanguinity.
    explanation: The PNAS abstract provides a usable prevalence range and notes strong founder effects.
- population: Japan
  notes: >-
    Japan has one of the highest reported xeroderma pigmentosum prevalences.
  evidence:
  - reference: DOI:10.1073/pnas.2217423120
    reference_title: "Deep intronic founder mutations identified in the ERCC4/XPF gene are potential therapeutic targets for a high-frequency form of xeroderma pigmentosum"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The worldwide prevalence of XP is ~1 to 4 in million, with higher
      incidence in some countries and regions including Japan (1 in 22,000) and
      North Africa due to founder mutations and a high degree of consanguinity.
    explanation: The abstract gives a specific Japan prevalence estimate.
progression:
- phase: Early cutaneous and ocular disease
  age_range: infancy to early childhood
  notes: >-
    Photosensitivity, freckle-like facial pigmentation, and ocular findings are
    typically recognized first and often precede later neurologic complications.
  evidence:
  - reference: PMID:20301571
    reference_title: Xeroderma Pigmentosum.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Acute sun sensitivity (severe sunburn with blistering, persistent
      erythema on minimal sun exposure) with marked freckle-like pigmentation
      of the face before age two years; Sunlight-induced ocular involvement
      (photophobia, severe keratitis, atrophy of the skin of the lids, ocular
      surface neoplasms);
    explanation: GeneReviews supports early-onset cutaneous and ocular manifestations.
- phase: Progressive neurologic disease in susceptible genotypes
  age_range: childhood through adulthood
  notes: >-
    Neurologic disease is genotype enriched, usually follows the cutaneous and
    ophthalmologic phenotype, and progresses measurably in XPA and XPD.
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Thirty-six (38.7%) reported neurological symptoms, especially in the
      XPA, XPD and XPG groups, with early-onset and late-onset forms, and
      typically appearing after cutaneous and ophthalmological symptoms.
    explanation: The UK cohort directly supports the typical temporal sequence and genotype dependence of neurologic progression.
pathophysiology:
- name: UV-induced DNA photoproduct formation
  description: >-
    Ultraviolet exposure creates DNA damage that XP cells cannot adequately
    process, making sunlight the dominant upstream trigger for disease biology
    in skin and ocular tissues.
  cell_types:
  - preferred_term: keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
  - preferred_term: melanocyte
    term:
      id: CL:0000148
      label: melanocyte
  biological_processes:
  - preferred_term: response to UV
    modifier: ABNORMAL
    term:
      id: GO:0009411
      label: response to UV
  evidence:
  - reference: PMID:35520754
    reference_title: "Xeroderma pigmentosum: an updated review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Xeroderma pigmentosum is a condition of abnormal DNA repair of
      ultraviolet radiation-induced and oxidative DNA damage, which leads to
      increased skin cancer susceptibility.
    explanation: The review supports UV-induced DNA damage as the initiating lesion in XP.
  downstream:
  - target: Impaired nucleotide-excision repair
    description: UV photoproducts persist because the canonical XP repair network is defective.
- name: Impaired nucleotide-excision repair
  description: >-
    Biallelic pathogenic variants in core XP genes compromise nucleotide-excision
    repair and prevent efficient removal of ultraviolet-induced bulky DNA
    lesions.
  genes:
  - preferred_term: XPA
    term:
      id: hgnc:12814
      label: XPA
  - preferred_term: XPC
    term:
      id: hgnc:12816
      label: XPC
  - preferred_term: ERCC2
    term:
      id: hgnc:3434
      label: ERCC2
  - preferred_term: ERCC3
    term:
      id: hgnc:3435
      label: ERCC3
  - preferred_term: DDB2
    term:
      id: hgnc:2718
      label: DDB2
  - preferred_term: ERCC4
    term:
      id: hgnc:3436
      label: ERCC4
  - preferred_term: ERCC5
    term:
      id: hgnc:3437
      label: ERCC5
  biological_processes:
  - preferred_term: nucleotide-excision repair
    modifier: ABNORMAL
    term:
      id: GO:0006289
      label: nucleotide-excision repair
  evidence:
  - reference: DOI:10.1038/s41467-023-38311-0
    reference_title: Genomic mutation landscape of skin cancers from DNA repair-deficient xeroderma pigmentosum patients
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Xeroderma pigmentosum (XP) is a genetic disorder caused by mutations
      in genes of the Nucleotide Excision Repair (NER) pathway (groups A-G) or
      in Translesion Synthesis DNA polymerase η (V).
    explanation: The Nature Communications abstract directly supports NER deficiency as the core XP mechanism.
  downstream:
  - target: Defective error-free translesion synthesis in XP-V
    description: POLH deficiency creates an alternative route to XP through failed lesion bypass during replication.
  - target: UV-signature mutagenesis and tumor mutation burden
    description: Persistent DNA lesions increase the mutational load in sun-exposed tissues.
- name: Defective error-free translesion synthesis in XP-V
  description: >-
    In XP-V, POLH deficiency impairs error-free translesion synthesis across UV
    photolesions, generating a distinct route to mutagenesis despite an intact
    excision machinery.
  genes:
  - preferred_term: POLH
    term:
      id: hgnc:9181
      label: POLH
  biological_processes:
  - preferred_term: translesion synthesis
    modifier: DECREASED
    term:
      id: GO:0019985
      label: translesion synthesis
  evidence:
  - reference: DOI:10.1038/s41467-023-38311-0
    reference_title: Genomic mutation landscape of skin cancers from DNA repair-deficient xeroderma pigmentosum patients
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mutational profile in XP-V tumors and experiments with POLH knockout
      cell line reveal the role of polymerase η in the error-free bypass of
      (i) rare TpG and TpA DNA lesions, (ii) 3' nucleotides in pyrimidine
      dimers, and (iii) TpT photodimers.
    explanation: The tumor-genomics paper supports XP-V as a lesion-bypass defect centered on POLH.
  downstream:
  - target: UV-signature mutagenesis and tumor mutation burden
    description: Failed lesion bypass contributes to the distinctive mutational spectra of XP-V tumors.
- name: UV-signature mutagenesis and tumor mutation burden
  description: >-
    Persistent unrepaired or inaccurately bypassed UV lesions produce the high
    mutational burden and UV-signature mutations that underlie XP skin-cancer
    susceptibility.
  cell_types:
  - preferred_term: keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
  - preferred_term: melanocyte
    term:
      id: CL:0000148
      label: melanocyte
  evidence:
  - reference: DOI:10.1038/s41467-023-38311-0
    reference_title: Genomic mutation landscape of skin cancers from DNA repair-deficient xeroderma pigmentosum patients
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      XP is associated with an increased skin cancer risk, reaching, for
      some groups, several thousand-fold compared to the general population.
    explanation: The 2023 tumor-genomics study links defective repair to extreme mutagenic cancer risk.
  downstream:
  - target: Cutaneous carcinogenesis
    description: Extreme UV-driven mutagenesis promotes early basal cell carcinoma, squamous cell carcinoma, and melanoma.
- name: Cutaneous carcinogenesis
  description: >-
    XP dramatically accelerates development of sunlight-induced basal cell
    carcinoma, squamous cell carcinoma, and melanoma, often beginning in the
    first decade of life.
  evidence:
  - reference: PMID:20301571
    reference_title: Xeroderma Pigmentosum.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Greatly increased risk of sunlight-induced cutaneous neoplasms (basal
      cell carcinoma, squamous cell carcinoma, melanoma) within the first decade
      of life.
    explanation: GeneReviews directly supports early carcinogenesis as a core downstream consequence of XP.
  downstream:
  - target: Progressive neurologic vulnerability
    description: In susceptible genotypes, DNA repair failure also contributes to neuronal damage and disability.
- name: Progressive neurologic vulnerability
  description: >-
    In neurologically affected XP genotypes, neural cells show impaired DNA
    repair and heightened apoptosis, providing a mechanistic route to ataxia,
    hearing loss, and cognitive decline.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: apoptotic process
    modifier: INCREASED
    term:
      id: GO:0006915
      label: apoptotic process
  evidence:
  - reference: PMID:26874523
    reference_title: Modeling xeroderma pigmentosum associated neurological pathologies with patients-derived iPSCs.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Mutation of XPA in either neural stem cells (NSCs) or neurons resulted
      in severe DNA damage repair defects, and these neural cells with mutant
      XPA were hyper-sensitive to DNA damage-induced apoptosis.
    explanation: Patient-derived neural-cell models support a repair-defect to apoptosis mechanism for XP neurodegeneration.
phenotypes:
- name: Photosensitivity
  category: Dermatologic
  diagnostic: true
  phenotype_term:
    preferred_term: Cutaneous photosensitivity
    term:
      id: HP:0000992
      label: Cutaneous photosensitivity
  description: >-
    Acute sun sensitivity with severe sunburn and persistent erythema on minimal
    sun exposure is a core early clinical feature.
  evidence:
  - reference: PMID:20301571
    reference_title: Xeroderma Pigmentosum.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Acute sun sensitivity (severe sunburn with blistering, persistent
      erythema on minimal sun exposure).
    explanation: GeneReviews directly supports severe photosensitivity as a defining XP phenotype.
- name: Freckling in sun-exposed skin
  category: Dermatologic
  diagnostic: true
  phenotype_term:
    preferred_term: Freckling
    term:
      id: HP:0001480
      label: Freckling
  description: >-
    Freckle-like hyperpigmentation of the face develops in early childhood,
    especially in sun-exposed skin.
  evidence:
  - reference: PMID:20301571
    reference_title: Xeroderma Pigmentosum.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      marked freckle-like pigmentation of the face before age two years
    explanation: GeneReviews directly supports early pigmentary change as a hallmark XP phenotype.
- name: Photophobia
  category: Ophthalmologic
  phenotype_term:
    preferred_term: Photophobia
    term:
      id: HP:0000613
      label: Photophobia
  description: >-
    Ocular UV injury commonly causes photophobia and related ocular surface
    disease.
  evidence:
  - reference: PMID:28554534
    reference_title: "Ophthalmic Manifestations of Xeroderma Pigmentosum: A Perspective from the United Kingdom."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ninety-three percent of XP patients in our cohort had ocular
      involvement, with 65% describing photophobia.
    explanation: The UK ophthalmology cohort quantifies photophobia as a common XP manifestation.
- name: Ocular involvement
  category: Ophthalmologic
  description: >-
    Ocular disease is highly prevalent and includes periocular skin disease,
    ocular surface pathology, and ocular neoplasia requiring regular
    ophthalmologic surveillance.
  evidence:
  - reference: PMID:28554534
    reference_title: "Ophthalmic Manifestations of Xeroderma Pigmentosum: A Perspective from the United Kingdom."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ninety-three percent of XP patients in our cohort had ocular
      involvement, with 65% describing photophobia. The most common
      abnormalities were in the periocular skin and ocular surface, including
      interpalpebral conjunctival melanosis (44%) and conjunctival injection
      (43%). Eleven percent of patients had required treatment for periocular
      cancers and 2% for ocular surface cancers.
    explanation: The UK cohort establishes ocular involvement as a highly prevalent clinical domain in XP.
- name: Basal cell carcinoma
  category: Oncologic
  phenotype_term:
    preferred_term: Basal cell carcinoma
    term:
      id: HP:0002671
      label: Basal cell carcinoma
  description: >-
    Basal cell carcinoma occurs at markedly earlier ages than in the general
    population as part of the sunlight-induced cancer phenotype.
  evidence:
  - reference: PMID:20301571
    reference_title: Xeroderma Pigmentosum.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Greatly increased risk of sunlight-induced cutaneous neoplasms (basal
      cell carcinoma, squamous cell carcinoma, melanoma) within the first decade
      of life.
    explanation: GeneReviews directly lists basal cell carcinoma as a characteristic early XP malignancy.
- name: Squamous cell carcinoma of the skin
  category: Oncologic
  phenotype_term:
    preferred_term: Squamous cell carcinoma of the skin
    term:
      id: HP:0006739
      label: Squamous cell carcinoma of the skin
  description: >-
    Cutaneous squamous cell carcinoma is a common malignant consequence of the
    XP mutagenic state.
  evidence:
  - reference: PMID:20301571
    reference_title: Xeroderma Pigmentosum.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Greatly increased risk of sunlight-induced cutaneous neoplasms (basal
      cell carcinoma, squamous cell carcinoma, melanoma) within the first decade
      of life.
    explanation: GeneReviews directly lists cutaneous squamous cell carcinoma as a characteristic XP malignancy.
- name: Cutaneous melanoma
  category: Oncologic
  phenotype_term:
    preferred_term: Melanoma
    term:
      id: HP:0002861
      label: Melanoma
  description: >-
    Melanoma risk is markedly elevated because UV-induced lesions are not
    repaired normally.
  evidence:
  - reference: PMID:20301571
    reference_title: Xeroderma Pigmentosum.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Greatly increased risk of sunlight-induced cutaneous neoplasms (basal
      cell carcinoma, squamous cell carcinoma, melanoma) within the first decade
      of life.
    explanation: GeneReviews directly lists melanoma as part of the classic XP cancer spectrum.
- name: Sensorineural hearing impairment
  category: Neurologic
  phenotype_term:
    preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  description: >-
    Progressive sensorineural hearing loss is a common neurologic manifestation,
    especially in XPA, XPD, and XPG disease.
  evidence:
  - reference: PMID:20301571
    reference_title: Xeroderma Pigmentosum.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Approximately 25% of affected individuals have neurologic
      manifestations (acquired microcephaly, diminished or absent deep tendon
      stretch reflexes, progressive sensorineural hearing loss, progressive
      cognitive impairment, and ataxia).
    explanation: GeneReviews directly lists progressive sensorineural hearing loss among core XP neurologic features.
- name: Peripheral neuropathy
  category: Neurologic
  phenotype_term:
    preferred_term: Peripheral neuropathy
    term:
      id: HP:0009830
      label: Peripheral neuropathy
  description: >-
    Axonal sensory and sensorimotor neuropathies are common ancillary-test
    findings in neurologically involved XP patients, particularly in the
    neurodegenerative subtypes.
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Cerebellar and global brain atrophy, axonal sensory and sensorimotor
      neuropathies, and sensorineural hearing loss were common findings in
      patients.
    explanation: The prospective cohort directly supports peripheral neuropathy as a common neurologic manifestation in XP.
- name: Hyporeflexia
  category: Neurologic
  phenotype_term:
    preferred_term: Hyporeflexia
    term:
      id: HP:0001265
      label: Hyporeflexia
  description: >-
    Reduced reflexes are frequent in the neurodegenerative XP subtypes,
    especially XPA, XPD, and XPG.
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Hyporeflexia, hypopallesthaesia, upper motor neuron signs, chorea,
      dystonia, oculomotor signs and cognitive impairment were frequent
      findings in XPA, XPD and XPG.
    explanation: The prospective cohort identifies hyporeflexia as a frequent neurologic sign in the neurodegenerative XP genotypes.
- name: Dystonia
  category: Neurologic
  phenotype_term:
    preferred_term: Dystonia
    term:
      id: HP:0001332
      label: Dystonia
  description: >-
    Dystonia is part of the extrapyramidal neurologic phenotype seen in the
    more severely neurologically affected XP subtypes.
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Hyporeflexia, hypopallesthaesia, upper motor neuron signs, chorea,
      dystonia, oculomotor signs and cognitive impairment were frequent
      findings in XPA, XPD and XPG.
    explanation: The prospective cohort identifies dystonia as a frequent neurologic sign in XPA, XPD, and XPG disease.
- name: Cognitive impairment
  category: Neurologic
  phenotype_term:
    preferred_term: Cognitive impairment
    term:
      id: HP:0100543
      label: Cognitive impairment
  description: >-
    Progressive cognitive impairment is part of the neurologic XP phenotype and
    is enriched in XPA, XPD, and XPG.
  evidence:
  - reference: PMID:20301571
    reference_title: Xeroderma Pigmentosum.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Approximately 25% of affected individuals have neurologic
      manifestations (acquired microcephaly, diminished or absent deep tendon
      stretch reflexes, progressive sensorineural hearing loss, progressive
      cognitive impairment, and ataxia).
    explanation: GeneReviews directly supports progressive cognitive impairment in XP.
- name: Progressive cerebellar ataxia
  category: Neurologic
  phenotype_term:
    preferred_term: Progressive cerebellar ataxia
    term:
      id: HP:0002073
      label: Progressive cerebellar ataxia
  description: >-
    Progressive ataxia is a measurable component of XP neurologic disease and
    worsens over time in XPA and XPD.
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      SARA total scores significantly increased over time in XPD (0.91
      points/year, 95% confidence interval: 0.61, 1.21) and XPA (0.63
      points/year, 95% confidence interval: 0.38, 0.89).
    explanation: The prospective cohort quantifies progressive ataxia in XPA and XPD.
genetic:
- name: Core nucleotide-excision repair genes
  association: Causative
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  notes: >-
    Classical XP is genetically heterogeneous and is caused by biallelic
    pathogenic variants in XPA, ERCC3, XPC, ERCC2, DDB2, ERCC4, and ERCC5;
    GeneReviews also lists ERCC1 among rare diagnostic causes.
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      XP results from biallelic mutations in any of eight genes involved in DNA
      repair systems, thus defining eight different genotypes (XPA, XPB, XPC,
      XPD, XPE, XPF, XPG and XP variant or XPV).
    explanation: The cohort abstract establishes the canonical complementation-group architecture of XP.
  variants:
  - name: Biallelic loss-of-function or hypomorphic variants in NER genes
    description: >-
      XP commonly results from pathogenic alleles that reduce nucleotide-excision
      repair capacity rather than from somatic events.
    evidence:
    - reference: DOI:10.1038/s41467-023-38311-0
      reference_title: Genomic mutation landscape of skin cancers from DNA repair-deficient xeroderma pigmentosum patients
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Xeroderma pigmentosum (XP) is a genetic disorder caused by mutations
        in genes of the Nucleotide Excision Repair (NER) pathway (groups A-G).
      explanation: The abstract supports a germline repair-deficiency architecture across NER-associated XP groups.
- name: POLH pathogenic variants
  gene_term:
    preferred_term: POLH
    term:
      id: hgnc:9181
      label: POLH
  association: Causative
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  subtype: XP-V
  notes: >-
    Biallelic POLH pathogenic variants cause xeroderma pigmentosum variant by
    disrupting error-free bypass of ultraviolet DNA lesions.
  evidence:
  - reference: DOI:10.1038/s41467-023-38311-0
    reference_title: Genomic mutation landscape of skin cancers from DNA repair-deficient xeroderma pigmentosum patients
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Xeroderma pigmentosum (XP) is a genetic disorder caused by mutations
      in genes of the Nucleotide Excision Repair (NER) pathway (groups A-G) or
      in Translesion Synthesis DNA polymerase η (V).
    explanation: The Nature Communications abstract directly supports POLH as the causative gene for XP-V.
  variants:
  - name: POLH p.Thr191Pro missense variant
    description: >-
      Homozygous POLH p.Thr191Pro is a functionally characterized pathogenic
      missense variant that abrogates polymerase activity and impairs UV lesion
      bypass in XP-V.
    evidence:
    - reference: PMID:38212351
      reference_title: Homozygous substitution of threonine 191 by proline in polymerase η causes Xeroderma pigmentosum variant.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        providing molecular evidence that the substitution abrogates
        polymerase activity and results in UV sensitivity through deficient
        damage bypass.
      explanation: This paper provides direct functional evidence for a pathogenic POLH missense mechanism in XP-V.
- name: XPA genotype-severity correlations
  gene_term:
    preferred_term: XPA
    term:
      id: hgnc:12814
      label: XPA
  association: Modifier of neurologic severity
  variant_origin: GERMLINE
  subtype: XP-A
  notes: >-
    XPA variant type and location correlate with severe, intermediate, or mild
    neurologic disease and with residual DNA repair capacity.
  evidence:
  - reference: DOI:10.1371/journal.pgen.1011265
    reference_title: "Different germline variants in the XPA gene are associated with severe, intermediate, or mild neurodegeneration in xeroderma pigmentosum patients"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Our findings revealed correlations between disease severity, DNA repair
      capacity, and XPA variant type and location.
    explanation: The 2024 XPA natural-history study supports genotype-based prognostic stratification within XP-A.
- name: ERCC4 deep intronic founder variants
  gene_term:
    preferred_term: ERCC4
    term:
      id: hgnc:3436
      label: ERCC4
  association: Causative
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  subtype: XP-F
  notes: >-
    Deep intronic founder variants in ERCC4 account for a substantial fraction
    of Japanese XP-F disease and are important to include in molecular testing.
  evidence:
  - reference: DOI:10.1073/pnas.2217423120
    reference_title: "Deep intronic founder mutations identified in the ERCC4/XPF gene are potential therapeutic targets for a high-frequency form of xeroderma pigmentosum"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The first variant, located in intron 1, is a Japanese founder mutation,
      which additionally accounts for ~10% of the entire Japanese XP cases.
    explanation: The PNAS abstract supports a clinically important non-coding ERCC4 founder mechanism in XP-F.
  variants:
  - name: Deep intronic ERCC4 founder variants
    description: >-
      Deep intronic ERCC4 alleles reduce XPF expression through aberrant
      splicing or alternative polyadenylation and can present with early-onset
      skin cancers.
    evidence:
    - reference: DOI:10.1073/pnas.2217423120
      reference_title: "Deep intronic founder mutations identified in the ERCC4/XPF gene are potential therapeutic targets for a high-frequency form of xeroderma pigmentosum"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Both mutations cause a reduction of the ERCC4/XPF gene expression,
        resulting in XP clinical manifestations. Most cases developed
        early-onset skin cancers.
      explanation: The abstract supports the mechanistic and clinical consequence of these ERCC4 non-coding variants.
environmental:
- name: Ultraviolet radiation exposure
  presence: trigger and disease modifier
  description: >-
    Ultraviolet radiation is the dominant environmental exposure that drives DNA
    damage, clinical photosensitivity, and carcinogenesis in xeroderma
    pigmentosum.
  effect: increases DNA damage burden and cutaneous cancer risk
  evidence:
  - reference: PMID:35520754
    reference_title: "Xeroderma pigmentosum: an updated review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Early recognition of xeroderma pigmentosum is important to minimize
      the complications arising from the harmful effects of exposure to
      ultraviolet radiation.
    explanation: The updated review identifies UV radiation exposure as the main harmful external driver of disease complications.
treatments:
- name: Rigorous ultraviolet avoidance
  description: >-
    Lifelong photoprotection with strict sun avoidance, protective clothing,
    sunscreen, and UV reduction is the core management strategy in XP.
  evidence:
  - reference: PMID:35520754
    reference_title: "Xeroderma pigmentosum: an updated review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Strict and consistent sun avoidance and protection and early detection
      and treatment of premalignant and malignant skin lesions are the mainstays
      of management.
    explanation: The updated review directly supports rigorous UV avoidance and protection as standard of care.
- name: Dermatologic and ophthalmologic surveillance
  description: >-
    Regular skin examinations, eye examinations, neurologic follow-up, and
    audiograms are recommended to detect premalignant lesions, ocular injury,
    and progressive neurologic complications early.
  treatment_term:
    preferred_term: supportive care
    term:
      id: MAXO:0000950
      label: supportive care
  evidence:
  - reference: PMID:20301571
    reference_title: Xeroderma Pigmentosum.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Surveillance: Skin examinations by a physician every three to 12
      months; eye exams for signs of UV exposure and damage every six months;
      routine eye and neurologic examinations for progressive neurologic
      abnormalities every 12 months; audiograms every six to12 months.
    explanation: GeneReviews provides explicit surveillance intervals for multidisciplinary XP follow-up.
- name: Local treatment of premalignant and malignant skin lesions
  description: >-
    Actinic keratoses and skin cancers are managed with local therapies such as
    cryotherapy, topical field therapy, curettage, Mohs surgery, or surgical
    excision depending on lesion burden and recurrence risk.
  evidence:
  - reference: PMID:20301571
    reference_title: Xeroderma Pigmentosum.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Premalignant skin lesions such as actinic keratoses can be treated by
      freezing with liquid nitrogen; larger areas can be treated with field
      treatments such as topical 5-fluorouracil or imiquimod preparations.
      Rarely, therapeutic dermatome shaving or dermabrasion has been used;
      skin neoplasms can be treated (as in persons without XP) with
      electrodesiccation and curettage or surgical excision; skin cancers that
      are recurrent or in locations at high risk for recurrence are best
      treated with Mohs micrographic surgery.
    explanation: GeneReviews directly supports lesion-directed dermatologic management in XP.
- name: Oral isotretinoin chemoprevention
  description: >-
    High-dose oral isotretinoin can reduce new skin-cancer formation in selected
    high-risk XP patients, but toxicity limits long-term use.
  evidence:
  - reference: PMID:3287161
    reference_title: Prevention of skin cancer in xeroderma pigmentosum with the use of oral isotretinoin.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      During two years of treatment with isotretinoin, there were 25 tumors
      (mean, 5; range, 3 to 9), with an average reduction in skin cancers of
      63 percent (P = 0.019).
    explanation: The prospective study provides direct chemoprevention evidence for isotretinoin in XP.
- name: Genetic counseling
  description: >-
    Genetic counseling supports recurrence-risk assessment, testing of at-risk
    relatives, and reproductive planning in affected families.
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: MAXO:0000079
      label: genetic counseling
  evidence:
  - reference: PMID:20301571
    reference_title: Xeroderma Pigmentosum.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Once the XP-related pathogenic variants have been identified in an
      affected family member, prenatal testing for a pregnancy at increased risk
      and preimplantation genetic testing for XP are possible.
    explanation: GeneReviews supports family counseling and cascade testing implications for XP.
epidemiology:
- name: Extreme skin-cancer risk
  description: >-
    XP confers several-thousand-fold elevation in skin-cancer risk relative to
    the general population, with especially severe non-melanoma skin-cancer
    burden.
  notes: up to 10,000-fold for non-melanoma skin cancer and 2,000-fold for melanoma in reported summaries
  evidence:
  - reference: DOI:10.1038/s41467-023-38311-0
    reference_title: Genomic mutation landscape of skin cancers from DNA repair-deficient xeroderma pigmentosum patients
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      XP is associated with an increased skin cancer risk, reaching, for
      some groups, several thousand-fold compared to the general population.
    explanation: The 2023 tumor-genomics paper supports extreme cancer-risk elevation in XP.
- name: Neurologic burden in a national cohort
  description: >-
    Neurologic manifestations affect a substantial minority of XP patients and
    cluster in XPA, XPD, and XPG.
  notes: 36 of 93 patients (38.7%) reported neurologic symptoms in the UK cohort
  evidence:
  - reference: DOI:10.1093/brain/awad266
    reference_title: "Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ninety-three XP patients were recruited. Thirty-six (38.7%) reported
      neurological symptoms, especially in the XPA, XPD and XPG groups.
    explanation: The prospective UK cohort quantifies neurologic burden across XP genotypes.
diagnosis:
- name: Molecular genetic confirmation
  description: >-
    A definite diagnosis is made by identifying biallelic pathogenic variants in
    XP-related genes after recognition of the characteristic cutaneous, ocular,
    and neurologic phenotype.
  presence: identification of biallelic pathogenic variants confirms the diagnosis
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: MAXO:0000533
      label: molecular genetic testing
  evidence:
  - reference: PMID:35520754
    reference_title: "Xeroderma pigmentosum: an updated review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      A definite diagnosis can be made by the identification of biallelic
      mutation in one of the causative genes.
    explanation: The updated review directly supports molecular confirmation of XP.
- name: Clinical phenotype and family-history assessment
  description: >-
    Diagnosis should be suspected in patients with increased photosensitivity,
    early pigmentary change, ocular involvement, and early skin neoplasia.
  evidence:
  - reference: PMID:35520754
    reference_title: "Xeroderma pigmentosum: an updated review."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The diagnosis should be suspected in patients with increased
      photosensitivity and characteristic cutaneous, ophthalmological and
      neurological findings.
    explanation: The updated review supports the characteristic XP clinical recognition pattern.
- name: Targeted genomic diagnosis in consanguineous XP-C
  description: >-
    In consanguineous families, SNP-array localization combined with long-range
    PCR-based targeted next-generation sequencing can rapidly identify the
    causal homozygous XPC variant and confirm XP-C.
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: MAXO:0000533
      label: molecular genetic testing
  evidence:
  - reference: PMID:38003022
    reference_title: "SNP Array Screening and Long Range PCR-Based Targeted Next Generation Sequencing for Autosomal Recessive Disease with Consanguinity: Insight from a Case of Xeroderma Pigmentosum Group C."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      NGS, with a minimal set of long-range PCR primers, detected a homozygous
      frameshift mutation in XPC; NM_004628.5:c.218_219insT
      p.(Lys73AsnfsTer9), confirmed by Sanger sequencing, leading to a rapid
      diagnosis of XP group C.
    explanation: This case report supports a concrete molecular-diagnostic workflow for XP-C in consanguineous settings.
differential_diagnoses:
- name: Cockayne syndrome
  disease_term:
    preferred_term: Cockayne syndrome
    term:
      id: MONDO:0016006
      label: Cockayne syndrome
  description: >-
    Cockayne syndrome can overlap clinically with xeroderma pigmentosum through
    ultraviolet sensitivity and neurologic dysfunction, particularly in patients
    with severe neurodegeneration out of proportion to cutaneous cancer burden.
  distinguishing_features:
  - Recovery of RNA synthesis after UV exposure is abnormal in Cockayne syndrome, whereas classic XP is defined by a DNA excision-repair defect or XP-variant replication defect.
  - Severe neurologic disease with relatively mild cutaneous abnormalities should raise concern for Cockayne syndrome or an overlap phenotype rather than classic XP alone.
  evidence:
  - reference: PMID:1372469
    reference_title: "Xeroderma pigmentosum and Cockayne syndrome: overlapping clinical and biochemical phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Rather, a failure of RNA synthesis to recover to normal levels after UV
      exposure was observed, a biochemical abnormality seen in Cockayne
      syndrome (CS), one of the premature-aging syndromes with clinical UV
      sensitivity.
    explanation: This abstract directly supports Cockayne syndrome as a biochemical and clinical differential for XP-like photosensitive neurologic disease.
- name: Trichothiodystrophy
  disease_term:
    preferred_term: trichothiodystrophy
    term:
      id: MONDO:0018053
      label: trichothiodystrophy
  description: >-
    Trichothiodystrophy caused by ERCC2 variants overlaps with XP because both
    disorders involve DNA-repair genes and photosensitivity-associated
    neurodevelopmental disease, but TTD has a distinct syndromic presentation.
  distinguishing_features:
  - Classic TTD findings and progressive hypomyelination can distinguish ERCC2-related TTD from XP.
  - Clinical and paraclinical evaluation can separate TTD from Cockayne syndrome and XP even when the causal gene overlaps.
  evidence:
  - reference: PMID:39976384
    reference_title: "Trichothiodystrophy due to ERCC2 Variants: Uncommon Contributor to Progressive Hypomyelinating Leukodystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clinical and paraclinical findings enabled differentiation of TTD from
      Cockayne syndrome and XP.
    explanation: This abstract directly supports trichothiodystrophy as an ERCC2-related differential diagnosis that can be separated from XP clinically.
clinical_trials:
- name: NCT00002811
  description: >-
    Phase III randomized trial of T4N5 liposome lotion versus placebo to reduce
    actinic keratoses and other sun-induced skin damage in XP.
  phase: PHASE_III
  evidence:
  - reference: clinicaltrials:NCT00002811
    reference_title: "A RANDOMIZED, DOUBLE BLIND, MULTI-CENTER CLINICAL STUDY TO TEST THE SAFETY AND EFFICACY OF T4N5 LIPOSOME LOTION ON PATIENTS WITH XERODERMA PIGMENTOSUM IN THE PROTECTION AGAINST ACTINIC KERATOSES"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Randomized double-blinded phase III trial to compare treatment using
      T4N5 liposome lotion with treatment using placebo in reducing actinic
      keratoses and other sun-induced skin damage in patients with xeroderma
      pigmentosum.
    explanation: The ClinicalTrials.gov record directly supports the T4N5 chemoprevention trial.
- name: NCT03445052
  description: >-
    XPAND is a randomized controlled trial testing a personalized adherence
    intervention to improve photoprotection behavior and reduce UVR reaching the
    face in adults with XP.
  phase: NOT_APPLICABLE
  evidence:
  - reference: clinicaltrials:NCT03445052
    reference_title: "The XPAND Evaluation of a Personalised Adherence Intervention to Improve Photoprotection Behaviour in Adults With Xeroderma Pigmentosum (XP): Randomised Controlled Trial."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      This research will test whether an intervention designed to enhance
      photoprotection activities is successful. It will use a randomised
      controlled trial design to compare the amount of UVR reaching the face.
    explanation: The trial record supports behavioral photoprotection as an active interventional research area in XP.
- name: NCT05159752
  description: >-
    Open-label phase IIa afamelanotide study in XP-C designed to assess safety,
    UV-provoked DNA damage, and reparative endpoints.
  phase: PHASE_II
  evidence:
  - reference: clinicaltrials:NCT05159752
    reference_title: "A Proof of Concept, Phase IIa, Open Label Study to Evaluate the Safety and Efficacy of Subcutaneous Implants of Afamelanotide in Patients With Xeroderma Pigmentosum (XP)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The CUV156 study will evaluate the safety of afamelanotide in XP-C
      patients, as well as the drug's ability to assist reparative processes
      following ultraviolet (UV) provoked DNA damage of the skin.
    explanation: The record supports afamelanotide as an active investigational therapy in XP-C.
- name: NCT05370235
  description: >-
    Open-label phase IIa afamelanotide study in XP-C and XP-V assessing safety,
    UV-provoked DNA damage, and repair-related endpoints.
  phase: PHASE_II
  evidence:
  - reference: clinicaltrials:NCT05370235
    reference_title: "A Proof of Concept, Phase IIa, Open Label Study to Evaluate the Safety and Efficacy of Subcutaneous Implants of Afamelanotide in Patients With Xeroderma Pigmentosum C and V (XPC and XPV)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The CUV152 study will evaluate the safety of afamelanotide in XP-C and
      XP-V patients, as well as the drug's ability to assist reparative
      processes following ultraviolet (UV) provoked DNA damage of the skin.
    explanation: The record supports ongoing genotype-targeted afamelanotide trials in XP.
notes: >-
  This curation was expanded from the initial draft using the Falcon deep
  research report and then grounded in cached abstract-level evidence from
  GeneReviews, recent cohort studies, tumor genomics, ophthalmology literature,
  chemoprevention studies, and ClinicalTrials.gov records.

📚

References & Deep Research

Deep Research

1

Falcon ▸

1. Disease Information

Edison Scientific Literature 30 citations 2026-05-13T14:06:46.549988

1. Disease Information

1.1 Disease overview (definition and current understanding)

XP is a multisystemic disorder in which defects in repair of UV-induced DNA lesions (primarily bulky photoproducts) lead to profound photosensitivity with cutaneous and ocular injury, premature skin aging, and multiple early skin malignancies; some genotypes are additionally associated with progressive neurological disease. A practical clinical summary emphasizes: “Strict and consistent sun avoidance and protection and early detection and treatment of premalignant and malignant skin lesions are the mainstays of management,” and that “At present, there is no cure for XP.” (srivastava2021xerodermapigmentosum pages 2-5)

1.2 Key identifiers and controlled vocabulary

MeSH: Xeroderma Pigmentosum (MeSH ID D014983) as used in ClinicalTrials.gov metadata. (NCT05159752 chunk 1)
OMIM: XP complementation groups are referenced in the literature excerpt as XP-A to XP-G plus XP-variant (XPV). (schubert2019xerodermapigmentosumand pages 5-6, garciamoreno2023neurologicaldiseasein pages 1-2)
MONDO / Orphanet / ICD-10 / ICD-11: Not reliably retrievable from the tool-accessible evidence during this run; therefore, MONDO and ORPHA identifiers are not asserted here.

1.3 Synonyms and alternative names

“Xeroderma pigmentosum”
“XP”
“Xeroderma pigmentosum variant” / “XPV” (POLH-associated) (garciamoreno2023neurologicaldiseasein pages 1-2, yurchenko2023genomicmutationlandscape pages 1-2)

1.4 Evidence provenance (patient-level vs aggregated)

The evidence used in this report includes (i) aggregated cohort studies (e.g., UK National XP Service prospective cohort), (ii) tumor genome profiling (multiple tumor genomes from multiple XP groups), (iii) mechanistic in vitro studies in patient-derived cells and engineered models, and (iv) clinical-trial registry data. (garciamoreno2023neurologicaldiseasein pages 1-2, yurchenko2023genomicmutationlandscape pages 1-2, kobaisi2024syntheticrescueof pages 1-2, NCT00002811 chunk 1)

2. Etiology

2.1 Disease causal factors

Primary causal factor: Germline (biallelic) pathogenic variants in DNA repair genes. XP is caused by mutations in NER genes (XPA–XPG; ERCC-family genes; DDB2) or POLH (translesion synthesis). (yurchenko2023genomicmutationlandscape pages 1-2, garciamoreno2023neurologicaldiseasein pages 1-2)

Environmental trigger: UV radiation exposure acts as the dominant environmental driver of DNA damage leading to photosensitivity and carcinogenesis in XP, motivating rigorous photoprotection as the key preventive/therapeutic strategy. (srivastava2021xerodermapigmentosum pages 2-5, NCT03445052 chunk 1)

2.2 Risk factors

Genetic: Genotype determines mechanism (GG-NER vs TC-NER vs TLS) and influences risk of neurodegeneration and some clinical patterns (see Sections 4 and 6). (garciamoreno2023neurologicaldiseasein pages 1-2, sagun2024differentgermlinevariants pages 1-2)
Environmental: UV exposure intensity and cumulative exposure are major modifiers of cutaneous carcinogenesis (behavioral adherence is therefore clinically critical). (NCT03445052 chunk 1)

2.3 Protective factors

Environmental/behavioral: Effective, sustained UV avoidance and photoprotection reduce UVR reaching the face and are the only proven strategy to prevent skin cancer and eye disease in XP; this is the explicit basis for the XPAND behavioral intervention trial. (NCT03445052 chunk 1, srivastava2021xerodermapigmentosum pages 2-5)

2.4 Gene–environment interactions

XP is the archetypal gene–environment interaction disorder: impaired repair of UV-induced lesions causes disproportionate mutagenesis and carcinogenesis under UV exposure, and conversely, strict reduction of UV exposure is expected to reduce mutational input and cancer burden. Tumor-genome data directly demonstrate UV-mutagenesis patterns (e.g., CC>TT signatures) in XP skin cancers. (yurchenko2023genomicmutationlandscape pages 3-5, NCT03445052 chunk 1)

3. Phenotypes

3.1 Core phenotype spectrum (with suggested HPO terms)

Below is a high-yield phenotype list with ontology suggestions (HPO terms are suggested conceptually; exact IDs are not asserted when not tool-verified):

Cutaneous * Severe photosensitivity / exaggerated sunburn reactions (HP: Photosensitivity) * Freckling / lentigines and pigmentary changes (HP: Freckling; HP: Hyperpigmentation; HP: Hypopigmentation) * Telangiectasia, atrophy, xerosis / premature photoaging (HP: Telangiectasia; HP: Cutaneous atrophy; HP: Xerosis) * Multiple early-onset skin cancers: basal cell carcinoma, squamous cell carcinoma, melanoma (HP: Basal cell carcinoma; HP: Squamous cell carcinoma; HP: Melanoma) * Clinical management text describes early detection and treatment of premalignant/malignant lesions as central. (srivastava2021xerodermapigmentosum pages 2-5)

Ophthalmological * Ocular UV sensitivity and damage requiring ophthalmologic surveillance (HP: Photophobia; HP: Keratitis) (not numerically quantified in tool evidence, but included in management follow-up recommendations). (srivastava2021xerodermapigmentosum pages 2-5)

Neurological (subset, genotype-enriched) UK prospective cohort quantified neurological burden and progression: * Neurological symptoms in 36/93 (38.7%) of XP patients. (garciamoreno2023neurologicaldiseasein pages 1-2) * Cerebellar ataxia progression tracked by SARA; significant annual progression in XPD (0.91 points/year, 95% CI 0.61–1.21) and XPA (0.63 points/year, 95% CI 0.38–0.89). (garciamoreno2023neurologicaldiseasein pages 1-2) * Cognitive impairment shows strong genotype dependence (percentages by complementation group): XPA 58.4%, XPC 17.6%, XPD 85.0%, XPE 15.1%, XPG 83.2%, XPV 4.3%. (garciamoreno2023neurologicaldiseasein pages 10-11) * Sensorineural hearing loss in 28/93 (30.1%). (garciamoreno2023neurologicaldiseasein pages 12-13)

Suggested HPO terms: HP: Cerebellar ataxia; HP: Cognitive impairment; HP: Sensorineural hearing impairment; HP: Peripheral neuropathy; HP: Hyporeflexia.

3.2 Age of onset, severity, and progression

The UK cohort supports that neurological symptoms typically occur after cutaneous/ophthalmologic symptoms and include early- and late-onset forms with genotype clustering in XPA/XPD/XPG. (garciamoreno2023neurologicaldiseasein pages 1-2)
XP-A genotype–neurodegeneration associations can be stratified into severe/intermediate/mild categories using a scoring approach at age 10 in a US natural-history cohort (n=18). (sagun2024differentgermlinevariants pages 1-2)

3.3 Quality-of-life impacts

XP is highly QoL-limiting due to lifelong UV avoidance, frequent procedures for lesions/cancers, and potential neurologic disability. XPAND explicitly targets adherence barriers to photoprotection because inadequate photoprotection increases cancer burden and life-threatening melanoma risk. (NCT03445052 chunk 1)

4. Genetic / Molecular Information

4.1 Causal genes and complementation groups

XP is defined by biallelic pathogenic variants in eight genotypes (XPA, XPB/ERCC3, XPC, XPD/ERCC2, XPE/DDB2, XPF/ERCC4, XPG/ERCC5, and XPV/POLH). (garciamoreno2023neurologicaldiseasein pages 1-2)

XP group / genotype	Causal gene	Core pathway role	Neurological involvement	High-signal recent evidence
XPA	XPA	Damage verification/scaffold in NER pre-incision complex; coordinates repair factors in GG-NER and TC-NER	Yes, often prominent; among the groups with the greatest neurologic burden and measurable progression	UK prospective cohort: XPA had frequent neurologic symptoms and significant SARA progression (~0.63 points/year); mutation severity correlated with faster progression. 2024 XP-A natural-history/genotype study linked variant class/location to severe, intermediate, or mild neurodegeneration. Management overview relevant for surveillance/supportive care. (garciamoreno2023neurologicaldiseasein pages 1-2, sagun2024differentgermlinevariants pages 1-2, srivastava2021xerodermapigmentosum pages 2-5)
XPB	ERCC3 (XPB)	TFIIH DNA translocase/helicase activity for DNA opening during NER; also transcription factor function	Variable / can occur; less common due to rarity, but neurologic disease can occur, especially in combined NER/transcription phenotypes	NER overview places XPB in TFIIH-mediated unwinding; UK cohort included very few XPB cases, limiting precision, but background notes combined GG-NER/TC-NER defect groups are more prone to neurodegeneration. Management overview relevant. (srivastava2021xerodermapigmentosum pages 2-5, garciamoreno2023neurologicaldiseasein pages 3-4, garciamoreno2023neurologicaldiseasein pages 2-3)
XPC	XPC	Primary lesion recognition in global-genome NER (GG-NER); damage sensing/handover to TFIIH	Usually no or mild/variable; neurologic involvement uncommon but not absent	UK cohort: only 2/22 XPC patients (9.1%) had neurologic symptoms. 2024 XP-C rescue study identified PIK3C3 knockdown as an experimental synthetic-rescue strategy. 2023 skin-cancer genomics showed strong mutational burden/signature effects in XP-C tumors. Management overview relevant. (garciamoreno2023neurologicaldiseasein pages 10-11, kobaisi2024syntheticrescueof pages 1-2, yurchenko2023genomicmutationlandscape pages 1-2, srivastava2021xerodermapigmentosum pages 2-5)
XPD	ERCC2 (XPD)	TFIIH 5'→3' helicase/translocase for lesion verification and DNA opening in NER	Yes, often prominent; one of the groups with fastest neurologic progression	UK prospective cohort: XPD showed high neurologic burden and fastest reported SARA progression (~0.91 points/year), with frequent cognitive impairment, neuropathy, hearing loss, and MRI abnormalities. Mechanistic work also supports XPD as core NER motor protein. Management overview relevant. (garciamoreno2023neurologicaldiseasein pages 1-2, garciamoreno2023neurologicaldiseasein pages 10-11, garciamoreno2023neurologicaldiseasein pages 11-12, srivastava2021xerodermapigmentosum pages 2-5)
XPE	DDB2 (XPE)	UV-photoproduct recognition in GG-NER (especially CPD/6-4PP recognition with DDB complex), facilitates XPC recruitment	Usually no / low frequency	UK cohort found no neurologic complaints in XPE in this series. 2023 tumor-genome study showed XP-E tumors can have very high mutation burden, supporting strong skin-cancer susceptibility despite limited neurologic disease. Management overview relevant. (garciamoreno2023neurologicaldiseasein pages 9-10, yurchenko2023genomicmutationlandscape pages 1-2, srivastava2021xerodermapigmentosum pages 2-5)
XPF	ERCC4 (XPF)	Structure-specific endonuclease; 5' incision in NER with ERCC1	Variable; can be mild in founder intronic forms, but neurologic disease exists in some XP-F/overlap cases	2023 PNAS identified deep intronic ERCC4/XPF founder mutations in 17 Japanese XP-F cases; one founder allele accounts for ~10% of Japanese XP, with early-onset skin cancers and generally typical XP-F cutaneous disease, and ASOs restored XPF expression/repair in cells. UK cohort had few XPF cases, limiting neurologic estimates. Management overview relevant. (senju2023deepintronicfounder pages 1-2, senju2023deepintronicfounder pages 5-6, senju2023deepintronicfounder pages 2-3, garciamoreno2023neurologicaldiseasein pages 2-3, srivastava2021xerodermapigmentosum pages 2-5)
XPG	ERCC5 (XPG)	Structure-specific endonuclease; 3' incision in NER; also stabilizes repair complex	Yes, often prominent	UK cohort: XPG grouped with XPA/XPD as having high SARA scores, frequent cognitive impairment, hearing loss, MRI abnormalities, and substantial disability. Management overview relevant. (garciamoreno2023neurologicaldiseasein pages 1-2, garciamoreno2023neurologicaldiseasein pages 10-11, garciamoreno2023neurologicaldiseasein pages 11-12, srivastava2021xerodermapigmentosum pages 2-5)
XPV	POLH	Translesion synthesis (TLS) polymerase eta; error-free bypass of UV photolesions, especially CPDs; not a core NER factor	Usually no / low frequency, but subtle abnormalities reported	UK cohort reported no neurologic complaints in XPV, though some exam/ancillary abnormalities were detected. 2023 skin-cancer genomics showed XP-V tumors have distinctive mutational spectra and high TMB linked to POLH deficiency. Management overview relevant. (garciamoreno2023neurologicaldiseasein pages 9-10, garciamoreno2023neurologicaldiseasein pages 11-12, yurchenko2023genomicmutationlandscape pages 1-2, yurchenko2023genomicmutationlandscape pages 9-11, srivastava2021xerodermapigmentosum pages 2-5)

Table: This table summarizes the main xeroderma pigmentosum complementation groups, their causal genes, core repair roles, and whether neurologic involvement is typical or variable. It emphasizes high-yield 2023-2024 evidence plus a practical management overview source useful for clinical interpretation.

4.2 Pathogenic variant classes and functional consequences

XP results from loss-of-function or hypomorphic variants that reduce NER or TLS capacity; the management-focused mechanism summary describes lesion recognition (XPE/XPC), TFIIH-dependent opening (XPB/XPD), and dual incision by XPG (3′) and XPF/ERCC1 (5′). (srivastava2021xerodermapigmentosum pages 2-5)

Genotype–phenotype (2024 XP-A focus): * A 2024 study of 18 XP-A patients (1973–2023) reports that variant type/location correlates with neurologic severity (severe vs intermediate vs mild) and that reduced repair is greatest in severe disease. (sagun2024differentgermlinevariants pages 1-2)

Founder deep intronic variants (2023 XP-F in Japan): * Senju et al. identified 17 XP-F cases with deep intronic ERCC4/XPF founder variants; an intron 1 founder allele (c.207+196T>A) has MAF ~1/508 and accounts for ~10% of Japanese XP cases; ASOs restored XPF protein and DNA repair activity in cells, motivating precision ASO therapeutics and inclusion of this variant in routine genetic testing for Japanese XP. (senju2023deepintronicfounder pages 5-6, senju2023deepintronicfounder pages 1-2)

4.3 Allele frequencies / population genetics

Japan has substantially higher XP prevalence than the US/Europe in recent synthesis: ~1 in 22,000 in Japan vs ~1 in 1,000,000 in the US/Europe (reported in 2024 XP-A paper background). (sagun2024differentgermlinevariants pages 1-2)
Japanese founder ERCC4/XPF intron 1 allele MAF ~0.002 and high contribution to national XP burden. (senju2023deepintronicfounder pages 1-2, senju2023deepintronicfounder pages 5-6)

4.4 Modifier genes (emerging)

A 2024 XP-C experimental study suggests cellular pathways outside canonical NER can modulate XP-C cellular phenotypes: * In XP-C cells, PIK3C3 downregulation increased post-UV survival and promoted ~20% repair of 6-4 photoproducts, with a major UVB resistance shift (LD50 0.056 J/cm² vs 0.013 J/cm² control), implicating autophagy/UVRAG-linked regulation as a phenotype modifier and potential therapeutic target class (preclinical). (kobaisi2024syntheticrescueof pages 2-5, kobaisi2024syntheticrescueof pages 1-2)

4.5 Genetic testing approaches (current practice patterns)

Diagnosis and trial eligibility often rely on functional DNA repair testing such as unscheduled DNA synthesis (UDS) assays (explicit inclusion criterion in the T4N5 chemoprevention trial) and genetic characterization, with complementation and sequencing used in national services. (NCT00002811 chunk 1, garciamoreno2023neurologicaldiseasein pages 1-2)

5. Epidemiology and Prognosis

5.1 Epidemiology

Prevalence estimates cited in 2024 XP-A work: ~1/1,000,000 (US/Europe) and ~1/22,000 (Japan). (sagun2024differentgermlinevariants pages 1-2)
A historical review excerpt reports incidence <1:1,000,000 in the USA/Europe and ~10-fold higher in more isolated populations, with consanguinity ~30% of cases (older data, used here only as context). (schubert2019xerodermapigmentosumand pages 5-6)

5.2 Cancer risk (statistics from recent studies)

Magnitude of risk: * 2023 tumor-genome study summarizes XP as having increased skin cancer risk reaching “several thousand-fold” for some groups, and provides explicit magnitudes: up to 10,000-fold increased risk for non-melanoma skin cancer and 2,000-fold for melanoma; it also notes ~34-fold increased risk of internal tumors (epidemiological evidence). (yurchenko2023genomicmutationlandscape pages 1-2)

Mutation burden as a mechanistic correlate (2023): * XP tumors (GG-NER defects: XP-C/XP-E; TLS defect: XP-V) “harbor 3.6-fold more mutations than sporadic skin cancers, on average.” (yurchenko2023genomicmutationlandscape pages 9-11) * UV-signature CC>TT double-base substitutions are enriched (e.g., XP-C ~0.2 vs sporadic ~0.03 in one comparison), supporting overwhelming UV mutational input when repair is defective. (yurchenko2023genomicmutationlandscape pages 1-2)

5.3 Neurologic prognosis

Neurological disease is common and progressive in genotype-enriched groups, with measurable annual progression in SARA for XPA and XPD (see Section 3). Mutation severity score can function as a prognostic stratification variable for progression in XPA and XPD and for ADL decline in XPA. (garciamoreno2023neurologicaldiseasein pages 1-2)

6. Diagnostics

6.1 Clinical diagnosis

XP diagnosis is based on clinical features (early photosensitivity, pigmentary change, early skin cancers) plus confirmatory laboratory/genetic evidence. A management-focused description emphasizes multidisciplinary follow-up (pediatrics, dermatology, ophthalmology, neurology). (srivastava2021xerodermapigmentosum pages 2-5)

6.2 Functional laboratory tests

UDS (unscheduled DNA synthesis) assays are explicitly used as a diagnostic confirmation method (e.g., inclusion for T4N5 trial; and as part of national cohort diagnostic workflows). (NCT00002811 chunk 1, garciamoreno2023neurologicaldiseasein pages 1-2)

6.3 Genetic testing

Genotype classification across XPA, XPB, XPC, XPD, XPE, XPF, XPG, XPV is core for prognosis (neurological risk), surveillance, and trial stratification; deep intronic founder ERCC4 variants highlight the need to consider non-coding pathogenic alleles in specific populations. (garciamoreno2023neurologicaldiseasein pages 1-2, senju2023deepintronicfounder pages 5-6)

6.4 Differential diagnosis

Not systematically retrievable from tool evidence in this run; however, clinical-trial eligibility explicitly excludes overlap syndromes (Cockayne syndrome, trichothiodystrophy) for some interventions, reflecting key differentials among NER disorders. (NCT00002811 chunk 1)

7. Treatment and Current Applications (real-world implementation)

7.1 Core standard of care (real-world)

There is no curative therapy; UV avoidance and photoprotection plus early lesion detection/treatment are foundational. (srivastava2021xerodermapigmentosum pages 2-5)
Recommended care includes “Regular paediatric, dermatological, ophthalmological and neurological follow-up.” (srivastava2021xerodermapigmentosum pages 2-5)

MAXO suggestions (not ID-verified): photoprotection; dermatologic surveillance; excision/ablation of premalignant lesions; topical field therapies; systemic chemoprevention; genetic counseling.

7.2 Chemoprevention and lesion-directed therapies

A clinical summary lists: * Oral isotretinoin (chemoprevention) (srivastava2021xerodermapigmentosum pages 2-5) * Treatment of actinic keratoses and skin cancers by local therapies; topical agents (e.g., imiquimod, fluorouracil) are referenced as part of management options (not quantified here). (srivastava2021xerodermapigmentosum pages 2-5)

7.3 DNA repair enzyme topical therapy (historical but still informative)

T4N5 liposome lotion trial (Phase 3 chemoprevention): * NCT00002811: randomized, double-blind, multicenter trial comparing T4 endonuclease V (T4N5) liposome lotion vs placebo to reduce actinic keratoses and protect against UV skin damage in XP. Enrollment projected 6–30; randomized 2:1 T4N5:placebo; diagnosis confirmed by UDS assay; ages 2–60. (NCT00002811 chunk 1)

7.4 Behavioral intervention to improve photoprotection (implementation science)

XPAND Trial (NCT03445052): * RCT testing a tailored adherence intervention to reduce UVR dose to the face, measured via wrist dosimeter (SEDs) plus 15-minute interval diary weighting for protection behaviors; target sample size 24 (15 actual enrolled). The intervention uses seven sessions and behavior-change techniques and motivational interviewing. (NCT03445052 chunk 2)

7.5 Melanocortin pathway photoprotection strategy (clinical trials; 2023 updates)

Afamelanotide (SCENESSE®) Phase IIa studies: * NCT05159752 (CUV156): open-label Phase IIa in XP-C, evaluating safety and efficacy; primary endpoint change in minimal erythema dose (MED) baseline to day 76; secondary endpoints include UV-induced DNA damage/repair capacity, skin severity measures, melanin density, and QoL tools; afamelanotide implant administered every two weeks for 12 weeks (n=6 planned). Last update posted 2023-06-18; primary completion estimated 2024-03. (NCT05159752 chunk 1) * NCT05370235 (CUV152): open-label Phase IIa in XP-C and XP-V, primary endpoints MED change for each genotype; similar DNA damage/repair and QoL endpoints; recruitment sites include Belgium and Spain; last update posted 2023-09-21; primary completion estimated 2024-06. (NCT05370235 chunk 1)

7.6 Immunotherapy and targeted therapy for XP-associated cancers

A clinical management summary lists immunotherapies and targeted agents used for advanced skin cancers in XP, including pembrolizumab, nivolumab, cemiplimab and vismodegib. (srivastava2021xerodermapigmentosum pages 2-5)

Mechanistic rationale is supported by high tumor mutational burden and UV-mutational signatures in XP skin cancers, which can increase neoantigen load and may contribute to ICI responsiveness (inference supported by tumor-genome findings and the management listing; response rates not quantified here). (yurchenko2023genomicmutationlandscape pages 1-2, srivastava2021xerodermapigmentosum pages 2-5)

8. Prevention

8.1 Primary prevention

Strict UV avoidance and rigorous photoprotection (protective clothing, sunscreen, limiting outdoor exposure) is the cornerstone preventive approach and is explicitly the only means to prevent skin cancer/eye disease in XP clinical management. (NCT03445052 chunk 1)

8.2 Secondary prevention

Frequent dermatologic surveillance and early treatment of premalignant lesions (actinic keratoses) and skin cancers is a major management theme and the basis for prevention trials (e.g., T4N5). (srivastava2021xerodermapigmentosum pages 2-5, NCT00002811 chunk 1)

8.3 Tertiary prevention

Disability prevention and symptomatic management for neurologic disease: no effective disease-modifying therapy for neurodegeneration is noted in clinical overview; however, validated scales (SARA, ADL) now quantify progression and can support monitoring and future clinical trials. (srivastava2021xerodermapigmentosum pages 2-5, garciamoreno2023neurologicaldiseasein pages 1-2)

9. Mechanism / Pathophysiology (molecular-to-clinical causal chain)

9.1 Core mechanism: defective NER or TLS

Upstream trigger: UV exposure induces bulky DNA photoproducts.

Molecular defect (NER): Damage recognition by XPE/XPC, assembly/verification via XPA/RPA and TFIIH, DNA unwinding by XPB/XPD, dual incision by XPG and XPF/ERCC1, followed by repair synthesis/ligation. (srivastava2021xerodermapigmentosum pages 2-5)

Variant mechanism (XPV): Defect in POLH compromises error-free bypass of UV lesions during replication, altering mutational spectra. (yurchenko2023genomicmutationlandscape pages 9-11, yurchenko2023genomicmutationlandscape pages 1-2)

Downstream consequences: Failure to remove/bypass UV lesions causes mutations with characteristic UV signatures, high tumor mutation burden, and carcinogenesis; neurologic disease arises in subsets (often those with combined GG-NER/TC-NER disruption). (yurchenko2023genomicmutationlandscape pages 3-5, garciamoreno2023neurologicaldiseasein pages 1-2)

9.2 Tumor genomics as mechanistic readout (2023)

XP skin cancers show markedly elevated mutational burden and enrichment for UV-associated mutation classes; GG-NER-defective and POLH-defective tumors exhibit distinctive patterns, and overall XP tumors average 3.6-fold more mutations than sporadic skin cancers. (yurchenko2023genomicmutationlandscape pages 9-11)

9.3 Neurological disease mechanisms (current evidence)

The 2023 prospective cohort links genotype to neurologic progression and disability, establishing clinical endpoints (SARA/ADL) and demonstrating mutation-severity association with progression in XPA/XPD. While mechanistic hypotheses (e.g., endogenous lesions such as cyclopurines) are discussed, the key evidence here is phenotypic quantification and genotype stratification. (garciamoreno2023neurologicaldiseasein pages 1-2)

Suggested GO biological-process terms (conceptual): nucleotide excision repair; response to UV; DNA damage recognition; DNA helicase activity; DNA incision, 5′/3′ endonuclease activity; translesion synthesis; regulation of apoptosis.

Suggested CL cell types (conceptual): keratinocyte; melanocyte; fibroblast; peripheral neuron; cochlear neuron.

10. Anatomical structures affected

Primary: skin (UV-exposed areas), eyes; in neurologic XP, brain (cerebellum/global atrophy), peripheral nervous system (neuropathy), auditory system (cochlear involvement). (garciamoreno2023neurologicaldiseasein pages 1-2, garciamoreno2023neurologicaldiseasein pages 12-13)

Suggested UBERON terms (conceptual): skin; epidermis; cornea; retina; cerebellum; peripheral nerve; cochlea.

11. Temporal development

XP is typically recognized in early life due to photosensitivity and pigmentary change; neurologic disease may present later and progresses measurably in XPA and XPD (annual SARA increases). (garciamoreno2023neurologicaldiseasein pages 1-2)

12. Inheritance and population

Inheritance: autosomal recessive (explicitly stated in clinical trial description and cohort literature). (NCT03445052 chunk 1)
Population structure: founder effects can markedly influence national case distributions (e.g., Japanese ERCC4/XPF deep intronic founder allele). (senju2023deepintronicfounder pages 5-6)

13. Other species / natural disease and 14. Model organisms

Model organism and cross-species natural disease information were not retrievable from the tool-accessible evidence in this run; therefore, no curated statements are made here.

15. Recent developments and latest research highlights (2023–2024)

1) Neurologic natural history and endpoints (Brain, Dec 2023): 93-patient prospective cohort; neurological symptoms in 38.7%; genotype-specific frequencies; quantified progression in XPA and XPD; proposes mutation severity as a prognostic biomarker for trial stratification. Publication date: Dec 2023. URL: https://doi.org/10.1093/brain/awad266 (garciamoreno2023neurologicaldiseasein pages 1-2)

2) XP-A genotype–neurodegeneration correlation (PLOS Genetics, Dec 2024): 18 XP-A patients examined across 1973–2023; XPA variant type/location associated with severe/intermediate/mild neurodegeneration; reinforces >1000-fold skin-cancer risk framing and provides contemporary prevalence estimates. Publication date: Dec 2024. URL: https://doi.org/10.1371/journal.pgen.1011265 (sagun2024differentgermlinevariants pages 1-2)

3) Tumor genome landscape (Nature Communications, May 2023): 38 XP skin-cancer genomes; high mutation burdens, UV signatures, and group-specific mutation patterns; provides quantitative risk magnitudes (up to 10,000-fold non-melanoma, 2,000-fold melanoma) and internal tumor risk framing. Publication date: May 2023. URL: https://doi.org/10.1038/s41467-023-38311-0 (yurchenko2023genomicmutationlandscape pages 1-2)

4) Precision therapeutics for founder deep intronic variants (PNAS, Jun 2023): ERCC4/XPF deep intronic founder alleles in Japan; ASO correction restores repair in patient cells; recommends including founder intron variant in testing. Publication date: Jun 2023. URL: https://doi.org/10.1073/pnas.2217423120 (senju2023deepintronicfounder pages 5-6)

5) Synthetic rescue strategy in XP-C (Cell Death & Disease, Nov 2024): kinase siRNA screen identifies PIK3C3; knockdown yields ~20% 6-4PP repair and improves UVB resistance (LD50 shift); supports autophagy/UVRAG-linked modulation as a potential therapeutic direction. Publication date: Nov 2024. URL: https://doi.org/10.1038/s41419-024-07186-4 (kobaisi2024syntheticrescueof pages 2-5)

Notes on evidence limitations

PMIDs: The tool-accessible excerpts provided DOIs and journal metadata but did not reliably surface PMIDs for the key 2023–2024 sources; therefore, PMIDs are not asserted.
MONDO/Orphanet/ICD identifiers: Not available from tool evidence in this run.
Model organism evidence: Not available from tool evidence in this run.

Key data points (quick reference)

Neurologic symptoms: 38.7% (36/93) in UK cohort; SARA progression 0.91 points/year (XPD) and 0.63 points/year (XPA). (garciamoreno2023neurologicaldiseasein pages 1-2)
Cognitive impairment frequencies: XPD 85.0%, XPG 83.2%, XPA 58.4%, XPC 17.6%, XPV 4.3%. (garciamoreno2023neurologicaldiseasein pages 10-11)
Skin cancer risk magnitude: up to 10,000-fold (non-melanoma) and 2,000-fold (melanoma) increases reported in 2023 tumor-genome study background. (yurchenko2023genomicmutationlandscape pages 1-2)
Tumor mutational burden: XP tumors average 3.6-fold more mutations than sporadic skin cancers. (yurchenko2023genomicmutationlandscape pages 9-11)
Founder ERCC4 intron 1 allele: MAF ~1/508, accounting for ~10% of Japanese XP; ASOs restore repair in cells. (senju2023deepintronicfounder pages 5-6)
Clinical trials: T4N5 topical DNA repair enzyme lotion (NCT00002811) (NCT00002811 chunk 1); afamelanotide Phase IIa studies (NCT05159752, NCT05370235) with MED and DNA damage endpoints (NCT05159752 chunk 1, NCT05370235 chunk 1); photoprotection adherence RCT XPAND (NCT03445052) using dosimetry (NCT03445052 chunk 2).

References

(garciamoreno2023neurologicaldiseasein pages 1-2): Hector Garcia-Moreno, Douglas R Langbehn, Adesoji Abiona, Isabel Garrood, Zofia Fleszar, Marta Antonia Manes, Ana M Susana Morley, Emma Craythorne, Shehla Mohammed, Tanya Henshaw, Sally Turner, Harsha Naik, Istvan Bodi, Robert P E Sarkany, Hiva Fassihi, Alan R Lehmann, and Paola Giunti. Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression. Brain, 146:5044-5059, Dec 2023. URL: https://doi.org/10.1093/brain/awad266, doi:10.1093/brain/awad266. This article has 20 citations and is from a highest quality peer-reviewed journal.
(sagun2024differentgermlinevariants pages 1-2): Jeffrey P. Sagun, Sikandar G. Khan, Kyoko Imoto, Deborah Tamura, Kyu-Seon Oh, John J. DiGiovanna, and Kenneth H. Kraemer. Different germline variants in the xpa gene are associated with severe, intermediate, or mild neurodegeneration in xeroderma pigmentosum patients. Dec 2024. URL: https://doi.org/10.1371/journal.pgen.1011265, doi:10.1371/journal.pgen.1011265. This article has 4 citations and is from a domain leading peer-reviewed journal.
(yurchenko2023genomicmutationlandscape pages 1-2): Andrey A. Yurchenko, Fatemeh Rajabi, Tirzah Braz-Petta, Hiva Fassihi, Alan Lehmann, Chikako Nishigori, Jinxin Wang, Ismael Padioleau, Konstantin Gunbin, Leonardo Panunzi, Fanny Morice-Picard, Pierre Laplante, Caroline Robert, Patricia L. Kannouche, Carlos F. M. Menck, Alain Sarasin, and Sergey I. Nikolaev. Genomic mutation landscape of skin cancers from dna repair-deficient xeroderma pigmentosum patients. Nature Communications, May 2023. URL: https://doi.org/10.1038/s41467-023-38311-0, doi:10.1038/s41467-023-38311-0. This article has 49 citations and is from a highest quality peer-reviewed journal.
(senju2023deepintronicfounder pages 1-2): Chikako Senju, Yuka Nakazawa, Taichi Oso, Mayuko Shimada, Kana Kato, Michiko Matsuse, Mariko Tsujimoto, Taro Masaki, Yasushi Miyazaki, Satoshi Fukushima, Satoshi Tateishi, Atsushi Utani, Hiroyuki Murota, Katsumi Tanaka, Norisato Mitsutake, Shinichi Moriwaki, Chikako Nishigori, and Tomoo Ogi. Deep intronic founder mutations identified in the ercc4/xpf gene are potential therapeutic targets for a high-frequency form of xeroderma pigmentosum. Proceedings of the National Academy of Sciences of the United States of America, Jun 2023. URL: https://doi.org/10.1073/pnas.2217423120, doi:10.1073/pnas.2217423120. This article has 14 citations and is from a highest quality peer-reviewed journal.
(kobaisi2024syntheticrescueof pages 1-2): Farah Kobaisi, Eric Sulpice, Ali Nasrallah, Patricia Obeïd, Hussein Fayyad-Kazan, Walid Rachidi, and Xavier Gidrol. Synthetic rescue of xeroderma pigmentosum c phenotype via pik3c3 downregulation. Cell Death & Disease, Nov 2024. URL: https://doi.org/10.1038/s41419-024-07186-4, doi:10.1038/s41419-024-07186-4. This article has 2 citations and is from a peer-reviewed journal.
(srivastava2021xerodermapigmentosum pages 2-5): Gautam Srivastava and G. Srivastava. Xeroderma pigmentosum. Oxford Medical Case Reports, Jan 2021. URL: https://doi.org/10.1093/omcr/omab107, doi:10.1093/omcr/omab107. This article has 3 citations and is from a peer-reviewed journal.
(NCT05159752 chunk 1): A Study to Evaluate the Safety and Efficacy of Afamelanotide in Patients With Xeroderma Pigmentosum (XP). Clinuvel Europe Limited. 2021. ClinicalTrials.gov Identifier: NCT05159752
(schubert2019xerodermapigmentosumand pages 5-6): Steffen Schubert and Steffen Emmert. Xeroderma pigmentosum and related diseases. ArXiv, pages 1743-1768, Dec 2019. URL: https://doi.org/10.1002/9781119142812.ch138, doi:10.1002/9781119142812.ch138. This article has 3 citations.
(NCT00002811 chunk 1): T4N5 Liposome Lotion Compared With Placebo Lotion for Preventing Actinic Keratoses in Patients With Xeroderma Pigmentosum. Applied Genetics. 1996. ClinicalTrials.gov Identifier: NCT00002811
(NCT03445052 chunk 1): XPAND Trial: Enhancing XP Photoprotection Activities - New Directions. Guy's and St Thomas' NHS Foundation Trust. 2018. ClinicalTrials.gov Identifier: NCT03445052
(yurchenko2023genomicmutationlandscape pages 3-5): Andrey A. Yurchenko, Fatemeh Rajabi, Tirzah Braz-Petta, Hiva Fassihi, Alan Lehmann, Chikako Nishigori, Jinxin Wang, Ismael Padioleau, Konstantin Gunbin, Leonardo Panunzi, Fanny Morice-Picard, Pierre Laplante, Caroline Robert, Patricia L. Kannouche, Carlos F. M. Menck, Alain Sarasin, and Sergey I. Nikolaev. Genomic mutation landscape of skin cancers from dna repair-deficient xeroderma pigmentosum patients. Nature Communications, May 2023. URL: https://doi.org/10.1038/s41467-023-38311-0, doi:10.1038/s41467-023-38311-0. This article has 49 citations and is from a highest quality peer-reviewed journal.
(garciamoreno2023neurologicaldiseasein pages 10-11): Hector Garcia-Moreno, Douglas R Langbehn, Adesoji Abiona, Isabel Garrood, Zofia Fleszar, Marta Antonia Manes, Ana M Susana Morley, Emma Craythorne, Shehla Mohammed, Tanya Henshaw, Sally Turner, Harsha Naik, Istvan Bodi, Robert P E Sarkany, Hiva Fassihi, Alan R Lehmann, and Paola Giunti. Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression. Brain, 146:5044-5059, Dec 2023. URL: https://doi.org/10.1093/brain/awad266, doi:10.1093/brain/awad266. This article has 20 citations and is from a highest quality peer-reviewed journal.
(garciamoreno2023neurologicaldiseasein pages 12-13): Hector Garcia-Moreno, Douglas R Langbehn, Adesoji Abiona, Isabel Garrood, Zofia Fleszar, Marta Antonia Manes, Ana M Susana Morley, Emma Craythorne, Shehla Mohammed, Tanya Henshaw, Sally Turner, Harsha Naik, Istvan Bodi, Robert P E Sarkany, Hiva Fassihi, Alan R Lehmann, and Paola Giunti. Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression. Brain, 146:5044-5059, Dec 2023. URL: https://doi.org/10.1093/brain/awad266, doi:10.1093/brain/awad266. This article has 20 citations and is from a highest quality peer-reviewed journal.
(garciamoreno2023neurologicaldiseasein pages 3-4): Hector Garcia-Moreno, Douglas R Langbehn, Adesoji Abiona, Isabel Garrood, Zofia Fleszar, Marta Antonia Manes, Ana M Susana Morley, Emma Craythorne, Shehla Mohammed, Tanya Henshaw, Sally Turner, Harsha Naik, Istvan Bodi, Robert P E Sarkany, Hiva Fassihi, Alan R Lehmann, and Paola Giunti. Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression. Brain, 146:5044-5059, Dec 2023. URL: https://doi.org/10.1093/brain/awad266, doi:10.1093/brain/awad266. This article has 20 citations and is from a highest quality peer-reviewed journal.
(garciamoreno2023neurologicaldiseasein pages 2-3): Hector Garcia-Moreno, Douglas R Langbehn, Adesoji Abiona, Isabel Garrood, Zofia Fleszar, Marta Antonia Manes, Ana M Susana Morley, Emma Craythorne, Shehla Mohammed, Tanya Henshaw, Sally Turner, Harsha Naik, Istvan Bodi, Robert P E Sarkany, Hiva Fassihi, Alan R Lehmann, and Paola Giunti. Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression. Brain, 146:5044-5059, Dec 2023. URL: https://doi.org/10.1093/brain/awad266, doi:10.1093/brain/awad266. This article has 20 citations and is from a highest quality peer-reviewed journal.
(garciamoreno2023neurologicaldiseasein pages 11-12): Hector Garcia-Moreno, Douglas R Langbehn, Adesoji Abiona, Isabel Garrood, Zofia Fleszar, Marta Antonia Manes, Ana M Susana Morley, Emma Craythorne, Shehla Mohammed, Tanya Henshaw, Sally Turner, Harsha Naik, Istvan Bodi, Robert P E Sarkany, Hiva Fassihi, Alan R Lehmann, and Paola Giunti. Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression. Brain, 146:5044-5059, Dec 2023. URL: https://doi.org/10.1093/brain/awad266, doi:10.1093/brain/awad266. This article has 20 citations and is from a highest quality peer-reviewed journal.
(garciamoreno2023neurologicaldiseasein pages 9-10): Hector Garcia-Moreno, Douglas R Langbehn, Adesoji Abiona, Isabel Garrood, Zofia Fleszar, Marta Antonia Manes, Ana M Susana Morley, Emma Craythorne, Shehla Mohammed, Tanya Henshaw, Sally Turner, Harsha Naik, Istvan Bodi, Robert P E Sarkany, Hiva Fassihi, Alan R Lehmann, and Paola Giunti. Neurological disease in xeroderma pigmentosum: prospective cohort study of its features and progression. Brain, 146:5044-5059, Dec 2023. URL: https://doi.org/10.1093/brain/awad266, doi:10.1093/brain/awad266. This article has 20 citations and is from a highest quality peer-reviewed journal.
(senju2023deepintronicfounder pages 5-6): Chikako Senju, Yuka Nakazawa, Taichi Oso, Mayuko Shimada, Kana Kato, Michiko Matsuse, Mariko Tsujimoto, Taro Masaki, Yasushi Miyazaki, Satoshi Fukushima, Satoshi Tateishi, Atsushi Utani, Hiroyuki Murota, Katsumi Tanaka, Norisato Mitsutake, Shinichi Moriwaki, Chikako Nishigori, and Tomoo Ogi. Deep intronic founder mutations identified in the ercc4/xpf gene are potential therapeutic targets for a high-frequency form of xeroderma pigmentosum. Proceedings of the National Academy of Sciences of the United States of America, Jun 2023. URL: https://doi.org/10.1073/pnas.2217423120, doi:10.1073/pnas.2217423120. This article has 14 citations and is from a highest quality peer-reviewed journal.
(senju2023deepintronicfounder pages 2-3): Chikako Senju, Yuka Nakazawa, Taichi Oso, Mayuko Shimada, Kana Kato, Michiko Matsuse, Mariko Tsujimoto, Taro Masaki, Yasushi Miyazaki, Satoshi Fukushima, Satoshi Tateishi, Atsushi Utani, Hiroyuki Murota, Katsumi Tanaka, Norisato Mitsutake, Shinichi Moriwaki, Chikako Nishigori, and Tomoo Ogi. Deep intronic founder mutations identified in the ercc4/xpf gene are potential therapeutic targets for a high-frequency form of xeroderma pigmentosum. Proceedings of the National Academy of Sciences of the United States of America, Jun 2023. URL: https://doi.org/10.1073/pnas.2217423120, doi:10.1073/pnas.2217423120. This article has 14 citations and is from a highest quality peer-reviewed journal.
(yurchenko2023genomicmutationlandscape pages 9-11): Andrey A. Yurchenko, Fatemeh Rajabi, Tirzah Braz-Petta, Hiva Fassihi, Alan Lehmann, Chikako Nishigori, Jinxin Wang, Ismael Padioleau, Konstantin Gunbin, Leonardo Panunzi, Fanny Morice-Picard, Pierre Laplante, Caroline Robert, Patricia L. Kannouche, Carlos F. M. Menck, Alain Sarasin, and Sergey I. Nikolaev. Genomic mutation landscape of skin cancers from dna repair-deficient xeroderma pigmentosum patients. Nature Communications, May 2023. URL: https://doi.org/10.1038/s41467-023-38311-0, doi:10.1038/s41467-023-38311-0. This article has 49 citations and is from a highest quality peer-reviewed journal.
(kobaisi2024syntheticrescueof pages 2-5): Farah Kobaisi, Eric Sulpice, Ali Nasrallah, Patricia Obeïd, Hussein Fayyad-Kazan, Walid Rachidi, and Xavier Gidrol. Synthetic rescue of xeroderma pigmentosum c phenotype via pik3c3 downregulation. Cell Death & Disease, Nov 2024. URL: https://doi.org/10.1038/s41419-024-07186-4, doi:10.1038/s41419-024-07186-4. This article has 2 citations and is from a peer-reviewed journal.
(NCT03445052 chunk 2): XPAND Trial: Enhancing XP Photoprotection Activities - New Directions. Guy's and St Thomas' NHS Foundation Trust. 2018. ClinicalTrials.gov Identifier: NCT03445052
(NCT05370235 chunk 1): A Study to Evaluate the Safety and Efficacy of Afamelanotide in Patients With Xeroderma Pigmentosum C and V. Clinuvel Europe Limited. 2022. ClinicalTrials.gov Identifier: NCT05370235

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Inheritance

Subtypes

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Treatments

Environmental Factors

Differential Diagnoses

Clinical Trials

Source YAML

References & Deep Research

Deep Research

1. Disease Information

1.1 Disease overview (definition and current understanding)

1.2 Key identifiers and controlled vocabulary

1.3 Synonyms and alternative names

1.4 Evidence provenance (patient-level vs aggregated)

2. Etiology

2.1 Disease causal factors

2.2 Risk factors

2.3 Protective factors

2.4 Gene–environment interactions

3. Phenotypes

3.1 Core phenotype spectrum (with suggested HPO terms)

3.2 Age of onset, severity, and progression

3.3 Quality-of-life impacts

4. Genetic / Molecular Information

4.1 Causal genes and complementation groups

4.2 Pathogenic variant classes and functional consequences

4.3 Allele frequencies / population genetics

4.4 Modifier genes (emerging)

4.5 Genetic testing approaches (current practice patterns)

5. Epidemiology and Prognosis

5.1 Epidemiology

5.2 Cancer risk (statistics from recent studies)

5.3 Neurologic prognosis

6. Diagnostics

6.1 Clinical diagnosis

6.2 Functional laboratory tests

6.3 Genetic testing

6.4 Differential diagnosis

7. Treatment and Current Applications (real-world implementation)

7.1 Core standard of care (real-world)

7.2 Chemoprevention and lesion-directed therapies

7.3 DNA repair enzyme topical therapy (historical but still informative)

7.4 Behavioral intervention to improve photoprotection (implementation science)

7.5 Melanocortin pathway photoprotection strategy (clinical trials; 2023 updates)

7.6 Immunotherapy and targeted therapy for XP-associated cancers

8. Prevention

8.1 Primary prevention

8.2 Secondary prevention

8.3 Tertiary prevention

9. Mechanism / Pathophysiology (molecular-to-clinical causal chain)

9.1 Core mechanism: defective NER or TLS

9.2 Tumor genomics as mechanistic readout (2023)

9.3 Neurological disease mechanisms (current evidence)

10. Anatomical structures affected

11. Temporal development

12. Inheritance and population

13. Other species / natural disease and 14. Model organisms

15. Recent developments and latest research highlights (2023–2024)

Notes on evidence limitations

Key data points (quick reference)

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