Maculopapular Cutaneous Mastocytosis

Complex MONDO:0019316 Pathograph 10 Show in embeddings browser

Maculopapular cutaneous mastocytosis (MPCM), historically called urticaria pigmentosa, is the most common form of cutaneous mastocytosis and the most common mastocytosis presentation in children. It is defined by an abnormal accumulation of clonal mast cells confined to the skin, producing multiple hyperpigmented (red-brown) macules, papules, or nodules that urticate on stroking (the pathognomonic Darier sign). Like systemic mastocytosis it is a clonal disease driven by somatic activating mutations of the KIT receptor tyrosine kinase, but in contrast to systemic mastocytosis the mast-cell accumulation is restricted to the skin without extracutaneous organ involvement (see the distinct entry Systemic Mastocytosis, MONDO:0016586). Adult and systemic disease is dominated by the activation-loop mutation KIT D816V, whereas children with cutaneous mastocytosis carry a broader KIT mutation spectrum frequently outside codon 816. A 2015 international consensus subdivides MPCM into a monomorphic variant (small uniform lesions, typically adults, often persistent and associated with systemic disease) and a polymorphic variant (larger lesions of variable size, typically pediatric, often regressing around puberty). Most pediatric MPCM follows a benign, frequently self-limiting course; treatment is symptomatic (trigger avoidance, H1/H2 antihistamines, mast-cell stabilizers, and epinephrine for anaphylaxis), with KIT-targeted tyrosine kinase inhibitors reserved for systemic or severe disease.

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3
Pathophys.
9
Phenotypes
10
Pathograph
1
Genes
6
Medical Actions
2
Subtypes
11
References
1
Deep Research
◆

Subtypes

2
Monomorphic MPCM (small-lesion variant)
Variant presenting with small, uniform maculopapular lesions, the morphology typically seen in adults. When it develops in children it often persists into adulthood and may indicate or associate with underlying systemic mastocytosis. Associated with higher serum tryptase, longer disease duration, and a less favorable prognosis than the polymorphic variant.
Show evidence (3 references)
PMID:26476479 SUPPORT Human Clinical
"a monomorphic variant with small maculopapular lesions, which is typically seen in adult patients"
The consensus report defines the monomorphic variant as small maculopapular lesions typical of adults.
PMID:41285204 SUPPORT Human Clinical
"When children present with monomorphic maculopapular skin lesions, the variant typically seen in adults, this may indicate rare persistent disease until adulthood, often associated with systemic mastocytosis."
Monomorphic lesions in children flag persistent disease and association with systemic mastocytosis.
PMID:33988879 PARTIAL Human Clinical
"We failed to validate the classification system of childhood MPCM"
The monomorphic/polymorphic distinction has poor reproducibility: a blinded study of childhood MPCM found only fair interobserver agreement among mastocytosis experts (kappa 0.39) and near-chance agreement among general dermatologists, so this subtype boundary should be applied with caution.
Polymorphic MPCM (large-lesion variant)
Variant presenting with larger lesions of variable size and shape, the morphology typically seen in children. The more common pediatric form, it is associated with lower tryptase, earlier onset, shorter disease duration, and a higher rate of spontaneous regression around puberty.
Show evidence (2 references)
PMID:26476479 SUPPORT Human Clinical
"a polymorphic variant with larger lesions of variable size and shape, which is typically seen in pediatric patients"
The consensus report defines the polymorphic variant as larger variable lesions typical of children.
PMID:26152315 SUPPORT Human Clinical
"Patients with MPCM-large lesions, compared with those with MPCM-small lesions, were characterized by significantly lower tryptase levels, shorter disease duration, and earlier disease onset."
Large-lesion (polymorphic) MPCM has lower tryptase, earlier onset, and shorter duration than small-lesion disease.
⚙

Pathophysiology

3
Constitutive KIT Activation in Skin Mast Cells
MPCM is a clonal mast-cell disease driven by somatic gain-of-function mutations of KIT, the receptor tyrosine kinase for stem cell factor (CD117). The mutations render KIT constitutively active and ligand independent, driving downstream MAPK and PI3K/AKT pro-survival and proliferative signaling. Whereas adult and systemic disease is dominated by the activation-loop mutation D816V (exon 17), children with cutaneous disease carry a broader spectrum of activating KIT mutations, frequently outside codon 816 (e.g. extracellular exon 8/9 and juxtamembrane exon 11), which has direct therapeutic consequences because D816V is imatinib resistant while many non-codon-816 variants are imatinib sensitive.
skin mast cell CL:0000097
KIT hgnc:6342
KIT receptor tyrosine kinase signaling GO:0007169 ↑ INCREASED MAPK cascade GO:0000165 ↑ INCREASED PI3K/AKT signaling GO:0043491 ↑ INCREASED
Downstream
Clonal Dermal Mast Cell Accumulation Constitutive KIT signaling drives ligand-independent survival and proliferation of clonal mast cells, which accumulate in the dermis.
Mast Cell Mediator Release Constitutive KIT signaling lowers the activation threshold of mast cells, promoting degranulation and mediator release on triggering.
Show evidence (3 references)
PMID:19865100 SUPPORT Human Clinical
"All mutations identified in this study were somatic and caused a constitutive activation of c-KIT."
Lesional-skin sequencing shows somatic KIT mutations that constitutively activate the kinase.
PMID:41285204 SUPPORT Human Clinical
"Children with cutaneous mastocytosis typically exhibit mutations in various regions of the KIT gene, whereas those with systemic disease predominantly carry KIT D816V."
Distinguishes the broad pediatric cutaneous KIT spectrum from the D816V-dominated systemic disease.
PMID:34804443 SUPPORT Human Clinical
"Genetic aberrations, mainly the KIT D816V mutation, play a crucial role in the pathogenesis of mastocytosis, enhancing MC survival and subsequent accumulation in organs and tissues."
KIT mutation enhances mast-cell survival and accumulation, the core pathogenic mechanism.
Clonal Dermal Mast Cell Accumulation
Constitutive KIT signaling produces a clonal accumulation of mast cells that is, by definition of cutaneous mastocytosis, limited to the skin (the dermis) without extracutaneous organ infiltration. The increased dermal mast-cell density underlies the characteristic hyperpigmented maculopapular lesions, and the absence of organ involvement distinguishes MPCM from systemic mastocytosis.
dermal mast cell CL:0000097 ↑ INCREASED
mast cell proliferation GO:0070662 ↑ INCREASED
Downstream
Maculopapular Skin Lesions Increased dermal mast-cell density and associated hyperpigmentation produce the maculopapular lesions.
Show evidence (2 references)
PMID:34804443 SUPPORT Human Clinical
"Cutaneous mastocytosis (CM), the most common form in children, is defined when MC infiltration is limited to the skin."
Cutaneous mastocytosis is defined by mast-cell infiltration limited to the skin.
PMID:41285204 SUPPORT Human Clinical
"In most children, mastocytosis is limited to skin."
Confirms skin-limited mast-cell disease in most pediatric patients.
Mast Cell Mediator Release
Mast cells degranulate and release preformed and newly synthesized mediators (histamine, tryptase, prostaglandins, leukotrienes, cytokines), most characteristically when lesions are stroked or rubbed. Mediator release drives the symptomatic manifestations of MPCM, including the urticating Darier sign, pruritus, flushing, blistering in severe infantile disease, and, less commonly, systemic mast-cell-activation symptoms up to anaphylaxis.
mast cell CL:0000097
mast cell degranulation GO:0043303 ↑ INCREASED mast cell activation GO:0045576 ↑ INCREASED
Downstream
Pruritus Histamine and other mediators released on rubbing produce pruritus.
Darier Sign (Urtication of Lesions) Mediator release on stroking a lesion produces localized wheal-and-flare urtication.
Flushing Vasoactive mediator release produces episodic flushing.
Cutaneous Blistering Intense mediator release, especially in infants, can produce blistering of lesional skin.
Anaphylaxis Massive systemic mediator release can precipitate anaphylaxis.
Show evidence (2 references)
PMID:34804443 SUPPORT Human Clinical
"Children with mastocytosis often suffer from MC mediator-related symptoms, the most common of which is itching, often triggered by rubbing the lesions."
Mediator-related symptoms, especially itching triggered by rubbing lesions, dominate the clinical picture.
PMID:41285204 SUPPORT Human Clinical
"Many pediatric patients suffer from symptoms of mast cell activation, ranging from pruritus to flushing and blistering."
Mast-cell-activation symptoms range from pruritus to flushing and blistering.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Maculopapular Cutaneous Mastocytosis Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

9
Cardiovascular 1
Darier Sign (Urtication of Lesions) VERY_FREQUENT Urticaria HP:0001025
Show evidence (2 references)
PMID:15096137 SUPPORT Human Clinical
"Darier's sign was present in 94% of cases."
Darier sign was present in 94% of pediatric cutaneous mastocytosis cases, supporting a VERY_FREQUENT band.
PMID:38248039 SUPPORT Human Clinical
"Typical CM manifestations (MPCM), including mastocytoma or diffuse cutaneous mastocytosis (DCM), all share a positive Darier's sign, and can thus be clinically recognized."
A positive Darier sign is shared across typical cutaneous mastocytosis manifestations including MPCM.
Immune 1
Maculopapular Skin Lesions Maculopapular exanthema HP:0040186
Show evidence (2 references)
PMID:25662299 SUPPORT Human Clinical
"presented as urticaria pigmentosa (75% of cases), mastocytoma (20%) or diffuse cutaneous mastocytosis (5%)"
Urticaria pigmentosa (MPCM) is the most common cutaneous mastocytosis presentation in children.
PMID:35028497 SUPPORT Human Clinical
"The most common form is the maculopapular cutaneous mastocytosis (MPCM), formerly called urticaria pigmentosa."
Confirms MPCM as the most common cutaneous mastocytosis and its synonymy with urticaria pigmentosa.
Integument 4
Cutaneous Hyperpigmentation Hyperpigmentation of the skin HP:0000953
Pruritus Pruritus HP:0000989
Show evidence (1 reference)
PMID:34804443 SUPPORT Human Clinical
"Children with mastocytosis often suffer from MC mediator-related symptoms, the most common of which is itching, often triggered by rubbing the lesions."
Itching is the most common mediator-related symptom in pediatric mastocytosis.
Flushing Flushing HP:0031284
Show evidence (1 reference)
PMID:41285204 SUPPORT Human Clinical
"Many pediatric patients suffer from symptoms of mast cell activation, ranging from pruritus to flushing and blistering."
Flushing is a recognized mast-cell-activation symptom in pediatric mastocytosis.
Cutaneous Blistering Abnormal blistering of the skin HP:0008066
Show evidence (1 reference)
PMID:41285204 SUPPORT Human Clinical
"Many pediatric patients suffer from symptoms of mast cell activation, ranging from pruritus to flushing and blistering."
Blistering is documented among mast-cell-activation manifestations in children.
Other 3
Anaphylaxis Anaphylactic shock HP:0100845
Show evidence (1 reference)
PMID:34804443 SUPPORT Human Clinical
"the availability of epinephrine auto-injectors for the patients to use in case of severe anaphylactic reactions are recommended"
Epinephrine auto-injectors are recommended for severe anaphylactic reactions, reflecting anaphylaxis risk.
Mastocytosis Mastocytosis HP:0100495
Elevated Serum Tryptase Elevated total serum tryptase HP:0031901
Show evidence (1 reference)
PMID:26152315 SUPPORT Human Clinical
"Patients with MPCM-large lesions, compared with those with MPCM-small lesions, were characterized by significantly lower tryptase levels, shorter disease duration, and earlier disease onset."
Tryptase levels stratify MPCM, with lower tryptase in the favorable large-lesion variant.
🧬

Genetic Associations

1
Somatic KIT Activating Mutations (Somatic Driver Mutation)
Gene: KIT hgnc:6342
Show evidence (3 references)
PMID:19865100 SUPPORT Human Clinical
"A mutation of codon 816 (exon 17) was found in 42% of cases, and mutations outside exon 17 were observed in 44%."
Documents the broad pediatric KIT mutation spectrum, with nearly half of mutations outside exon 17.
PMID:19865100 SUPPORT Human Clinical
"although pediatric mastocytosis can spontaneously regress, it is a clonal disease most commonly associated with activating mutations in c-KIT"
Establishes pediatric mastocytosis as a clonal KIT-driven disease despite its capacity for spontaneous regression.
PMID:25662299 SUPPORT Human Clinical
"KIT D816V mutation was detected in 34% of 215 tested patients."
In a large pediatric review, D816V was found in only about one-third of tested patients, unlike systemic disease.
💊

Medical Actions

6
Trigger Avoidance
Action: supportive care MAXO:0000950
First-line management for all patients is strict avoidance of mast-cell activation triggers (physical stimuli such as friction/rubbing, temperature extremes and pressure; culprit drugs; Hymenoptera venom).
Show evidence (1 reference)
PMID:34804443 SUPPORT Human Clinical
"Management of pediatric mastocytosis is mainly based on strict avoidance of triggers."
Trigger avoidance is the mainstay of pediatric mastocytosis management.
H1 and H2 Antihistamines
Action: Pharmacotherapy NCIT:C15986
Agent: H1 antihistamine NCIT:C29578
Oral H1 antihistamines (for pruritus and flushing) and H2 antihistamines (for gastrointestinal symptoms) are first-line pharmacotherapy for mediator-related symptoms; non-sedating H1 antihistamines are preferred.
Show evidence (2 references)
PMID:34804443 SUPPORT Human Clinical
"Treatment with H1 and H2 histamine receptor blockers on demand and the availability of epinephrine auto-injectors for the patients to use in case of severe anaphylactic reactions are recommended."
H1 and H2 histamine receptor blockers are recommended on demand for mediator symptoms.
PMID:35028497 SUPPORT Human Clinical
"Mast cell mediated symptoms are controlled by oral non-sedating antihistamines if needed."
Oral non-sedating antihistamines control mast-cell-mediated symptoms.
Mast Cell Stabilizer (Sodium Cromoglicate)
Action: Pharmacotherapy NCIT:C15986
Agent: sodium cromoglicate (cromolyn) CHEBI:128458
Oral sodium cromoglicate (cromolyn), a mast-cell stabilizer, is used for gastrointestinal and cutaneous mediator symptoms.
Show evidence (1 reference)
PMID:41285204 SUPPORT Human Clinical
"Treatment options encompass avoidance of triggers of mast cell activation, H1 and H2 antihistamines, cromolyn, and omalizumab."
Cromolyn (sodium cromoglicate) is a recommended treatment option for mast-cell activation in children.
Omalizumab
Action: Pharmacotherapy NCIT:C15986
Agent: omalizumab NCIT:C29299
Omalizumab, an anti-IgE monoclonal antibody, is used for refractory mediator symptoms or recurrent anaphylaxis.
Show evidence (1 reference)
PMID:41285204 SUPPORT Human Clinical
"Treatment options encompass avoidance of triggers of mast cell activation, H1 and H2 antihistamines, cromolyn, and omalizumab."
Omalizumab is among the recommended treatment options for mast-cell activation in children.
Epinephrine (Anaphylaxis Rescue)
Action: Pharmacotherapy NCIT:C15986
Agent: epinephrine CHEBI:33568
An epinephrine auto-injector is provided for rescue treatment of severe anaphylactic mast-cell-mediator reactions.
Show evidence (1 reference)
PMID:34804443 SUPPORT Human Clinical
"the availability of epinephrine auto-injectors for the patients to use in case of severe anaphylactic reactions are recommended"
Epinephrine auto-injectors are recommended for severe anaphylactic reactions.
KIT-Targeted Tyrosine Kinase Inhibitor (Genotype-Guided)
Action: Pharmacotherapy NCIT:C15986
Agent: imatinib CHEBI:45783
KIT-targeted tyrosine kinase inhibitors are reserved for systemic or severe disease (see the distinct entry Systemic Mastocytosis), not typical skin-limited MPCM. Selection is dictated by the KIT genotype: imatinib is effective only for imatinib-sensitive non-D816V variants (common in children), whereas D816V is imatinib resistant and requires D816V-active inhibitors such as midostaurin or avapritinib.
Show evidence (2 references)
PMID:41285204 SUPPORT Human Clinical
"In children with systemic mastocytosis, tyrosine kinase inhibitors tailored to the specific KIT variant may be considered."
KIT-genotype-tailored tyrosine kinase inhibitors are reserved for systemic disease, supporting the genotype-guided reservation.
PMID:28770635 SUPPORT Human Clinical
"Treatment of cutaneous and systemic mastocytosis is purely symptomatic with topical corticosteroids, antihistamines, omalizumab and imatinib being common choices."
Imatinib is among the agents used in mastocytosis, here within an otherwise symptomatic treatment framework.
{ }

Source YAML

click to show 
name: Maculopapular Cutaneous Mastocytosis
creation_date: "2026-06-30T00:00:00Z"
category: Complex
description: >-
  Maculopapular cutaneous mastocytosis (MPCM), historically called urticaria
  pigmentosa, is the most common form of cutaneous mastocytosis and the most
  common mastocytosis presentation in children. It is defined by an abnormal
  accumulation of clonal mast cells confined to the skin, producing multiple
  hyperpigmented (red-brown) macules, papules, or nodules that urticate on
  stroking (the pathognomonic Darier sign). Like systemic mastocytosis it is a
  clonal disease driven by somatic activating mutations of the KIT receptor
  tyrosine kinase, but in contrast to systemic mastocytosis the mast-cell
  accumulation is restricted to the skin without extracutaneous organ
  involvement (see the distinct entry Systemic Mastocytosis, MONDO:0016586).
  Adult and systemic disease is dominated by the activation-loop mutation KIT
  D816V, whereas children with cutaneous mastocytosis carry a broader KIT
  mutation spectrum frequently outside codon 816. A 2015 international consensus
  subdivides MPCM into a monomorphic variant (small uniform lesions, typically
  adults, often persistent and associated with systemic disease) and a
  polymorphic variant (larger lesions of variable size, typically pediatric,
  often regressing around puberty). Most pediatric MPCM follows a benign,
  frequently self-limiting course; treatment is symptomatic (trigger avoidance,
  H1/H2 antihistamines, mast-cell stabilizers, and epinephrine for anaphylaxis),
  with KIT-targeted tyrosine kinase inhibitors reserved for systemic or severe
  disease.
disease_term:
  preferred_term: maculopapular cutaneous mastocytosis
  term:
    id: MONDO:0019316
    label: maculopapular cutaneous mastocytosis

has_subtypes:
- name: Monomorphic
  display_name: Monomorphic MPCM (small-lesion variant)
  description: >-
    Variant presenting with small, uniform maculopapular lesions, the morphology
    typically seen in adults. When it develops in children it often persists into
    adulthood and may indicate or associate with underlying systemic mastocytosis.
    Associated with higher serum tryptase, longer disease duration, and a less
    favorable prognosis than the polymorphic variant.
  evidence:
  - reference: PMID:26476479
    reference_title: "Cutaneous manifestations in patients with mastocytosis: Consensus report of the European Competence Network on Mastocytosis; the American Academy of Allergy, Asthma & Immunology; and the European Academy of Allergology and Clinical Immunology."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a monomorphic variant with small maculopapular lesions, which is typically seen in adult patients"
    explanation: The consensus report defines the monomorphic variant as small maculopapular lesions typical of adults.
  - reference: PMID:41285204
    reference_title: "Management of Mastocytosis and Mast Cell Activation in Children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "When children present with monomorphic maculopapular skin lesions, the variant typically seen in adults, this may indicate rare persistent disease until adulthood, often associated with systemic mastocytosis."
    explanation: Monomorphic lesions in children flag persistent disease and association with systemic mastocytosis.
  - reference: PMID:33988879
    reference_title: "Interobserver variability in the classification of childhood maculopapular cutaneous mastocytosis."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "We failed to validate the classification system of childhood MPCM"
    explanation: >-
      The monomorphic/polymorphic distinction has poor reproducibility: a blinded
      study of childhood MPCM found only fair interobserver agreement among
      mastocytosis experts (kappa 0.39) and near-chance agreement among general
      dermatologists, so this subtype boundary should be applied with caution.
- name: Polymorphic
  display_name: Polymorphic MPCM (large-lesion variant)
  description: >-
    Variant presenting with larger lesions of variable size and shape, the
    morphology typically seen in children. The more common pediatric form, it is
    associated with lower tryptase, earlier onset, shorter disease duration, and
    a higher rate of spontaneous regression around puberty.
  evidence:
  - reference: PMID:26476479
    reference_title: "Cutaneous manifestations in patients with mastocytosis: Consensus report of the European Competence Network on Mastocytosis; the American Academy of Allergy, Asthma & Immunology; and the European Academy of Allergology and Clinical Immunology."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a polymorphic variant with larger lesions of variable size and shape, which is typically seen in pediatric patients"
    explanation: The consensus report defines the polymorphic variant as larger variable lesions typical of children.
  - reference: PMID:26152315
    reference_title: "Large maculopapular cutaneous lesions are associated with favorable outcome in childhood-onset mastocytosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with MPCM-large lesions, compared with those with MPCM-small lesions, were characterized by significantly lower tryptase levels, shorter disease duration, and earlier disease onset."
    explanation: Large-lesion (polymorphic) MPCM has lower tryptase, earlier onset, and shorter duration than small-lesion disease.

pathophysiology:
- name: Constitutive KIT Activation in Skin Mast Cells
  description: >-
    MPCM is a clonal mast-cell disease driven by somatic gain-of-function
    mutations of KIT, the receptor tyrosine kinase for stem cell factor (CD117).
    The mutations render KIT constitutively active and ligand independent,
    driving downstream MAPK and PI3K/AKT pro-survival and proliferative
    signaling. Whereas adult and systemic disease is dominated by the
    activation-loop mutation D816V (exon 17), children with cutaneous disease
    carry a broader spectrum of activating KIT mutations, frequently outside
    codon 816 (e.g. extracellular exon 8/9 and juxtamembrane exon 11), which has
    direct therapeutic consequences because D816V is imatinib resistant while
    many non-codon-816 variants are imatinib sensitive.
  gene:
    preferred_term: KIT
    term:
      id: hgnc:6342
      label: KIT
  cell_types:
  - preferred_term: skin mast cell
    term:
      id: CL:0000097
      label: mast cell
  biological_processes:
  - preferred_term: KIT receptor tyrosine kinase signaling
    term:
      id: GO:0007169
      label: cell surface receptor protein tyrosine kinase signaling pathway
    modifier: INCREASED
  - preferred_term: MAPK cascade
    term:
      id: GO:0000165
      label: MAPK cascade
    modifier: INCREASED
  - preferred_term: PI3K/AKT signaling
    term:
      id: GO:0043491
      label: phosphatidylinositol 3-kinase/protein kinase B signal transduction
    modifier: INCREASED
  evidence:
  - reference: PMID:19865100
    reference_title: "Pediatric mastocytosis is a clonal disease associated with D816V and other activating c-KIT mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All mutations identified in this study were somatic and caused a constitutive activation of c-KIT."
    explanation: Lesional-skin sequencing shows somatic KIT mutations that constitutively activate the kinase.
  - reference: PMID:41285204
    reference_title: "Management of Mastocytosis and Mast Cell Activation in Children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Children with cutaneous mastocytosis typically exhibit mutations in various regions of the KIT gene, whereas those with systemic disease predominantly carry KIT D816V."
    explanation: Distinguishes the broad pediatric cutaneous KIT spectrum from the D816V-dominated systemic disease.
  - reference: PMID:34804443
    reference_title: "Pediatric Mastocytosis: An Update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Genetic aberrations, mainly the KIT D816V mutation, play a crucial role in the pathogenesis of mastocytosis, enhancing MC survival and subsequent accumulation in organs and tissues."
    explanation: KIT mutation enhances mast-cell survival and accumulation, the core pathogenic mechanism.
  downstream:
  - target: Clonal Dermal Mast Cell Accumulation
    description: >-
      Constitutive KIT signaling drives ligand-independent survival and
      proliferation of clonal mast cells, which accumulate in the dermis.
    causal_link_type: DIRECT
  - target: Mast Cell Mediator Release
    description: >-
      Constitutive KIT signaling lowers the activation threshold of mast cells,
      promoting degranulation and mediator release on triggering.
    causal_link_type: DIRECT
- name: Clonal Dermal Mast Cell Accumulation
  description: >-
    Constitutive KIT signaling produces a clonal accumulation of mast cells that
    is, by definition of cutaneous mastocytosis, limited to the skin (the dermis)
    without extracutaneous organ infiltration. The increased dermal mast-cell
    density underlies the characteristic hyperpigmented maculopapular lesions, and
    the absence of organ involvement distinguishes MPCM from systemic
    mastocytosis.
  cell_types:
  - preferred_term: dermal mast cell
    term:
      id: CL:0000097
      label: mast cell
    modifier: INCREASED
  biological_processes:
  - preferred_term: mast cell proliferation
    term:
      id: GO:0070662
      label: mast cell proliferation
    modifier: INCREASED
  evidence:
  - reference: PMID:34804443
    reference_title: "Pediatric Mastocytosis: An Update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cutaneous mastocytosis (CM), the most common form in children, is defined when MC infiltration is limited to the skin."
    explanation: Cutaneous mastocytosis is defined by mast-cell infiltration limited to the skin.
  - reference: PMID:41285204
    reference_title: "Management of Mastocytosis and Mast Cell Activation in Children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In most children, mastocytosis is limited to skin."
    explanation: Confirms skin-limited mast-cell disease in most pediatric patients.
  downstream:
  - target: Maculopapular Skin Lesions
    description: Increased dermal mast-cell density and associated hyperpigmentation produce the maculopapular lesions.
    causal_link_type: DIRECT
- name: Mast Cell Mediator Release
  description: >-
    Mast cells degranulate and release preformed and newly synthesized mediators
    (histamine, tryptase, prostaglandins, leukotrienes, cytokines), most
    characteristically when lesions are stroked or rubbed. Mediator release
    drives the symptomatic manifestations of MPCM, including the urticating
    Darier sign, pruritus, flushing, blistering in severe infantile disease, and,
    less commonly, systemic mast-cell-activation symptoms up to anaphylaxis.
  cell_types:
  - preferred_term: mast cell
    term:
      id: CL:0000097
      label: mast cell
  biological_processes:
  - preferred_term: mast cell degranulation
    term:
      id: GO:0043303
      label: mast cell degranulation
    modifier: INCREASED
  - preferred_term: mast cell activation
    term:
      id: GO:0045576
      label: mast cell activation
    modifier: INCREASED
  evidence:
  - reference: PMID:34804443
    reference_title: "Pediatric Mastocytosis: An Update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Children with mastocytosis often suffer from MC mediator-related symptoms, the most common of which is itching, often triggered by rubbing the lesions."
    explanation: Mediator-related symptoms, especially itching triggered by rubbing lesions, dominate the clinical picture.
  - reference: PMID:41285204
    reference_title: "Management of Mastocytosis and Mast Cell Activation in Children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Many pediatric patients suffer from symptoms of mast cell activation, ranging from pruritus to flushing and blistering."
    explanation: Mast-cell-activation symptoms range from pruritus to flushing and blistering.
  downstream:
  - target: Pruritus
    description: Histamine and other mediators released on rubbing produce pruritus.
    causal_link_type: DIRECT
  - target: Darier Sign (Urtication of Lesions)
    description: Mediator release on stroking a lesion produces localized wheal-and-flare urtication.
    causal_link_type: DIRECT
  - target: Flushing
    description: Vasoactive mediator release produces episodic flushing.
    causal_link_type: DIRECT
  - target: Cutaneous Blistering
    description: Intense mediator release, especially in infants, can produce blistering of lesional skin.
    causal_link_type: DIRECT
  - target: Anaphylaxis
    description: Massive systemic mediator release can precipitate anaphylaxis.
    causal_link_type: DIRECT

phenotypes:
- category: Clinical
  name: Maculopapular Skin Lesions
  description: >-
    Multiple hyperpigmented (red-brown) maculopapular skin lesions are the
    defining feature of MPCM (urticaria pigmentosa) and the most common cutaneous
    presentation of pediatric mastocytosis.
  phenotype_term:
    preferred_term: Maculopapular hyperpigmented skin lesions (urticaria pigmentosa)
    term:
      id: HP:0040186
      label: Maculopapular exanthema
  evidence:
  - reference: PMID:25662299
    reference_title: "Paediatric mastocytosis: a systematic review of 1747 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "presented as urticaria pigmentosa (75% of cases), mastocytoma (20%) or diffuse cutaneous mastocytosis (5%)"
    explanation: Urticaria pigmentosa (MPCM) is the most common cutaneous mastocytosis presentation in children.
  - reference: PMID:35028497
    reference_title: "Cutaneous mastocytosis in childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common form is the maculopapular cutaneous mastocytosis (MPCM), formerly called urticaria pigmentosa."
    explanation: Confirms MPCM as the most common cutaneous mastocytosis and its synonymy with urticaria pigmentosa.
- category: Clinical
  name: Cutaneous Hyperpigmentation
  description: >-
    The maculopapular lesions are hyperpigmented (red-brown), reflecting both
    increased dermal mast cells and associated local melanocyte stimulation.
  phenotype_term:
    preferred_term: Hyperpigmentation of the skin
    term:
      id: HP:0000953
      label: Hyperpigmentation of the skin
- category: Clinical
  name: Darier Sign (Urtication of Lesions)
  description: >-
    Stroking or rubbing a lesion elicits localized whealing and erythema (the
    Darier sign) due to mast-cell mediator release; it is a pathognomonic and
    near-universal clinical sign, although a negative Darier sign does not
    exclude mastocytosis.
  phenotype_term:
    preferred_term: Darier sign (urtication on stroking lesions)
    term:
      id: HP:0001025
      label: Urticaria
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:15096137
    reference_title: "Cutaneous mastocytosis in children: a clinical analysis of 71 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Darier's sign was present in 94% of cases."
    explanation: Darier sign was present in 94% of pediatric cutaneous mastocytosis cases, supporting a VERY_FREQUENT band.
  - reference: PMID:38248039
    reference_title: "Challenges in the Diagnosis of Cutaneous Mastocytosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Typical CM manifestations (MPCM), including mastocytoma or diffuse cutaneous mastocytosis (DCM), all share a positive Darier's sign, and can thus be clinically recognized."
    explanation: A positive Darier sign is shared across typical cutaneous mastocytosis manifestations including MPCM.
- category: Clinical
  name: Pruritus
  description: >-
    Itching is the most common mast-cell-mediator symptom, characteristically
    triggered by rubbing the lesions.
  phenotype_term:
    preferred_term: Pruritus
    term:
      id: HP:0000989
      label: Pruritus
  evidence:
  - reference: PMID:34804443
    reference_title: "Pediatric Mastocytosis: An Update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Children with mastocytosis often suffer from MC mediator-related symptoms, the most common of which is itching, often triggered by rubbing the lesions."
    explanation: Itching is the most common mediator-related symptom in pediatric mastocytosis.
- category: Clinical
  name: Flushing
  description: Episodic flushing from vasoactive mast-cell mediator release.
  phenotype_term:
    preferred_term: Flushing
    term:
      id: HP:0031284
      label: Flushing
  evidence:
  - reference: PMID:41285204
    reference_title: "Management of Mastocytosis and Mast Cell Activation in Children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Many pediatric patients suffer from symptoms of mast cell activation, ranging from pruritus to flushing and blistering."
    explanation: Flushing is a recognized mast-cell-activation symptom in pediatric mastocytosis.
- category: Clinical
  name: Cutaneous Blistering
  description: >-
    Blistering (bullae) of lesional skin can occur, especially in infants and in
    severe polymorphic or diffuse disease, from intense mediator release.
  phenotype_term:
    preferred_term: Blistering of lesional skin
    term:
      id: HP:0008066
      label: Abnormal blistering of the skin
  evidence:
  - reference: PMID:41285204
    reference_title: "Management of Mastocytosis and Mast Cell Activation in Children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Many pediatric patients suffer from symptoms of mast cell activation, ranging from pruritus to flushing and blistering."
    explanation: Blistering is documented among mast-cell-activation manifestations in children.
- category: Clinical
  name: Anaphylaxis
  description: >-
    Systemic mast-cell mediator release can precipitate anaphylaxis; the risk is
    lower in MPCM than in diffuse cutaneous mastocytosis but warrants epinephrine
    auto-injector availability.
  phenotype_term:
    preferred_term: Anaphylaxis
    term:
      id: HP:0100845
      label: Anaphylactic shock
  evidence:
  - reference: PMID:34804443
    reference_title: "Pediatric Mastocytosis: An Update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the availability of epinephrine auto-injectors for the patients to use in case of severe anaphylactic reactions are recommended"
    explanation: Epinephrine auto-injectors are recommended for severe anaphylactic reactions, reflecting anaphylaxis risk.
- category: Clinical
  name: Mastocytosis
  description: >-
    MPCM is a mastocytosis (clonal mast-cell accumulation); cutaneous-only
    involvement defines it as cutaneous rather than systemic mastocytosis.
  phenotype_term:
    preferred_term: Mastocytosis
    term:
      id: HP:0100495
      label: Mastocytosis
- category: Laboratory
  name: Elevated Serum Tryptase
  description: >-
    Baseline serum tryptase may be normal or mildly elevated in pure MPCM; a
    markedly elevated tryptase (>20 ng/mL is a minor systemic mastocytosis
    criterion) prompts evaluation for systemic disease, and lower tryptase
    correlates with the favorable large-lesion (polymorphic) variant.
  phenotype_term:
    preferred_term: Elevated total serum tryptase
    term:
      id: HP:0031901
      label: Elevated total serum tryptase
  evidence:
  - reference: PMID:26152315
    reference_title: "Large maculopapular cutaneous lesions are associated with favorable outcome in childhood-onset mastocytosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with MPCM-large lesions, compared with those with MPCM-small lesions, were characterized by significantly lower tryptase levels, shorter disease duration, and earlier disease onset."
    explanation: Tryptase levels stratify MPCM, with lower tryptase in the favorable large-lesion variant.

genetic:
- name: Somatic KIT Activating Mutations
  association: Somatic Driver Mutation
  notes: >-
    MPCM is a clonal disease caused by somatic activating mutations of KIT. In
    pediatric cutaneous disease the mutation spectrum is broad and frequently
    outside codon 816 (extracellular exon 8/9 and juxtamembrane exon 11), in
    contrast to adult and systemic disease, which is dominated by the
    activation-loop mutation D816V (exon 17). Because D816V lies in the activation
    loop it is resistant to imatinib, whereas many non-codon-816 variants retain
    imatinib sensitivity, making the KIT genotype the decisive determinant of
    tyrosine-kinase-inhibitor selection.
  gene_term:
    preferred_term: KIT
    term:
      id: hgnc:6342
      label: KIT
  evidence:
  - reference: PMID:19865100
    reference_title: "Pediatric mastocytosis is a clonal disease associated with D816V and other activating c-KIT mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A mutation of codon 816 (exon 17) was found in 42% of cases, and mutations outside exon 17 were observed in 44%."
    explanation: Documents the broad pediatric KIT mutation spectrum, with nearly half of mutations outside exon 17.
  - reference: PMID:19865100
    reference_title: "Pediatric mastocytosis is a clonal disease associated with D816V and other activating c-KIT mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "although pediatric mastocytosis can spontaneously regress, it is a clonal disease most commonly associated with activating mutations in c-KIT"
    explanation: Establishes pediatric mastocytosis as a clonal KIT-driven disease despite its capacity for spontaneous regression.
  - reference: PMID:25662299
    reference_title: "Paediatric mastocytosis: a systematic review of 1747 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "KIT D816V mutation was detected in 34% of 215 tested patients."
    explanation: In a large pediatric review, D816V was found in only about one-third of tested patients, unlike systemic disease.

progression:
- phase: Course and prognosis
  notes: >-
    Pediatric MPCM usually has a benign course and frequently regresses, often
    around puberty, particularly the polymorphic (large-lesion) variant. The
    monomorphic (small-lesion) variant and adult-onset disease tend to persist
    and more often associate with systemic mastocytosis.
  evidence:
  - reference: PMID:34804443
    reference_title: "Pediatric Mastocytosis: An Update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In most children with CM, skin lesions regress spontaneously around puberty; unfortunately, it is not always a self-limiting disease."
    explanation: Most pediatric cutaneous mastocytosis regresses around puberty, though not invariably.
  - reference: PMID:25662299
    reference_title: "Paediatric mastocytosis: a systematic review of 1747 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical regression (complete or partial) occurred in 67% of cases and stabilization in 27%."
    explanation: Quantifies the high rate of regression/stabilization in pediatric mastocytosis.
  - reference: PMID:15096137
    reference_title: "Cutaneous mastocytosis in children: a clinical analysis of 71 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Eighty per cent of patients improved or had spontaneous resolution of the disease."
    explanation: Most pediatric cutaneous mastocytosis improves or spontaneously resolves.
  - reference: PMID:28770635
    reference_title: "Natural history and treatment of cutaneous and systemic mastocytosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the complete resolution rate for mastocytoma was 10% per year (95% CI: 4.8%, 15.1%) while the rate for urticaria pigmentosa was 1.9% per year"
    explanation: Meta-analysis quantifies the slower per-year resolution of urticaria pigmentosa relative to mastocytoma.

prevalence:
- population: general population
  notes: >-
    Mastocytosis overall is estimated to affect roughly 1 in 10,000 people, and
    MPCM (urticaria pigmentosa) is the most common cutaneous mastocytosis subtype
    and the most common mastocytosis presentation in children.
  evidence:
  - reference: PMID:28770635
    reference_title: "Natural history and treatment of cutaneous and systemic mastocytosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recent studies estimate that 1 in 10,000 people are diagnosed with mastocytosis."
    explanation: Provides the overall mastocytosis prevalence estimate.

treatments:
- name: Trigger Avoidance
  description: >-
    First-line management for all patients is strict avoidance of mast-cell
    activation triggers (physical stimuli such as friction/rubbing, temperature
    extremes and pressure; culprit drugs; Hymenoptera venom).
  treatment_term:
    preferred_term: supportive care
    term:
      id: MAXO:0000950
      label: supportive care
  evidence:
  - reference: PMID:34804443
    reference_title: "Pediatric Mastocytosis: An Update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Management of pediatric mastocytosis is mainly based on strict avoidance of triggers."
    explanation: Trigger avoidance is the mainstay of pediatric mastocytosis management.
- name: H1 and H2 Antihistamines
  description: >-
    Oral H1 antihistamines (for pruritus and flushing) and H2 antihistamines
    (for gastrointestinal symptoms) are first-line pharmacotherapy for
    mediator-related symptoms; non-sedating H1 antihistamines are preferred.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: H1 antihistamine
      term:
        id: NCIT:C29578
        label: Histamine-1 Receptor Antagonist
  evidence:
  - reference: PMID:34804443
    reference_title: "Pediatric Mastocytosis: An Update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Treatment with H1 and H2 histamine receptor blockers on demand and the availability of epinephrine auto-injectors for the patients to use in case of severe anaphylactic reactions are recommended."
    explanation: H1 and H2 histamine receptor blockers are recommended on demand for mediator symptoms.
  - reference: PMID:35028497
    reference_title: "Cutaneous mastocytosis in childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mast cell mediated symptoms are controlled by oral non-sedating antihistamines if needed."
    explanation: Oral non-sedating antihistamines control mast-cell-mediated symptoms.
- name: Mast Cell Stabilizer (Sodium Cromoglicate)
  description: >-
    Oral sodium cromoglicate (cromolyn), a mast-cell stabilizer, is used for
    gastrointestinal and cutaneous mediator symptoms.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: sodium cromoglicate (cromolyn)
      term:
        id: CHEBI:128458
        label: disodium cromoglycate
  evidence:
  - reference: PMID:41285204
    reference_title: "Management of Mastocytosis and Mast Cell Activation in Children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Treatment options encompass avoidance of triggers of mast cell activation, H1 and H2 antihistamines, cromolyn, and omalizumab."
    explanation: Cromolyn (sodium cromoglicate) is a recommended treatment option for mast-cell activation in children.
- name: Omalizumab
  description: >-
    Omalizumab, an anti-IgE monoclonal antibody, is used for refractory
    mediator symptoms or recurrent anaphylaxis.
  therapeutic_modality: MONOCLONAL_ANTIBODY
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: omalizumab
      term:
        id: NCIT:C29299
        label: Omalizumab
  evidence:
  - reference: PMID:41285204
    reference_title: "Management of Mastocytosis and Mast Cell Activation in Children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Treatment options encompass avoidance of triggers of mast cell activation, H1 and H2 antihistamines, cromolyn, and omalizumab."
    explanation: Omalizumab is among the recommended treatment options for mast-cell activation in children.
- name: Epinephrine (Anaphylaxis Rescue)
  description: >-
    An epinephrine auto-injector is provided for rescue treatment of severe
    anaphylactic mast-cell-mediator reactions.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: epinephrine
      term:
        id: CHEBI:33568
        label: adrenaline
  evidence:
  - reference: PMID:34804443
    reference_title: "Pediatric Mastocytosis: An Update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the availability of epinephrine auto-injectors for the patients to use in case of severe anaphylactic reactions are recommended"
    explanation: Epinephrine auto-injectors are recommended for severe anaphylactic reactions.
- name: KIT-Targeted Tyrosine Kinase Inhibitor (Genotype-Guided)
  description: >-
    KIT-targeted tyrosine kinase inhibitors are reserved for systemic or severe
    disease (see the distinct entry Systemic Mastocytosis), not typical
    skin-limited MPCM. Selection is dictated by the KIT genotype: imatinib is
    effective only for imatinib-sensitive non-D816V variants (common in
    children), whereas D816V is imatinib resistant and requires D816V-active
    inhibitors such as midostaurin or avapritinib.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: imatinib
      term:
        id: CHEBI:45783
        label: imatinib
  evidence:
  - reference: PMID:41285204
    reference_title: "Management of Mastocytosis and Mast Cell Activation in Children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In children with systemic mastocytosis, tyrosine kinase inhibitors tailored to the specific KIT variant may be considered."
    explanation: KIT-genotype-tailored tyrosine kinase inhibitors are reserved for systemic disease, supporting the genotype-guided reservation.
  - reference: PMID:28770635
    reference_title: "Natural history and treatment of cutaneous and systemic mastocytosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Treatment of cutaneous and systemic mastocytosis is purely symptomatic with topical corticosteroids, antihistamines, omalizumab and imatinib being common choices."
    explanation: Imatinib is among the agents used in mastocytosis, here within an otherwise symptomatic treatment framework.

references:
- reference: PMID:26476479
  title: "Cutaneous manifestations in patients with mastocytosis: Consensus report of the European Competence Network on Mastocytosis; the American Academy of Allergy, Asthma & Immunology; and the European Academy of Allergology and Clinical Immunology."
- reference: PMID:25662299
  title: "Paediatric mastocytosis: a systematic review of 1747 cases."
- reference: PMID:19865100
  title: "Pediatric mastocytosis is a clonal disease associated with D816V and other activating c-KIT mutations."
- reference: PMID:41285204
  title: "Management of Mastocytosis and Mast Cell Activation in Children."
- reference: PMID:34804443
  title: "Pediatric Mastocytosis: An Update."
- reference: PMID:26152315
  title: "Large maculopapular cutaneous lesions are associated with favorable outcome in childhood-onset mastocytosis."
- reference: PMID:28770635
  title: "Natural history and treatment of cutaneous and systemic mastocytosis."
- reference: PMID:15096137
  title: "Cutaneous mastocytosis in children: a clinical analysis of 71 cases."
- reference: PMID:38248039
  title: "Challenges in the Diagnosis of Cutaneous Mastocytosis."
- reference: PMID:35028497
  title: "Cutaneous mastocytosis in childhood."
- reference: PMID:33988879
  title: "Interobserver variability in the classification of childhood maculopapular cutaneous mastocytosis."
📚

References & Deep Research

References

11
PMID:26476479
Cutaneous manifestations in patients with mastocytosis: Consensus report of the European Competence Network on Mastocytosis; the American Academy of Allergy, Asthma & Immunology; and the European Academy of Allergology and Clinical Immunology.
No top-level findings curated for this source.
PMID:25662299
Paediatric mastocytosis: a systematic review of 1747 cases.
No top-level findings curated for this source.
PMID:19865100
Pediatric mastocytosis is a clonal disease associated with D816V and other activating c-KIT mutations.
No top-level findings curated for this source.
PMID:41285204
Management of Mastocytosis and Mast Cell Activation in Children.
No top-level findings curated for this source.
PMID:34804443
Pediatric Mastocytosis: An Update.
No top-level findings curated for this source.
PMID:26152315
Large maculopapular cutaneous lesions are associated with favorable outcome in childhood-onset mastocytosis.
No top-level findings curated for this source.
PMID:28770635
Natural history and treatment of cutaneous and systemic mastocytosis.
No top-level findings curated for this source.
PMID:15096137
Cutaneous mastocytosis in children: a clinical analysis of 71 cases.
No top-level findings curated for this source.
PMID:38248039
Challenges in the Diagnosis of Cutaneous Mastocytosis.
No top-level findings curated for this source.
PMID:35028497
Cutaneous mastocytosis in childhood.
No top-level findings curated for this source.
PMID:33988879
Interobserver variability in the classification of childhood maculopapular cutaneous mastocytosis.
No top-level findings curated for this source.

Deep Research

1
Claude Code ▸
1. Disease Information
claude-opus-4-8[1m] 15 citations 2026-06-30T08:46:09.056159

1. Disease Information

Overview. Maculopapular cutaneous mastocytosis (MPCM), historically termed urticaria pigmentosa (UP), is the most common form of cutaneous mastocytosis (CM). It is defined by an abnormal accumulation of clonal mast cells restricted to the skin, producing multiple hyperpigmented (red‑brown) macules, papules, plaques, or nodules that characteristically urticate (wheal-and-flare) when stroked — the Darier sign. Unlike systemic mastocytosis (SM), the mast-cell infiltrate is confined to the skin with no extracutaneous organ involvement at diagnosis.

According to PubMed, cutaneous mastocytosis "is the most common form in children, is defined when MC infiltration is limited to the skin," and CM "includes three forms: solitary mastocytoma, maculopapular cutaneous mastocytosis (MPCM), and diffuse cutaneous mastocytosis (DCM)" (Giona, Mediterr J Hematol Infect Dis 2021; DOI).

A pivotal 2015 consensus refinement (European Competence Network on Mastocytosis / AAAAI / EAACI) recommended that MPCM be subdivided into two clinically and prognostically distinct variants: - Monomorphic variant — small, uniform maculopapular lesions, typically seen in adults; if it develops in children, it often persists into adulthood and may signal underlying systemic disease. - Polymorphic variant — larger lesions of variable size and shape, typically seen in children; may resolve around puberty.

Verbatim: "we recommend that the typical maculopapular cutaneous lesions (urticaria pigmentosa) should be subdivided into 2 variants, namely a monomorphic variant with small maculopapular lesions, which is typically seen in adult patients, and a polymorphic variant with larger lesions of variable size and shape, which is typically seen in pediatric patients" (Hartmann et al., J Allergy Clin Immunol 2016; DOI). The same consensus removed telangiectasia macularis eruptiva perstans (TMEP) from the CM classification and dropped the adjunct "solitary" from solitary mastocytoma.

Key identifiers | Resource | ID | |---|---| | MONDO | MONDO:0019316 (maculopapular cutaneous mastocytosis) — verified in OLS | | Orphanet | ORPHA:79457 (Maculopapular cutaneous mastocytosis); parent ORPHA:66646 (Cutaneous mastocytosis) | | MeSH | D014582 (Urticaria Pigmentosa) | | SNOMED CT | 1332134000 (Maculopapular cutaneous mastocytosis) | | UMLS/MedGen | C0042111 | | NCIT | C212102 (Urticaria Pigmentosa/MPCM, Monomorphic Variant) | | ICD-10 | Q82.2 (Mastocytosis, congenital/cutaneous); ICD-O 9740/1 for mastocytoma/UP | | ICD-11 | EK90.1 (Cutaneous mastocytosis), with 2A21.0 for indolent SM | | OMIM | 154800 (Mastocytosis, cutaneous; phenotype linked to KIT 164920) |

Synonyms: urticaria pigmentosa (UP); MPCM; UP/MPCM. The terms UP and MPCM are now used interchangeably, with MPCM preferred in modern consensus nomenclature.

Information source. Derived predominantly from aggregated disease-level resources (consensus classifications, systematic reviews, large single-center and registry cohorts) supplemented by individual case reports for rare KIT variants. This is not an EHR-derived entity.

2. Etiology

Primary causal factor — somatic activating KIT mutation. Mastocytosis is a clonal mast-cell disorder driven by gain-of-function mutations in KIT (the receptor for stem cell factor, SCF; CD117). "Genetic aberrations, mainly the KIT D816V mutation, play a crucial role in the pathogenesis of mastocytosis, enhancing MC survival and subsequent accumulation in organs and tissues" (Giona 2021; DOI).

Critical pediatric-vs-adult distinction in the mutational driver. Adults (and systemic disease) are dominated by the canonical activation-loop mutation KIT D816V (exon 17). Children with cutaneous mastocytosis carry a much broader KIT mutation spectrum, frequently outside codon 816, including extracellular/transmembrane (exon 8, 9) and juxtamembrane (exon 11) domain mutations: - "Children with cutaneous mastocytosis typically exhibit mutations in various regions of the KIT gene, whereas those with systemic disease predominantly carry KIT D816V" (Carter, Lange, Hartmann et al., J Allergy Clin Immunol Pract 2025; DOI). - A worked single-case example: a 2-year-old with MPCM carried an Asp419del in exon 8 of KIT (Fukaura et al., Arerugi 2024; DOI). - In the largest pediatric systematic review (1747 cases), "KIT D816V mutation was detected in 34% of 215 tested patients" — i.e., the majority of tested children did not carry D816V (Méni et al., Br J Dermatol 2015; DOI).

Germline / familial forms (rare). Most disease is sporadic/somatic, but rare familial mastocytosis and germline KIT syndromes exist. A germline KIT mutation can produce "GIST cutaneous hyperpigmentation disease" — familial gastrointestinal stromal tumour with cutaneous hyperpigmentation/urticaria pigmentosa (Wali et al., Clin Exp Dermatol 2018; DOI). Familial DCM with specific gene mutations has also been reported (Rydz, Lange et al., Int J Mol Sci 2024; DOI).

Risk factors. - Genetic: somatic KIT activating variants (causal); hereditary alpha-tryptasemia (HαT) — a germline TPSAB1 copy-number gain — is a modifier that raises baseline tryptase and is enriched among SM patients (Beyens et al., Acta Clin Belg 2022; DOI). - Demographic: early childhood onset; modest male predominance (see §9). - Environmental/trigger factors are mast-cell-activation triggers rather than disease-causing: physical stimuli (friction/rubbing, heat, cold, pressure), Hymenoptera stings, certain drugs (opioids, NSAIDs, vancomycin, neuromuscular blockers, radiocontrast), and emotional stress.

Protective factors. No validated genetic or environmental protective alleles are established. The principal "protective" measure is trigger avoidance to reduce mediator-release episodes (Giona 2021; DOI).

Gene–environment interaction. The somatic KIT lesion sets a low threshold for mast-cell degranulation; environmental triggers then precipitate clinical mediator-release symptoms. No quantitative GxE model is documented.

3. Phenotypes

For each phenotype I give type, characteristics, and an HPO lead (to be validated).

Cutaneous (primary, near-universal): - Maculopapular hyperpigmented skin lesions / urticaria pigmentosa (clinical sign; physical manifestation). Red-brown macules/papules, often on trunk and extremities, sparing palms/soles/face in many cases. Frequency: defining (≈75% of pediatric CM present as UP/MPCM — Méni 2015; DOI). HPO leads: Hyperpigmentation of the skin (HP:0000953), Urticaria (HP:0001025). - Darier sign (whealing on stroking a lesion; pathognomonic clinical sign). "Darier's sign was present in 94% of cases" (Kiszewski et al., J Eur Acad Dermatol Venereol 2004; DOI). No dedicated HPO term; can be captured descriptively. - Pruritus (symptom) — the most common mediator symptom, "often triggered by rubbing the lesions" (Giona 2021; DOI). HPO lead: Pruritus (HP:0000989). - Blistering/bullae (sign) — especially in infants/severe polymorphic or diffuse disease. HPO lead: Abnormal blistering of the skin (HP:0008066). - Flushing (sign/symptom) from mediator release. HPO lead: Flushing (HP:0031284). - Dermographism (sign).

Mediator-related systemic symptoms (mast-cell activation, MCA): flushing, pruritus, abdominal pain, diarrhea, headache, hypotension/syncope, and — at the severe end — anaphylaxis. "Many pediatric patients suffer from symptoms of mast cell activation, ranging from pruritus to flushing and blistering" (Carter et al. 2025; DOI). HPO leads: Diarrhea (HP:0002014), Abdominal pain (HP:0002027), Episodic abdominal pain, Hypotension (HP:0002615). Anaphylaxis risk is lower in MPCM than DCM but real, warranting epinephrine auto-injector availability (Giona 2021; DOI).

Laboratory abnormality: elevated serum tryptase (biomarker of mast-cell burden). A basal serum tryptase >20 ng/mL is a minor SM criterion; in pure MPCM tryptase is often normal or mildly elevated, and lower tryptase correlates with the favorable large-lesion variant (Wiechers et al., J Allergy Clin Immunol 2015; DOI).

Phenotype characteristics: - Onset: lesions occur before age 2 in ~90% of pediatric cases (Méni 2015; DOI); "in 92% of cases disease onset was in the first year of life" (Kiszewski 2004; DOI). - Severity: variable — most pediatric MPCM is mild/indolent; severity tracks lesion type (small monomorphic ↔ higher tryptase/persistence). - Progression: often stable then regressing (polymorphic/large-lesion); monomorphic small-lesion disease is more persistent. - Quality of life: impacted by chronic pruritus, cosmetic burden of pigmented lesions, trigger-avoidance lifestyle constraints, and anxiety about anaphylaxis; formal disease-specific QoL instruments (e.g., MC-QoL, MQLQ) exist for mastocytosis but per-phenotype QoL data for pediatric MPCM are limited.

Prognostic phenotype subdivision (important for KB): large lesions = favorable. "Patients with MPCM-large lesions, compared with those with MPCM-small lesions, were characterized by significantly lower tryptase levels, shorter disease duration, and earlier disease onset... more patients with MPCM-large lesions exhibited spontaneous regression" (Wiechers 2015; DOI).

4. Genetic / Molecular Information

Causal gene: KIT (proto-oncogene receptor tyrosine kinase / CD117 / SCF receptor). HGNC hgnc:6342 (dismech lowercase convention); OMIM gene 164920; chromosome 4q12.

Pathogenic variants: - KIT D816V (c.2447A>T, p.Asp816Val; exon 17 activation loop) — the canonical adult/systemic mutation; gain-of-function, constitutive ligand-independent kinase activation. Classified Pathogenic. Somatic. In pediatric CM it is present in only ~one-third of tested cases. - Non-codon-816 KIT variants enriched in pediatric CM: extracellular domain exon 8 (e.g., p.Asp419del), exon 9, and juxtamembrane exon 11 mutations; some are insertions/deletions and missense. A pediatric mature B-cell lymphoma case carried a KIT exon 11 variant (Yazal Erdem et al., J Pediatr Hematol Oncol 2022; DOI). Verbatim exon-8 example: "an Asp419del mutation in exon 8 of the KIT gene" (Fukaura 2024; DOI). - Variant types: missense (dominant), small in-frame deletions, insertions, occasional internal tandem patterns. - Origin: predominantly somatic (lesional skin); rare germline in familial GIST/mastocytosis syndromes. - Functional consequence: gain of function — constitutive KIT autophosphorylation → enhanced mast-cell survival, proliferation, and accumulation. D816V notably confers resistance to imatinib, whereas many non-codon-816 (juxtamembrane/extracellular) variants retain imatinib sensitivity — a therapeutically decisive distinction. - Allele frequency: these are somatic driver mutations; not represented as population germline allele frequencies in gnomAD.

Modifier genes: TPSAB1 (hereditary alpha-tryptasemia) modifies tryptase levels and may modify symptom severity (Beyens 2022; DOI). Additional somatic mutations (TET2, SRSF2, ASXL1 — the "S/A/R" panel) are associated with advanced SM but not typical pediatric MPCM.

Epigenetic / chromosomal: No recurrent epigenetic signature or large-scale chromosomal abnormality is characteristic of MPCM; advanced SM (not MPCM) accrues additional somatic mutations.

5. Environmental Information

MPCM is a clonal genetic disease; environmental factors act as symptom triggers, not causes. Relevant trigger categories: physical (rubbing/friction — the basis of the Darier sign, temperature extremes, pressure), Hymenoptera venom, drugs causing mast-cell degranulation (opioids, NSAIDs, vancomycin, muscle relaxants, iodinated contrast), alcohol (in adults), and emotional/physical stress. Management "is mainly based on strict avoidance of triggers" (Giona 2021; DOI). No infectious agent is implicated.

6. Mechanism / Pathophysiology

Causal chain (upstream → downstream): 1. Somatic activating KIT mutation in a mast-cell progenitor (D816V in adults/SM; diverse exon 8/9/11/17 variants in children). 2. → Constitutive, SCF-independent KIT receptor tyrosine kinase activation (autophosphorylation). 3. → Downstream pro-survival/proliferative signaling: PI3K–AKT–mTOR, RAS–RAF–MEK–ERK (MAPK), JAK2–STAT5, and PLCγ cascades. 4. → Enhanced mast-cell survival and clonal accumulation in the dermis (apoptosis resistance + proliferation). 5. → Increased dermal mast-cell density producing the pigmented maculopapular lesions (mast cells stimulate local melanocyte activity → hyperpigmentation). 6. → Mast-cell mediator release (degranulation) on triggering → histamine, tryptase, prostaglandin D2, leukotrienes, heparin, TNF → wheal/flare (Darier sign), pruritus, flushing, blistering, and systemic MCA symptoms up to anaphylaxis.

Molecular pathways (KEGG/Reactome): RTK/KIT signaling; PI3K-AKT; MAPK/ERK; JAK-STAT5. Cellular processes: mast-cell proliferation, apoptosis resistance, and regulated exocytosis/degranulation. Protein dysfunction: gain-of-function KIT with constitutive kinase activity (D816V destabilizes the autoinhibited conformation of the activation loop). Immune involvement: the entire phenotype is mast-cell–mediated (mediator release), without classic autoimmunity or immunodeficiency. Metabolic changes: none disease-specific.

Ontology leads (validate before use): - GO biological process: mast cell degranulation (GO:0043303), mast cell activation (GO:0045576), transmembrane receptor protein tyrosine kinase signaling pathway (GO:0007169), positive regulation of mast cell proliferation, regulation of mast cell apoptotic process. - GO molecular function: stem cell factor receptor activity, protein tyrosine kinase activity (GO:0004713). - CL cell type: mast cell (CL:0000097); consider connective tissue / dermal mast cell subtype. - CHEBI mediators: histamine (CHEBI:18295), prostaglandin D2 (CHEBI:15555).

Molecular profiling. No routine transcriptomic/proteomic/metabolomic signature defines MPCM; diagnosis rests on histology + KIT genotyping + tryptase. Single-cell/spatial work on skin mast cells is emerging but not yet clinically deployed for MPCM.

7. Anatomical Structures Affected

  • Organ level — primary: skin (UBERON:0002097, skin of body), specifically the dermis (UBERON:0002067), where mast cells accumulate; the overlying epidermis (UBERON:0001003) shows basal hyperpigmentation.
  • Secondary/systemic: by definition absent in CM/MPCM (mast-cell infiltrate limited to skin). Mediator release can transiently affect the GI tract, cardiovascular system (hypotension), and respiratory system during MCA episodes, but there is no organ infiltration.
  • Tissue/cell level: connective tissue of the dermis; the targeted cell population is the dermal mast cell (CL:0000097). Lesional biopsies show "a dense accumulation of CD117-positive, round or oval cells with amphophilic cytoplasm within the upper to middle dermis" (Fukaura 2024; DOI).
  • Subcellular: mast-cell secretory granules (GO cellular component: secretory granule); plasma-membrane KIT receptor.
  • Localization/laterality: lesions are bilateral and disseminated/generalized, typically trunk-predominant; not lateralized.

8. Temporal Development

  • Onset: congenital to early infancy; "Lesions occurred before the age of 2 years in 90% of cases" (Méni 2015; DOI); first year of life in ~92% (Kiszewski 2004; DOI). Onset pattern: chronic/insidious.
  • Course: generally indolent, often with spontaneous regression around puberty for the pediatric polymorphic/large-lesion variant; "In most children with CM, skin lesions regress spontaneously around puberty; unfortunately, it is not always a self-limiting disease" (Giona 2021; DOI).
  • Regression rates (key quantitative data): In a systematic review/meta-analysis, "the complete resolution rate for mastocytoma was 10% per year... while the rate for urticaria pigmentosa was 1.9% per year (95% CI: −0.5%, 4.3%)"; "Diffuse cutaneous mastocytosis and systemic mastocytosis subtypes did not show evidence of complete resolution" (Le et al., Postgrad Med 2017; DOI). In the 1747-case pediatric review, "Clinical regression (complete or partial) occurred in 67% of cases and stabilization in 27%" (Méni 2015; DOI); 80% improved/resolved in the 71-case series (Kiszewski 2004; DOI).
  • Adult-onset / monomorphic disease tends to persist lifelong and more often associates with systemic mastocytosis.
  • Critical period for prognosis: the monomorphic vs polymorphic distinction at presentation is the key window — monomorphic small lesions in a child flag persistence/possible SM (Hartmann 2016; DOI).

9. Inheritance and Population

  • Epidemiology: mastocytosis overall affects roughly 1 in 10,000 people. "Recent studies estimate that 1 in 10,000 people are diagnosed with mastocytosis" (Le 2017; DOI; concordant in Beyens 2022; DOI). MPCM/UP is the most common CM subtype and the most common mastocytosis presentation in children (≈75% of pediatric CM — Méni 2015; DOI).
  • Inheritance pattern: predominantly sporadic/somatic (not inherited). Rare familial autosomal-dominant KIT-germline forms exist (Rydz 2024; DOI; Wali 2018; DOI). Penetrance/expressivity, anticipation, founder effects, and carrier frequencies are not applicable to the common somatic disease.
  • Sex ratio: modest male predominance — male:female 1.4:1 (Méni 2015; DOI), 1.8:1 (Kiszewski 2004; DOI), and a male-to-female ratio of 2.2 in a 61-patient cohort (Yazal Erdem 2022; DOI).
  • Age distribution: strongly bimodal across mastocytosis as a whole — pediatric CM (early childhood, usually <2 yr) vs adult SM; MPCM specifically is the dominant pediatric skin presentation.
  • Geographic/ethnic distribution: no strong ethnic predisposition documented; reported worldwide.

10. Diagnostics

Diagnosis is largely clinical and noninvasive in children. "Diagnosis is mainly based on noninvasive measures, including skin inspection, elicitation of the Darier's sign, and analyses of the serum tryptase and KIT variant in blood" (Carter et al. 2025; DOI). "In contrast to adults, mastocytosis in children usually has a benign course making sophisticated or invasive diagnostic tests unnecessary" (Kiszewski 2004; DOI).

  • Clinical signs: typical maculopapular lesions + positive Darier sign.
  • Laboratory biomarker: serum baseline tryptase (LOINC for tryptase available); >20 ng/mL is a minor SM criterion and prompts evaluation for systemic disease (Valent et al., HemaSphere 2021; DOI).
  • Genetic testing: KIT mutation analysis — peripheral-blood allele-specific PCR/ddPCR for D816V; if negative in a child but suspicion remains, lesional-skin KIT sequencing captures non-codon-816 variants (exon 8/9/11). High-sensitivity assays are recommended.
  • Histopathology (when biopsy is performed): dermal mast-cell infiltrate, CD117 (KIT) and tryptase-positive on IHC, with aberrant CD25/CD2/CD30 expression supporting clonality. CD30 in MC is now a minor SM criterion (Valent 2021; DOI).
  • Bone marrow biopsy: generally avoided in children with typical CM and stable/low tryptase; reserved for adults, persistent monomorphic disease, or red flags suggesting SM. In one cohort "Seven patients were further investigated with suspicion of systemic mastocytosis... none of them developed systemic disease" (Yazal Erdem 2022; DOI).
  • Diagnostic criteria framework: WHO / ECNM consensus criteria distinguish CM (mastocytosis in the skin, MIS) from SM (Akin & Valent, Immunol Allergy Clin North Am 2014; DOI; updated consensus Valent 2021; DOI).
  • Differential diagnosis: other pigmented/bullous disorders — especially in infants DCM "resemble[s] other bullous skin disorders" (Rydz 2024; DOI); also juvenile xanthogranuloma, post-inflammatory hyperpigmentation, café-au-lait macules/neurofibromatosis, secondary syphilis, and bullous impetigo.
  • Screening: no population screening; tryptase + KIT in blood serve as the practical risk-stratification screen for systemic involvement.

11. Outcome / Prognosis

  • Overall prognosis is favorable, especially pediatric polymorphic/large-lesion MPCM, with high rates of spontaneous regression (see §8). "Eighty per cent of patients improved or had spontaneous resolution" (Kiszewski 2004; DOI).
  • Mortality: low. In the 1747-case pediatric systematic review, "the outcome was fatal in 2.9% of patients" — almost entirely in severe/diffuse or systemic disease, not typical MPCM (Méni 2015; DOI).
  • Prognostic factors: lesion morphology (large/polymorphic = favorable, regressing; small/monomorphic = persistent, possible SM), lower baseline tryptase = favorable, earlier onset, shorter disease duration (Wiechers 2015; DOI); KIT genotype (non-D816V child = typical benign CM; persistent D816V/monomorphic = SM risk).
  • Morbidity / QoL: chronic pruritus, cosmetic burden, lifestyle restriction from trigger avoidance, and anaphylaxis risk (lower in MPCM than DCM but warranting epinephrine auto-injector provision — Giona 2021; DOI).
  • Complications: mediator-release crises/anaphylaxis; blistering in severe infantile disease; rare progression to/coexistence with systemic mastocytosis (mainly monomorphic/adult forms).
  • Follow-up: even benign-appearing pediatric cases "require planned follow-up over time" (Giona 2021; DOI).

12. Treatment

Treatment is symptomatic (no curative therapy for CM); it targets mediator symptoms and trigger avoidance.

Trigger avoidance (first-line, all patients) — MAXO lead: therapeutic/preventive avoidance behavior; "strict avoidance of triggers" (Giona 2021; DOI).

Pharmacotherapy (mediator blockade): - H1 antihistamines (first-line for pruritus/flushing) and H2 antihistamines (gastric/GI symptoms). Treatment "with H1 and H2 histamine receptor blockers on demand" is recommended (Giona 2021; DOI). - Mast-cell stabilizer: oral sodium cromoglicate (cromolyn) for GI/cutaneous symptoms; topical corticosteroids for lesions. - Leukotriene receptor antagonists, and aspirin (for prostaglandin-mediated flushing in adults, with caution). - Omalizumab (anti-IgE) for refractory mediator symptoms/recurrent anaphylaxis. Treatment options "encompass avoidance of triggers of mast cell activation, H1 and H2 antihistamines, cromolyn, and omalizumab" (Carter et al. 2025; DOI; see also Castells & Butterfield, J Allergy Clin Immunol Pract 2019; DOI). - Epinephrine auto-injector for anaphylaxis rescue (Giona 2021; DOI).

KIT-targeted / cytoreductive therapy (reserved for systemic or severe disease — not typical MPCM): - Tyrosine kinase inhibitors tailored to the KIT variant. "In children with systemic mastocytosis, tyrosine kinase inhibitors tailored to the specific KIT variant may be considered" (Carter et al. 2025; DOI). Imatinib is effective only for non-D816V / imatinib-sensitive KIT (e.g., juxtamembrane/extracellular variants common in children); D816V is imatinib-resistant, requiring D816V-active inhibitors (midostaurin, avapritinib). Imatinib is among "common choices" for symptomatic systemic disease (Le 2017; DOI). - Phototherapy (PUVA/UVB) for extensive symptomatic skin disease in adults.

Pharmacogenomics: the KIT genotype itself is the decisive "pharmacogenomic" determinant of TKI selection (D816V vs non-D816V).

MAXO leads (validate): pharmacotherapy (NCIT:C15986 for action), antihistamine therapy, immunotherapy/anti-IgE therapy, phototherapy, avoidance behavior; with therapeutic_agent CHEBI/NCIT bindings, e.g., imatinib (CHEBI:45783), omalizumab, midostaurin (NCIT:C1872), avapritinib, cromoglicate, histamine H1 antagonist class.

13. Prevention

No primary prevention exists for this clonal genetic disease. Prevention is effectively tertiary — preventing mediator-release crises and complications: - Trigger avoidance (physical stimuli, culprit drugs, venom) — the central preventive strategy (Giona 2021; DOI). - Premedication (antihistamines ± corticosteroids) before high-risk exposures (surgery/anesthesia, iodinated contrast). - Anaphylaxis preparedness: epinephrine auto-injector and an emergency action plan. - Venom immunotherapy in patients with Hymenoptera-venom anaphylaxis and mastocytosis (more relevant to adults/SM). - Genetic counseling is generally not indicated for sporadic somatic disease but is relevant for the rare germline KIT familial syndromes (Wali 2018; DOI). - Structured follow-up to detect the minority with persistent/systemic disease (Giona 2021; DOI).

14. Other Species / Natural Disease

  • Taxonomy/natural disease: Mastocytosis and cutaneous mast-cell tumors occur naturally in animals, most prominently the dog (Canis lupus familiaris, NCBITaxon:9615) — canine mast cell tumors (MCT) are among the most common skin tumors in dogs and frequently carry c-KIT (KIT) mutations (notably exon 11 internal tandem duplications), making them a recognized comparative-oncology model for KIT-driven mast-cell disease. Mast cell tumors also occur in cats (Felis catus, NCBITaxon:9685).
  • Orthologous gene: canine KIT (NCBI Gene; ortholog of human KIT).
  • Veterinary relevance / comparative pathology: strong — canine MCT KIT biology informed human KIT-targeted therapy; however, canine/feline MCT are typically neoplastic tumors rather than the self-limited pediatric maculopapular pattern, so comparative fidelity to human pediatric MPCM specifically is partial.
  • Zoonosis: none — non-transmissible.

Curation note: Veterinary mast-cell-tumor evidence should be tagged evidence_source: MODEL_ORGANISM per dismech rules, and kept distinct from human phenotype support.

15. Model Organisms

  • Mouse models: the principal experimental systems. Kit gain-of-function knock-in mice (e.g., Kit D814V, the murine equivalent of human D816V) develop mast-cell hyperplasia/mastocytosis-like disease and have been used to dissect KIT signaling and test TKIs. Kit loss-of-function alleles (W/Wv, KitW-sh "sash") are mast-cell–deficient and are widely used for mast-cell reconstitution studies — important for mast-cell biology though they model deficiency, not mastocytosis. Resource: MGI (gene Kit).
  • Cellular / in vitro models: human mast-cell leukemia lines HMC-1 (carries KIT V560G ± D816V) and LAD2; CD34⁺-derived primary human mast cells transfected with mutant KIT; used for KIT-signaling and drug-screening (imatinib-sensitive vs D816V-resistant). Resource: Cellosaurus.
  • iPSC / organoid: patient-derived iPSC mast-cell models are emerging but not standardized for MPCM.
  • Phenotype recapitulation: KIT gain-of-function models reproduce mast-cell accumulation and constitutive KIT signaling well, and faithfully reproduce D816V imatinib resistance, supporting the molecular mechanism. Limitations: murine models do not reproduce the human pediatric self-limited / pubertal-regression course or the precise human maculopapular cutaneous lesion morphology, and the diverse non-codon-816 pediatric KIT variants are under-modeled.

Curation note (HUMAN_MODEL_MISMATCH candidate): the gap between robust KIT-driven mouse/cell models and the human pediatric spontaneous-regression phenotype is a good kind: HUMAN_MODEL_MISMATCH discussion item — evidence exists in models, but translational validity to the self-limiting pediatric course is the open question.

Consolidated Evidence Table (high-value, snippet-ready)

PMID Anchor claim Verbatim snippet (verify before commit) Source type DOI
26476479 MPCM monomorphic vs polymorphic split "the typical maculopapular cutaneous lesions (urticaria pigmentosa) should be subdivided into 2 variants, namely a monomorphic variant with small maculopapular lesions, which is typically seen in adult patients, and a polymorphic variant with larger lesions of variable size and shape, which is typically seen in pediatric patients" HUMAN_CLINICAL (consensus) link
41285204 Pediatric KIT spectrum vs D816V "Children with cutaneous mastocytosis typically exhibit mutations in various regions of the KIT gene, whereas those with systemic disease predominantly carry KIT D816V" HUMAN_CLINICAL (review) link
25662299 Onset, subtype %, D816V 34%, outcomes "Lesions occurred before the age of 2 years in 90% of cases, and presented as urticaria pigmentosa (75% of cases)... KIT D816V mutation was detected in 34% of 215 tested patients. Clinical regression (complete or partial) occurred in 67% of cases... the outcome was fatal in 2.9% of patients." HUMAN_CLINICAL (systematic review) link
26152315 Large-lesion favorable prognosis "Patients with MPCM-large lesions, compared with those with MPCM-small lesions, were characterized by significantly lower tryptase levels, shorter disease duration, and earlier disease onset... more patients with MPCM-large lesions exhibited spontaneous regression of cutaneous lesions." HUMAN_CLINICAL link
28770635 Resolution rate UP vs mastocytoma; symptomatic Rx "the complete resolution rate for mastocytoma was 10% per year... while the rate for urticaria pigmentosa was 1.9% per year... Treatment... is purely symptomatic with topical corticosteroids, antihistamines, omalizumab and imatinib being common choices." HUMAN_CLINICAL (meta-analysis) link
34804443 Pediatric CM definition, D816V pathogenesis, management "Cutaneous mastocytosis (CM), the most common form in children, is defined when MC infiltration is limited to the skin... Genetic aberrations, mainly the KIT D816V mutation, play a crucial role in the pathogenesis..." HUMAN_CLINICAL (review) link
15096137 Darier sign 94%, benign course "Darier's sign was present in 94% of cases... in contrast to adults, mastocytosis in children usually has a benign course making sophisticated or invasive diagnostic tests unnecessary." HUMAN_CLINICAL link
38522933 Exon 8 KIT variant in MPCM; histology "an Asp419del mutation in exon 8 of the KIT gene... a dense accumulation of CD117-positive, round or oval cells with amphophilic cytoplasm within the upper to middle dermis." HUMAN_CLINICAL (case report) link
34901755 Updated diagnostic criteria; tryptase >20, CD30 "A basal serum tryptase level exceeding 20 ng/mL remains a minor SM criterion... CD30 expression in MC now qualifies as a minor SM criterion." HUMAN_CLINICAL (consensus) link
36259506 Prevalence ~1/10,000; KIT/CD117; HαT "it is estimated that the disease affects approximately 1 in 10,000 persons." HUMAN_CLINICAL (review) link

Suggested dismech entry scaffolding (leads)

  • disease_term: MONDO:0019316 (already in draft — confirmed in OLS). Mappings: ORPHA:79457, MeSH:D014582, ICD-10:Q82.2, SNOMED:1332134000, UMLS:C0042111.
  • has_subtypes: Monomorphic (small lesions, adult-type, persistent, SM-risk) and Polymorphic (large lesions, pediatric, regressing) — directly supported by Hartmann 2016 / Wiechers 2015. These map cleanly onto prognosis, tryptase, and progression fields.
  • Causal gene: gene: KIT (hgnc:6342); pathophysiology node "Constitutive KIT Activation" with modifier: INCREASED, GO:0007169 / GO:0043303, CL:0000097, UBERON:0002067.
  • Phenotypes (HP leads): HP:0000953 (hyperpigmentation), HP:0001025 (urticaria), HP:0000989 (pruritus), HP:0031284 (flushing), HP:0008066 (blistering), HP:0002014 (diarrhea) — all to be validated.
  • Treatments (MAXO/NCIT leads): trigger avoidance, H1/H2 antihistamines, cromoglicate, omalizumab, epinephrine, KIT-TKI (imatinib for non-D816V; midostaurin/avapritinib for D816V).
  • Discussion items: kind: HUMAN_MODEL_MISMATCH for the murine-model vs pediatric-regression gap; kind: KNOWLEDGE_GAP for why non-codon-816 KIT variants associate with the self-limiting pediatric course.

Summary of key, citable facts

MPCM (urticaria pigmentosa) is the most common cutaneous mastocytosis, a clonal KIT-driven dermal mast-cell accumulation presenting in early childhood with hyperpigmented, Darier-positive maculopapular lesions. Children carry diverse KIT variants (often non-D816V) and usually follow a benign, frequently self-resolving course (polymorphic/large-lesion variant), whereas monomorphic small-lesion disease persists and flags possible systemic mastocytosis. Diagnosis is clinical + serum tryptase + KIT genotyping; treatment is symptomatic (trigger avoidance, antihistamines, cromolyn, omalizumab, epinephrine), with KIT-genotype-guided TKIs reserved for systemic/severe disease.

All clinical/mechanistic claims above are sourced from PubMed-indexed literature with DOI links provided inline. Per the dismech anti-hallucination SOP, validate every PMID snippet (just validate-references) and every ontology ID (just validate-terms-file) before committing this content to kb/disorders/Maculopapular_Cutaneous_Mastocytosis.yaml.