Well-differentiated systemic mastocytosis: genetics, mast cell immunophenotypes, and KIT autophosphorylation

Brandon J Schornack; Jeremy C McMurray; Maria Leondaridis; Xiaoping Sun; Jeffrey R Stinson; Amaya James; Janet A Brunader; Kip R Hartman; Joaquin Villar; Clifton L Dalgard; Lydia D Hellwig; Aubrey N Montebello; Pinar Engin Zerk; Anna L Guarnieri; Yeyun Zhou; Ravi K Jalluri; Eric M Pryor; Andrew L Snow; Tracy I George; Melody C Carter; Irina Maric; Nathan A Boggs

doi:10.1016/j.jaci.2025.07.029

Well-differentiated systemic mastocytosis: genetics, mast cell immunophenotypes, and KIT autophosphorylation

Brandon J Schornack, Jeremy C McMurray, Maria Leondaridis, Xiaoping Sun, Jeffrey R Stinson, Amaya James, Janet A Brunader, Kip R Hartman, Joaquin Villar, Clifton L Dalgard, Lydia D Hellwig, Aubrey N Montebello, Pinar Engin Zerk, Anna L Guarnieri, Yeyun Zhou, Ravi K Jalluri, Eric M Pryor, Andrew L Snow, Tracy I George, Melody C CarterIrina Maric, Nathan A Boggs

Research output: Contribution to journal › Article › peer-review

Abstract

BACKGROUND: Well-differentiated systemic mastocytosis (WDSM) is a rare myeloid neoplasm where the genetic etiology is often unknown.

OBJECTIVE: We aimed to assess WDSM patients for novel KIT variants, mast cell (MC) aberrant immunophenotypes, and KIT autophosphorylation patterns.

METHODS: Next-generation sequencing (NGS), MC immunophenotyping, and KIT autophosphorylation studies were performed.

RESULTS: Among 454 SM patients, there were 432 with KIT p.D816V+SM and 4 with KIT p.D816Y+SM - notably, none of these patients had WDSM. Of the remaining patients, we identified 7 with WDSM (1.5%) and 2 relatives with mastocytosis-in-skin. NGS revealed that 6/9 subjects carried known or novel germline KIT variants corresponding to regions outside of codon 816. Three patients had germline KIT p.K509I, two had germline KIT p.A533D, one had two germline KIT variants p.F681L and p.M541L, and three had no KIT mutation. Intracellular expression of CD2 and CD25 and less robust expression of CD30 was observed in MCs from WDSM patients. By developing a novel transient transfection assay in 293T cells, we found that unlike KIT p.D816F/V/Y variants that exhibit nearly exclusive intracellular localization and strong ligand-independent autophosphorylation ("class II"), WDSM associated KIT variants showed enhanced ligand-dependent autophosphorylation relative to wild-type ("class I").

CONCLUSIONS: Our study doubles the number of KIT variants identified in WDSM patients. No KIT p.D816V+SM patient had WDSM. Intracellular CD2 and CD25 expression was more robustly detected in MCs from WDSM patients compared to CD30.

CLINICAL IMPLICATION: Class I KIT activating mutations are linked to mostly intracellular expression of aberrant MC immunophenotypes and the WDSM morphological pattern.

Original language	English
Journal	Journal of Allergy and Clinical Immunology
DOIs	https://doi.org/10.1016/j.jaci.2025.07.029
State	E-pub ahead of print - 9 Aug 2025
Externally published	Yes

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10.1016/j.jaci.2025.07.029

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Schornack, B. J., McMurray, J. C., Leondaridis, M., Sun, X., Stinson, J. R., James, A., Brunader, J. A., Hartman, K. R., Villar, J., Dalgard, C. L., Hellwig, L. D., Montebello, A. N., Zerk, P. E., Guarnieri, A. L., Zhou, Y., Jalluri, R. K., Pryor, E. M., Snow, A. L., George, T. I., ... Boggs, N. A. (2025). Well-differentiated systemic mastocytosis: genetics, mast cell immunophenotypes, and KIT autophosphorylation. Journal of Allergy and Clinical Immunology. Advance online publication. https://doi.org/10.1016/j.jaci.2025.07.029

@article{87604b91709d499783cbe0f13275fadf,

title = "Well-differentiated systemic mastocytosis: genetics, mast cell immunophenotypes, and KIT autophosphorylation",

abstract = "BACKGROUND: Well-differentiated systemic mastocytosis (WDSM) is a rare myeloid neoplasm where the genetic etiology is often unknown.OBJECTIVE: We aimed to assess WDSM patients for novel KIT variants, mast cell (MC) aberrant immunophenotypes, and KIT autophosphorylation patterns.METHODS: Next-generation sequencing (NGS), MC immunophenotyping, and KIT autophosphorylation studies were performed.RESULTS: Among 454 SM patients, there were 432 with KIT p.D816V+SM and 4 with KIT p.D816Y+SM - notably, none of these patients had WDSM. Of the remaining patients, we identified 7 with WDSM (1.5%) and 2 relatives with mastocytosis-in-skin. NGS revealed that 6/9 subjects carried known or novel germline KIT variants corresponding to regions outside of codon 816. Three patients had germline KIT p.K509I, two had germline KIT p.A533D, one had two germline KIT variants p.F681L and p.M541L, and three had no KIT mutation. Intracellular expression of CD2 and CD25 and less robust expression of CD30 was observed in MCs from WDSM patients. By developing a novel transient transfection assay in 293T cells, we found that unlike KIT p.D816F/V/Y variants that exhibit nearly exclusive intracellular localization and strong ligand-independent autophosphorylation ({"}class II{"}), WDSM associated KIT variants showed enhanced ligand-dependent autophosphorylation relative to wild-type ({"}class I{"}).CONCLUSIONS: Our study doubles the number of KIT variants identified in WDSM patients. No KIT p.D816V+SM patient had WDSM. Intracellular CD2 and CD25 expression was more robustly detected in MCs from WDSM patients compared to CD30.CLINICAL IMPLICATION: Class I KIT activating mutations are linked to mostly intracellular expression of aberrant MC immunophenotypes and the WDSM morphological pattern.",

author = "Schornack, {Brandon J} and McMurray, {Jeremy C} and Maria Leondaridis and Xiaoping Sun and Stinson, {Jeffrey R} and Amaya James and Brunader, {Janet A} and Hartman, {Kip R} and Joaquin Villar and Dalgard, {Clifton L} and Hellwig, {Lydia D} and Montebello, {Aubrey N} and Zerk, {Pinar Engin} and Guarnieri, {Anna L} and Yeyun Zhou and Jalluri, {Ravi K} and Pryor, {Eric M} and Snow, {Andrew L} and George, {Tracy I} and Carter, {Melody C} and Irina Maric and Boggs, {Nathan A}",

note = "Copyright {\textcopyright} 2025. Published by Elsevier Inc.",

year = "2025",

month = aug,

day = "9",

doi = "10.1016/j.jaci.2025.07.029",

language = "English",

journal = "Journal of Allergy and Clinical Immunology",

issn = "0091-6749",

publisher = "Elsevier Inc.",

}

Schornack, BJ, McMurray, JC, Leondaridis, M, Sun, X, Stinson, JR, James, A, Brunader, JA, Hartman, KR, Villar, J, Dalgard, CL, Hellwig, LD, Montebello, AN, Zerk, PE, Guarnieri, AL, Zhou, Y, Jalluri, RK, Pryor, EM, Snow, AL, George, TI, Carter, MC, Maric, I & Boggs, NA 2025, 'Well-differentiated systemic mastocytosis: genetics, mast cell immunophenotypes, and KIT autophosphorylation', Journal of Allergy and Clinical Immunology. https://doi.org/10.1016/j.jaci.2025.07.029

TY - JOUR

T1 - Well-differentiated systemic mastocytosis

T2 - genetics, mast cell immunophenotypes, and KIT autophosphorylation

AU - Schornack, Brandon J

AU - McMurray, Jeremy C

AU - Leondaridis, Maria

AU - Sun, Xiaoping

AU - Stinson, Jeffrey R

AU - James, Amaya

AU - Brunader, Janet A

AU - Hartman, Kip R

AU - Villar, Joaquin

AU - Dalgard, Clifton L

AU - Hellwig, Lydia D

AU - Montebello, Aubrey N

AU - Zerk, Pinar Engin

AU - Guarnieri, Anna L

AU - Zhou, Yeyun

AU - Jalluri, Ravi K

AU - Pryor, Eric M

AU - Snow, Andrew L

AU - George, Tracy I

AU - Carter, Melody C

AU - Maric, Irina

AU - Boggs, Nathan A

PY - 2025/8/9

Y1 - 2025/8/9

N2 - BACKGROUND: Well-differentiated systemic mastocytosis (WDSM) is a rare myeloid neoplasm where the genetic etiology is often unknown.OBJECTIVE: We aimed to assess WDSM patients for novel KIT variants, mast cell (MC) aberrant immunophenotypes, and KIT autophosphorylation patterns.METHODS: Next-generation sequencing (NGS), MC immunophenotyping, and KIT autophosphorylation studies were performed.RESULTS: Among 454 SM patients, there were 432 with KIT p.D816V+SM and 4 with KIT p.D816Y+SM - notably, none of these patients had WDSM. Of the remaining patients, we identified 7 with WDSM (1.5%) and 2 relatives with mastocytosis-in-skin. NGS revealed that 6/9 subjects carried known or novel germline KIT variants corresponding to regions outside of codon 816. Three patients had germline KIT p.K509I, two had germline KIT p.A533D, one had two germline KIT variants p.F681L and p.M541L, and three had no KIT mutation. Intracellular expression of CD2 and CD25 and less robust expression of CD30 was observed in MCs from WDSM patients. By developing a novel transient transfection assay in 293T cells, we found that unlike KIT p.D816F/V/Y variants that exhibit nearly exclusive intracellular localization and strong ligand-independent autophosphorylation ("class II"), WDSM associated KIT variants showed enhanced ligand-dependent autophosphorylation relative to wild-type ("class I").CONCLUSIONS: Our study doubles the number of KIT variants identified in WDSM patients. No KIT p.D816V+SM patient had WDSM. Intracellular CD2 and CD25 expression was more robustly detected in MCs from WDSM patients compared to CD30.CLINICAL IMPLICATION: Class I KIT activating mutations are linked to mostly intracellular expression of aberrant MC immunophenotypes and the WDSM morphological pattern.

AB - BACKGROUND: Well-differentiated systemic mastocytosis (WDSM) is a rare myeloid neoplasm where the genetic etiology is often unknown.OBJECTIVE: We aimed to assess WDSM patients for novel KIT variants, mast cell (MC) aberrant immunophenotypes, and KIT autophosphorylation patterns.METHODS: Next-generation sequencing (NGS), MC immunophenotyping, and KIT autophosphorylation studies were performed.RESULTS: Among 454 SM patients, there were 432 with KIT p.D816V+SM and 4 with KIT p.D816Y+SM - notably, none of these patients had WDSM. Of the remaining patients, we identified 7 with WDSM (1.5%) and 2 relatives with mastocytosis-in-skin. NGS revealed that 6/9 subjects carried known or novel germline KIT variants corresponding to regions outside of codon 816. Three patients had germline KIT p.K509I, two had germline KIT p.A533D, one had two germline KIT variants p.F681L and p.M541L, and three had no KIT mutation. Intracellular expression of CD2 and CD25 and less robust expression of CD30 was observed in MCs from WDSM patients. By developing a novel transient transfection assay in 293T cells, we found that unlike KIT p.D816F/V/Y variants that exhibit nearly exclusive intracellular localization and strong ligand-independent autophosphorylation ("class II"), WDSM associated KIT variants showed enhanced ligand-dependent autophosphorylation relative to wild-type ("class I").CONCLUSIONS: Our study doubles the number of KIT variants identified in WDSM patients. No KIT p.D816V+SM patient had WDSM. Intracellular CD2 and CD25 expression was more robustly detected in MCs from WDSM patients compared to CD30.CLINICAL IMPLICATION: Class I KIT activating mutations are linked to mostly intracellular expression of aberrant MC immunophenotypes and the WDSM morphological pattern.

U2 - 10.1016/j.jaci.2025.07.029

DO - 10.1016/j.jaci.2025.07.029

M3 - Article

C2 - 40789457

SN - 0091-6749

JO - Journal of Allergy and Clinical Immunology

JF - Journal of Allergy and Clinical Immunology

ER -