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1.
J Am Acad Dermatol ; 90(4): 716-726, 2024 Apr.
Article in English | MEDLINE | ID: mdl-38040338

ABSTRACT

BACKGROUND: Pediatric melanoma presents with distinct clinical features compared to adult disease. OBJECTIVE: Characterize risk factors and negative outcomes in pediatric melanoma. METHODS: Multicenter retrospective study of patients under 20 years diagnosed with melanoma between January 1, 1995 and June 30, 2015 from 11 academic medical centers. RESULTS: Melanoma was diagnosed in 317 patients, 73% of whom were diagnosed in adolescence (age ≥11). Spitzoid (31%) and superficial spreading (26%) subtypes were most common and 11% of cases arose from congenital nevi. Sentinel lymph node biopsy was performed in 68% of cases and positive in 46%. Fatality was observed in 7% of cases. Adolescent patients with melanoma were more likely to have family history of melanoma (P = .046) compared to controls. LIMITATIONS: Retrospective nature, cohort size, control selection, and potential referral bias. CONCLUSION: Pediatric melanoma has diverse clinical presentations. Better understanding of these cases and outcomes may facilitate improved risk stratification of pediatric melanoma.


Subject(s)
Melanoma , Skin Neoplasms , Adult , Humans , Child , Adolescent , Melanoma/pathology , Retrospective Studies , Skin Neoplasms/pathology , Sentinel Lymph Node Biopsy , Risk Factors
2.
Am J Dermatopathol ; 45(12): 825-827, 2023 Dec 01.
Article in English | MEDLINE | ID: mdl-37883931

ABSTRACT

ABSTRACT: Periodic acid-Schiff (PAS) stain is a commonly used ancillary test for inflammatory and infectious dermatoses, yet infrequently changes the diagnosis. Previous studies have shown that clinical suspicion and histopathologic features are poor predictors of PAS positivity. Current appropriate use criteria from the American Society of Dermatopathology supports PAS staining when histopathologic features could be consistent with a dermatophyte infection. At the authors' institution, PAS stains are preordered on biopsies of inflammatory and infectious diagnoses to aid in a timelier sign out. Our aim was to reduce the percentage of PAS stains preordered on all dermatology specimens over a 6-month period without reducing the percentage of fungal infections identified. Review of a 12-month preintervention period found that our laboratory received 6104 biopsies for which PAS stain was preordered on 616 (10.1%). Based on a review of the preintervention period, preordering PAS on cases with clinical suspicion for cutaneous T-cell lymphoma was stopped unless there was clinical suspicion for eczematous dermatitis, vesiculobullous disorders, or fungal infection. The proposed intervention resulted in a 3.7% reduction in the number of PAS stains ordered while PAS-positivity rate remained unchanged. The described quality improvement process may be used as a model for other laboratories.


Subject(s)
Quality Improvement , Skin Neoplasms , Humans , Periodic Acid , Coloring Agents , Staining and Labeling
4.
JAMA Dermatol ; 158(11): 1300-1303, 2022 11 01.
Article in English | MEDLINE | ID: mdl-36169963

ABSTRACT

Importance: Dermatologists with specialty training in pediatric dermatology are scarce, which can mean extended wait times and reduced access to care for patients. Lower compensation for pediatric dermatology visits compared with adult visits may affect physician career choice and contribute to workforce shortages. Objective: To evaluate differences in work relative value units (wRVUs) generated by pediatric and adult outpatient dermatology encounters. Design, Setting, and Participants: This cross-sectional study used data from outpatient dermatology encounters at a single-site academic center in Atlanta, Georgia, from September 1, 2016, to March 31, 2020. Encounters with patients younger than 18 years were classified as pediatric, and encounters with those 18 years or older were classified as adult. Encounters with missing data were excluded as were those generating 0 wRVUs, inpatient visits, nursing visits, postoperative encounters, cosmetic procedures, phototherapy visits, and Mohs surgery encounters. Main Outcomes and Measures: Work relative value units generated per encounter type were assessed through multivariable linear regression models adjusted for the potential confounder of sex. Results: The study included 12 989 pediatric dermatology encounters (mean [SD] age, 7.3 [5.2] years; 7586 [58.4%] girls) and 78 057 adult dermatology encounters (mean [SD] age, 54.9 [18.9] years; 45 724 [58.6%] women). Pediatric encounters were associated with 0.23 (95% CI, 0.21-0.25; P < .001) fewer wRVUs than adult encounters after adjusting for sex. In a mediation analysis, biopsies and destruction of premalignant lesions explained 74.1% (95% CI, 69.6%-77.9%; P < .001) of the wRVU difference between pediatric and adult encounters. Conclusions and Relevance: This cross-sectional study found significant differences in wRVUs generated between adult and pediatric dermatology encounters that were largely attributable to biopsies and destruction of premalignant lesions. Policies that increase the value of cognitive services to be on par with procedural care may mitigate wRVU differences and improve reimbursement for pediatric dermatologists.


Subject(s)
Dermatology , Adult , Humans , Child , Female , Middle Aged , Male , Cross-Sectional Studies , Outpatients , Mohs Surgery
7.
Urol Case Rep ; 39: 101826, 2021 Nov.
Article in English | MEDLINE | ID: mdl-34522619

ABSTRACT

Pyoderma gangrenosum is a sterile inflammatory disease of unknown etiology characterized by recurrent cutaneous ulcers. It can occur in extracutaneous locations, especially at operative sites, and has been reported following gynecologic surgery. This report is the first case of pyoderma gangrenosum as a remote complication of pelvic surgery with associated ureteral stricture. It demonstrates the diagnostic challenge of this rare disease and the importance of broadening the differential diagnosis when apparent infections do not respond to treatment to minimize the morbidity of ineffective antibiotic and surgical interventions.

8.
JAMA Dermatol ; 157(4): 406-412, 2021 04 01.
Article in English | MEDLINE | ID: mdl-33595596

ABSTRACT

Importance: Clinical productivity measures may be factors in financial incentives for providing care to specific patient populations and thus may perpetuate inequitable health care. Objective: To identify the association of patient race, age, and sex with work relative value units (wRVUs) generated by outpatient dermatology encounters. Design, Setting, and Participants: This cross-sectional study obtained demographic and billing data for outpatient dermatology encounters (ie, an encounter performed within a department of dermatology) from September 1, 2016, to March 31, 2020, at the Emory Clinic, an academic dermatologic practice in Atlanta, Georgia. Participants included adults aged 18 years or older with available age, race, and sex data in the electronic health record system. Main Outcomes and Measures: The primary outcome was wRVUs generated per encounter. Results: A total of 66 463 encounters among 30 036 unique patients were included. Patients had a mean (SD) age of 55.9 (18.5) years and were predominantly White (46 575 [70.1%]) and female (39 598 [59.6%]) individuals. In the general dermatologic practice, the mean (SD) wRVUs per encounter was 1.40 (0.71). In adjusted analysis, Black, Asian, and other races (eg, American Indian or Native American, Native Hawaiian or Other Pacific Islander, and multiple races); female sex; and younger age were associated with fewer wRVUs per outpatient dermatology encounter. Compared with general dermatologic visits with White patients, visits with Black patients generated 0.27 (95% CI, 0.25-0.28) fewer wRVUs per encounter, visits with Asian patients generated 0.22 (95% CI, 0.20-0.25) fewer wRVUs per encounter, and visits with patients of other race generated 0.19 (95% CI, 0.14-0.24) fewer wRVUs per encounter. Female sex was also associated with 0.11 (95% CI, 0.10-0.12) fewer wRVUs per encounter, and wRVUs per encounter increased by 0.006 (95% CI, 0.006-0.006) with each 1-year increase in age. In the general dermatologic practice excluding Mohs surgeons, destruction of premalignant lesions and biopsies were mediators for the observed differences in race (56.2% [95% CI, 53.1%-59.3%] for Black race, 53.2% [95% CI, 45.6%-63.8%] for Asian race, and 53.6% [95% CI, 40.4%-77.4%] for other races), age (65.6%; 95% CI, 60.5%-71.4%), and sex (82.3%; 95% CI, 72.7%-93.1%). In a data set including encounters with Mohs surgeons, the race, age, and sex differences in wRVUs per encounter were greater than in the general dermatologic data set. Mohs surgery for basal cell and squamous cell carcinomas was a mediator for the observed differences in race (46.0% [95% CI, 42.6%-49.4%] for Black race, 41.9% [95% CI, 35.5%-49.2%] for Asian race, and 34.6% [95% CI, 13.8%-51.5%] for other races), age (49.2%; 95% CI, 44.9%-53.7%), and sex (47.9%; 95% CI, 42.0%-54.6%). Conclusions and Relevance: This cross-sectional study found that dermatology encounters with racial minority groups, women, and younger patients generated fewer wRVUs than encounters with older White male patients. This finding suggests that physician compensation based on wRVUs may encourage the provision of services that exacerbate disparities in access to dermatologic care.


Subject(s)
Ambulatory Care/economics , Dermatology/economics , Episode of Care , Health Expenditures , Relative Value Scales , Adult , Age Factors , Aged , Cross-Sectional Studies , Ethnicity/statistics & numerical data , Female , Humans , Male , Middle Aged , Retrospective Studies , Sex Factors , White People/statistics & numerical data
9.
J Am Acad Dermatol ; 83(5): 1274-1281, 2020 Nov.
Article in English | MEDLINE | ID: mdl-32622142

ABSTRACT

BACKGROUND: Pediatric melanoma is rare and diagnostically challenging. OBJECTIVE: To characterize clinical and histopathologic features of fatal pediatric melanomas. METHODS: Multicenter retrospective study of fatal melanoma cases in patients younger than 20 years diagnosed between 1994 and 2017. RESULTS: Of 38 cases of fatal pediatric melanoma identified, 57% presented in white patients and 19% in Hispanic patients. The average age at diagnosis was 12.7 years (range, 0.0-19.9 y), and the average age at death was 15.6 years (range, 1.2-26.2 y). Among cases with known identifiable subtypes, 50% were nodular (8/16), 31% were superficial spreading (5/16), and 19% were spitzoid melanoma (3/16). One fourth (10/38) of melanomas arose in association with congenital melanocytic nevi. LIMITATIONS: Retrospective nature, cohort size, and potential referral bias. CONCLUSIONS: Pediatric melanoma can be fatal in diverse clinical presentations, including a striking prevalence of Hispanic patients compared to adult disease, and with a range of clinical subtypes, although no fatal cases of spitzoid melanoma were diagnosed during childhood.


Subject(s)
Melanoma/diagnosis , Skin Neoplasms/diagnosis , Adolescent , Adult , Child , Child, Preschool , Female , Humans , Infant , Male , Melanoma/mortality , Retrospective Studies , Skin Neoplasms/mortality , Young Adult
10.
Dermatol Pract Concept ; 9(2): 132-138, 2019 Apr.
Article in English | MEDLINE | ID: mdl-31106016

ABSTRACT

BACKGROUND/OBJECTIVES: Although total body skin examination (TBSE) is the primary screening mechanism for melanoma, there is no consensus on which anatomic sites a screening TBSE should include. We sought to establish which anatomic sites are examined during routine (>90%) TBSEs of patients at high risk for skin cancer. METHODS: A Google survey was emailed to 173 international dermatologist skin cancer specialists. RESULTS: More than 75% of participants reported routinely examining the scalp, ears, face and neck, trunk, breasts, inframammary areas, axillae, extremities, palms and soles, nails, interdigital spaces, and buttocks. The least frequently inspected anatomic sites included genitalia, with male genitalia more frequently examined than female (penis n = 39; 52%; labia majora n = 21; 28%; P = 0.003), the perianal region (n = 26; 34.7%), and the ocular conjunctiva and oral mucosa (n = 35; 46.7%). Participants cited not screening these areas because of perceived patient discomfort, low prevalence of malignancy, and the expectation that other specialists examine the area. CONCLUSIONS: The role of routine surveillance of neglected anatomic sites is unclear and warrants further discussion weighing potential mortality benefit against the incidence of melanoma in obscure sites, morbidity of intervention in sensitive sites, cost-effectiveness, and potential for patient discomfort.

11.
J Pediatr ; 211: 152-158, 2019 08.
Article in English | MEDLINE | ID: mdl-31103258

ABSTRACT

OBJECTIVE: To identify risk factors associated with nonmelanoma skin cancer (NMSC) occurrence and survival in children. STUDY DESIGN: This was a multicenter, retrospective, case-control study of patients <20 years of age diagnosed with NMSC between 1995 and 2015 from 11 academic medical centers. The primary outcome measure was frequency of cases and controls with predisposing genetic conditions and/or iatrogenic exposures, including chemotherapy, radiation, systemic immunosuppression, and voriconazole. RESULTS: Of the 124 children with NMSC (40 with basal cell carcinoma, 90 with squamous cell carcinoma), 70% had at least 1 identifiable risk factor. Forty-four percent of the cases had a predisposing genetic condition or skin lesion, and 29% had 1 or more iatrogenic exposures of prolonged immunosuppression, radiation therapy, chemotherapy, and/or voriconazole use. Prolonged immunosuppression and voriconazole use were associated with squamous cell carcinoma occurrence (cases vs controls; 30% vs 0%, P = .0002, and 15% vs 0%, P = .03, respectively), and radiation therapy and chemotherapy were associated with basal cell carcinoma occurrence (both 20% vs 1%, P < .0001). Forty-eight percent of initial skin cancers had been present for >12 months prior to diagnosis and 49% of patients were diagnosed with ≥2 skin cancers. At last follow-up, 5% (6 of 124) of patients with NMSC died. Voriconazole exposure was noted in 7 cases and associated with worse 3-year overall survival (P = .001). CONCLUSIONS: NMSC in children and young adults is often associated with a predisposing condition or iatrogenic exposure. High-risk patients should be identified early to provide appropriate counseling and management.


Subject(s)
Carcinoma, Basal Cell/epidemiology , Carcinoma, Squamous Cell/epidemiology , Skin Neoplasms/epidemiology , Adolescent , Antifungal Agents/adverse effects , Antineoplastic Agents/adverse effects , Case-Control Studies , Child , Child, Preschool , Female , Genetic Predisposition to Disease/epidemiology , Humans , Immunosuppressive Agents/adverse effects , Infant , Male , Radiotherapy/adverse effects , Retrospective Studies , Risk Factors , United States/epidemiology , Voriconazole/adverse effects , Young Adult
12.
J Am Acad Dermatol ; 80(2): 341-363, 2019 02.
Article in English | MEDLINE | ID: mdl-30321581

ABSTRACT

Dermoscopy is increasingly used by clinicians (dermatologists, family physicians, podiatrists, doctors of osteopathic medicine, etc) to inform clinical management decisions. Dermoscopic findings or images provided to pathologists offer important insight into the clinician's diagnostic and management thought process. However, with limited dermoscopic training in dermatopathology, dermoscopic descriptions and images provided in the requisition form provide little value to pathologists. Most dermoscopic structures have direct histopathologic correlates, and therefore dermoscopy can act as an excellent communication bridge between the clinician and the pathologist. In the first article in this continuing medical education series, we review dermoscopic features and their histopathologic correlates.


Subject(s)
Carcinoma, Basal Cell/pathology , Carcinoma, Squamous Cell/pathology , Dermoscopy/methods , Skin Neoplasms/pathology , Adult , Aged , Biopsy, Needle , Carcinoma, Basal Cell/diagnosis , Carcinoma, Squamous Cell/diagnosis , Diagnosis, Differential , Education, Medical, Continuing , Female , Humans , Immunohistochemistry , Male , Middle Aged , Sensitivity and Specificity , Skin Neoplasms/diagnosis
13.
J Am Acad Dermatol ; 80(2): 365-377, 2019 Feb.
Article in English | MEDLINE | ID: mdl-30321580

ABSTRACT

Multiple studies have shown that dermoscopy increases the sensitivity and specificity for the detection of skin cancers compared with examination by the naked eye. Dermoscopy can also lead to the detection of thinner and smaller cancers. In addition, dermoscopy leads to the more precise selection of lesions requiring excision. In essence, dermoscopy helps clinicians differentiate benign from malignant lesions through the presence or absence of specific dermoscopic structures. Therefore, because most dermoscopic structures have direct histopathologic correlates, dermoscopy can allow the prediction of certain histologic findings present in skin cancers, thus helping select management and treatment options for select types of skin cancers. Visualizing dermoscopic structures in the ex vivo specimens can also be beneficial. It can improve the histologic diagnostic accuracy by targeted step-sectioning in areas of concern, which can be marked by the clinician before sending the specimen to the pathologist, or by the pathologist on the excised specimen in the laboratory. In addition, ex vivo dermoscopy can also be used to select tumor areas with genetic importance because some dermoscopic structures have been related to mutations with theragnostic relevance. In the second article in this continuing medical education series, we review the impact of dermoscopy on the diagnostic accuracy of skin cancer, how dermoscopy can affect the histopathologic examination, and which dermoscopic features may be more relevant in terms of histologic and genetic prediction.


Subject(s)
Carcinoma, Basal Cell/diagnosis , Carcinoma, Squamous Cell/diagnosis , Dermoscopy/methods , Melanoma/diagnosis , Skin Neoplasms/diagnosis , Biopsy, Needle , Carcinoma, Basal Cell/pathology , Carcinoma, Squamous Cell/pathology , Diagnosis, Differential , Education, Medical, Continuing , Female , Humans , Immunohistochemistry , Male , Melanoma/pathology , Neoplasm Staging , Sensitivity and Specificity , Skin Neoplasms/pathology
14.
JAMA Dermatol ; 154(12): 1401-1408, 2018 12 01.
Article in English | MEDLINE | ID: mdl-30304348

ABSTRACT

Importance: Little evidence exists to guide the management of moderately dysplastic nevi excisionally biopsied without residual clinical pigmentation but with positive histologic margins (hereafter referred to as moderately dysplastic nevi with positive histologic margins). Objective: To determine outcomes and risk for the development of subsequent cutaneous melanoma (CM) from moderately dysplastic nevi with positive histologic margins observed for 3 years or more. Design, Setting, and Participants: A multicenter (9 US academic dermatology sites) retrospective cohort study was conducted of patients 18 years or older with moderately dysplastic nevi with positive histologic margins and 3 years or more of follow-up data collected consecutively from January 1, 1990, to August 31, 2014. Records were reviewed for patient demographics, biopsy type, pathologic findings, and development of subsequent CM at the biopsy site or elsewhere on the body. The χ2 test, the Fisher exact test, and analysis of variance were used to assess univariate association for risk of subsequent CMs, in addition to multivariable logistic regression models. To confirm histologic grading, each site submitted 5 random representative slide cases for central dermatopathologic review. Statistical analysis was performed from October 1, 2017, to June 22, 2018. Main Outcomes and Measures: Development of CM at a biopsy site or elsewhere on the body where there were moderately dysplastic nevi with positive histologic margins. Results: A total of 467 moderately dysplastic nevi with positive histologic margins from 438 patients (193 women and 245 men; mean [SD] age, 46.7 [16.1] years) were evaluated. No cases developed into CM at biopsy sites, with a mean (SD) follow-up time of 6.9 (3.4) years. However, 100 patients (22.8%) developed a CM at a separate site. Results of multivariate analyses revealed that history of CM was significantly associated with the risk of development of subsequent CM at a separate site (odds ratio, 11.74; 95% CI, 5.71-24.15; P < .001), as were prior biopsied dysplastic nevi (odds ratio, 2.55; 95% CI, 1.23-5.28; P = .01). The results of a central dermatopathologic review revealed agreement in 35 of 40 cases (87.5%). Three of 40 cases (7.5%) were upgraded in degree of atypia; of these, 1 was interpreted as melanoma in situ. That patient remains without recurrence or evidence of CM after 5 years of follow-up. Conclusions and Relevance: This study suggests that close observation with routine skin surveillance is a reasonable management approach for moderately dysplastic nevi with positive histologic margins. However, having 2 or more biopsied dysplastic nevi (with 1 that is a moderately dysplastic nevus) appears to be associated with increased risk for subsequent CM at a separate site.


Subject(s)
Dermatologic Surgical Procedures/methods , Dysplastic Nevus Syndrome/diagnosis , Margins of Excision , Melanoma/diagnosis , Skin Neoplasms/diagnosis , Adolescent , Adult , Aged , Aged, 80 and over , Biopsy , Dysplastic Nevus Syndrome/surgery , Female , Follow-Up Studies , Humans , Male , Melanoma/surgery , Middle Aged , Retrospective Studies , Risk Factors , Skin , Skin Neoplasms/surgery , Young Adult , Melanoma, Cutaneous Malignant
15.
Dermatol Clin ; 35(4): 417-437, 2017 Oct.
Article in English | MEDLINE | ID: mdl-28886798

ABSTRACT

Dermoscopy increases the sensitivity for skin cancer detection, decreases the number of benign lesions biopsied for each malignant diagnosis, and enables the diagnosis of thinner melanomas compared with naked eye examination. Multiple meta-analyses have identified that dermoscopy improves the diagnostic accuracy for melanoma when compared with naked eye examination. In addition, studies have established that dermoscopy can aid in the detection of keratinocyte carcinomas. Dermoscopy triage algorithms have been developed to help novices decide when a biopsy or a referral is most appropriate. In this article, the authors illustrate the dermoscopic features that assist in identifying melanoma and keratinocyte carcinomas.


Subject(s)
Carcinoma, Basal Cell/diagnostic imaging , Carcinoma, Squamous Cell/diagnostic imaging , Dermoscopy , Melanoma/diagnostic imaging , Skin Neoplasms/diagnostic imaging , Algorithms , Humans , Keratoacanthoma/diagnostic imaging , Keratosis, Actinic/diagnostic imaging
16.
J Am Acad Dermatol ; 77(6): 1133-1144.e4, 2017 Dec.
Article in English | MEDLINE | ID: mdl-28716435

ABSTRACT

BACKGROUND: Few studies have characterized reference values of normal human skin microanatomy parameters. OBJECTIVE: To quantify histologic measurements of epidermal thickness, melanocyte density, hair follicle density, and eccrine gland density as a function of age and anatomic site. METHOD: We searched the PubMed, Embase, Web of Science, and Cochrane databases for articles published through May 25, 2017. Two reviewers independently screened 2016 articles; 327 relevant articles and 151 additional articles found via forward or reference citations underwent full-text review by 1 of 4 reviewers for relevance, data extraction, and critical appraisal. Weighted averages, meta-analysis, and meta-regression were used in statistical analysis. RESULTS: A total of 56 articles were included; when all anatomic locations were used, the overall estimates for epidermal thickness, melanocyte density, hair follicle density, and eccrine gland density were 99.75 µm (95% confidence interval [CI], 83.25-116.25), 955.05 cells/mm2 (95% CI. 880.89-1029.21), 1.40 hairs/mm2 (95% CI. 0.91-1.89), and 1.28 glands/mm2 (95% CI. 0.91-1.64), respectively. LIMITATIONS: There was significant data heterogeneity across studies, possibly because of differences in histological techniques and absence of standardized microanatomy definitions. CONCLUSIONS: We established summary estimates for normal human skin microanatomy parameters.


Subject(s)
Skin/anatomy & histology , Humans , Reference Values
17.
Dermatol Pract Concept ; 7(1): 19-22, 2017 Jan.
Article in English | MEDLINE | ID: mdl-28243489
18.
Dermatol Online J ; 23(9)2017 Sep 15.
Article in English | MEDLINE | ID: mdl-29469722

ABSTRACT

Elastomas are connective tissue nevi or hamartomas. They may occur in isolation or can be associated with familial syndromes such as Buschke-Ollendorff syndrome. Elastomas typically present in childhood as small ivory papules or firm skin-colored nodules that can coalesce into larger yellow plaques. These lesions are typically distributed over the extremities, abdomen, and back. Herein, we report an unusual case of a renal transplant recipient who presented with an acquired subungual papule with associated koilonychia and distal nail plate dystrophy. Histopathologic findings were consistent with subungual elastoma.


Subject(s)
Anus Neoplasms/complications , Carcinoma, Squamous Cell/complications , Nail Diseases/complications , Nevus/complications , Humans , Immunosuppression Therapy , Kidney Failure, Chronic/complications , Kidney Failure, Chronic/surgery , Kidney Transplantation , Male , Middle Aged , Nail Diseases/pathology , Nails, Malformed/complications , Nevus/pathology
19.
Proc Natl Acad Sci U S A ; 109(10): 3903-8, 2012 Mar 06.
Article in English | MEDLINE | ID: mdl-22355127

ABSTRACT

Nonhomologous end joining (NHEJ), a major pathway of DNA double-strand break (DSB) repair, is required during lymphocyte development to resolve the programmed DSBs generated during Variable, Diverse, and Joining [V(D)J] recombination. XRCC4-like factor (XLF) (also called Cernunnos or NHEJ1) is a unique component of the NHEJ pathway. Although germ-line mutations of other NHEJ factors abrogate lymphocyte development and lead to severe combined immunodeficiency (SCID), XLF mutations cause a progressive lymphocytopenia that is generally less severe than SCID. Accordingly, XLF-deficient murine lymphocytes show no measurable defects in V(D)J recombination. We reported earlier that ATM kinase and its substrate histone H2AX are both essential for V(D)J recombination in XLF-deficient lymphocytes, despite moderate role in V(D)J recombination in WT cells. p53-binding protein 1 (53BP1) is another substrate of ATM. 53BP1 deficiency led to small reduction of peripheral lymphocyte number by compromising both synapse and end-joining at modest level during V(D)J recombination. Here, we report that 53BP1/XLF double deficiency blocks lymphocyte development at early progenitor stages, owing to severe defects in end joining during chromosomal V(D)J recombination. The unrepaired DNA ends are rapidly degraded in 53BP1(-/-)XLF(-/-) cells, as reported for H2AX(-/-)XLF(-/-) cells, revealing an end protection role for 53BP1 reminiscent of H2AX. In contrast to the early embryonic lethality of H2AX(-/-)XLF(-/-) mice, 53BP1(-/-)XLF(-/-) mice are born alive and develop thymic lymphomas with translocations involving the T-cell receptor loci. Together, our findings identify a unique function for 53BP1 in end-joining and tumor suppression.


Subject(s)
Cell Cycle Proteins/genetics , Chromosomal Proteins, Non-Histone/metabolism , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Gene Expression Regulation , Lymphocytes/cytology , Protein Serine-Threonine Kinases/genetics , Tumor Suppressor Proteins/genetics , Animals , Ataxia Telangiectasia Mutated Proteins , DNA Damage , Mice , Mice, SCID , Mice, Transgenic , Plasmids/metabolism , Protein Structure, Tertiary , Recombination, Genetic , Tumor Suppressor p53-Binding Protein 1 , VDJ Recombinases/metabolism
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