Urticaria and the risk of cancer: a Danish population-based cohort study.

BACKGROUND: Urticaria has been tentatively linked to cancer, but epidemiological evidence supporting this link is sparse and conflicting. We therefore conducted a population-based cohort study using healthcare databases of the Danish population (January 1980-December 2022). We followed 87,507 people for a median of 10.1 years after first hospital contact for urticaria. OBJECTIVES: To examine associations of a hospital diagnosis of urticaria with incident cancer. METHODS: We computed absolute risk of cancer and standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) standardized to Danish national cancer rates. In a cross-sectional analysis, we examined whether the extent of cancer spread differed between people with vs. without a previous urticaria diagnosis. RESULTS: The overall SIR for all types of cancer was 1.09 (95% CI, 1.06-1.11) based on 7,788 observed vs. 7,161 expected cases. The risk for any cancer was 0.7% (95% CI, 0.6-0.7) for the first year of follow-up. Cancer was diagnosed in 588 people with urticaria during the first year of follow-up (SIR 1.49, 95% CI, 1.38-1.62) and in 7,200 people thereafter (SIR 1.06, 95% CI, 1.04-1.09). During the first year of follow-up, we found strong associations with hematological cancers (e.g., non-Hodgkin lymphoma SIR 2.91, 95% CI, 1.92-4.23). Cancer stage was similar in people with vs. without previous urticaria diagnosis. CONCLUSIONS: At the time of urticaria diagnosis, or in the first year afterwards, we found a large increase in the risk for cancer. In subsequent years, a persistent 6% increase in risk remained. Diagnostic efforts may partly explain the elevated short-term risk, but occult cancer may promote urticaria, or cancer and urticaria share common risk factors.

Social Characteristics and Adherence to Adjuvant Endocrine Therapy in Premenopausal Women With Breast Cancer.

PURPOSE: Social characteristics, including cohabitation/marital status and socioeconomic position (SEP)-education level, employment status, and income-influence breast cancer prognosis. We investigated the impact of these social characteristics on adherence to adjuvant endocrine therapy (AET) from treatment initiation to 5 years after diagnosis. METHODS: We assembled a nationwide, population-based cohort of premenopausal women diagnosed in Denmark with stage I-III, estrogen receptor-positive breast cancer during 2002-2011. We ascertained prediagnostic social characteristics from national registries. AET adherence was based on information from the Danish Breast Cancer Group and operationalized as (1) adherence trajectories (from group-based trajectory modeling) and (2) early discontinuation. We computed odds ratios (ORs) and associated 95% CI to estimate the association of cohabitation and SEP with AET adherence using multinomial and logistic regression models adjusted according to directed acyclic graphs. RESULTS: Among 4,353 patients, we identified three adherence trajectories-high adherence (57%), slow decline (36%), and rapid decline (6.9%). Compared with cohabiting women, those living alone had higher ORs of slow (1.26 [95% CI, 1.08 to 1.46]) or rapid decline (1.66 [95% CI, 1.27 to 2.18]) versus high adherence. The corresponding ORs for women not working versus employed women were 1.22 (95% CI, 1.02 to 1.45) and 1.76 (95% CI, 1.30 to 2.38). For early discontinuation (17%), the ORs were 1.48 (95% CI, 1.23 to 1.78) for living alone and 1.44 (95% CI, 1.17 to 1.78) for women not working. CONCLUSION: Adherence to AET was lower among women living alone or unemployed than cohabiting or employed women, respectively. These women may benefit from support programs to enhance AET adherence.

Renal cell carcinoma and risk of second primary cancer: A Danish nationwide cohort study.

AIM: To examine the risk of second primary cancer in patients with incident renal cell carcinoma (RCC). METHODS: We identified all patients diagnosed with incident RCC during 1995-2019, using population-based Danish medical registries. Patients were followed from the date of RCC diagnosis until any second primary cancer diagnosis, death, emigration, or December 31, 2019, whichever came first. We computed the absolute risk, standardized incidence ratio (SIR), and excess absolute risk of second primary cancer, with 95% confidence intervals (CIs), among patients with RCC compared to the general population. RESULTS: The absolute 1- and 20-year risks of any second primary cancer were 2.8% and 17.8%, respectively. Within 1 year after RCC diagnosis, we detected 20 excess cancer cases per 1000 person-years (PY) (SIR, 2.3; 95% CI: 2.1-2.6). Moreover, we detected an additional four excess cancer cases per 1000 PY during 1 to <5 years of follow-up (SIR, 1.3; 95% CI: 1.2-1.4), and 6 per 1000 PY beyond 5 years of follow-up (SIR, 1.4; 95% CI: 1.3-1.5). The sustained elevated cancer risk beyond 1 year of follow-up was mainly attributed to excess risk of lung and bladder cancer. The risk of second primary cancer was higher in 2006-2019 than in 1995-2005, but only during the first year of follow-up. CONCLUSION: Patients with incident RCC have a sustained 40% elevated long-term risk of second primary cancer, compared with the general population. This increased risk is mainly attributed to lung and bladder cancer.

Clinical factors associated with patterns of endocrine therapy adherence in premenopausal breast cancer patients.

INTRODUCTION: Patients with hormone receptor positive breast cancer are recommended at least five years of adjuvant endocrine therapy, but adherence to this treatment is often suboptimal. We investigated longitudinal trends in adjuvant endocrine therapy (AET) adherence among premenopausal breast cancer patients and identified clinical characteristics, including baseline comorbidities and non-cancer chronic medication use, associated with AET adherence. METHODS: We included stage I-III premenopausal breast cancer patients diagnosed during 2002-2011 and registered in the Danish Breast Cancer Group clinical database who initiated AET. We used group-based trajectory modeling to describe AET adherence patterns. We also linked patients to Danish population-based registries and fit multinomial logistic models to compute odds ratios (ORs) and 95% confidence intervals (95% CIs) associating clinical characteristics with AET adherence patterns. RESULTS: We identified three adherence patterns among 4,353 women-high adherers (57%), slow decliners (36%), and rapid decliners (6.9%). Women with stage I disease (vs. stage II; OR: 1.9, 95% CI 1.5, 2.5), without chemotherapy (vs. chemotherapy; OR: 4.3, 95% CI 3.0, 6.1), with prevalent comorbid disease (Charlson Comorbidity Index score ≥ 1 vs. 0; OR: 1.6, 95% CI 1.1, 2.3), and with a history of chronic non-cancer medication use (vs. none; OR: 1.3, 95% CI 1.0, 1.8) were more likely to be rapid decliners compared with high adherers. CONCLUSIONS: Women with stage I cancer, no chemotherapy, higher comorbidity burden, and history of chronic non-cancer medication use were less likely to adhere to AET. Taking steps to promote adherence in these groups of women may reduce their risk of recurrence.

Social characteristics and social benefit use among premenopausal breast cancer survivors in Denmark: a population-based cohort study.

PURPOSE: In 2020, one million women aged < 55 years were diagnosed with breast cancer globally. The impact of breast cancer and its treatments on these women's ability to work and need for social benefits may differ by social characteristics. We evaluated social benefit use following breast cancer by education and cohabitation. METHODS: We conducted a nationwide population-based cohort study, including women aged 18-55 years diagnosed with stage I-III breast cancer in Denmark during 2002-2011. Statistics Denmark provided information on cohabitation, education, and social benefit use from 1 year pre-diagnosis to 10 years post-diagnosis. We calculated weekly proportions of self-support, unemployment, disability pension, flexi jobs, and sick leave according to education and cohabitation. RESULTS: Of 5345 women, 81.8% were self-supporting, 4.5% received disability pensions, 1.6% had flexi jobs, 3.6% were on sick leave, and 5.5% were unemployed 1 year pre-diagnosis. Ten years post-diagnosis, the proportions were 69.0%, 13.0%, 10.5%, 3.4%, and 2.0% of 3663 survivors. Disability pensions and flexi jobs increased from 12.1 to 26.4% and 2.8 to 13.5% in women with short education, from 4.1 to 12.8% and 1.8 to 12.2% in women with medium education, and from 0.8 to 6.0% and 0.9 to 6.9% in longer educated. Disability pensions increased more in women living alone (7.8 to 19.9%), than in cohabiting women (3.6 to 11.3%). CONCLUSIONS: Use of social benefits reflecting lost ability to work was highest in less educated women and in women living alone. IMPLICATIONS FOR CANCER SURVIVORS: Awareness of these groups is crucial when tailoring efforts to support work participation in cancer survivors.

Risk of Cancer in Patients With Diverticular Disease: A Population-Based Cohort Study.

BACKGROUND & AIMS: Several studies have investigated the association between diverticular disease (DD) and colorectal cancer. However, whether there is an association between DD and malignancies other than those in the colorectum remains uncertain. METHODS: For the 1978-2019 period, we conducted a nationwide, population-based cohort study using national Danish health care data. We followed patients with DD for up to 20 years, beginning 1 year after the date of DD diagnosis until the first occurrence of incident cancer, emigration, death, 20 years of follow-up, or December 31, 2019. We calculated cumulative incidence proportions of cancer and standardized incidence ratios (SIRs) comparing cancer incidence among patients with DD with that in the general population. RESULTS: We identified 200,639 patients with DD, of whom 20,498 were diagnosed with cancer during the 1-20 years after their DD diagnosis. The SIRs were increased for most cancer sites except for those in the colorectum (SIR, 0.75; 95% confidence interval, 0.72-0.78). The highest SIRs were observed for cancers of the lung, bronchi, and trachea (SIR, 1.20; 95% confidence interval, 1.15-1.24) and kidney (SIR, 1.27; 95% confidence interval, 1.16-1.39). CONCLUSIONS: Our findings show an increased long-term relative risk of cancer following a diagnosis of DD. These findings are likely caused by prevalence of numerous risk factors in patients with DD that confer an increased risk of cancer. The decreased relative risk of colorectal cancer might be explained by an increased likelihood of patients with DD undergoing colonoscopy with polypectomy.

Risk of primary haematologic cancers following incident non-metastatic breast cancer: A Danish population-based cohort study.

BACKGROUND: Breast cancer survivors may have increased risk of subsequent haematologic cancer. We compared their risk of haematologic cancers with the general population during 38 years of follow-up. METHODS: Using population-based Danish medical registries, we assembled a nationwide cohort of women diagnosed with incident non-metastatic breast cancer during 1980-2017, with follow-up through 2018. We compared breast cancer survivors with the general population by computing standardised incidence ratios (SIR) and 95% confidence intervals (CI). RESULTS: Among 101,117 breast cancer survivors, we observed 815 incident haematologic cancers (median follow-up: 7.9 years). We observed excess risk of acute myeloid leukaemia (AML) (SIR: 1.65, 95%CI: 1.33-2.01), particularly in women who received chemotherapy (SIR: 3.33, 95%CI: 2.24-4.75) and premenopausal women (SIR: 3.23, 95%CI: 2.41-4.25). The risk of acute lymphoid leukaemia (ALL) was increased (SIR: 2.25, 95%CI: 1.29-3.66), whereas the risk of chronic lymphoid leukaemia (CLL) was decreased (SIR: 0.66, 95%CI: 0.53-0.82). An additional analysis showed elevated risk of CLL 0-6 months after breast cancer diagnosis (SIR: 3.00 95%CI: 1.75-4.80). CONCLUSION: Compared to the general population, breast cancer survivors had elevated risk of AML, particularly when treated with chemotherapy. The risk of ALL was elevated, whereas the risk of CLL was lower. The higher risk of CLL in the first six months after diagnosis likely reflects surveillance bias-due to intensified diagnostic efforts at breast cancer diagnosis and treatment-prompting earlier detection. This has likely reduced the long-term risk of CLL in breast cancer survivors.

Fever of Unknown Origin: A Validation Study of Danish ICD-10 Diagnosis Codes.

Background: Real-world data in form of routinely collected clinical data are a valuable resource for epidemiological research in infectious disease. We examined the validity of a discharge diagnosis of fever of unknown origin from hospital discharge registries. Methods: We identified patients with a first in- or outpatient diagnosis (primary or secondary) of fever of unknown origin (ICD-10 code R50.0; R50.8, R50.9) recorded in the Danish National Patient Registry (DNPR) between 2010 and 2017 in the North Denmark Region. We based the validation cohort on a mix of patients diagnosed at a highly specialized university department of infectious diseases (n=100), other internal medicine departments (n=50), and patients diagnosed at a regional non-university hospital (n=50). We estimate positive predictive value (PPV) of diagnosis for fever of unknown origin using medical records as reference. Results: The PPV of a diagnosis of fever of unknown origin for patients diagnosed at the infectious disease department was 61% (95% CI: 51-71%). For other internal medicine departments, it was 14% (95% CI: 6-27%), and for the non-university hospital it was 16% (95% CI: 7-29%). To achieve higher PPVs, we excluded immunocompromised patients, patients who were diagnosed with infection, cancer or rheumatic disease within 7 days after admission, and/or patients with a short hospital stay (maximum 3 days) and no subsequent hospital contact within 1 month. The PPV for diagnoses from the Department of Infectious Diseases improved to 82% (95% CI: 68-91%) for other internal medicine departments it improved to 31% (95% CI: 11-59%), and for the non-university hospital it improved to 36% (95% CI: 13-65%). Conclusion: We found that only diagnoses made in the Department of Infectious Diseases accurately identified fever of unknown origin, whereas diagnoses made in other units mainly covered infection-related fever, cancer-related fever, or short unspecific fever without further diagnostic work-up.

Venous Thromboembolism and Risk of Cancer in Users of Low-Dose Aspirin: A Danish Population-Based Cohort Study.

Background Aspirin may reduce the risk of cancer, particularly gastrointestinal cancer, and venous thromboembolism (VTE). VTE can be the first symptom of occult cancer, but whether it is also a marker of occult cancer in aspirin users remains unknown. Therefore, we investigated the risk of cancer subsequent to VTE among users of low-dose aspirin. Methods We conducted a population-based cohort study using data from Danish health registries for the years 2001 to 2018. We identified all patients with a first-time diagnosis of VTE who also redeemed a prescription for low-dose aspirin (75-150mg) within 90 days prior to the first-time VTE. We categorized aspirin users by the number of prescriptions filled as new users (<5 prescriptions), short-term users (5-19 prescriptions), and long-term users (>19 prescriptions). We computed the absolute cancer risks and standardized incidence ratios (SIRs) for cancer using national cancer incidence rates. Results We followed-up 11,759 users of low-dose aspirin with VTE. Long-term users comprised 50% of aspirin users. The 1-year absolute risk of cancer was 6.0% for new users and 6.7% for short-term and long-term users, with corresponding SIRs of 3.3 (95% confidence interval [CI]: 2.8-4.0), 3.2 (95% CI: 2.9-3.7), and 2.8 (95% CI: 2.6-3.2), respectively. After the first year of follow-up, the SIR decreased to 1.2 (95% CI: 1.1-1.4) for new users, 1.1 (95% CI: 1.1-1.3) for short-term users, and 1.1 (95% CI: 1.0-1.2) for long-term users. Conclusion VTE may be a harbinger of cancer, even in users of low-dose aspirin, regardless of duration of use.

Venous Thromboembolism and Risk of Cancer in Patients with Dementia: A Danish Population-Based Cohort Study.

BACKGROUND: Venous thromboembolism (VTE) may be the first manifestation of occult cancer. Dementia has been linked to reduced cancer risk. OBJECTIVE: We examined the risk of cancer following VTE in people with dementia in comparison to the risk in the general population. METHODS: We conducted a population-based Danish registry-based cohort study following patients with a first-time VTE and a previous or concurrent diagnosis of dementia during the period 1 April 1996 -31 December 2017. We followed the study participants from date of VTE until diagnosis of cancer, death, emigration, or end of study period, whichever came first. The absolute risk of cancer within one year after VTE was computed, treating death as a competing risk. We calculated gender, age, and calendar-period standardized incidence ratios (SIRs) of cancer based on national cancer rates. RESULTS: We followed 3,552 people with dementia and VTE for a median of 1.3 years. Within the first year after VTE, they had a 90% increased risk of cancer in comparison with the general population [SIR: 1.9 (95% confidence interval: 1.6-2.4)]. During subsequent follow-up years, the SIR fell to 0.7 (95% confidence interval: 0.5-0.8). Findings for Alzheimer's disease and VTE were similar. CONCLUSION: People with dementia have an increased risk of a cancer diagnosis during the first year following VTE, perhaps related to increased surveillance, and a lower risk thereafter. Overall risk is similar to that of the general population.

Prevalence of Colorectal Neoplasms and Mortality in New Users of Low-Dose Aspirin With Lower Gastrointestinal Bleeding.

BACKGROUND: Aspirin inhibits platelet function and may therefore accelerate early lower gastrointestinal bleeding (LGIB) from colorectal cancer (CRC) precursor polyps. The bleeding may increase endoscopic polyp detection. STUDY QUESTION: To estimate the prevalence of polyps and CRC comparing new users of low-dose aspirin with nonusers who all received a diagnosis of LGIB and to investigate the mortality among these patients. STUDY DESIGN: Using Danish nationwide health registries, we conducted a cohort study (2006-2013) of all new aspirin users who also received a diagnosis of LGIB (n = 40,578). Each new user was matched with 5 nonusers with LGIB by gender and age at the LGIB diagnosis date. MEASURES AND OUTCOMES: We computed the prevalence and prevalence ratios (PRs) of colorectal polyps and CRCs, and the mortality ratios within 6 months after the LGIB, comparing new users with nonusers. RESULTS: We identified 1038 new aspirin users and 5190 nonusers with LGIB. We observed 220 new users and 950 nonusers recorded with endoscopically detected polyps. New aspirin users had a higher prevalence of conventional {PR = 1.28 [95% confidence interval (CI): 1.06-1.55]} and serrated [PR = 1.31 (95% CI: 0.95-1.80)] polyps. New users and nonusers had a similar prevalence of CRC [PR = 1.04 (95% CI: 0.77-1.39)]. However, after stratifying by location of CRC, the prevalence of proximal tumors was lower [PR = 0.71 (95% CI: 0.35-1.43)] in new users than in nonusers. No difference in mortality was observed. CONCLUSIONS: These findings indicate that new use of low-dose aspirin is associated with an increased detection of colorectal polyps compared with nonuse.

Risk factors and lifelong impact of community-acquired pneumonia in congenital heart disease.

INTRODUCTION: The prevalence of congenital heart disease (CHD) in adults is rising necessitating a greater understanding of acquired diseases such as community-acquired pneumonia, which remains a leading cause of age-related mortality and morbidity in the general population. We hypothesise that the CHD population, given cardiopulmonary mechanics and altered immune function, bears a uniquely high risk for pneumonia-related hospitalisations and mortality. METHODS: A countrywide cohort study was performed to calculate the relative risk and cumulative incidence of pneumonia hospitalisations and resultant 30-day mortality amongst the adult CHD population, matched 1:10 with non-CHD persons by gender, age, and adjusted for comorbidities. Cox proportional hazard regression quantified the impact of CHD severity and extracardiac defects. RESULTS: The CHD cohort includes 17,162 adults. The majority demonstrate mild/moderate CHD complexity. The cumulative incidence of pneumonia hospitalisation was higher for adults with CHD (hazard ratio 1.90; 95% confidence interval: 1.74-2.06) than the comparison cohort. This risk was increased for those with extracardiac defects or a syndrome (hazard ratio: 4.34; 95% confidence interval: 3.39-5.54). Additionally, CHD individuals with severe/univentricular subtypes demonstrate a heightened risk compared to the non-CHD cohort (hazard ratio: 2.35; 95% confidence interval: 1.94-2.84), as well as compared to those with mild/moderate CHD (hazard ratio: 1.28; 95% confidence interval: 1.07-1.53). In addition, pneumonia hospitalisation mortality was elevated above the comparison population with a 30-day mortality rate ratio of 1.31 (95% confidence interval: 1.00-1.73). CONCLUSION: Adults with CHD are at elevated risk of pneumonia hospitalisations and pneumonia-associated mortality. This risk is further elevated in those with severe CHD and extracardiac defects.

Vaginal bleeding in early pregnancy and risk of occult cancer.

Vaginal bleeding in early pregnancy is not associated with a higher cancer risk compared with pregnancies in women from the general population of similar age.

Risk of Upper Gastrointestinal Bleeding and Gastroduodenal Ulcers in Persons With Schizophrenia: A Danish Cohort Study.

INTRODUCTION: There is little evidence about gastrointestinal (GI) disorders in patients with schizophrenia. We examined association of schizophrenia with upper GI bleeding (UGIB) and nonbleeding ulcers and associated risk factors and mortality. METHODS: We used the data linked from population-based registries in Denmark. Among patients with incident schizophrenia in 1980-2011, we computed cumulative incidences and standardized incidence ratios of UGIB, bleeding ulcers, and nonbleeding ulcers compared with the general population; evaluated risk factors for the 3 GI endpoints, including somatic and psychiatric comorbidity; and examined subsequent all-cause mortality. RESULTS: Among 39,998 patients with schizophrenia, the standardized incidence ratios were 2.92 (95% confidence interval (CI), 2.76-3.08) for UGIB, 2.36 (95% CI, 2.15-2.58) for bleeding ulcers, and 2.00 (95% CI, 1.87-2.15) for nonbleeding ulcers. Risk factors for UGIB and nonbleeding ulcers included age, somatic comorbidity, and medication use. UGIB and nonbleeding ulcers were associated with the subsequent increase in mortality. CONCLUSIONS: Schizophrenia is associated with an increased risk of UGIB and nonbleeding ulcers, whose risk factors in patients with schizophrenia are similar to those in the general population.

Cancer Risk and Prognosis after a Hospital Contact for an Elevated Erythrocyte Sedimentation Rate.

BACKGROUND: An elevated erythrocyte sedimentation rate (ESR) may be a marker of occult cancer. METHODS: We linked Danish medical databases to examine cancer incidence in patients with a first-time hospital contact for elevated ESR during 1980 to 2013. We calculated standardized incidence ratios (SIR) of cancer compared with the general population, and comorbidity-adjusted HRs (aHR) versus matched population comparisons without elevated ESR. We also compared survival among patients with cancer with elevated ESR with that among patients with cancer without elevated ESR. RESULTS: During median follow-up of 4.9 years, we observed 3,926 cancers among 18,540 patients with a first-time hospital contact for elevated ESR. The risk for any cancer diagnosed during the first year following the contact for elevated ESR was 8.5% [95% confidence interval (CI), 8.1%-8.9%]. The overall 1-year cancer incidence was markedly elevated [SIR 5.3 (95% CI, 5.1-5.6); aHR 5.8 (95% CI, 5.4-6.3)] and was more than 3-fold elevated for most hematologic cancers and for cancers of the peritoneum and connective tissue in the abdominal wall, kidney, and adrenal glands. After the first year, patients were at increased risk of developing especially hematologic cancers. Patients diagnosed with cancer within 1 year after a contact for elevated ESR had poorer survival compared with matched cancer comparisons [adjusted mortality rate ratio 1.2 (95% CI, 1.1-1.3)]. CONCLUSIONS: Elevated ESR is a strong marker of undiagnosed cancer and is associated with poorer survival. IMPACT: Our findings may help clinicians in assessing absolute risk, common sites, and prognosis of cancers discovered after hospital contact with elevated ERS.

Hyper- and hypothyroidism and gastrointestinal cancer risk: a Danish nationwide cohort study.

OBJECTIVE: The association between thyroid dysfunction and gastrointestinal cancer is unclear. DESIGN: We conducted a nationwide population-based cohort study to examine this potential association. METHODS: We used Danish medical registries to assemble a nationwide population-based cohort of patients diagnosed with hyperthyroid or hypothyroid disease from 1978 through 2013. We computed standardized incidence ratios (SIRs) with corresponding 95% confidence intervals (CI) as measures of the relative risk of each cancer, comparing patients with thyroid dysfunction with that expected in the general population. RESULTS: We included 163,972 patients, of which 92,783 had hyperthyroidism and 71,189 had hypothyroidism. In general, we found an increased risk of all gastrointestinal cancers within the first year after thyroid disease diagnosis. After more than five years of follow-up, patients with hyperthyroidism had a slightly increased risk of pancreatic and gallbladder and biliary tract cancer. Patients with hypothyroidism had a slightly increased risk of stomach, anal, liver, gallbladder and biliary tract, and pancreatic cancer after more than five years of follow-up, but the observed numbers of cancers were in general similar to the expected. CONCLUSIONS: The increased risks of all gastrointestinal cancers in the first year following hyper- or hypothyroidism diagnosis are likely due to detection bias. After more than five years of follow-up, there does not seem to be a consistent causal association between thyroid disease and gastrointestinal cancer.

Risk of cancer in patients with epistaxis and haemoptysis.

This corrects the article DOI: 10.1038/bjc.2017.85.

Risk of venous thromboembolism in patients with mycosis fungoides and parapsoriasis: A Danish nationwide population-based cohort study.

BACKGROUND: Mycosis fungoides (MF) and parapsoriasis are characterized by malignant proliferation and chronic inflammation, which may affect the risk for venous thromboembolism (VTE). OBJECTIVES: To examine the risk for VTE in patients with MF and parapsoriasis. METHODS: We conducted a nationwide population-based cohort study in Denmark to examine the relative risk (RR) of VTE in 525 patients with MF and 634 patients with parapsoriasis compared with that in sex- and age-matched controls from the general population. RESULTS: In patients with MF, the 10-year absolute risk for VTE was 3.4% (95% confidence interval [CI], 2.0-5.4). The adjusted RRs were 2.41 (95% CI, 1.49-3.90) for VTE and 4.01 (95% CI, 2.16-7.46) for pulmonary embolism. Notably, within the first 5 years after diagnosis with MF, the RR of pulmonary embolism was increased 6.7-fold (to 6.71 [95% CI, 2.86-15.72]). Patients with parapsoriasis had a 2.7-fold increased RR of VTE (to 2.67 [95% CI, 1.32-5.40]) in the absence of other established VTE risk factors. LIMITATIONS: We had no information regarding disease stage of MF and prescribed drugs. CONCLUSION: Patients with MF and parapsoriasis had an increased RR of VTE, although the absolute risk remained low. These findings should increase awareness of comorbidities in patients with MF and parapsoriasis.