Klinefelter's syndrome manifesting as an acute pulmonary embolus in a 52-year-old man

Association of Supernumerary Sex Chromosome Aneuploidies With Venous Thromboembolism

IMPORTANCE

An increased risk of venous thromboembolism (VTE) has been reported in men with an additional sex chromosome. The association between other sex chromosome aneuploidies and VTE is not well characterized.

OBJECTIVE

To determine if sex chromosome aneuploidy is associated with VTE.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort study of sex chromosome aneuploidy and VTE, performed by analyzing X- and Y-chromosome dosage and VTE incidence in 642 544 individuals from 2 population-scale biobanks: the US Geisinger MyCode Community Health Initiative (N = 154 519) and the UK Biobank (N = 488 025); analysis was limited to participants self-identified as White because of inadequate sample sizes for other race and ethnicity groups. A total of 108 461 unrelated MyCode participants with electronic health record follow-up ranging from September 1996 to December 2020 and 418 725 unrelated British and Irish UK Biobank participants who attended the baseline assessment between March 2006 and October 2010, with follow-up extending to November 2020, were included in analyses of VTE.

EXPOSURES

Sex chromosome aneuploidies.

MAIN OUTCOMES AND MEASURES

Individuals with 1 primary inpatient VTE diagnosis, 2 primary outpatient VTE diagnoses, or a self-reported VTE diagnosis were defined as VTE cases. P values were adjusted for multiple comparisons.

RESULTS

Identification of sex chromosome aneuploidy was undertaken among 642 544 individuals aged 18 to 90 years. Identification of a diagnosis of VTE was undertaken among 108 461 unrelated MyCode participants (65 565 [60.5%] female; mean age at last visit, 58.0 [SD, 17.6] years; median follow-up, 15.3 [IQR, 9.7] years) and among 418 725 unrelated UK Biobank participants (224 695 [53.7%] female; mean age at baseline interview, 56.9 [SD, 8.0] years; median follow-up, 12.0 [IQR, 1.6] years). Among MyCode participants, during 10 years of follow-up, 17 incident VTE events per 1353 person-years were detected among those with supernumerary sex chromosome aneuploidy (1.3% per person-year) compared with 2060 per 816 682 person-years among those with 46,XX or 46,XY (0.25% per person-year) (hazard ratio, 5.4 [95% CI, 3.4-8.7]; 10-year risk difference, 8.8% [95% CI, 4.2%-14.0%]; P < .001). Among UK Biobank participants, during 10 years of follow-up, 16 incident VTE events per 3803 person-years were detected among those with supernumerary sex chromosome aneuploidy (0.42% per person-year) compared with 4491 per 3 970 467 person-years among those with 46,XX or 46,XY (0.11% per person-year) (hazard ratio, 4.1 [95% CI, 2.5-6.7]; 10-year risk difference, 3.7% [95% CI, 1.4%-5.9%]; P < .001).

CONCLUSIONS AND RELEVANCE

Adults with supernumerary sex chromosome aneuploidies compared with 2 sex chromosomes had a small but statistically significant increased risk of VTE. Further research is needed to understand the clinical implications of this association.

Acute pulmonary embolism as an initial presentation of Klinefelter syndrome

Venous thromboembolism (VTE) includes deep vein thrombosis and its complications and pulmonary embolism. Cancer, surgery, prolonged immobilization, fractures, paralysis, use of oral contraceptives, and hereditary coagulopathies are classic risk factors for VTE. An increased incidence of VTE has been reported in patients with Klinefelter syndrome (KS), with a reported prevalence of 0.1–0.2% in the general population and up to 3.1% in infertile men. Despite the high rate of thromboembolic disease in patients with KS, the etiology of this phenomenon is not well understood, and most of our current knowledge is limited to small sample studies. We present the case of a 56-year-old man admitted for the management of a pulmonary embolism in whom a KS was accidentally discovered.

Thrombophilia in Klinefelter Syndrome With Deep Venous Thrombosis, Pulmonary Embolism, and Mesenteric Artery Thrombosis on Testosterone Therapy: A Pilot Study

We compared thrombophilia and hypofibrinolysis in 6 men with Klinefelter syndrome (KS), without previously known familial thrombophilia, who had sustained deep venous thrombosis (DVT)-pulmonary emboli (PE) or mesenteric artery thrombosis on testosterone replacement therapy (TRT). After the diagnosis of KS, TRT had been started in the 6 men at ages 11, 12, 13, 13, 19, and 48 years. After starting TRT, DVT-PE or mesenteric artery thrombosis was developed in 6 months, 1, 11, 11, 12, and 49 years. Of the 6 men, 4 had high (>150%) factor VIII (177%, 192%, 263%, and 293%), 3 had high (>150%) factor XI (165%, 181%, and 193%), 1 was heterozygous for the factor V Leiden mutation, and 1 was heterozygous for the G20210A prothrombin gene mutation. None of the 6 men had a precipitating event before their DVT-PE. We speculate that the previously known increased rate of DVT-PE and other thrombi in KS reflects an interaction between prothrombotic, long-term TRT with previously undiagnosed familial thrombophilia. Thrombophilia screening in men with KS before starting TRT would identify a cohort at increased risk for subsequent DVT-PE, providing an optimally informed estimate of the risk/benefit ratio of TRT.

High Risk of Venous Thromboembolism in Klinefelter Syndrome

Background

Klinefelter syndrome (KS) is the most common sex chromosome disorder. The genetic background is the extra X chromosome. Venous thromboembolism (VTE) has been observed among KS patients. The aim of the present study was to examine whether KS is associated with VTE.

Methods and Results

We followed up all hospital in‐ and outpatients (N=1085) in Sweden with a diagnosis of KS between January 1, 1969, and December 31, 2010, for diagnosis of VTE. The reference population was the total male populace of Sweden. We calculated standardized incidence ratios for VTE, adjusted for age, sex, education, time period, and region of residence. The standardized incidence ratio for KS was 6.43 (95% CI 5.15–7.93), with the highest ratio observed at young age. The standardized incidence ratios for VTE were 12.10 (95% CI 6.22–21.21) before age 30 years, 11.00 (95% CI 7.86–14.99) between ages 30 and 49 years, 4.83 (95% CI 3.23–6.95) between ages 50 and 69 years, and 2.07 (95% CI 0.74–4.53) for ages ≥70 years. The cumulative incidence of VTE for KS patients was 8.6% at age 50 years and 20.8% at age 70 years.

Conclusions

KS is associated with high risk of VTE. KS could be considered a genetic hypercoagulable state. This has clinical implications for the prevention and diagnosis of VTE among patients with KS.