The results of this study suggest that women with vulvar lichen sclerosus presenting to our tertiary referral vulvar care clinic suffer from a large number of comorbidities. Our findings are generally higher than the published rates for the same conditions in the general population. The only comorbidity for which the prevalence in women with LS is lower is overactive bladder, which we find at approximately 1/3 of the prevalence in the general population.
The rate of thyroid dysfunction in our patients is also higher than would be expected in the population. Similar to the results of Birenbaum and Young (28
), thyroid dysfunction was identified in approximately 30% of our subjects, which is 5-fold greater than the reported rates for the general population (30
). These findings are consistent with previously published works suggesting that women with vulvar lichen sclerosus are at increased risk of having coexistent autoimmune disorders, including thyroid disease, psoriasis, alopecia areata and vitiligo (28
Kennedy and colleagues have also identified high rates of urinary, gastrointestinal and pain disorders in women with vulvar diseases (6
). Similar to our results, these previously published studies found women with LS to be at elevated risk of painful bladder syndrome and IBS. However, in contrast to our findings, Kennedy et al. suggest that urinary incontinence is less common in women with LS than women presenting to a general gynecology clinic for annual examinations (6
). The reasons for this discrepancy are not clear, but may stem from differences in patient populations, study sizes, and/or the method by which urinary incontinence was diagnosed.
There are several limitations to this study that we must acknowledge. Firstly, all of these subjects were identified from a tertiary referral vulvar care clinic. As such, the results of this study may not extend to all patient populations, but may rather reflect a selection bias. Similarly, since the patients referred to the University of Michigan Center for Vulvar Diseases are often those that have proven difficult to diagnose and/or treat, they may represent a cohort of patients with more severe forms of vulvar diseases. The results from this population may therefore not be representative of the bulk of women with vulvar LS. Furthermore, the predominantly Caucasian cohort in this study, while reflective of the patient population at the University of Michigan, may limit the generalizability of our results to other racial and/or ethnic groups. In addition, this is a cross-sectional study, so we cannot determine causality or temporal associations between the comorbidities evaluated and lichen sclerosus. With the exception of thyroid dysfunction, we relied on self-report to calculate prevalences of all comorbidities. Furthermore, validated, published screening instruments were not used in this process. As such, our data may reflect elements of recall bias and/or lack of reliability (33
). We did not adjust our analysis to reflect the fact that we made multiple comparisons between our LS subjects and the general population, such as a Bonferroni adjustment. As such, there may be a statistical bias resulting in identification of associations simply due to the number of tests performed, rather than to a true rejection of the null hypothesis. It should be noted, however, that a back of the envelope Bonferroni adjustment would suggest that we use a p value of 0.005, rather than 0.05, to ascribe statistical significance as we tested for 10 different conditions. The p values calculated for the all of the prevalences in our study were less than 0.001, with the exception of urinary incontinence (p = 0.02), IBD (p = 0.01) and IBS (p = 0.02). Finally, all of the prevalences calculated for comorbidities in our subjects with LS were compared to published rates for the general population. However, the published prevalences of all of the comorbidities examined in this study cover wide ranges, depending on the definition of the diagnosis and the population studied. For example, although we note that the overall rate of OAB in the general population to be 40%, several studies suggests the prevalence is closer to 16% (34
). The results of comparisons between women with LS and the general population are therefore highly dependent on information about disease states in the community. Future investigations exploring the relative associations between vulvar lichen sclerosus and other comorbidities are necessary. The findings from this report may serve as benchmark data for such studies.
Strengths of this study include its large sample size, the use of a standardized questionnaire for all subjects, and the broad range and large number of comorbidities investigated.