Leukocytoclastic vasculitis is a histopathologic term that defines small-vessel vasculitis in which the perivascular inflammatory infiltrate is composed of neutrophils.1 This term is typically used for skin-predominant vasculitis, which most commonly presents with palpable or nonpalpable purpura on the lower extremities. LCV is often idiopathic in nature but may be associated with some underlying conditions, such as infections, exposure to certain medications, connective tissue disorders, or neoplasms.2 Leukocytoclastic vasculitis can be limited to the skin, but extracutaneous involvement (renal, gastrointestinal, articular, etc.) is not rare and was reported to be present in 12.5% to 57% of patients with LCV in different studies.3–9

LCV is often mediated by immune complex deposition in the postcapillary venule walls and by activation of the complement system, which results in neutrophil recruitment and finally, destruction of the vessel wall.10 Due to the immunological nature of its pathophysiology, LCV has been subject to Direct Immunofluorescence (DIF) studies for many years, and it is recommended to be performed, whenever possible, in the setting of LCV.11 DIF can aid in the determination of some specific subtypes of LCV (for example IgA vasculitis) and the identification of the possible underlying etiologies.6,12,13 Furthermore, recently some studies tried to determine its possible prognostic significance in LCV, by relating results of DIF examination with specific systemic involvement. The presence of IgM deposition of the vessel walls was associated with renal involvement in some studies,14,15 but this finding couldn’t be confirmed by other studies.6,7,16–18 The prognostic role of DIF studies in LCV is still controversial and currently lacks specificity.19

In this study, we aimed to evaluate the potential association between the skin DIF results and extracutaneous involvement in adult LCV patients.

The evaluation of the patient with cutaneous lesions suspicious of vasculitis should include a detailed anamnesis and physical examinations with some specific laboratory tests not to miss a potential systemic involvement. Treatment approach and follow-up schedules vary depending on whether there is systemic involvement or not. In the present study, we have retrospectively searched for the systemic involvement rate in LCV patients and potential clinical and laboratory associations with systemic involvement, including DIF findings.

Systemic involvement was documented in 58% of all LCVs in the present study, which is in the upper range of previous reports: from 12.5% to 57% depending on the design of studies and the inclusion criteria of the patients.4,6–9 Joint involvement is usually reported to be the most frequent site of involvement, followed by renal and GI involvement.8,9 However, in this study, renal involvement was the most frequent systemic involvement. The relatively lower renal involvement rates in some other studies could be explained by the strict criteria they used for defining renal involvement, such as the necessity of histological-proven nephropathy.6

In most centers, DIF analysis is routinely performed in clinically suspected cases of cutaneous vasculitis. Small vessel vasculitis of the skin is mediated by immune complex deposition in the post-capillary venules. Circulating antigens due to drug exposure, infectious agents, connective tissue disease, or neoplasia are bound by antibodies, forming immune complexes, which then can be detected by direct immunofluorescence studies.20 The overall positivity rate of DIF in LCV cases varies in the literature from 39% to as high as 97%.17,21–24 In the present study, we found positive DIF for at least one immunoglobulins and/or complement and/or fibrinogen in 90.1% of the cases, compatible with the previous reports. The most common positive immunoreactant was C3, and the most common positive immunoglobulin was IgA. Regarding the positivity pattern, the present findings are in line with the current literature where C3 is the most common immunoreaction in almost all of the studies.6,17,22,25,26 Although the exact reason for this finding is not known, we can assume that it may be related to the timing of the skin biopsy as immunoglobulins tend to be disappearing faster compared to the complement, and C3 is known to be deposited in relatively later lesions of vasculitis.9,27

For an ideal evolution of DIF specimens, it is advised to choose a newer lesion, between 8 h and 24 h of age, to biopsy. It has been shown that the DIF positivity rates drop concerningly in older lesions, especially if they are >1 week old. In a study reported by Nandeesh et al., the DIF positivity rate was 85% if the biopsy was taken within one week of onset of symptoms, whereas it was only 14% if was taken after a week.22 In the present study DIF positivity rate was found to be higher if the samples were taken early during the course of the disease (95.8% for <7 days vs. 84.2% for >28 days), however, the difference was not as obvious as it is in the report of Nandeesh et al. But these results should be interpreted carefully, because in the report of Nandeesh et al., as in ours, the exact age of each individual lesion that was biopsied could not be detected, due to retrospective design of both studies. Instead, the time from the appearance of the first lesion to the biopsy was included in the analyses. In the present clinic, we always tend to find a fresh appearing individual skin lesion to biopsy, even in the setting of a longer disease course. We believe that the results of the present study are interesting, as it showed that even if the vasculitic skin rash is present for a longer period of time, DIF can still be positive and diagnostic, especially if we manage to find a fresh appearing lesion to biopsy.

The most frequent etiological causes of LCV are infections, drug exposure, neoplasm, and connective tissue disorders, while almost half of the cases are idiopathic in which no etiological cause can be determined.28–30 Consistent with the previous reports, in the present study, idiopathic cases ranked at the top, at 59.3%, and concomitant infections and antibiotic use were second, at 16%.

We have investigated if some clinical features could be a clue for systemic involvement in patients with LCV. In some previous reports, presenting cutaneous vasculitic lesions above the waist has been found to point out renal or gastrointestinal involvement in HSP patients.20,27,31 Severe cutaneous involvement with vesiculobullous lesions was found to be indicative of systemic involvement in some reports, but this correlation could not be validated in some others.14,28,32 In the present study, the presence of lesions above the waist was significantly associated with both renal and GI involvement, thus emphasizing the importance of a thorough clinical exam. However, severe cutaneous involvement (in form of bullae, ulcers, and/or necrosis) was not associated with systemic involvement. In other words, in the present study systemic involvement was not related to the severity or type of skin lesions, but to their localization.

For patients diagnosed with LCV, any laboratory changes possibly indicating systemic involvement are important. In the literature, high ESR was reported to be the most frequently seen laboratory finding among LCV patients.4,26,28 In some of those studies, high ESR was associated with systemic involvement, whereas in some others no such relationship could be found. Similarly, high ESR was the most common laboratory alteration in the present study, being present in 70.3% of patients, and neither it nor leukocytosis was related to systemic involvement.

Numerous studies have attempted to correlate DIF findings with systemic disease in patients with cutaneous vasculitis. The findings of the previous studies related to DIF findings in LCV are summarized in Table 5.6,7,9,17,23,26 The presence of IgA in the lesional skin of LCV patients was associated with renal involvement in two different case series.7,17 However, Takatu et al. couldn’t revalidate this finding, but instead, they found that C3 deposition at the blood vessel wall was related to renal involvement.6 In some other reports, no association was found between any extracutaneous involvement and DIF results.9,26 In the present study, the presence of IgG in lesional skin was associated with renal involvement and the presence of C3 with joint involvement. Furthermore, the absence of IgM was associated with renal involvement. Unlike ours, in some studies which only included HSP patients, the authors concluded that there was a positive correlation between IgM deposition and renal involvement.14,15

Limitations of this study include a single-center study with a relatively small sample size, though comparable to other DIF-related studies in LCV. Due to the retrospective design of the study not all patients had exactly the same work-up performed, which may lead to an overestimation of idiopathic cases in the present series. Another important limitation is the lack of long-term follow-up information on patients with systemic involvement, so their prognosis remains unknown.

In conclusion, DIF seems to be a useful ancillary diagnostic tool in the evaluation of cutaneous vasculitis, being positive in more than 90% of all patients. Systemic involvement was not rare and was detected in 58% of patients. Deposition of IgG and absence of IgM were associated with renal involvement, whereas deposition of C3 was associated with joint involvement. In light of the results of this study and contradictory data in the literature, we believe that the potential relationship between DIF findings and systemic involvement needs to be further elucidated, as differences in the results may generate discordant interpretations. Distribution of the skin lesions above the waist was a reliable indicator of renal and gastrointestinal disease in adults with LCV, thus emphasizing the importance of a thorough clinical exam.

The research protocol received approval from the Research Ethics Committee of the Istanbul Training and Research Hospital (IRB number: IEAH-KAEK-2830).

None declared.

Sümeyre Seda Ertekin: Study concept and design; data collection, or analysis and interpretation of data; statistical analysis; writing of the manuscript or critical review of important intellectual content; effective participation in the research guidance; intellectual participation in the propaedeutic and/or therapeutic conduct of the studied cases; critical review of the literature; final approval of the final version of the manuscript.

Ayşe Esra Koku Aksu: Study concept and design; writing of the manuscript or critical review of important intellectual content; effective participation in the research guidance; intellectual participation in the propaedeutic and/or therapeutic conduct of the studied cases; final approval of the final version of the manuscript.

Cem Leblebici: Study concept and design; data collection, or analysis and interpretation of data, effective participation in the research guidance; final approval of the final version of the manuscript.

Vefa Aslı Erdemir: Writing of the manuscript or critical review of important intellectual content; effective participation in the research guidance; intellectual participation in the propaedeutic and/or therapeutic conduct of the studied cases; final approval of the final version of the manuscript.

Ozan Erdem: Data collection, or analysis and interpretation of data; statistical analysis; writing of the manuscript or critical review of important intellectual content; critical review of the literature; final approval of the final version of the manuscript.

Elif Bal Avcı: Data collection, or analysis and interpretation of data; critical review of the literature; final approval of the final version of the manuscript.

Mehmet Salih Gürel: Study concept and design; effective participation in the research guidance; intellectual participation in the propaedeutic and/or therapeutic conduct of the studied cases; final approval of the final version of the manuscript.

None declared.