tempp-青斑狀(青斑樣)血管炎(livedoid vasculitis)

青斑狀(青斑樣)血管炎(livedoid vasculitis)，又稱為青斑狀血管病變(livedoid vasculopathy)，其特徵為反覆發作，且伴隨疼痛感的下肢皮膚潰瘍，潰瘍痊癒後，會留下白色

星狀疤痕，稱為「白色萎縮症」(atrophie blanche)。

此病較常影響成年女性(男女皆可能發生)，具反覆發作的傾向。

青斑狀血管病變在皮膚病理下的特徵，為真皮層的血管內皮增生，血管壁出現增厚，



http://emedicine.medscape.com/article/1082675-overview

Livedoid vasculopathy (LV), or livedoid vasculitis, is a disease characterized by ulceration of the lower extremities. It can evolve into a dermatologic

finding termed atrophie blanche (AB). LV is a distinct condition that is not usually the result of other diseases, as Jorizzo elegantly noted in 1998.1

Biopsy specimens of LV aid in diagnosing this condition, but they are not pathognomonic. The skin manifests with segmental hyalinizing vascular involvement

of thickened dermal blood vessels, endothelial proliferation, and focal thrombosis without nuclear dust. Direct immunofluorescence study reveals

immunoglobulin and complement components in the superficial, mid-dermal, and deep dermal vessels.


Frequency
United States

LV is an uncommon disorder in the United States.
International

LV is an uncommon condition worldwide.
Mortality/Morbidity

LV, although painful, is not associated with any loss of life or limb.
Sex

Women are affected more often than men.
Age

LV lesions can occur at any age, but LV is most commonly a disease of adulthood.



Pathophysiology

While the etiology of LV is not yet fully defined, it likely has a procoagulant pathogenesis.5 Factor V Leiden mutation, heterozygous protein C deficiency,6

and other inherited hypercoagulable states have been linked to LV.7 In particular, states such as hyperhomocysteinemia, which results in increased clotting,

plays a role in LV.8 Plasminogen activator inhibitor (PAI) – 1 is an important inhibitor of the fibrinolytic system, and the PAI-1 promoter 4G/4G genotype,

in which PAI-1 is increased, has been liked to LV.7

The histology of LV evolves according to the temporal stage of the lesion. AB is a scarring condition of white stellate scars that is an end stage of LV.

Venous stasis and other conditions, such as leukocytoclastic vasculitis, can lead to identical white scars on the legs.

Most commonly, LV shows fibrin deposition within both the wall and the lumen of affected vessels. The absence of a substantial perivascular infiltrate or

leukocytoclasia argues against a vasculitis, being more in keeping with a thrombo-occlusive process.

The underlying mechanism of the development of LV may be related to (1) the development of a fibrin cuff, (2) white-cell trapping, (3) microthrombi, (4) a

defect of endothelial cell plasminogen activator, (5) platelet dysfunction, and (6) enhanced fibrin formation. The following is a summary of the excellent

discussion of these mechanisms by Maessen-Visch et al9 in 1999.

Browse and Burnand10 posited the fibrin cuff theory. The fibrin cuff theory postulates that because of chronic venous compromise, fibrinogen leaks from the

capillaries. This fibrinogen coagulates and hardens to form a fibrin cuff. This cuff surrounds the capillaries. The cuff establishes a barrier that prevents

oxygen and nutrients from reaching the skin. However, Maessen-Visch et al9 note that fibrin is an effective barrier to prevent the diffusion of oxygen to

tissue. The cuffs then are an artifact rather than a seal. The fibrin cuffs are more an indication of disturbed microcirculation rather than an etiologic

factor in chronic venous insufficiency; therefore, this theory is of uncertain accuracy.

In 1988, Coleridge Smith et al11 suggested the white-cell trapping theory. In this schema, white cells adhere (trap) to the endothelium of the capillaries as

a result of venous hypertension. This results in the induction of proteolytic enzymes and superoxide metabolites. These enzymes and metabolites cause tissue

destruction. This molecular degrading effect on tissue appears to be a nonimmunologic phenomenon. Its etiology is due to the low flow in the wide

capillaries. No up-regulation of binding molecules, such as intercellular adhesion molecule, vascular cellular adhesion molecule, and endothelial leucocyte

adhesion molecule, occurs. A defect of endothelial cell plasminogen activator exists in some patients with LV. However, at least 20% of the 118 control

subjects showed the same values as patients with LV.

Tissue-type plasminogen activator (tPA) levels appear to be lower in patients with LV. The average plasma level of releasable tPA was only 0.03 IU/mL in one

study, versus an average tPA level of 0.70 IU/mL in 118 healthy controls.12 Furthermore, Klein and Pittelkow13 reported a high incidence of defective release

of tPA and increased levels of PAI and a high incidence of antiphospholipid antibodies in patients with LV. levels of tPA in the reference range were found

in patients with chronic venous insufficiency and AB or lipodermatosclerosis.

Other evidence has implicated platelet dysfunction; one study noted that 7 patients with AB and LV had increased platelet aggregation. These 7 patients were

treated successfully with antiplatelet therapy.14 The value of this study is limited because it was not controlled or designed to evaluate these factors and

enzyme levels.

Enhanced fibrin formation, as evidenced by elevated levels of total fibrin-related antigen and D-dimer, has also been suggested as the cause for LV. This

theory also needs to be tested via double-blinded studies. As of yet, well-crafted and adequate studies have not been performed.

LV seems to be primarily an occlusive condition rather than an inflammatory condition.