Cutaneous Small Vessel Vasculitis

A leukocytoclastic vasculitis confined to the skin, without evidence of systemic vasculitic involvement, representing either an idiopathic process or a reaction pattern secondary to an identifiable trigger, most commonly infection or medication, and requiring careful clinical evaluation to exclude an underlying systemic vasculitis or other systemic disease before the diagnosis is accepted as purely cutaneous.

Causes

Infection, particularly upper respiratory tract infection preceding the rash by one to three weeks, and medications (antibiotics, particularly beta lactams and sulfonamides, and a wide range of other drugs) are the commonest identifiable triggers.

Idiopathic disease, in which no cause is identified despite reasonable evaluation, accounts for a substantial proportion of cases.

Cutaneous small vessel vasculitis can also represent the skin manifestation of an underlying systemic vasculitis (IgA vasculitis, antineutrophil cytoplasmic antibody associated vasculitis, cryoglobulinaemic vasculitis), connective tissue disease, or malignancy (particularly haematological malignancy), making systemic evaluation an essential part of the assessment even when cutaneous findings appear isolated.

Palpable purpura, typically distributed over dependent areas (lower limbs, buttocks in patients who have been sitting) and appearing in crops, is the characteristic finding, reflecting the postcapillary venule predominant site of inflammation.

Lesions may also present as urticarial plaques that persist longer than typical urticaria (beyond twenty four hours) and leave residual pigmentation or purpura on resolution, an important distinguishing feature from ordinary urticaria.

Occasional vesiculobullous or ulcerative lesions occur in more severe cutaneous disease.

The presence of systemic symptoms (fever, arthralgia, abdominal pain) or evidence of other organ involvement (renal impairment, haematuria, neuropathy) should prompt evaluation for an underlying systemic vasculitis rather than isolated cutaneous disease.

Skin biopsy, ideally taken from a lesion less than forty eight hours old, shows leukocytoclastic vasculitis with neutrophilic infiltration, fibrinoid necrosis of vessel walls and nuclear debris, with direct immunofluorescence helping characterise the immune deposits present (IgA deposition supporting IgA vasculitis, for example).

Urinalysis and renal function are essential in every patient to screen for renal involvement suggesting a systemic rather than purely cutaneous process.

Full blood count, inflammatory markers, and where clinically indicated, antineutrophil cytoplasmic antibody, cryoglobulins, complement levels, hepatitis serology and a careful medication review help identify an underlying cause or exclude systemic vasculitis.

A thorough history focusing on recent infection, new medications and systemic symptoms guides the diagnostic workup, and the extent of investigation should be tailored to clinical suspicion rather than applied uniformly, avoiding unnecessary testing in a straightforward, self limiting, isolated cutaneous presentation with no systemic features.

Isolated cutaneous disease without systemic involvement is generally self limiting and managed conservatively with leg elevation, rest, and identification and withdrawal of any causative medication.

Antihistamines and nonsteroidal anti inflammatory drugs provide symptomatic relief for associated itch or discomfort.

A short course of corticosteroids may be used for more extensive, persistent or troublesome cutaneous disease, though most cases resolve without specific treatment within several weeks.

Chronic or recurrent cutaneous vasculitis, or disease not responding to simple measures, may require dapsone, colchicine or, for more persistent disease, immunosuppression, with the specific approach guided by any identified underlying cause.

Where an underlying systemic vasculitis, connective tissue disease or malignancy is identified, management shifts to treatment of that specific underlying condition, following the principles detailed under each respective diagnosis.

Patient reassurance regarding the generally benign, self limiting course of isolated cutaneous small vessel vasculitis, together with clear safety netting advice to seek review if systemic symptoms develop, completes routine management for the majority of straightforward cases.