Vasculitis Mimics

, David G. I. Scott² and Chetan Mukhtyar²

(1)

Department of Rheumatology, Ipswich Hospital NHS Trust, Ipswich, UK

(2)

Department of Rheumatology, Norfolk and Norwich University Hospital, Norwich, UK

15.1 Introduction

The presenting features of the systemic vasculitides are protean and diagnosis is based on a combination of clinical, laboratory and histopathological features. Clinical features alone are not always diagnostic as a variety of other diseases can mimic systemic vasculitis (Table 15.1). These mimics usually present with multiorgan illness or evidence of vascular damage, or a combination of both. Biopsy of involved organs is, therefore, important to identify noninflammatory vascular changes such as embolism or thrombosis. For example, angiographic features including aneurysms, though typical of PAN, can occur in other conditions such as myxoma and bacterial endocarditis.

Table 15.1

Vasculitis mimics

Systemic multisystem disease
Infection	Subacute bacterial endocarditis
	Neisseria
	Rickettsiae
Malignancy	Metastatic carcinoma
Paraneoplastic
Other	Sweet syndrome
	Scurvy
	Cocaine abuse
Occlusive vasculopathy
Embolic	Cholesterol crystals
	Atrial myxoma
	Infection
Thrombotic	Antiphospholipid syndrome
	Procoagulant states
	Calciphylaxis
Others	Ergot
	Radiation
	Köhlmeier–Degos
	Severe Raynaud’s
	Acute digital loss
Angiographic
Aneurysmal	Fibromuscular dysplasia
	Neurofibromatosis
Occlusion	Coarctation

15.2 Cholesterol Crystal Embolism

Cholesterol crystal embolism has been recognized for more than a century; however, it remains under diagnosed and is sometimes called “trash foot.” Risk factors for cholesterol embolism are male gender, age >60 years, Caucasian ethnicity, hypertension, tobacco use, and diabetes mellitus [1]. Cholesterol embolism may occur spontaneously or after trauma to the aortic wall during vascular surgery including endovascular or angiographic procedures. Other etiological factors include anticoagulation therapy with either heparin or warfarin and thrombolysis [2]. The clinical consequences of cholesterol crystal embolism are variable. Embolization may be completely asymptomatic and the diagnosis made at renal biopsy, or cause an ischemic digit or a multisystem disease that mimics systemic vasculitis. The distribution of end-organ damage depends on the location of the original atherosclerotic plaques.

15.2.1 Clinical Features

Clinically significant renal involvement occurs in around 50 % of patients [1], the onset of renal disease after the triggering event may be immediate but can be more insidious with a delay of weeks or months. There may be acute renal impairment following massive embolization, alternatively there may be a gradual deterioration in renal function due to crystal embolic showers, or an ischemic nephropathy.

Cutaneous manifestations are typically ischemic digits, particularly the toes from abdominal atheroma emboli, or a livedo reticularis appearance typically affecting the legs. Limb ischemia usually presents as sudden onset of a small, cool, cyanotic and painful area of the foot (usually the toe). The lesions are tender to touch and may progress to ulceration, digital infarction, and gangrene. The peripheral pulses are usually well-preserved despite the digital cyanosis (Fig. 15.1). Other common features include abdominal pain, central nervous system involvement, fever, and weight loss.

Figure 15.1

Ischemic digits in cholesterol embolism

15.2.2 Laboratory Features

Laboratory investigations are often nonspecific including uremia, thrombocytopenia, eosinophilia, elevated ESR, hypocomplementemia and disseminated intravascular coagulation. ANCA is not usually detected in the serum. Diagnosis is based on the clinical features with a typical history, supported by histological demonstration of the typical cholesterol clefts or cholesterol emboli in vessels (Fig. 15.2).

Figure 15.2

Skin biopsy from a patient with cholesterol embolism showing typical cleft due to cholesterol emboli. The cholesterol has dissolved during processing leaving the cleft

15.2.3 Treatment

Treatment is aimed at halting the progression of tissue ischemia and prevention of further embolization. Anticoagulation should be avoided as this may exacerbate embolization. Antiplatelet therapy is unsuccessful. Modification of traditional risk factors for atherosclerosis such as smoking, hypertension and hypercholsterolaemia is essential.

15.3 Calciphylaxis

Calciphylaxis is rare, but potentially fatal. It occurs in patients with chronic renal failure with secondary hyperparathyroidism. Disturbance of calcium and phosphate metabolism results in painful necrosis of skin, subcutaneous tissue, and acral gangrene. Appearance of the lesions is distinctive but the pathogenesis remains uncertain. Correction of hyperphosphatemia or occasionally hypercalcemia is vital, and parathyroidectomy may be of benefit [3].

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