Background/Purpose: Blue or purple digit syndrome (or sign) is a cutaneous manifestation of multiple diseases that produce acute or subacute ischemic compromise in one or more fingers or toes. The most frequent cause of this syndrome is a reduction in arterial blood flow due to compromise or occlusion of small peripheral vessels, with preservation of the distal pulses.

The finger or toe affected by ischemia turns blue or violet and may develop necrosis. Whatever the cause, blue digit syndrome is a medical emergency requiring rapid diagnosis and specific treatment, given the risk of progression to irreversible necrosis. Only a very small percentage of cases need surgical intervention; the great majority of patients can be safely managed by medical therapy. Given their nature, medical cases should be managed by rheumatology services. Our aim was to evaluate the frequency, etiology and outcome in a series of patients admitted with blue digit syndrome in the Department of Rheumatology of the University Hospital of Bellvitge, a tertiary care teaching institution in Barcelona, Spain.

Methods: Ambispective cohort study of all patients admitted to our department with blue digit syndrome between 1990 and the first quarter of 2014.

Results: 41 patients (12 women and 19 men) were identified, with a mean age at diagnosis of 55 ± 18.8 years (range: 23-86 years). In 75% (31/41) of patients showed ischemic compromise of one or more fingers (being the second and third fingers most commonly affected), in 15% (6/41) were affected one or several fingers feet, and in 10% (4/41) remaining fingers and toes are affected simultaneously. The main etiologies are summarized in Table 1.

	Number of   cases
Autoimmune diseases Buerger’s disease Crioglobulinemia related to Sjogren’s syndrome or HCV infection Other primary systemic vasculitis or Vasculitis Associated with Systemic Disease (RA, SLE) Systemic sclerosis (scleroderma) Mixed connective tissue disease (MCTD)	11 3 7            10            1
Pseudovasculitis Cholesterol crystal embolism Antiphospholipid syndrome Paraneoplastic acral vascular síndrome Hypothenar hammer syndrome	2 2           2           1
Myeloproliferative síndromes (essential thrombocythemia)	1
Arteriosclerosis	1

Sixty per cent of patients (24/41) also had cardiovascular risk factors, the most common being active smoking and high blood pressure. Three of the patients with Buerger’s disease were cannabis smokers.

Ninety per cent of patients (37/41) progressed well with conservative medical treatment and only 10% (4/41) required amputation (one case with arteriosclerosis and three patients with scleroderma).

Conclusion: In our experience, the most common causes of blue digit syndrome are systemic sclerosis and vasculitis. Differential diagnosis should also include pseudovasculitis, observed in a considerable percentage (17%) of these patients. Despite its severity, the ischemia usually responds to conservative medical treatment and amputation is unnecessary in most cases.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/blue-digit-syndrome-the-rheumatologists-perspective/