Background/Purpose: Blue Digit Syndrome (BDS) represents the cutaneous manifestation of numerous diseases that cause blue discoloration in one or more fingers in the absence of trauma and with preserved pulses. The diagnosis of the underlying cause is crucial to preserve the affected extremity and treat the underlying disease. While it may not be the most common etiology, many systemic autoimmune and inflammatory diseases can present with cutaneous manifestations such as BDS. These conditions may include connective tissue diseases like systemic sclerosis (SSc), vasculitis, and other rheumatic disorders. Being sometimes the only exploratory finding, diagnosis may be challenging.

This study aimed to define the prevalence of different etiologies in patients with BDS. Additionally, the clinical characteristics, assessment findings, complementary investigations, and patient outcomes were described.

Methods: Ambispective cohort study. All patients admitted to the Rheumatology Department of Hospital Universitari Germans Trias i Pujol for blue digit syndrome between January 2017 and December 2022 were included.

Results: Forty-five patients (20 males and 25 females) were included with a mean age of 56.4 years. 46.7% were smokers. 48.9% had cardiovascular risk factors. The most frequent diagnoses were thromboangiitis obliterans (TAO) (22.2%) systemic sclerosis (SSc) (15.6%), severe atherosclerosis (8.9%), haematological disorder (8.9%) and cryoglobulinemia (8.9%). 10% of cases were considered idiopathic, and 12.5% were multifactorial. To be noted, a patient initially diagnosed of idiopathic blue finger syndrome was ultimately diagnosed with prostate cancer. Half of the cases presented with involvement limited to the upper extremities. 28.9% of patients had systemic symptoms. Examinations included autoimmunity tests, echocardiogram, arteriography, blood analysis among others. Skin biopsies were performed in 13 out of 40 patients, of which 2 out of 13 showed diagnostic findings of cholesterol emboli, 1 out of 13 showed calciphylaxis, 1 out of 13 showed vasculitis, and the remaining cases (9 out of 13) had no specific findings. 56% of the cases resolved with medical treatment. 8 patients (17.8) of patients required surgical amputation of the affected finger.

Conclusion: In our experience, the most common cause of BDS was TAO, followed by SSc. The differential diagnosis is broad and requires multiple complementary investigations, although some may have limited utility and carry the risk of iatrogenic harm. Therefore, a reasoned and systematic diagnostic approach based on initial suspicion is crucial.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/blue-digit-syndrome-as-the-initial-presentation-of-various-diseases-a-case-series/