A very rare cause of blue finger: A case-based review.

Introduction: Cryofibrinogen is an abnormal, cold-insoluble protein composed of a combination of fibrinogen, fibrin, and fibronectin. Cryofibrinogenemia can be essential (e.g. primary) or secondary to various conditions. While low levels of cryofibrinogen can be seen in asymptomatic healthy individuals without evidence of clinical features typical of cryofibrinogenemia, cryofibrinogenemia associated with clinical features is considered very rare. The clinical features of cryofibrinogenemia ranges from skin manifestations, including Raynaud's phenomenon and livedo reticularis, to more severe organ-threatening manifestations such as tissue ischemia and gangrene.

Case description: We report a case of a 48-year-old male who presented with blue finger and palpable purpura on his distal extremities. Laboratory workup was positive for anti-nuclear antibodies, anti-double-stranded DNA, anti-ribonucleoprotein, and rheumatoid factor, while antineutrophil cytoplasmic antibodies and cryoglobulins were negative. Testing for hypercoagulable states and infectious etiologies was unrevealing. Later, angiographic computed tomography showed multiple pulmonary embolisms and disruption of blood flow to the left fifth digit. As the aforementioned workup could not explain the presence of the thrombus by a thromboembolic cause, a search for an in situ cause other than antiphospholipid syndrome was initiated and concentrated mainly on cryofibrinogenemia. Blood samples collected using prewarmed anticoagulant containing tubes were sent to central lab familiar with performing the test. Two weeks later, a positive result for the presence of cryofibrinogen confirmed the diagnosis of cryofibrinogenemia. Due to the presence of multiple signs compatible with mixed connective tissue disease, he was diagnosed with cryofibrinogenemia secondary to mixed connective tissue disease, and treatment with prednisone, low-molecular-weight heparin, prostacyclin and hydroxychloroquine was initiaed with favorable outcome.

Conclusion: Cryofibrinogenemia is a rare and underdiagnosed condition. Clinicians should be aware of this cryopathy especially in the cases of Raynaud's phenomenon and ischemic ulcers not explained by other causes. Precautions must be taken during the diagnostic process, and therapy should be given as soon as possible.