Primary Raynaud's phenomenon (RP) is a common sign characterized by episodic color changes of acral parts of the body (pallor, cyanosis, rubor) lasting from a few minutes to hours, which are usually triggered by cold temperature and/or stress [1],[2]. Secondary RP is a symptom of an underlying disease. Raynaud's phenomenon has to be distinguished from other color changes of the distal extremities like acrocyanosis, erythromelalgia, perniosis, and Chilblain-Lupus [3].

Autoimmune rheumatic diseases like systemic sclerosis and systemic lupus erythematosus, as well as vascular diseases like arterial occlusions and compression syndromes, are also possibilities that should be taken into account in the differential diagnosis. The rheumatologist or general practitioner, therefore, should be aware of clinical findings that may differentiate to benign causes or syndromes/diseases that require specific treatment [3].

On the basis of physical examination, as well as the use of complementary exams, such as nail capillaroscopy and immunological tests, it is possible to differentiate primary from secondary RP situations. Treatment is aimed at preventing RP, thus avoiding the possibility of irreversible ischemic damage. We present a case of Raynaud's phenomenon associated with exposure to cold, but also a discussion of its pathophysiology and differential diagnosis.

A 42-year-old male patient (physician by profession) reported that the first signs and symptoms emerged at approximately 16 years of age, mainly after exposure to cold temperatures and, in some cases, after emotional stress. Whenever he was exposed to baths with cold water, like in swimming pools or waterfalls, he noticed that certain fingers had pale color. A slight progressive worsening of the condition was observed, initially, the clinical picture was located only in the little finger and, later, the second and third metacarpals of the left hand were also affected (feeling of cold, cyanosis, and partial loss of touch). Recently, he had noticed that other fingers on both hands had shown such a clinical finding, which lasted about 10 minutes, and improved after exposure to heat, when they become acyanotic. During events, there was loss of tactile sensitivity in the affected region. No family history had been referred.

At the time of onset of symptoms, laboratory tests were performed to rule out secondary causes. Inflammatory and immune-mediated diseases such as systemic lupus erythematosus and other rheumatologic diseases had been excluded. He was submitted to electrocardiogram and echodopplercardiogram. All these exams showed without significant changes. Figure 1 illustrates the vasomotor alteration presented in the report.

Raynaud's phenomenon (RP), as described in 1862 by Maurice Raynaud, is characterized by reversible episodes of extremity vasospasms, associated with changes in typical coloring that occur after exposure to cold or in stress situations [4].

Color changes are classically described in three successive phases: paleness (ischemic phase), cyanosis (caused by venostasis and deoxygenation), and flushing (hyperemia reactive/reperfusion). Pain and/or paresthesia may also be associated with attacks, causing discomfort to the individual [5]. The patient in the present study shows his clinical condition only with the pallor of the fingers and superficial hypoesthesia (tactile and painful) [5].

Mainly in RP secondary to systemic sclerosis (SS), the vasospastic events are usually more intense and frequent, and often associated with ischemic ulcers. Additionally, progressive resorption of the extremities is the manifestation that does not occur in the present case. In recent years, advances in the study of the pathophysiology of the RP and vascular disease in SS, for example, led to the onset of new therapeutic options for this manifestation [6].

The average age of onset of primary RP is 14 years of age (as reported in the present case), and only 27% of cases start with around 40 years old or more. In contrast, the secondary RP tends to start in adulthood. The frequency and severity of episodes are influenced by daily temperature variations, with clear exacerbation during the winter and cold water [7].

The vascular tone is controlled by the interaction between endothelial cells, vascular wall smooth muscle, soluble mediators, and neuronal stimulation. An imbalance between vasoconstriction and vasodilation, favoring vasoconstriction, is a central event in the pathophysiology of RP; although part of this mechanism still has question gaps. Patients who present primary Raynaud's phenomena should only be instructed about the triggers for the beginning of the clinical process [5],[6],[7].

In patients with primary RP, pharmacological treatment is generally not necessary, and non-drug measures such as patient education and protection from cold are sufficient. On the other hand, RP secondary to autoimmune rheumatic diseases will often require drug treatment. In these cases, the severity and associated complications must be evaluated and the treatment must be stratified for each case. We emphasize the need for differential diagnosis.