Acrocyanosis (benign)

Acrocyanosis refers to a persistent blue or cyanotic discoloration of the digits, most commonly occurring in the hands although also occurring in the face and feet as well. ^{[1] [2] [3]} The principle form of acrocyanosis is that of a benign cosmetic condition^[1], sometimes caused by a relatively benign neurohormonal disorder.^[2] Regardless of its cause, the benign form typically does not require medical treatment. A medical emergency would ensue if the extremities experience prolonged periods of exposure to the cold, particularly in children and patients with poor general health.^[2] However, frostbite differs from acrocyanosis because pain (via thermal nociceptors) often accompanies the former condition, while the latter is very rarely associated with pain.

Acrocyanosis may be a sign of a more serious and larger medical problem, such as connective tissue diseases and diseases associated with central cyanosis.^[1]

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Incidence, Prevalence, and Epidemiology

Although there is no definitive reporting on its incidence, acrocyanosis shows prevalence in children and young adults than in patients thirty years of age or older.^[2] Epidemiological data suggests that cold climate, outdoor occupation, and low body mass index are significant risk factors for developing acrocyanosis.^[4] As expected, acrocyanosis would be more prevalent in women than in men due to differences in BMI.^[3] However, the incidence rate of acrocyanosis often decreases with increasing age, regardless of regional climate.^[4] Case reports have found acrocyanosis to be more prevalent in patients with autistic disorders such as Asperger's Syndrome.^[5]

Pathophysiology

The precise etiology of acrocyanosis is unknown. The current line of thinking goes that vasospasms in the cutaneous arteries and arterioles produce cyanotic discoloration, while compensatory dilatation in the postcapillary venules causes sweating.^[1][3] Persistent vasoconstriction at the precapillary sphincter creates a local hypoxic environment, thus releasing adenosine into the capillary bed.^[6] Vasospasms force adenosine to enter the capillary bed, where it vasodilates the postcapillary venules.^[6] Such differences in vessel tone create a countercurrent exchange system that attempts to retain heat. Profuse sweating would then be caused by an overwhelmed countercurrent exchange system. In addition to adenosine, other hormones may contribute to acrocyanosis such as increase blood levels of serotonin.^[5] This would seem to support case studies reporting acrocyanosis as an unusual side effect for pediatric patients taking tricyclic antidepressants, as these medications can inhibit the reuptake of serotonin and thus increase their blood concentrations.^[7]

Clinical Manifestations and Presentation

Acrocyanosis is characterized by peripheral cyanosis: persistent cyanosis of the hands or of the hands, feet, or face.^[3] The extremities often are cold and clammy and may exhibit some swelling.^[1] The palms and soles exhibit a wide range of sweating from moderately moist to profuse, but all peripheral pulses should have normal rate, rhythm, and quality.^[2][3] Exposure to cold temperatures worsens the cyanosis, while it often improves on warming.^[1] Patients normally are asymptomatic and therefore there is usually no associated pain; the most common sign, discoloration, usually is what prompts patients to seek medical care.^[2][3]

Diagnosis

Acrocyanosis is diagnosed clinically, based on a medical history and physical examination; laboratory studies or imaging studies are not necessary. The normal peripheral pulses rule out peripheral arterial occlusive disease, where arterial narrowing limits blood flow to the extremities. Pulse oximetry will show a normal oxygen saturation. Unlike the closely related Raynaud's phenomenon, cyanosis is continually persistent. In addition, there is usually no associated trophic skin changes, localized pain, or ulcerations.^[1][3]

Treatment

There is no standard medical or surgical treatment for acrocyanosis, and treatment, other than reassurance and avoidance of cold, is usually unnecessary. The patient is reassured that no serious illness is present. A sympathectomy would alleviate the cyanosis by disrupting the fibers of the sympathetic nervous system to the area.^[2] However, such an extreme procedure would rarely be appropriate. The same effect could be accomplished with α-adrenergic blocking agents or caclium channel blockers.^[1]

Prognosis

While there is no cure for acrocyanosis, patients otherwise have excellent prognosis.^[1] Unless the condition is not benign, there is no associated increased risk of disease or death, and there are no known complications. Aside from the discoloration, there are no other symptoms: no pain, and no loss of function. Patients can expect to lead normal lives.

Newborn Considerations

Acrocyanosis is common initially after delivery in the preterm and full term newborn^[8] Intervention normally is not required, although hospitals opt to provide supplemental oxygen for precautionary measures.

See also

• Acrocyanosis (not benign)
• Pernio (Chilblains)
• Cyanosis
• Peripheral artery occlusive disease
• Raynaud's phenomenon

References