Chilblains

Chilblains — also called pernio — are an abnormal inflammatory response of the small blood vessels of the skin to cold. They are not a freezing injury: they occur at temperatures well above freezing, typically in cold, damp weather rather than in extreme cold.

The mechanism is a failure of normal rewarming. Cold causes the cutaneous arterioles to constrict, which is appropriate. The injury comes with rewarming: when the skin is warmed too quickly, the deeper vessels dilate before the constricted superficial vessels have recovered, and fluid leaks into the surrounding tissue. The result is a localized inflammatory infiltrate around the small vessels, producing the characteristic swelling and itch. Repeated cycles of chilling and rapid rewarming — coming in from the cold and putting the hands straight onto a radiator — are the classic provocation.

Several factors raise susceptibility:

• Cold, damp climates without central heating, especially in autumn and early spring
• Poor peripheral circulation, including Raynaud’s phenomenon
• Low body mass — chilblains are notably more common in slender people
• Tight footwear or clothing restricting circulation to the extremities
• Smoking, through its vasoconstrictive effect
• Female sex and young adulthood, where most idiopathic cases occur

Most chilblains are idiopathic and self-limiting. A minority are secondary — persistent, severe, ulcerating, or occurring outside cold weather — and in those cases an underlying connective tissue disease, most often systemic lupus erythematosus, or a circulating paraprotein or cryoglobulin, should be sought.

Lesions appear hours after cold exposure, usually on the toes, and less often on the fingers, heels, nose or ears. They begin as small, firm, red or purple-blue swellings, typically one to two centimetres across and often multiple.

The dominant symptom is intense itching or burning, which characteristically worsens on entering a warm room — patients often describe it as unbearable at night in bed. Pain and tenderness are common. The skin over the lesion may become dry and fissured, and in more severe cases blisters or shallow ulcers form. Untreated lesions typically resolve over one to three weeks, though pigmentation can persist. Recurrence each winter is the rule rather than the exception, and chronic cases may leave thickened, permanently discoloured skin.

The diagnosis is clinical, made from the appearance, the site, and a clear relationship to cold exposure. No test confirms it.

Investigation is directed at excluding the secondary causes rather than proving the diagnosis. Where lesions are unusually severe, ulcerate, persist into warm weather, or occur in an older adult, it is reasonable to check antinuclear antibodies, a full blood count, and cryoglobulins, and to consider a connective tissue disease. Peripheral pulses should be assessed in anyone with risk factors for arterial disease. Biopsy is rarely needed but shows a dense perivascular lymphocytic infiltrate with dermal edema when performed.