What are chilblains?
Chilblains are tender and/or itchy bumps on acral sites following exposure to damp, cold, non-freezing conditions causing a localised form of vasculitis. Chilblains are also called pernio or perniosis.
Chilblains on fingers and toes
Who gets chilblains?
Chilblains can affect all age groups, but is most common in young to middle-aged adults, with a female predominance. Childhood chilblains are well-described but appear to be uncommon. Primary chilblains are unusual in the elderly and an underlying cause should be looked for.
Risk factors predisposing to the development of chilblains include:
- Low body mass index and poor nutrition
- Occupational hazard for outdoor workers, such as fishermen and farmers
- Participation in ice-skating sports
- Underlying bone marrow disorders eg, chronic myelomonocytic leukaemia
- Underlying connective tissue disorders, particularly systemic lupus erythematosus (when it is called chilblain lupus)
- Underlying acrocyanosis and primary or secondary Raynaud phenomenon
- Familial tendency to developing chilblains.
Chilblains are seen in temperate climates rather than in countries with extreme cold where the air is often dry, and appropriate clothing and living conditions minimise the risk. Late winter and early spring, when it is wet and temperatures are above freezing, are the peak seasons for chilblains.
Chilblains and COVID-19
During the COVID-19 pandemic, many cases of chilblain-like changes on the toes ('COVID-toes') have been reported as a late manifestation in children and young adults after a mild illness suspected of being due to the novel coronavirus SARS-CoV-2; PCR swabs and antibodies for the virus have been mostly (but not always) negative. Many reported patients had no recent exposure to cold, and a robust antiviral interferon response has been postulated to induce changes in the small blood vessels. Histology has been performed on a small number of cases and the changes described have been typical of chilblains, chilblain lupus, or a thrombotic vasculopathy pattern. The association between COVID-19 and chilblains is still being defined. However, the development of chilblain-like lesions in the absence of exposure to damp cold or secondary causes, should be suspected as being related to SARS-CoV-2 infection.
Suspected COVID-19 rash on toes
What causes chilblains?
Cold causes constriction of small arteries and veins but a protective physiological reflex intermittently dilates the blood vessels to prevent skin ischaemia. Persistent or prolonged vasoconstriction due to an abnormal vascular reaction to cold may result in hypoxaemia and inflammation to produce chilblains.
What are the clinical features of chilblains?
Chilblains commonly occur on the fingers, toes, and ears (acral sites). However, chilblains can develop on any areas exposed to chronic cold, such as the thighs/hips of horse riders (‘equestrian panniculitis’). Chilblains develop several hours after exposure to damp cold and last for more than 24 hours.
Chilblains typically present as:
- Itch and/or burning pain
- Localised swelling
- Blanchable red/purple discolouration.
Dermoscopy is not very informative, but examination of the nailfold capillaries may be useful if an underlying connective tissue disease is suspected.
What are the complications of chilblains?
Severe chilblains may blister, or become eroded and ulcerated.
How are chilblains diagnosed?
Chilblains are usually diagnosed clinically. Investigations are sometimes required to exclude differential diagnoses or look for causes of secondary chilblains.
Skin biopsy of primary idiopathic chilblains shows a superficial and deep lymphocytic vasculitis, lymphocytes around the eccrine sweat glands, subepidermal oedema, with or without interface changes. [see Perniosis pathology].
The Mayo Clinic has developed diagnostic criteria for chilblains:
Major criterion (required) — localised redness and swelling of acral sites lasting at least 24 hours.
Minor criteria (at least one of the following):
- Onset and/or worsening in cooler months
- Histopathology consistent with chilblains
- Improvement with warming and drying.
Chilblains are classified as idiopathic (primary) if there is no associated cause, and secondary if a cause can be identified.
Investigations for secondary causes of chilblains may include:
- Full blood count
- ANA, rheumatoid factor, antiphospholipid antibodies
- Complement levels
- Protein electrophoresis
- Cold agglutinins and, in children, cryoglobulins.
What is the differential diagnosis for chilblains?
Differential diagnoses of chilblains
What is the treatment for chilblains?
Prevention of chilblains
- Avoiding cold, wet environments if possible
- Wearing warm, dry clothing during cold weather to protect hands, feet, and ears
- Vigorous exercise to keep warm and improve circulation
- Keep indoor areas warm and dry
- Soaking hands in warm water before exposure
- Cessation of smoking and other vasoconstrictors
- Topical nitroglycerine 0.2%
- Topical betamethasone valerate 0.1% twice daily — may relieve itch
- Nifedipine 20–60 mg three times daily — hastens healing time and reduces the risk of relapse
What is the outcome for chilblains?
Chilblains usually resolve spontaneously in 1–3 weeks. However, chilblains can become chronic. Recurrences may occur with subsequent exposures or annually.