Discoid lupus erythematosus is a primarily dermatological condition affecting both humans and canines. Although minor joint pain can occur in discoid lupus, there are no systemic manifestations such as neuropsychiatric lupus or lupus nephritis.
Symptoms and Signs of Chilblain Lupus
Chilbain lupus is a form of subacute discoid lupus erythematosus causing blue-purple (violaceous) or red-purple nodules, rashes, or lesions that primarily occur on the fingers and toes. These lesions, which affect the acral areas, can also occur on the heels, calves, hands, knees, nose, and ears. The nodules or plaques of chilbain lupus erythematosus appear most prominent over the dorsal joints of the hands.
In about half of all cases, the chilbain lesions develop years after the discoid lesions of lupus appear, although they can occur at the same time as the discoid lesions or in the absence of discoid lesions. About 15 percent of patients with chilbain lupus go on to develop systemic lupus erythematosus.
Chilbain lupus with depigmentation can also occur and this condition may be confused with vitiligo.
Laboratory Findings
Approximately 75 percent of patients with chilbain lupus have a positive ANA test, and about 50 percent of patients test positive for rheumatoid factor RF). In 40-100 percent of patients antibodies to Ro/SSa are positive. In a small number of patients the SSb antibody test is also positive. Less than two percent of patients test positive for ds-DNA antibodies. Up to 40 percent of patients with chilbain lupus have thyroid antibodies. Histologic and immunofluorescent evidence of lupus is present in the skin lesions.
It’s thought that autoantibodies in chilbain lupus predispose the blood vessels to autoimmune inflammation and vasculitis.
Who is Affected by Chilbain Lupus?
People of all ages and ethnicities may develop chilbain lupus. However, most cases occur in middle-aged women. The female to male ratio is 3:2.
Familial Chilbain Lupus
In recent years, familial cases of chilbain lupus have also been reported. These cases frequently occur in childhood and are associated with a heterozygous mutation in the TREX1 gene, which encodes a 3'-5' DNA exonuclease. A similar mutation is seen in one form of the rare autoimmune disorder Aicardi-Goutieres syndrome.
Drug Related Lupus
Chilbain lupus may occur as a form of drug related lupus. In reported cases, the diuretic hydrochlorothiazide and drugs of the calcium channel blocker class are the most common causes. Chilbain and other forms of discoid lupus can also be triggered by the anti-fungal drug terbinafine. These drugs are known to trigger new cases of chilbain lupus and to reactivate previously quiescent cases. Histone antibodies are positive in drug-related chilbain lupus.
Differentiating Chilbain (Perniosis) from Chilbain Lupus
The word chilbain is derived from the Anglo-Saxon words meaning, “to be cold.” Primary or idiopathic chilbains (or chilblains) are localized inflammatory vascular lesions associated with cold exposure, sun exposure, and smoking. In chilbain lupus, lesions do not primarily develop in response to cold although they can.
While the ANA test is frequently positive in chilbain lupus, and the ANCA test is positive in lesions associated with conditions of autoimmune vasculitis, these tests are negative in primary chilbain. Primary chilbains typically develop acutely and resolve within a few days to several weeks although repeated exposure to cold can cause persistent blistering and ulcerations.
Secondary forms of chilbain, such as chilbain lupus, occur in association with systemic conditions including systemic lupus erythematosus, cryoglobulin disorders, and antiphospholipid syndrome. In Raynaud’s syndrome, chilbain lesions resolve within hours rather than the chronic conditions of chilbain seen in secondary chilbain disorders.
Tissue findings in primary chilbain showed edema and a reticular dermis infiltrate with a perieccrine reinforcement. This combination of changes wasn’t seen in chilbain lupus. In chilbain lupus the primary tissue change was the presence of necrotic keratinocytes.
Treatment for Chilbain Lupus
Discoid lupus erythematosus lesions respond more quickly to treatment than lesions in chilblain lupus erythematosus. Treatment with antimalarial agents, prednisone, pentoxifylline, nifedipine, and dapsone is reported to offer benefits.
Source:
The Lupus Foundation of America.
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