DLE is the most common form of chronic cutaneous erythematosus and can occur as a localized form (80%) with lesions on the face, ears, and scalp or as disseminated DLE (20%) with lesions above and below the neck. The disseminated form of DLE, especially when involving the trunk, is associated with an increased risk of progression to SLE. It is unusual for discoid lesions to be present below the neck without lesions also being present above the neck. Occasionally, discoid lesions develop on mucosal surfaces, including the lips, nasal mucosa, conjunctivae, and genital mucosa. Some patients with discoid lesions exhibit a photodistribution. Sun exposure seems to play a role in the development of lesions.
For discoid lupus erythematosus without associated SLE (CDLE), the evidence does not show whether circulating inflammatory cells and autoantibodies are involved in the pathogenesis, but it is evident that the cutaneous inflammatory infiltrates are dominated by Th1.
The first morphological sign of DLE is a well-defined, annular erythematous patch or plaque of varying size followed by follicular hyperkeratosis, which is adherent to the skin. By removing the adherent scale, follicle-sized keratotic spikes similar to carpet tacks can be seen ("carpet tack sign"). The lesions slowly expand with active inflammation and hyperpigmentation at the periphery leaving depressed central atrophy and scarring, telangiectasia, and hypopigmentation. DLE can progress to irreversible scarring alopecia on the scalp. Although uncommon, a squamous cell carcinoma can develop in a longstanding discoid lesion.
A biopsy from the lesion for routine histologic examination is usually diagnostic of DLE. Atrophic epidermis, keratotic plugging of the follicles, hydropic degeneration of the basal cells, and patchy perivascular and perifollicular lymphocytic infiltrate are characteristic.
Early treatment of discoid lupus lesions may lead to the total clearing of skin lesions, but treatment failure results in permanent scarring. Hair loss, depressed scars, and pigmentary changes are often disfiguring, particularly in darker-skinned people. Some general measures, such as sun avoidance and liberal application of sunscreen, are encouraged because cutaneous lesions are known to be exacerbated by sunlight. Smoking cessation is encouraged, as this can increase DLE disease activity.
While antimalarials such as hydroxychloroquine have been widely used as a first-line treatment for lupus-associated skin lesions, 30% of patients with lupus do not respond to this medication. Other available therapies such as corticosteroids and thalidomide can also be applied, however, their toxic side effects limit their clinical use. Recent studies by the investigators have shown that nicotinamide, a water-soluble vitamin whose side effects are considered minimal, can protect against skin lesions and autoantibody production. Thus it is hypothesized that nicotinamide treatment could be a novel therapy for lupus-associated skin lesions in patients with LE.
Nicotinamide is the amide form of vitamin B3 . It is the precursor of numerous reactions in the body including adenosine triphosphate (ATP) production and consequently can be used in many dermatological disorders.
