Approach
The diagnosis of DLE is primarily clinical. Although it is possible for non-specialists to make the diagnosis clinically, it is by no means easy. Referral to a specialist dermatologist is usually necessary. It is important to recognise and treat DLE lesions early. If it is left untreated, the risk of scarring, permanent alopecia, and hypo- or hyperpigmentation is known to be increased. Chronic refractory lesions are often associated with psychological and social distress.
Clinical presentation
Two subsets of DLE have been recognised: localised/limited DLE, involving only the head and neck; and disseminated DLE, involving other areas regardless of head and neck involvement.[12]
Patients with disseminated DLE are more likely to develop systemic lupus erythematosus (SLE) and are more difficult to treat.
The most common age of onset is between 20 and 40 years.[4] Patients should be questioned about ultraviolet light exposure and smoking history.
Classic DLE presents with disc-shaped lesions, primarily affecting the face and scalp; the neck, ears, and extensor surfaces of the arms are also commonly involved at presentation. At onset, the lesions are scaly, erythematous macules or papules. The scale is follicular in all cases, and this is an early and diagnostic sign, preceding more general scaling of the lesion. In hair-bearing areas, follicular plugging (scale at hair follicle) is often seen. Characteristically, the lesions are neither painful nor pruritic, but some patients may experience occasional pain within the lesion and/or mild pruritus. Over time, the lesions slowly expand, producing areas of peripheral inflammation or hyperpigmentation, leaving a central region of scarring with telangiectasia and hypopigmentation. If left untreated, DLE scalp lesions inevitably result in alopecia, which becomes permanent once scarring occurs.
Approximately 5% to 10% of patients develop a mild form of SLE.[2] Therefore, a complete physical examination should be performed to look for signs suggestive of underlying systemic disease such as arthritis, serositis (pleuritis, pericarditis), central nervous system involvement (seizures, psychosis), or renal involvement. DLE is considered to have progressed to SLE if systemic features are present and the patient meets the criteria for diagnosis.[13] However, if the patient does not meet diagnostic criteria for SLE, a diagnosis of undifferentiated connective tissue disease is made.
Investigations
Serological tests should be performed in all patients presenting with DLE, to detect progression to SLE as early as possible. Antinuclear antibody (ANA) titre is low in 30% to 40% of patients. High-titre ANA, anti-double-stranded DNA antibodies, and anti-ribonucleoprotein antibodies may suggest SLE or overlapping connective tissue disease. Anti-Ro (SS-A) antibodies can occasionally be found in patients with DLE, whereas anti-La (SS-B) antibodies are distinctly unusual in patients with isolated DLE.
Full blood count (FBC) and erythrocyte sedimentation rate (ESR) should also form part of the initial work-up. Although FBC is usually normal, a small number of patients may have a mild leukopenia. ESR may also be mildly elevated. In addition, urea, electrolytes, and urinalysis are indicated to exclude any systemic involvement, particularly renal impairment, associated with SLE.
If the diagnosis is in doubt, a skin biopsy is indicated. Characteristic changes include hyperkeratosis, follicular plugging, basal layer vacuolar changes, and mononuclear cell infiltration at the dermal-epidermal junction.[12][14][Figure caption and citation for the preceding image starts]: Skin biopsy showing hyperkeratosis, thinning of the epidermis, degeneration of the basal layer of the epidermis (arrow), and a predominantly lymphocytic inflammatory cell infiltrate in the dermisFrom the collection of Dr K. Blessing, used with permission [Citation ends].
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