Differential Diagnoses

There are many other skin diseases which can resemble rosacea and occasionally it is difficult to differentiate between them. Investigations including skin biopsy for histology or DIF, skin allergy tests and additional blood tests may be needed to exclude other differential diagnosis.

Differential diagnosis of rosacea depends on the subtypes of rosacea as shown in tables 11, 12, 13 and these include: (1)

Table 11 - Differential Diagnosis of ETR:

No Differential diagnosis How to differentiate it from ETR

1 Disorder of flushing History, clinical examination, blood test. 2 Lupus erythematosus History, clinical examination, blood test, skin

biopsy.

3 Seborrheic eczema History, clinical examination. 4 Atopic dermatitis History, clinical examination. 5 Contact and photo contact

dermatitis

History, clinical examination, patch test, photo patch test

6 Facial sarcoid History, clinical examination, blood test, skin biopsy.

7 Topical steroid misuse History, clinical examination. 8 Facial erysipelas History, clinical examination. 9 Jessner's lymphocytic

infiltration

History, clinical examination, skin biopsy. 10 Polymorphic light eruption History, clinical examination.

11 Dermatomyositis History, clinical examination, skin biopsy, blood test.

Table 12 - Differential Diagnosis of PPR:

No Differential diagnosis How to differentiate it from PPR

1 Acne vulgaris History, clinical examination.

2 Acne agminata History, clinical examination, skin biopsy 3 Perioral dermatitis History, clinical examination.

4 Seborrheic eczema History, clinical examination.

5 Facial sarcoid History, clinical examination, skin biopsy, blood test. 6 Tinea faceii / candida History, clinical examination, skin scraping / swabs. 7 Pityriasis folliculorum History, clinical examination, skin scraping.

8 Jessner's lymphocytic infiltration

History, clinical examination, skin biopsy. 9 Polymorphic light

eruption

History, clinical examination.

Table 13 - Differential Diagnosis of PR:

No Differential diagnosis How to differentiate it from PR

1 Lupus pernio (Sarcoid) History, clinical examination, skin biopsy, blood test. 2 Lupus erythematosis History, clinical examination, skin biopsy, blood test. 3 Lupus vulgaris History, clinical examination, skin biopsy, blood test. 4 BCC / SCC/ Lymphoma History, clinical examination, skin biopsy.

5 Angiosarcoma History, clinical examination, skin biopsy. 6 Acrocyanosis History, clinical examination.

9.1 - Lupus Erythematosus (LE):

Lupus erythematosus (LE) is a heterogeneous connective-tissue disease associated with polyclonal B-cell activation and is believed to result from the interplay of genetic, environmental, and hormonal factors. LE is more common in women than men especially the systemic variety by at least 6 to 1. It also varies between different ethnicities. For example, the prevalence of SLE in African American women is 4 in 1000 compared to Caucasian American women at 1 in 1000 (90).

The spectrum of lupus disease involvement can vary from limited cutaneous involvement to devastating systemic disease. Cutaneous lupus erythematosus (CLE) is the second most common presenting symptom of autoimmune LE. Lesions precede the onset of systemic symptoms in 25% of patients, many of whom present to dermatologists for their initial evaluation (91).

The main subtypes of cutaneous lupus (CLE) according to the James Gilliam classification, based on the presence of interface dermatitis, are acute cutaneous (ACLE), subacute cutaneous (SCLE) and chronic cutaneous (CCLE) (92). Further subdivisions of CCLE include discoid LE (DLE) and other atypical LE specific lesions, including chilblain LE, LE tumidus (LET), and LE panniculitis.

ACLE accounts for about 6% of patients with CLE and it is characterized by the classic “butterfly rash” overlying the malar cheeks and nose as in figure 14. The rash is photo-aggravated and strongly associated with exacerbations of SLE. Lesions typically resolve without atrophic scarring although areas of post-inflammatory dyspigmentation may persist (93).

Figure 14 - Butterfly rash of Lupus Erythematosus

DLE is the most common form of CCLE and classically presents as erythematous, coin-shaped plaques with central hyperkeratosis as in figure 15, with 70% of cases limited to the head and scalp. This pattern is rarely associated with systemic disease (94).

Figure 15 - Discoid Lupus Erythematosus

SCLE is characterised by a photosensitive rash in up to 85% of patients and the lesions are mainly located to sun exposed areas; neck, chest, upper back, shoulders, dorsal parts of the arms and hands but surprisingly the face and scalp are seldom involved. The lesions start as erythematosus plaques or papules and then

become either widespread annular, polycyclic lesions that clear centrally or papulosquamous (psoriasiform) lesions or rarely a combination of these two forms as in figure 16. The lesions are non-scarring but often heal with pigmentary changes that are long lasting.

Figure 16 - Subacute Cutaneous Lupus Erythematosus

A diagnosis of chronic cutaneous lupus is made based on the clinical findings of photosensitivity, erythema, follicular plugging, dyspigmentation, telangiectasia, and skin atrophy. Scarring and skin atrophy are characteristic of DLE. The diagnosis is supported by skin biopsy for histology and DIF studies as well as the detection of autoantibodies in the blood in some patients. SCLE is strongly associated with the presence of anti-Ro/SSA antibodies, found in about 70% of patients, and positive ANA antibodies in 60 - 80%, whilst between 30 - 50% display the anti-La/SSB antibody which is almost always seen together with the anti-Ro/SSA antibody. In DLE the involvement of autoantibodies is less clear but up to 50% may display low titres of ANA (95).

The histological features of cutaneous lupus depend on the subtype to a degree; however, an overlap in histological findings can occur between the various clinical phenotypes, particularly ACLE, SCLE and DLE. The most characteristic features of

keratinocytes (vacuolar degeneration or hydropic changes) and lymphohistiocytic inflammatory infiltrates in the early stages as shown in figure 17. However, in the late chronic stage of those phenotypes that resolve with scarring, thickening of the basement membrane and dermal fibrosis and scarring are characteristic features as shown in figure 18. In DLE, periadnexal inflammation, follicular plugging and scaring are common features, whilst in SCLE, epidermal changes and superficial lymphocytic infiltrates are more common. In contrast to DLE lesions, SCLE lesions tend to have little or no hyperkeratosis, basement membrane thickening, periadnexal infiltrate, follicular plugging, deep dermal infiltrate, or scarring (96). Despite these reported differences, blind assessment of histology from different sub-types of LE by experienced skin pathologists is usually unable to accurately diagnose the sub-type.

Figure 17 - Lupus Histology Figure 18 - Lupus Histology