Clinical presentation

The generalized eruption is preceded in most patients by the appearance of a single lesion, 2–5 cm in diameter, known as a ‘herald patch’ (Fig. 1). Some days later, many smaller plaques appear, mainly on the trunk but also on the upper arms and thighs. Individual plaques are oval, pink and have a delicate peripheral ‘collarette’ of scale. They are distributed parallel to the lines of the ribs, radiating away from the spine. Itching is mild or moderate. The eruption fades spontaneously in 4–8 weeks. It tends to affect teenagers and young adults. The cause is unknown, but epidemiological evidence of ‘clustering’ suggests an infective aetiology.

Fig. 1 Pityriasis rosea, showing a herald patch on the lower abdomen and associated oval scaly plaques.

Differential diagnosis and management

Guttate psoriasis, pityriasis versicolor and secondary syphilis may cause confusion. A serological test for syphilis is needed in doubtful cases. The condition is self-limiting, and treatment does not hasten clearance, although a moderate potency topical steroid can help to relieve pruritus.

Clinical presentation

The condition is caused by overgrowth of the mycelial form of the commensal yeast Malassezia (previously Pityrosporum ovale) and is particularly common in humid or tropical conditions. In Europe, it mainly affects young adults, appearing on the trunk and proximal parts of the limbs (Fig. 2). In untanned, white caucasians, brown or pinkish oval or round superficially scaly patches are seen, but, in tanned or racially pigmented skin, hypopigmentation is found as a result of the release by the organism of dicarboxylic acids that inhibit melanogenesis.

Fig. 2 Pityriasis versicolor on the chest: brown scaly patches are evident.

Differential diagnosis

Differentiation from vitiligo is important: usually pityriasis versicolor has a fine scale, and scrapings readily show the ‘grapes and bananas’ appearance of the spores and short hyphae on microscopy. Pityriasis rosea and tinea corporis may occasionally appear similar.

Management

Treatment involves either the topical application of one of the imidazole antifungals (e.g. Canesten or Daktarin cream) or the use of 2.5% selenium sulphide (Selsun) shampoo applied for 30 min (or ketoconazole (Nizoral) shampoo applied for 30 min) and showered off (use three times a week for 2 weeks). Itraconazole, 200 mg by mouth daily for 7 days, is effective for resistant cases. Recurrences are common, and patients are advised that re-treatment may be required.

Clinical presentation and management

Reiter’s disease almost invariably affects males who have the HLA-B27 genotype and commonly follows a genitourinary or bowel infection. The joint and eye changes are often severe. Skin involvement includes a balanitis (p. 121) and red, scaly, pustular, psoriasiform plaques on the feet (keratoderma blenorrhagicum).

Severe skin changes are unresponsive to topical therapy, and methotrexate or acitretin by mouth is often needed.

Clinical presentation

In chronic superficial dermatitis, scaly patches develop, usually on the abdomen, buttocks or thighs (Fig. 3). The onset is in young to mid-adult life, and the plaques are indolent. It may be difficult to predict which cases will progress to mycosis fungoides (p. 104), especially as the evolution may take place over many years, but the ‘benign’ lesions tend to be small and finger-like in shape, whereas the ‘premalignant’ plaques are larger, asymmetrical, atrophic and can show associated poikiloderma (reticulate pigmentation, telangiectasia and atrophy). Biopsy is necessary to look for the changes of mycosis fungoides, and further biopsy of any changed area is required. The disease is often indolent and may persist over a period of several years.

Fig. 3 Plaques of chronic superficial dermatitis on the back of a middle-aged man.

Differential diagnosis and management

Psoriasis, discoid eczema and tinea corporis may need to be considered in the diagnosis, but the plaques of chronic superficial dermatitis are distinguished by being fixed.

The first-line treatment with moderately potent topical steroids is sometimes helpful. Ultraviolet B (UVB) or psoralen with UVA (PUVA) will often be needed for the large plaque variant. Long-term follow-up is recommended.

Definition

Secondary syphilis is an inflammatory response in the skin and mucous membranes to the disseminated Treponema pallidum spirochaete. There has been a resurgence of syphilis in recent years.

Clinical presentation

The secondary phase of syphilis (p. 120) starts 4–12 weeks after the appearance of the primary chancre and consists of an eruption, lymphadenopathy and variable malaise. Pink or copper-coloured macules, which later develop into papules, appear in a symmetrical distribution on the trunk and limbs and are non-itchy (Fig. 5). Annular patterns are not uncommon, and involvement of the palms and soles is distinctive. Other signs are moist warty lesions (condyloma lata) in the anogenital area, buccal erosions that may be arcuate (snail-track ulcers) and a diffuse patchy alopecia. Mucosal lesions are infectious. Without treatment, the lesions of secondary syphilis resolve spontaneously in 1–3 months.

Fig. 5 Secondary syphilis. Coppery red-coloured macules and papules are evident on the trunk.

Differential diagnosis and management

Pityriasis rosea, psoriasis, drug eruption, infectious mononucleosis, rubella and measles may need to be considered. Treponemal serology is positive in all patients with secondary syphilis. Treatment is with intramuscular benzathine benzylpenicillin (p. 120). Patients with syphilis are best managed by physicians familiar with the treatment of genitourinary infections.