An 18-year-old male bank clerk developed a scaly erythematous plaque on the left elbow (Fig. 1) 6 months before presentation. It spread to involve the other elbow and both knees, but was not itchy. He developed scaliness in the scalp and nail dystrophy. His mother once had a similar rash.

Fig. 1 Psoriatic plaque on elbow.

Diagnosis: psoriasis (p. 28).

A 29-year-old woman was referred from the department of respiratory medicine where she had recently been diagnosed as having pulmonary sarcoidosis. Three weeks previously, she had developed tender, warm erythematous nodules (Fig. 2) on the shins. She was on no medication. An incisional biopsy confirmed the clinical impression.

Fig. 2 Erythema nodosum on the lower legs.

From Weller R, Hunter JAA, Savin J, Dahl, M 2009 Clinical Dermatology, 4th Edn, Wiley-Blackwell, with permission.

Diagnosis: erythema nodosum (p. 83).

A 45-year-old male printer engineer gave a 6-month history of hand dermatitis (Fig. 3). A few months previously, he had started to use the solvent trichloroethylene in his job. Patch testing was negative. On substituting a different solvent, the eruption cleared.

Fig. 3 Irritant contact dermatitis on the palm of the hand.

Diagnosis: irritant contact dermatitis (p. 34).

An 18-year-old male student gave a 3-month history of an intensely itchy papular eruption affecting the hands, wrists and penis (Table 1). Several lesions were excoriated (Fig. 4). Treatment with a potent topical steroid was of little benefit. His girlfriend had also recently developed itchy lesions. Close examination showed burrows in the skin.

Table 1 Itchy eruption: diagnosis

Fig. 4 Excoriated lesions of scabies.

Diagnosis: scabies (p. 63).

A 25-year-old female shop assistant complained of brownish macules over her back (Fig. 5) and chest, which had first appeared in childhood and had gradually increased in number and size. During her teens, she had developed several soft pinkish, painless nodules on the trunk, some of which had become pedunculated. Her father had developed a few similar nodules in later life, and one of her two brothers had brown patches on his skin.

Fig. 5 Multiple neurofibromas on the back.

Diagnosis: von Recklinghausen’s neurofibromatosis (NF-1; p. 92).

A 68-year-old woman had a minor irritating eruption on her forehead. She applied an antihistamine-containing cream that she bought in a pharmacy. Within 24 hours of applying it, her face became severely swollen (Fig. 6). Patch testing carried out later showed an allergic reaction to the cream.

Fig. 6 Acute allergic contact dermatitis to a topical antihistamine cream.

Diagnosis: medicament dermatitis (p. 35).

An 18-year-old female secretary was given griseofulvin for a fungal infection. She went sunbathing and, 12 hours later, developed an eruption with a distribution in light-exposed areas (Fig. 7).

Fig. 7 Acute phototoxic drug eruption.

Diagnosis: phototoxic drug eruption (p. 47).