Chapter 114: Acute skin eruptions

INTRODUCTION

The sudden appearance of a rash, which is a common presentation in children (see CHAPTER 86), usually provokes patients and doctors alike to consider an infectious aetiology, commonly of viral origin. However, an important cause to consider is a reaction to a drug.

A knowledge of the relative distribution of the various causes of rashes helps with the diagnostic methodology. Many of the eruptions are relatively benign and undergo spontaneous remission. Fortunately, the potentially deadly rash of smallpox is no longer encountered.

The diagnostic model is outlined in TABLE 114.1.

A DIAGNOSTIC APPROACH

The diagnostic approach to skin eruptions presupposes a basic knowledge of the causes; key features of the history and physical examination should logically follow.

The history should include:

• site and mode of onset of the rash

• mode of progression

• drug history

• constitutional disturbance (e.g. pyrexia, pruritus)

• respiratory symptoms

• ?herald patch

• diet—unaccustomed food

• exposure to irritants

• contacts with infectious disease

• bleeding or bruising tendency

  The examination should include:

• skin of whole body

• nature and distribution of rash, including lesion characteristics

• soles of feet

• nails

• scalp

• mucous membranes, including oropharynx

• conjunctivae and lymphopoietic system (lymphadenopathy, splenomegaly)

  Laboratory investigations may include:

• FBE, ESR, CRP, U&Es

• specific serology (as clinically indicated) for syphilis, parvovirus, rubella, measles, coronavirus

• Epstein-Barr mononucleosis test

• HIV test

• viral and bacterial cultures

• biopsy

DERMATOLOGICAL MANIFESTATIONS OF SYSTEMIC DISEASE

• Painful red nodules

  • – erythema nodosum

• Photosensitive rash

  • – dermatomyositis (inflamed muscles + rash)— cause unknown, malignancy known association

  • systemic lupus erythematosis

• Palpable purpura

  • – vasculitis—primary or secondary (e.g. sepsis), various causes

• Painful ulceration

  • – pyoderma granulosum—causes include inflammatory bowel disease, rheumatoid arthritis, haematological malignancies

ACUTE SKIN ERUPTIONS

The following skin eruptions in ...