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Chapter 122: Acute skin eruptions

INTRODUCTION

They say love’s like the measles—all the worse when it comes late in life.

DOUGLAS JERROLD (1803–57)

The sudden appearance of a rash, which is a common presentation in children (see CHAPTER 93), 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 122.1.

Table 122.1Acute skin eruptions: diagnostic strategy model
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Table 122.1 Acute skin eruptions: diagnostic strategy model

Probability diagnosis

Hand, foot and mouth disease

Erythema infectiosum (slapped cheek disease or fifth disease)

Roseola infantum (sixth disease)

Other viral exanthema (e.g. enterovirus)

Pityriasis rosea

Impetigo

Folliculitis (e.g. pseudomonas, staphylococcus)

Varicella (chickenpox)

Herpes zoster (shingles)

Herpes simplex

Urticaria

Drug reaction (see TABLE 122.4)

Serious disorders not to be missed

Vascular/vasculitis:

  • Henoch–Schönlein purpura

  • Stevens–Johnson syndrome/toxic epidermal necrolysis

  • other vasculitides e.g. polyarteritis nodosa

Infection:

  • purpura of meningococcus, typhoid, other sepsis

  • scarlet fever

  • primary HIV infection

  • secondary syphilis

  • measles

  • rubella (in pregnancy)

Other:

  • erythema nodosum

Pitfalls (often missed)

  • guttate psoriasis

  • Epstein–Barr virus (EBV) mononucleosis

  • arbovirus infection (e.g. dengue, Ross River fever, Barmah Forest virus, Japanese encephalitis)

  • scabies

  • Kawasaki disease

  • eczema herpeticum

  • zoonoses (e.g. listeriosis, Q fever)

Rarities:

  • filovirus diseases (e.g. Ebola, Marburg virus)

  • erythema multiforme

A DIAGNOSTIC APPROACH

The diagnostic approach to skin eruptions presupposes a basic knowledge of the causes; a careful 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

  • oropharynx

  • conjunctivae and the lymphopoietic system (? lymphadenopathy ? splenomegaly)

Laboratory investigations may include:

  • a full blood examination

  • syphilis serology

  • Epstein–Barr mononucleosis test

  • HIV test

  • rubella haemagglutination tests (x 2)

  • viral and bacterial cultures

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

    • – inflammatory bowel disease

    • – rheumatoid arthritis

    • – haematological malignancies

ACUTE SKIN ERUPTIONS IN CHILDREN

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