Images of the various rashes may be available by clicking links. In some cases links are to factual information needed for recognition/management of a systemic disease with dermatological manifestations. The online dermatological atlas in the internet section will be useful to find any additional images.

Has the rash got fluid-filled (vesiculobullous) lesions?

Clear fluid

Consider:

• Chickenpox (varicella) - vesicles (initially papules, often not noticed), appearing as 'drops of water'. Superficial, thin-walled with surrounding erythema rapidly changing to pustules and crusts. Appears in crops with all stages represented. First appears on the face and scalp and then spreads to the trunk and extremities. Crusts fall off in 1-3 weeks leaving a pink base. Initial fever is classically high before becoming low-grade. Beware of dyspnoea/cough which may indicate varicella-zoster virus (VZV) pneumonitis.¹
• Herpes simplex viral (HSV) infection - eczema herpeticum (HSV infection superimposed on pre-existing, often mild, eczema causing an eruption of crusty vesicles and eczematous patches).²
• Impetigo - this usually takes the form of itchy lesions with macules, vesicles, bullae, pustules and gold-coloured crusts caused by Staphylococcus aureus or group A beta-haemolytic streptococci.² Staphylococcal scalded skin syndrome (appears as scalded skin, due to focal staphylococcal infection – e.g. phage type 71 – releasing an exotoxin).³
• Erythema multiforme, classically appearing as target lesions (erythematous ring with central bulla)²
• Stevens-Johnson syndrome⁴
• Toxic epidermal necrolysis⁴
• Pompholyx (on the hands/feet)⁵

Pustular rashes

Consider:

• Acne vulgaris (there should be accompanying comedones)⁶
• Folliculitis (small pustules at the base of hairs)⁷
• Pustular psoriasis²

Is the rash papular (raised)?^2,7

Consider:

• Urticaria⁸
• Molluscum contagiosum (pearly or fleshy, umbilicated, i.e. central depression in papule)
• Scabies (itchy, excoriated, S-shaped burrows, which should be visible with a magnifying glass)
• Insect bites
• Keratosis pilaris (keratin accumulation at the base of hair follicles)⁹

Is it red and scaly?

With epidermal breakage (eczematous)?

Atopic eczema, typically involves itching erythematous patches, papules and plaques with moist crusted erosions on the face, neck and upper trunk, and also the elbows and knees.

Without epidermal breakage²

Consider:

• Seborrhoeic dermatitis
• Psoriasis
• Tinea corporis/capitis
• Pityriasis rosea

Is it red but not scaly (and NOT purpuric)?

Consider:

• Cellulitis¹⁰
• Kawasaki's disease¹¹
• Scarlet fever and the viral exanthemas, for example:
  • Roseola infantum – (sixth disease).¹²
  • Primary human herpes virus (HHV-6 and HHV-7). The most common age is under two years. It is a frequent cause of infantile febrile seizures. Small blanchable pink macules and papules found on the trunk and neck. It is associated with high fever prior to defervescence and appearance of a rash on the fourth day. It is often asymptomatic.¹³
  • Erythema infectiosum - (slapped cheek syndrome or fifth disease) caused by parvovirus B19.^14,15
  • Measles - presents as erythematous macules and papules - initially discrete, may become confluent on the face, neck and shoulders.¹⁶ On mucous membranes, Koplik's spots (tiny bluish-white papules with erythematous areolae) may develop. Also, upper respiratory tract infection with cough, malaise and fever subsiding as the rash increases (measles prodrome = the 4 Cs - cough, coryza, conjunctivitis and very cranky!).
  • Rubella (German measles) pink macules and papules starting on the forehead and spreading to the face, trunk and extremities on the first day. Fades from the face on the second day and the rest of the body by the third day. Petechiae on the soft palate before the rash. Low fever.
  • Scarlet fever (= scarlatina) exotoxin-mediated rash (Group A streptococcus) - sore throat, then general erythema (classically with perioral sparing), followed by confluent petechiae in skin folds (Pastia's sign) due to increased capillary fragility. Strawberry tongue (initially white, then red). Skin desquamation (peeling) frequently follows the rash.¹⁷

Is it red and purpuric?

Consider:

• Meningococcal meningitis (not common but it should be excluded). Early on there may be a 2-10 mm macular or maculopapular rash (becoming apparent within the first 24 hours of disease) which is is sparsely distributed on the face, trunk and lower extremities and planches on pressure.¹⁸ Later as the disease develops, petechiae in the centre of macules become haemorrhagic (and do not blanche). Use the 'glass test' to assess 'blanchability' of the rash by placing a glass tumbler against lesions and applying pressure.
• Henoch-Schönlein purpura^19,20
• Idiopathic thrombocytopenic purpura (ITP), leukaemia and other haematological disorders²¹
• Trauma, nonaccidental injury
• Enteroviral infections²²

Other miscellaneous conditions

• Warts²
• Verrucas
• Head lice⁷

Algorithm

Summary of Paediatric Skin Rashes: adapted by Dr Adrian M Bonsall, BA (Hons), MBBS (London) (Hons), MRCPCh (I), FACEM (Primary) from the Paediatric Handbook 6th Ed. Royal Children's Hospital, Melbourne.

Footnotes^23,24

The full list of the original exanthems is:

• First disease = measles or rubeola
• Second disease = scarlet fever
• Third disease = rubella or German measles
• Fourth disease = Filatov's or Dukes' disease
• Fifth disease = erythema infectiosum (slapped cheek syndrome)
• Sixth disease = exanthem subitum or roseola infantum

This ordinal nomenclature came about because, at the turn of the century, there were classically three exanthematous diseases recognised: measles, rubella and scarlet fever. Then, in 1900, Dr. Clement Dukes, medical officer at Rugby School, described another exanthem which he called 'fourth disease'. In 1905 erythema infectiosum (a term already in use for 6 years applying to the disease described previously by Tshamer and later by Escherich) was the fifth disease added to the list. Later, sixth disease (roseola infantum) was recognised and fourth disease was rejected by most observers because of insufficient evidence to support its existence as an independent entity. So first, second, third and sixth diseases are now referred to by their more common names, leaving fifth disease as a solitary reminder of the days when, unaided by sophisticated microbiology, observant clinician-epidemiologists were able to categorise a group of confusing exanthems.

Document references

1. Chickenpox, Clinical Knowledge Summaries (January 2008)
2. Sladden MJ, Johnston GA; Common skin infections in children. BMJ. 2004 Jul 10;329(7457):95-9.
3. King R, Victor P; Staphylococcal Scalded Skin Syndrome eMedicine.com 2009.
4. Klein P; Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis eMedicine.com 2009.
5. Oakley A; Pompholyx, DermNet (NZ), 2009; Photographs of pompholyx
6. Webster GF; Acne vulgaris. BMJ. 2002 Aug 31;325(7362):475-9.
7. Sladden MJ, Johnston GA; More common skin infections in children. BMJ. 2005 May 21;330(7501):1194-8.
8. Greaves MW; Chronic urticaria in childhood. Allergy. 2000 Apr;55(4):309-20.
9. Keratosis Pilaris; DermAtlas 2007
10. Curtis D; Cellulitis eMedicine.com 2009.
11. Freeman AF, Shulman ST; Kawasaki disease: summary of the American Heart Association guidelines. Am Fam Physician. 2006 Oct 1;74(7):1141-8. [abstract]
12. Lewis L; Pediatrics, Roseola Infantum eMedicine.com 2009.
13. Asano Y, Yoshikawa T, Suga S, et al; Clinical features of infants with primary human herpesvirus 6 infection (exanthem subitum, roseola infantum). Pediatrics. 1994 Jan;93(1):104-8. [abstract]
14. DermNet NZ; Fifth disease; Illustrations of 'slapped cheek' and lace patterns of rash
15. Parvovirus, Health Protection Agency
16. Picture of Measles Rash; Red Book Online 2007
17. Streptococcal and Enterococcal Infections; Merck Manuals 2009.
18. Yung AP, McDonald MI; Early clinical clues to meningococcaemia. Med J Aust. 2003 Feb 3;178(3):134-7. [abstract]
19. Kraft DM, Mckee D, Scott C; Henoch-Schonlein purpura: a review. Am Fam Physician. 1998 Aug;58(2):405-8, 411. [abstract]
20. Khalid S, Khurshid M; Presentation of a patient with palpable purpuric rash. J Pak Med Assoc. 2009 Jan;59(1):46-7. [abstract]
21. Watts RG; Idiopathic thrombocytopenic purpura: a 10-year natural history study at the childrens hospital of alabama. Clin Pediatr (Phila). 2004 Oct;43(8):691-702. [abstract]
22. Dyne P, Sawtelle S, DeVore H; Pediatrics, Henoch-Schönlein Purpura eMedicine.com 2009.
23. Weisse M; The fourth disease, 1900-2000 The Lancet 2001; 357:299-301
24. No authors listed; Fourth, fifth, and sixth. Br Med J. 1974 Nov 23;4(5942):429.

Internet and further reading

• Dermatology Online Atlas; Homepage
• Common Childhood Diseases and Rashes; Worcester VTS 2009; PowerPoint presentation

Acknowledgements