Rashes cause a great deal of concern to parents and are often dismissed as either inconsequential or confusing by health care practitioners. While the majority of rashes have trivial consequences, others are manifestations of serious and potentially fatal disease.

Rashes cause a great deal of concern to parents and are often dismissed as either inconsequential or confusing by health care practitioners. While the majority of rashes have trivial consequences, others are manifestations of serious and potentially fatal disease. A careful evaluation of a rash can be extremely rewarding. Serious diseases can be diagnosed with a reasonable degree of certainty and appropriate therapy rapidly instituted. For example, Kawasaki disease often presents with fever and a rash and failure to recognise it in time and give intravenous gammaglobulin will result in coronary artery aneurysms in 20% of patients. In contrast, parents can often be reassured of the benign nature of many rashes.

Specific features of rashes

A good clinical history and physical examination are important for accurate diagnosis. Important points in the history are presented in Table I. An important and often neglected feature is the tempo of development. For example, the petechiae seen in meningococcaemia develop over minutes to hours, while in papulonecrotic tuberculid (PNT), a form of cutaneous tuberculosis, the lesions develop over weeks.

Important points in physical examination are shown in Table II. Kawasaki disease is diagnosed by a constellation of physical signs such as maculopapular rash, bulbar conjunctivitis, swollen digits and unilateral cervical adenopathy. Occasionally, severe disease such as ecthyma gangrenosum might be missed if the nappy is not removed.

Type of rash (Table III)

There are many types of rashes, including maculopapular, erythrodermal, vesicular or bullous, petechial or purpuric and erythema nodosum. The majority of rashes are maculopapular. Some rashes may begin as either macular or maculopapular and evolve over time. For example, both meningococcal disease and Henoch-Schönlein purpura may begin as macules/papules that become purpuric over one or two days.

Probably the most serious viral cause of a maculopapular rash is measles. The rash is accompanied by coryza, coughing and conjunctivitis. Koplik’s spots are patho-gnomonic of measles and should always be sought. They are seen on the buccal mucosa a day preceding and two days into the rash. Measles spreads very rapidly and immuno compromised patients are extremely vulnerable. Failure to recognise measles, especially in the hospital environment, and institute post-exposure prophylaxis to unimmunised contacts (vaccine in immunocompetent contact and immunoglobulins in severely immuno-compromised) will have serious consequences. Due to successful mass vaccination programs, measles is now rare and may not be recognised by many clinicians. Also, the maculopapular rash may be harder to identify in patients with dark skin. (Figure 1A and B.)

Figure 1A : 18 year old girl with measles. Note the discharge from eyes and nose.

Fig 1B : Maculopapular rash on dark skin

Figure 2 : Meningococcaemia showing small well circumscribed purpuric lesions in 9 month-old infant on legs

The other common appearance is vesicular. The most well known vesicular rash is due to varicella (chicken pox). Others include hand-foot-and-mouth disease due to coxsackie A virus and also herpes simplex virus (HSV).

Distribution of rash
This may also give a clue. For example, vesicles in the mouth and on the hands and feet are characteristic of hand-foot-and-mouth disease. The maculopapular rash of enterovirus and rickettsial diseases characteristically involve the palms of the hands and soles of the feet. The purpuric lesions of Henoch Schön-lein purpura are classically most prominent on the distal aspects of the lower limbs and lesions above the buttocks are rare.

Varicella zoster occurs more commonly in immunocompromised than immuno-competent children and an underlying cause for immunosuppression should be excluded. It may also disseminate in immunocompromised children. Herpetic lesions caused by HSV also cause disseminated vesicles in immuno-compromised children.

Progression
Many rashes have characteristic features and diagnoses can be made with relative certainty. Specific aspects of rashes in children are shown in table I. An important and yet often neglected feature of a rash is its natural history. For example, a petechial rash or even isolated petechial spots (macules that do not blanche on pressure), papules or more rarely a maculopapular rash, progressing rapidly with new spots appearing over minutes and hours in a toxic child, is almost certainly meningo-coccaemia (Figure 2). Of note is that the characteristic black appearance is not immediately apparent and appears with time. The lesions vary in size and may be only millimetres in diameter. Failure to recognise these features might cause a delay in treatment and might have fatal consequences.

Rashes from most viral illnesses progress over hours to days. For example, in measles, the rash starts behind the ears after a prodrome of three to four days (fever, coryza, conjunc-tivitis, cough and Koplik spots), gradually progresses to the trunk and limbs over the next two to three days, resolving over the next two to three days in reverse sequence with fading of the rash and desquamation.

In infective endocarditis, development of new lesions may be episodic over days (Figure 3). Lesions are well circumscribed (Figure 3). Failure to auscultate the heart in a febrile child may contribute to progressive valve damage, again with fatal consequences.

Cutaneous tuberculosis, (papulonecrotic tuberculosis), persist for weeks and may be prominent on the ears (Figure 4). In juvenile chronic arthritis with systemic onset, a pathognomonic feature is the presence of a generalised papular eruption only during fever.

Figure 3 : Endocarditis showing focal skin infarcts

Figure 4 : Papulonecrotic tuberculosis

Well circumscribed versus coalescent lesions
One useful distinguishing feature between viral and bacterial (or rickettsial) skin lesions is that viral rashes often coalesce whereas in bacterial infections, the papules are often very distinct. Exceptions are toxin-mediated skin lesions from toxic shock syndrome (TSS), staphylococcal scalded skin syndrome and scarlet fever, where the skin manifestations are extensive and coalescent (and intensely erythematous in nonpigmented skin). Occasionally, the rash may also be coalescent in severe rickettsial or bacterial infections. On the other hand, the maculopapular rash associated with rubella is not coalescent.

HIV
With the advent of HIV disease, children are presenting with new expressions of dermatological disease. Most conditions are seen in children without HIV infection as well, but are more intense and more extensive in HIV-infected children. Conditions include papular pruritic eruptions and severe scabies, often alone or in combination and easy to confuse. Herpetic infections are also more common and more extensive.

Physical signs that assist in establishing the cause of a rash
A number of exanthematous diseases in children have distinctive features where failure to make a diagnosis has serious consequences for the child or the com-munity. Examples include Kawasaki disease (KD) and measles. With KD, there is a 20 percent chance of developing coronary aneurysms if correct treatment is not given early in the disease, and for measles, failure to identify and prevent spread of the disease will promote the spread in vulnerable infants especially if immuno-compromised or under 9 months of age. South African tick-bite fever presents with a maculopapular rash often involving the hands and feet.

Eschar
Tick-bite fever presents with headache, fever and a papular rash a week after the tick bite. Often, the child may have been camping or hiking on the previous weekend. Once the eschar has been located, the diagnosis is obvious and specific therapy can be instituted. The eschar is commonly found above the hairline. If tick bite fever is suspected, and the eschar is not found above the hairline, the clinician should make a careful inspection of other sites such as the external auditory canal, axillae and perineum. The eschar may be easily overlooked, especially if the skin is pigmented and a thorough search is not made (Figure 5). Occasionally, there is no eschar, but this should not prevent the institution of appropriate therapy.

Figures 5A and B : Eschar associated with South African tick bite fever A (above) above the hairline

B (below) on the shoulder (also note characteristic well-circumscribed papules – thick arrow)

Mouth and lips
A strawberry tongue is seen with infection by group A beta-haemolytic Streptococcus, KD and toxic shock syndrome. Initially, if the tongue is coated, with inflamed papillae peeping through, the condition is termed a “white strawberry tongue” and once the coating has disappeared, a “red strawberry tongue” (Figure 6).

Other conditions associated with mucositis include KD, often reflected by extremely inflamed lips that then become chapped, and Stevens Johnson syndrome (Figure 7). Koplik’s spots in the early phase of measles has already been mentioned. The dermatosis associated with protein energy malnutri-tion (hyper- and hypopigmented areas and “crazy paving” dermatosis) may be associated with angular stomatitis.

Desquamation of skin
Desquamation, especially of the hands, is characteristic of a number of conditions, especially where bacterial toxins have been implicated. Conditions include TSS, KD and scarlet fever. The most prominent site for desquamation is on the hands. In KD especially, the desquamation can be extremely subtle, occurring at the junction of the nail bed and fingertip (Figure 8). Occasionally, it may occur in other areas, for example, in the groin (KD) or even on atypical areas such as the knees.

Figure 6 : Red strawberry tongue in a patient with scarlet fever – white coating seen centrally. Note also the erythematous rash, less prominent because of the pigmented skin

Figure 7 : Cheilosis associated with Kawasaki syndrome

Figure 8 : A Desquamation of skin on fingertips (Kawasaki syndrome). Note the swollen digits.

“Slapped cheek” appearance
Parvovirus B19 causes a red appearance of the cheeks and is often associated with a reticular “lattice-like” maculo-papular rash (Figure 9). While trivial in most patients, it can be associated with erythroblastosis foetalis if a pregnant susceptible woman is exposed and is also associated with aplastic crises in children with haemolytic anaemia.

The nappy area
Nappy rashes occur commonly and are usually well managed. The satellite lesions associated with candida infection are well known and easily managed. Rarely, in immune compromised infants, ecthyma gangrenosum, an aggressive vasculitic disease caused by Pseudo-monas aeruginosa, occurs in the inguinal area. This condition requires early recognition and specific anti-pseudomonal treatment. Failure to examine the nappy area in a critically ill patient will result in serious consequences (Figure 10).

Figure 8B :   Note the swollen digits.Toxic shock syndrome associated with desquamation on hands (typical site)

Figure 8 C:   Toxic shock syndrome associated with desquamation on hands (typical site) and on knees

Figure 9 : Parvovirus infection is associated with  a “slapped cheek” appearance

Lymphadenopathy, hepatomegaly and splenomegaly
Infectious mononucleosis (Epstein Barr virus) presents with a combination of lymphadenopathy, hepatosplenomegaly, palatal petechiae and a maculopapular rash. The rash is usually elicited or accentuated by ampicillin.

HIV causes multisystem disease and is commonly associated with lympha-denopathy and hepatosplenomegaly. Because of progressive immune dysregulation, intercurrent patho-logical infectious and non-infectious processes may be more severe. For example, varicella is more severe. Scabies is also more severe and is also commonly confused with papular pruritic eruption of HIV. Healing is associated with pigmentation, leading to extensive hyperpigmented macules with widespread distribution. Papular urticaria may be related to, or confused with, insect bites (Figure 11). Psoriasis may be seen in children with HIV, with skin lesions being confused as non-resolving fungal infections. Clues to psoriasis may be the presence of arthropathy and pitting of the nails.

Figure 9 :reticular “lace-like” rash

Vesicular rashes
Chickenpox usually does not present diagnostic problems. The lesions begin as macules and rapidly progress to vesicles and crusts. All stages of the lesions are present at any one time. Usually less than 500 lesions occur over the course of 2 to 3 days but occasionally the eruption may be worse (Figure 12).

Stevens-Johnson syndrome and toxic epidermal necrolysis is associated with a rash, usually described as “target lesions”. Although lesions may initially appear papular, they may rapidly become bullous and after rupture or resorption of fluid, may appear vasculitic (Figure 13).

Non-infectious causes of skin rashes
Drug reactions
Any drug, some more often than others, such as antibiotics (penicillin deriva-tives, sulfonamides), antituberculotics (isoniazid, fluoroquinolones) and anticonvulsants (barbiturates, carbama-zepine), may be associated with a rash. A history of drug exposure is extremely important. The type of rash varies but is most commonly maculo-papular and is often itchy. With some medications, skin rash is a common side effect. For example, it is often seen within the first 6 weeks of using nevirapine (NVP), a non-nucleoside reverse transcriptase inhibitor for HIV infection. Although this drug is used in combination with two nucleoside reverse transcriptase inhibitors, the rash is so characteristic for NVP, that it, alone, can be sub-stituted if the rash is severe, progressive, associated with mucosal changes or raised liver enzymes. A NVP-associated rash is shown in Figure 14.

Collagen vascular disease
Collagen vascular diseases often have skin manifestations. Probably the best known of these is the butterfly rash or small vessel vasculitis associated with systemic lupus erythromatosis (SLE) and discoid lupus. The maculopapular eruption seen in systemic onset of juvenile chronic arthritis has already been mentioned, and should be carefully sought when the patient is febrile. Because juvenile chronic arthritis is often associated with prolonged fever, expensive investigations are undertaken to find a source. By observing the rash, much expense and anxiety can be avoided.

Figure 10 : Erythema gangrenosum due to Pseudomonas aeruginosia in an infant with acute lymphoblastic leukaemia	Figure 11 : Papular lesions possibly associated with fleabites in a HIV-infected infant on cotrimoxazole prophylaxis for 6 months. Note the linearity of the lesions and also older lesion (thick arrow)	Figure 12 : A (above). Severe chicken pox in a 10 year old girl and B (right) in an HIV-infected infant. Note the different stages of lesions
Figure 12 : B	Figure 13 : Toxic epidermal necrolysis. Fluid-filled blisters and lesions after reabsorption of fluid.	Figure 14 : Nevirapine-associated rash

RECOMMENDED READING

1. Mandell, Douglas and Bennett’s Principles and Practice of Infectious Diseases 5th ed 2000, Churchill Livingstone, Philadelphia, PE, USA
2. American Academy of Pediatrics. Pickering LK ed. 2000 Red Book: Report of the Committee of Infectious Diseases, 25th ed. Elk Grove Village, IL: American Academy of Pediatrics, 2000