• Incontinentia pigmenti – a linear arrangement of blisters, particularly on the limbs (Fig. 21.1.3), following the lines of Blaschko (see below). An X-linked recessive disease, so presents predominantly in girls. The mother may have late stigmata of disease, including brown Blaschko-distributed lesions, patchy alopecia and partial anodontia. Infant may have early seizures.

Fig. 21.1.2 Langerhans cell histiocytosis with crusted purpuric papules.

Fig. 21.1.3 Incontinentia pigmenti with a linear array of blisters and pustules.

Purpura in the neonate

This may be due to the early presentation of any cause of childhood purpura (see below), but particular causes in the neonate are mentioned here.

• Systemic congenital infections – including rubella, cytomegalovirus, toxoplasmosis, herpes simplex.

• Haemolytic disease of the newborn – for example with Rhesus incompatibility.

• Malignancy – including neuroblastoma, Langerhans cell histiocytosis, leukaemia.

• Iatrogenic injury – including birth trauma, extravasation of drugs, arterial injury during catheterization.

Red, scaly rashes in the neonate or young infant

A number of important conditions can present with diffuse redness and variable scaliness in the neonate; affected infants often have major problems with temperature regulation and fluid balance, and may seriously fail to thrive.

• Seborrhoeic dermatitis – dull red erythema with a greasy, yellow scale involving particularly the scalp, centrofacial area and all flexures, major and minor. The scale may be absent in the flexures, and secondary monilia is common. Usually asymptomatic and self-limiting after the early months of life. Responds to weak steroids and anti-monilial agents. In cases in which there is a failure to respond to appropriate treatment, or the presence of any brownish scale or purpura, the possibility of Langherhans cell histiocytosis, which also occurs in the ‘seborrhoeic areas’, must be considered.

• Atopic dermatitis – rarely this condition presents in very early infancy with a widespread red, scaly and itchy rash. These patients often have food allergies and will go on to develop difficult long-term disease.

• Ichthyoses – some of these conditions present with the child covered in a shiny, red membrane that peels off in the early weeks of life to leave a red scaly skin. Some commence with a dramatic degree of redness and scale without the membrane. An early possible complication is hypernatraemic dehydration. The high metabolic state may lead to failure to thrive. Some are associated with neurological abnormalities.

• Metabolic disorders – a red, scaly rash can occur in neonates with inherited carboxylase deficiencies and essential fatty acid deficiency secondary to any severe malabsorption. The former may be associated with severe acidosis and coma.

• Immunodeficiencies – patients with severe combined immune deficiency (SCID) and other immunodeficiencies may present with a widespread, red, scaly rash in the neonatal period or early infancy. In some cases this represents a congenital graft-versus-host disease.

• Staphylococcal scalded skin syndrome – after the blistering and erosive phase there may be a striking scaly and crusted rash, still on a residual erythematous background.

• Congenital candidiasis – usually presents with small pustules, but as they resolve a widespread scaly red rash can ensue.

Birthmarks and other naevoid conditions

Some naevoid conditions are not present till some time after birth, despite being ‘programmed’ from birth. These will be included in this section.

Pigmented birthmarks

Mongolian spot

These are flat, blue or slate-grey lesions with poorly defined margins. They may be single or multiple and occur particularly on the lumbosacral area, although the shoulders, upper back and other areas may be involved. They are found in over 80% of Oriental and black infants and in up to 10% of white infants, particularly those of Mediterranean origin. They usually fade considerably by puberty, but may remain unaltered throughout life.

Naevus of Ota

This is a patchy blue–grey discoloration of the skin of the face, particularly on the cheek, periorbital area and brow. It is usually unilateral and often there is a similar pigmentation of the sclera of the ipsilateral eye. It is most common in Oriental individuals and is present at birth in over 50% of cases. It is a permanent lesion. Associated sensorineural deafness is reported, and very rarely these lesions may be complicated in adult life by development of malignant melanoma.

Congenital melanocytic naevi (CMN)

These occur at birth as raised verrucous or lobulated lesions of varying shades of brown to black, sometimes with blue or pink components, with an irregular margin and often growing long dark hairs. They may become increasingly hairy with time. Giant-sized lesions may produce considerable redundancy of skin and often occur in a ‘garment’ distribution on the trunk and adjacent limbs. In patients with large naevi an eruption of smaller, but essentially similar, lesions may occur during the first few years of life. Malignancy in giant naevi can occur in childhood and the incidence over a lifetime is possibly of the order of 2%. In medium and small lesions the risk is much lower and any development of malignancy is always post-pubertal. When large lesions occur over the axial spine, and in particular when multiple satellite lesions are present, there is a risk of intracranial lesions, both melanocytic involving the meninges and structural in the posterior cranial fossa, which may be further complicated by obstructive hydrocephalus. CMN over the lower spine may be associated with a tethered cord (Fig. 21.1.4). Neuroimaging is required in all these patients.

Fig. 21.1.4 Congenital melanocytic naevus over the lumbosacral area.

Naevoid pigmentary disorders

These are flat areas of hyperpigmented or hypopigmented skin, obvious at or very soon after birth. They occur in characteristic patterns – either segmental, or whorled and streaky following the lines of Blaschko (Fig. 21.1.5). These lines represent the tracks taken by genetically identical cells in the embryo and are a marker for genetic mosaic patterns. The lesions usually have rather irregular edges. Sometimes the condition is extensive, resembling a marble cake, and both hypopigmented and hyperpigmented lesions are present in the one individual. These lesions usually occur as isolated phenomena but may be associated, as part of certain mosaic phenotypes, with neurological, skeletal and other abnormalities. One syndrome with hyperpigmented lesions and skeletal abnormalities is McCune–Albright syndrome.

Fig. 21.1.5 Lines of Blaschko.

Important in the differential diagnosis of brown lesions are the café-au-lait spots of neurofibromatosis, which are rarely present at birth, are more rounded in shape, and which continue to increase in number. In the differential of hypopigmented lesions are the ash leaf-shaped white spots of tuberous sclerosis. These also often appear after birth. Vitiligo, which can occur at any age, is totally depigmented rather than hypopigmented; it usually occurs in otherwise healthy children but can be associated with endocrine diseases. Leprosy is another important cause of acquired hypopigmented lesions.

Epidermal naevi

Epidermal naevi arise from the basal layer of the embryonic epidermis, which gives rise to skin appendages as well as keratinocytes. These naevi have been classified, according to the tissue of origin, into keratinocytic, sebaceous and follicular types. They can involve any area of skin. They may be present at birth or appear in the first few years of life; subsequently they may simply grow with the patient or new areas of involvement may become evident. On the scalp and face the naevi have a yellowish colour, due to prominent sebaceous glands, and present as a hairless, often linear, plaque, usually flat in infancy and childhood and becoming verrucous at puberty. Lesions elsewhere are usually dark brown but are occasionally paler than the normal skin. They occur as single or multiple warty plaques or lines, often arranged in a linear or swirled pattern (Fig. 21.1.6).

Fig. 21.1.6 Epidermal naevus with brown, warty lesions following the lines of Blaschko.

It is now clear that the linear and swirled patterns taken by epidermal naevi follow the lines of Blaschko and that all epidermal naevi can be explained on the basis of genetic mosaicism, with each type of naevus representing the cutaneous manifestation of a different mosaic phenotype. In most patients the naevus is the only detectable manifestation, but in some patients there are associated abnormalities in other organ systems, particularly skeletal, neurological and ocular. Skeletal abnormalities occur particularly with large naevi of keratinocytic type on the limbs, and neurological and ocular abnormalities with large or centrally located naevi of sebaceous type on the head.

Vascular birthmarks

These can be divided into haemangiomas, which are proliferative vascular tumours, and vascular malformations, representing fixed collections of dilated abnormal vessels.

Haemangiomas

Presentation and terminology

Haemangiomas usually appear just after birth, undergo a fast growth phase and then, over a long period, tend to resolve spontaneously. All infantile haemangiomas, whether superficially or deeply located in the skin, have the same structure, being composed in the early stage of proliferating masses of endothelial cells with occasional lumina and later, as they resolve, of large endothelium-lined spaces. The terms capillary, cavernous and capillary–cavernous are misleading and should be abandoned in favour of the simple term haemangioma. However, the terms superficial and deep remain useful.

• Superficial haemangiomas usually appear in the first weeks of life as an area of pallor, followed by a telangiectatic patch. They then grow rapidly into a lobulated, well demarcated, bright red tumour. Rapid growth continues over the first 6 months of life; the growth rate then slows and further growth after 10 months is unusual. After a stationary phase, signs of involution begin, with the appearance of grey areas that enlarge and coalesce. The tumour becomes softer and less bulky and then disappears in 90% of cases by 9 years of age. Residual skin changes at the site may persist.

• Deeper haemangiomas may occur alone or beneath a superficial lesion (Fig. 21.1.7). The overlying skin is normal or bluish in colour. As they resolve, they soften and shrink, and most disappear completely.

Fig. 21.1.7 Combined deep and superficial haemangioma with ulceration.

Complications of haemangiomas

Although many haemangiomas resolve without sequelae, significant complications can occur.

• Incomplete resolution – redundant tissue, residual telangiectasia, scarring following ulceration.

• Ulceration – inevitable scarring, full-thickness tissue loss on ‘edge structures’ (lip, lid, ala), cicatricial ectropion from scarring of eyelids, cicatricial alopecia.

• Obstruction of vital structures:

• Large eyelid lesions can obstruct vision producing amblyopia. Lesions that press on the globe, even without obstructing vision, can cause astigmatism and a degree of amblyopia.

• Lesions around the nares can lead to difficulty in breathing during feeding.

• Large, or painfully ulcerated, lesions of the lip can lead to problems with sucking.

• Haemangiomas of the larynx can cause stridor followed by complete obstruction and represent a medical emergency. A ‘beard’ distribution haemangioma is a marker for possible laryngeal involvement and these patients should be investigated with a lateral airways X-ray even when stridor is not present.

Clinical example

Harriet was born with a blanched area of skin bilaterally on the lower face, extending under the chin. A week later there was a tracery of telangiectases and over the subsequent 3 weeks bright red, raised dots appeared in the area, gradually coalescing into an extensive red haemangioma. When the baby was 4 weeks old her mother noticed that Harriet’s breathing had become noisy when feeding. Urgent referral to investigate the stridor was followed by a lateral airways X-ray, which demonstrated narrowing in the subglottic area. Endoscopy confirmed subglottic haemangioma. The infant was admitted to hospital and observed carefully. Oral propranolol was commenced. After 1 day the stridor had gone and the birthmark was less angry-looking. A tracheostomy was not needed. The propranolol treatment was continued over an 8-month period during which there was considerable fading and shrinking of the haemangiomata. Harriet remained free of respiratory symptoms.

Possible associations of haemangiomas

• Lumbosacral lesions – tethered spinal cord.

• Perineal segmental lesions – abnormalities of the genitalia and lower urogenital and gastrointestinal tracts.

• Large segmental facial lesions – posterior cranial fossa malformations, abnormalities of heart, aorta and other major arteries, and ocular abnormalities.

• Multiple small cutaneous haemangiomas – haemangiomas in the liver, brain and other internal organs; high-output cardiac failure.

Appropriate imaging studies should be performed in all patients with these presentations.

Management of haemangiomas

Simple observation and reassurance while awaiting natural resolution is the ideal approach for most haemangiomas.

Ulceration should be managed with a combination of topical anaesthetic, topical antibiotic, dressings and/or oral antibiotics as appropriate.

Systemic treatments should be considered for lesions with anticipated long-term appearance problems, an alarming growth rate, ulceration in areas where serious complications could ensue (e.g. lips), interference with vital structures and severe bleeding. The first-line systemic treatment has been high-dose oral prednisolone to try to slow or stop growth. This is associated with predictable steroid side-effects, limiting its use to more serious cases. More recently, oral propranolol has been used as initial treatment. This change has occurred because propranolol appears to be more effective at stopping growth and hastening involution in many haemangiomas and has a better side-effect profile. Unlike the situation with oral steroids, propranolol may shrink lesions that have ceased growing. Some haemangiomas do not respond to propranolol, and propranolol does not help heal ulcerated lesions and might worsen ulceration. This is a new treatment and needs continuing evaluation.

Vascular malformations

These are collections of dilated abnormal vessels, classified according to the vessels of origin. All vascular malformations are present at birth (although occasionally not evident) and grow only in proportion to the growth of the child. They show no tendency to involution. The most appropriate terminology refers to the component vessels and many outdated terms (in brackets below) can be abandoned:

Capillary malformation (port wine stain)

This presents as a flat purple stain, most commonly on the face, but it may occur anywhere. When it involves the upper lid and central forehead it may be a part of Sturge–Weber syndrome, associated with glaucoma, cerebral calcification and seizures. Careful ophthalmological assessment and follow-up, and neuroimaging are indicated in patients with this presentation.

Venous malformation (varix)

This presents as a bluish tumour that empties with pressure and when elevated, and fills when dependent; phleboliths may develop within it and be seen on ultrasonography or X-ray.

Lymphatic malformation (lymphangioma, cystic hygroma)

This may be macrocystic, microcystic, or a combination of both. Macrocystic lesions are deep and present as skin-coloured tumours, often with bruising; rarely these lesions become clinically apparent only when bleeding into them occurs. Microcystic lesions are deep or superficial and present on the skin as groups of haemorrhagic vesicles or warty lesions.

Arteriovenous malformation

This presents as a pulsatile skin-coloured or erythematous lump. These always need experienced assessment and management because of the significant risk of expansion and problems such as pain and bleeding, particularly at puberty.

Other mixed malformations

Some are very complex and associated with limb hypertrophy. Klippel–Trenaunay syndrome is a capillary–venous–lymphatic malformation with limb hypertrophy; Parkes–Weber syndrome is a capillary–arteriovenous malformation with limb hypertrophy and risk of ulceration from the shunting.

Moles (acquired melanocytic naevi)

These usually first appear after the age of 1 year and increase in number throughout childhood. They commence as brown or black macules, some of which become raised and enlarge laterally as they develop. They are usually of uniform colour and well circumscribed. The risk of melanoma arising from acquired melanocytic naevi is very low (less than 0.1%); melanoma almost never occurs in childhood so their prophylactic removal in young patients is not justified.

Halo naevi

A depigmented halo may occur around a melanocytic naevus; the lesion may appear inflamed and often disappears, leaving a white spot, which may eventually repigment. This is a completely benign change. Although often apparently isolated, the condition can occur in the setting of vitiligo (Fig. 21.1.8) and may in some patients indicate a predisposition to this condition.

Fig. 21.1.8 Halo naevus in a patient with vitiligo.

Dysplastic or atypical naevi

A subtype of acquired melanocytic naevi with characteristic clinicopathological features is a marker for an increased risk of developing malignant melanoma. Atypical naevi differ from more typical moles by being larger (more than 5 mm in diameter), having irregular and indistinct margins and irregular tan-brown colouration, often with an erythematous component. They are predominantly macular, sometimes with a central elevated portion. They may appear in childhood as small, typical-appearing naevi, which after puberty develop the atypical features. Characteristic dysplastic naevi may appear on the scalp in childhood. The final confirmation is based on the finding of some or all of a constellation of histopathological features. Patients with multiple dysplastic naevi should be observed frequently and monitored with serial photography. Any such naevus showing significant alteration should be removed immediately.

Lumbosacral birthmarks

Congenital lesions over the lumbosacral area may be associated with occult spinal abnormalities such as a tethered cord. These spinal anomalies may not cause problems until later in childhood, when they can present insidiously with irreversible bladder, bowel or limb dysfunction. These problems can be prevented by early magnetic resonance imaging (MRI) and surgical correction. Congenital lesions that have been associated with underlying spinal problems include haemangiomas, capillary malformations, lipomas, dimples, sinuses, congenital melanocytic naevi and hairy patches.

Cutaneous infections and infestations

Viral exanthems

This term refers to the cutaneous manifestation of a viral illness (enanthem is the manifestation in the mouth).

The patterns may be:

• specific – where the appearance of the exanthem enables a clinical diagnosis of the causative virus.

• non-specific – where the same pattern of exanthem may be caused by many different viruses.

Specific patterns

The aetiological virus can usually be identified clinically from the pattern of rash in the following situations:

• Chickenpox – scattered vesicles, pustules and dark crusts; lesions occur in crops (see Chapter 12.1).

• Herpes zoster – vesicles and pustules following the distribution of sensory nerves (see Chapter 12.1).

• Herpes simplex – see below.

• Erythema infectiosum – caused by a parvovirus B19, presenting with a slapped cheek appearance followed by a lacy erythematous rash mainly on the limbs (Fig. 21.1.9) (see Chapter 12.1).

• Mollusca – caused by a pox virus (see below).

• Hand, foot and mouth disease – due to one of the Coxsackie group of enteroviruses; presents with pustules and purpuric lesions limited to hands and feet with oral blistering.

Fig 21.1.9 Lacy erythematous lesions of erythema infectiosum.

Non-specific patterns

Each of these patterns may be produced by a wide variety of viruses, and the same virus may produce many different patterns of exanthem.

The viruses usually involved are:

• Enteroviruses

• Adenoviruses

• Hepatitis A and B viruses

• Epstein–Barr virus

• Cytomegalovirus

• Human herpesvirus (HHV) 6 and HHV7

• Parvovirus (can produce non-specific as well as specific rashes).

The patterns include:

• Urticarial exanthems – raised erythematous lesions that may be annular or figurate; itch is variable and the pattern changes from hour to hour. In young children there may be a central non-palpable purpuric element that resolves over several days rather than hours, leading to misdiagnosis as erythema multiforme. In children under 6 years old, more than 90% of cases of urticaria are caused by a viral illness.

• Macular exanthems – these are composed of flat red spots of variable size, sometimes becoming confluent. These are usually widespread and are characteristically difficult to differentiate from allergic reactions to drugs. In general the occurrence of lesions in a linear distribution along scratch marks, exaggeration in areas of sunburn or previous skin disease, and the presence of lymphadenopathy favour a viral over a drug aetiology.

• Papular exanthems – papules, which are raised erythematous lesions, may be few or multiple and vary in size from tiny pinpoint lesions to 0.5–1.0 cm in diameter. A linear distribution of groups of lesions is commonly seen and the limbs are usually affected more than the trunk.

• Purpuric exanthems – enteroviruses are the commonest causes of purpuric exanthems. Clearly the most important condition to be differentiated is meningococcal septicaemia. The purpuric lesions caused by enteroviruses tend to be small petechial macules but larger, angulated lesions sometimes occur.

• Vesicular and/or pustular exanthems – these lesions start as vesicles but often, as in varicella, become pustular and an admixture of lesions is seen. The lesions are often concentrated mainly on the limbs. The buttocks are another common site of involvement.

• Erythrodermic exanthems – these are rare, with widespread erythema and variable scaling. They are particularly difficult to differentiate from bacterial toxic reactions and drug reactions.

Conditions that may mimic viral exanthems, or which viral exanthems may mimic, include:

• Drug reactions – urticarial, macular, papular or erythrodermic exanthems. History of exposure and timing are helpful in differentiation. An allergic reaction to ampicillin is more common in patients with Epstein–Barr virus infection.

• Kawasaki disease – macular, urticarial, erythrodermic exanthems. An erythematous rash accompanied by oedema of the palms and soles is often prominent in Kawasaki disease. Other early features include prolonged high fever, conjunctivitis, redness, swelling or ulceration of mucosal surfaces, and enlargement of lymph nodes. Desquamation of the hands and feet, especially of the digit tips, is a later finding.

• Meningococcal septicaemia – purpuric exanthem (see Chapter 12.3). Small purpuric spots and larger stellate areas of purpura developing central necrosis. Associated with high fever and shock.