Category Archives: Dermatology

Scabies

Dermatology, General paediatrics

Serpiginous burrows between the fingers, in the flexures of the wrist, genitalia etc characteristic but rare. More usually papules, pustules – pruritus often on unaffected skin and esp at night. In infants, lesions on head, nappy area, occ palms and soles.

Caused by the mite sarcoptes scabiei, which does not fly or jump – direct skin contact, mostly. Infection by contact with fomites is very rare.

Rash is partly hypersensitivty so not related to number of mites, may take several weeks after inital infestation to appear – on reinfection just a few days. Cross reaction with related house dust mite.

Topical steroids will mask rash/itch. Superinfection common. Differential is contact dermatitis, animal scabies (do not form burrows, do not complete life cycle so self limited), lichen planus.

Rarely, nodular form (esp groin, axillae) – hypersensivity reaction. 

Norwegian or crusted scabies esp immunosuppressed (but not necessarily) – psoriaform, not always itchy, very infectious.

Treat with Permethrin 5% (=Lyclear) dermal cream [Permethrin 1% rinse cream ineffective in scabies cf head lice]. Safe in infants (rarely CNS side effects). An alternative treatment is Malathion (safe in pregnancy). All household members should be treated simultaneously. After treatment the itching from scabies can take weeks to settle. Treatment should be extended to the scalp, neck, face and ears in children up to the age of 2 years. All skin surfaces should have the agent applied for 24 hours for malathion and for 8-12 hours for Permethrin 5% and have treatment repeated at 7 days.

Oral ivermectin in single dose is effective in over 70%, given twice 2 weeks apart 95% effective. Use for crusted (along with keratolytics), epidemics. Lancet Infectious Diseases Volume 6, Number 12, December 2006

Juvenile xanthogranuloma

Dermatology, General paediatrics

Well circumscribed, raised yellow/brown firm papule or nodule, typically solitary. Can be congenital but otherwise typically very young boys, head and neck area, asymptomatic.

Can affect the iris – presents with a red eye…

Can ulcerate, otherwise they tend to atrophy and disappear after 3-6 years.

Seen in 10% of Neurofibromatosis type 1.

Can rarely be multiple and internal (liver, bone marrow etc). Screening of asymptomatic cases probably only justified if multiple.

Differential – mastocytoma, Langerhans histiocytosis, molluscum.

Nappy rash

Common, Dermatology, General paediatrics

Nappy rash is an irritant contact dermatitis affecting the skin where the moist nappy is in contact. It spares intertriginous areas.

Change nappies 6-8 times a day, dry thoroughly, use barrier eg zinc oxide cream.

Differential diagnosis:

  • candidiasis,
  • atopic dermatitis, seborrhoeic dermatitis
  • psoriasis,
  • Langerhans cell histiocytosis,
  • Acrodermatitis enteropathica (autosomal recessive zinc disorder), else nutritional zinc deficiency – +/- acral dermatitis, alopecia, malabsorptive diarrhoea)

Intertrigo (inflammation in the creases) can similarly be infective (bacterial or candidal), eczematous/seborrhoeic or psoriatic.

Blistering rashes

Clinical, Dermatology, General paediatrics

Common, typically vesicular rather than bullous:

  • Varicella – tends not to affect mouth or palms/soles cf below, but more toxic
  • Coxsackie – Enteroviruses such as coxsackie nearly always involve buccal mucosa and tongue (eg Hand-Foot-Mouth). If nowhere else, Herpangina tends to be posterior mouth ie tonsils, soft palate.
  • HSV stomatitis tend to be more unwell, higher fever, gingivitis, cervical adenopathy, no cutaneous lesions.
  • Gianotti-Crosti syndrome
  • eczema herpeticum ie HSV superinfection of eczema;
  • mycoplasma (but mycoplasma has been associated with every kind of rash!)

Rare:

  • disseminated zoster (starts in a dermatome, immunosuppressed);
  • disseminated HSV;
  • vaccinia

For more dramatic blistering:

  • Bullous impetigo
  • Stevens Johnson syndrome esp with plaques, conjunctivitis, lesions at mucocutaneous junctions
  • Urticaria (rarely)
  • Dermatitis herpetiformis
  • Pemphigoid (v rare in children)
  • Acrodermatitis enteropathica – genetic (recessive) disorder leading to Zn deficiency. Blistering rash esp peripheries, face and nappy; diarrhoea (Normal Zn is 10-23).

Hereditary haemorrhagic telangiectasia

Dermatology, General paediatrics, Genetics, Surgical

=Osler-Weber-Rendu disease.

Autosomal dominant with high penetrance. 

Not a problem in early life.  Usually presents with recurrent nose bleeds.  Red spots on lips, tongue and fingertips, not so obvious in young children. But potential for GI and pulmonary haemorrhage, pulmonary/liver/brain AVMs.  Migraine common.

Iron deficiency a problem, of course!

Screening for AVMs done from age 16. Annual full blood count. Beware nasogastric interventions!

Keratosis pilaris

Common, Dermatology, General paediatrics

Common (familial) – rough, bumpy skin on upper arms, usually asymptomatic but cosmetically not great. Follicular plugging, basically.

Can get quite inflamed in some people.

Exfoliating, moisturizing may help.

Sometimes goes with inflamed cheeks – Keratosis pilaris rubra faciei, so typical KP of the arms (often perifollicular redness), but can lead to hair loss and atrophy of eyebrows and scalp. 

Urea containing (Balneum, Hydromol Intensive, Eucerin intensive) creams or salicylic acid (in zinc oxide) paste may help. Topical steroids can be tried if very red but risky for face, given tendency to atrophy anyway.

Contact dermatitis

Dermatology, General paediatrics

Type 4 delayed hypersensitivity seen to a range of things including:

  • Nickel (for example in jewellery, belt buckles, fastenings)
  • Limonene, found in many cleaning products and cosmetics
  • Sodium lauryl sulfate, found in cleaning products and cosmetics
  • Lanolin and other wool products

Mechanism is complicated as metals are clearly not proteins so not identified by HLA class 2 as happens in type 1 allergy. Presumably happens through toll like receptors.

Testing is by patch testing, done by dermatology.