Paediatric dermatology

Notes29 October 2010

Descriptive terms forskin lesions

Macule

• Non palpable, w/o elevation or depression

• Various in size, normally <1 cm

• Vary in surrounding skin pigmentation

• E.g drug allergy, neuroectodermal rash (neuroectoderm includes neural crest and neural tube), measles

Patch

• Large macule, >1cm in diameter

• Non palpable, flat lesion• The picture shows

mixed presentation of macule and patch.

Plaque

• palpable lesions, elevated compared to the skin surface

• > 10 mm in diameter, diameter is greater than the thickness

• may be flat topped or rounded

• E.g psoriasis, granuloma annulare

Psoariasis, plaques covered with thick, silvery, shiny scales

Papule

• Palpable, elevated lesions • < 5 mm in diameter• Maybe isolated or

grouped• E.g early chicken pox.

nevi, warts, lichen planus, insect bites, seborrheic and actinic keratoses, some lesions of acne, and skin cancers

Lichen planus

Nodule

• Palpable, papules or lesions that extend into the dermis or subcutaneous tissue.

• =/> 6mm in diameter• Maybe isolated or

grouped• E.g erythema nodosum,

cysts, lipomas, fibromas.

Pustule

• Small, circumscribed skin papules containing purulent material

• Vesicle + pus• <1 cm in diameter• >1 cm in diameter = abscess• Commonly due to infection,

others in inflammatory disease

• E.g chicken pox, impetigo, pustular psoarisis

Pustule complicated with acne

Vesicle

• Papule + serous• Small, circumscribed (5mm

in diameter)• E.g characteristic of herpes

infections (herpes rash, herpes simplex, chicken pox)

• Others - acute allergic contact dermatitis, autoimmune blistering disorders (dermatitis herpetiformis)

Dermatitis herpetiformis

Bullae • Large (=/> 6 mm) vesicles• E.g impetigo, severe bacterial

skin infection• Other causes - burns, bites,

irritant or allergic contact dermatitis, and drug reactions.

• Classic autoimmune bullous diseases - pemphigus vulgaris and bullous pemphigoid.

• may occur in inherited disorders of skin fragility.

Bullous pemphigoid - characterized by eruptions of tense bullae on normal-appearing or reddened skin in elderly patients.

Wheal / Urticaria / Hives

• elevated lesions caused by localized oedema.

• Typically last very short time – up to hours – then disappear

• common manifestation of hypersensitivity to drugs, stings or bites, autoimmunity

• less commonly, physical stimuli including temperature, pressure, and sunlight.

Urticaria (wheals or hives) are migratory, elevated, pruritic, reddish lesions caused by local dermal edema.

Scales

• heaped-up accumulations of epithelium (specifically, outermost layer so called stratum corneum which filled with keratin) or desquamating skin cells

• E.g. psoriasis, seborrheic dermatitis, and fungal infections.

• characteristic feature of many dermatophytoses, including tinea capitis

noticeable at the back side of the neck.

Crusting (scabs)

• Accumulation of dried exudate/transudate i.e serum, blood, or pus

• Usually mixed with epithelial

• occur in inflammatory or infectious skin diseases (e.g. impetigo).

Erosion • open areas of skin that result

from circumscribed loss of epidermis.

• lesions heal without scarring - does not extend to the dermis

• can be traumatic or with various inflammatory or infectious skin diseases.

• excoriation – hollow, crusted or linear erosion caused by scratching, rubbing, or picking.

Ulcer • Lesion involve epidermis and

dermis. • Deep and irregular in shape

that may bleed and leave a scar• Causes - trauma, bacterial

infection, certain condition such as disorder involving peripheral arteries and veins (venous stasis, PAD, vasculitis)

• E.g. Pressure sores or decubitus ulcer, chancres and stasis ulcer.

Fissure

• Linear crack with edges in inflamed or thickened skin

• crack extends into the dermis

• E.g Athlete’s foot, cracks at the mouth or in the hand

Atrophy • Thinning of one / several layer of

skin (can be epidermis, dermis and subcutaneous)

• Epidermal atrophy - dry, translucent, thin, sometimes wrinkled surface resulting from wasting of the skin due to collagen and elastin loss.

• Causes - chronic sun exposure, aging, inflammatory illness, neoplastic skin diseases (cutaneous T-cell lymphoma, lupus erythematosus)

• May result from long-term use of potent topical corticosteroids.

Steroid atrophy

Lichenification

• thickening and induration of the skin with accentuated normal skin markings

• secondary to chronic inflammation caused by scratching or other irritation (chronic eczema)

lichenification during the chronic phase of atopic dermatitis.

Scars • Areas of fibrosis that replace

normal skin after injury.• New scar – purple or red• Older scar – white brown or silver• E.g. from acne, surgical wound

injury • Keloid - very thick, raised and

irregular hypertrophic scar that extend beyond the original wound margin

• darkened area is caused by excessive collagen formation during healing.

• E.g. from piercing and surgery

Petechiae • Small (1-2mm), non - blanchable

red or purple spot on the body, caused by a minor haemorrhage

• Smallest of the three purpuric skin eruptions

• Causes – physical trauma i.e hard coughing (most common, completely harmless, disappear within days), platelet abnormalities (thrombocytopenia, platelet dysfunction), vasculitis, infections (meningococcemia, Rocky Mountain spotted fever, other rickettsioses, dengue).

Meningococcal petechiae on the back

Purpura • Non – blanchable, red or purple

discolouration of skin that may be palpable.

• One of the purpuric skin condition with 3-10mm in diameter,

• Palpable purpura is considered the hallmark of leukocytoclastic vasculitis. May indicate a coagulopathy.

• Common presentation in typhus and meningococcal meningitis or septicaemia.

• Endotoxin released by meningococcus when it lyses, activates the Hageman factor (clotting factor XII) and causes disseminated intravascular coagulation. (DIC)

Schonlein-Henoch purpura

Ecchymoses • Non – blachable

subcutaneous purpura larger than 1 cm or a hematoma, commonly called a bruise.

• can be located both in the skin as well as in a mucous membrane.

• After local trauma, RBC are phagocytosed and degraded by macrophages. The blue-red colour is produced by the enzymatic conversion of hb into bilirubin, which is more blue-green. The bilirubin is then converted into hemosiderin, a golden brown colour, which accounts for the colour changes of the bruise.

acute myelogenous leukemia

Telangiectasias • Small, permanently dilated blood vessels

near the surface of the skin or mucous membrane

• Present as tiny spider-like superficial blood vessles, usually red to blue, that radiate out from a centrifugal point.

• On their own they don’t cause damage, however they are another indicator of venous hypertension

• Most often idiopathic• Others in:

– Rosacea (chronic condition characterized by facial erythema)

– systemic diseases (esp. scleroderma)– inherited diseases (e.g, ataxia-

telangiectasia, hereditary hemorrhagic telangiectasia)

– long-term therapy with topical fluorinated corticosteroids.

Conjunctiva ataxia-telangiectasa

Eschar • Slough or piece of dead tissue that is cast

off from the surface of the skin• Seen in - burn injury, gangrene,

ulcer, fungal infections, necrotizing spider bite wounds, and exposure to cutaneous anthrax.

• Sometimes called a black wound because the wound is covered with thick, dry, black necrotic tissue.

• Rx - allowed to slough off naturally, or debridement to prevent infection, especially in immunocompromised patients (require skin graft post op)

• Important to assess peripheral pulses of the affected limb to make sure blood and lymphatic circulation is not compromised. If circulation is compromised - escharotomy

multiple petechial rashes seen and a solitary well demarcated lesion with erythematous edge and a central necrotic area known as eschar. Preferential diagnosis is Scrub Typhus