Venous (stasis) ezcema

• Incompetence of deep perforating veins increases hydrostatic P in dermal capillaries. Pericapillary fibrin deposition impedes oxygen diffusion and leads to clinical changes.
• Leashes of venules and haemosideirin pigmentation around the ankles are early signs.
• Eczema develops, sometimes with fibrosis of the dermis and subcutaneous tissue (lipodermatosclerosis) and ulceration.
• Contact allergy to an applied medicament can complicate the picture.

Rx:

• Treat underlying disease.
• An emollient +/- moderately potent steroid ointment.
• Tar-impregnated bandages applied once or twice weekly.

Discoid (nummular) eczema

• Unknown aetiology.
• Coin-shaped lesions on the limbs. Oftne symmetrical.
• Can be intensely itchy.
• The eczema may be vesicular or chronic and lichenified.
• May clear after a few weeks, but tends to recur.
• Secondary bacterial infection is common.
• Typically affects middle-aged or elderly men. Younger subjects may have atopic eczema.
• ∆∆: Tinea corporis, contact dermatitis.
• Rx: A potent or very potent topical steroid + antimicrobial or antibiotic.

Seborrhoeic dermatitis

A chronic, red, scaly, inflammatory eruption usually affecting the scalp and face.

∆∆ scalp: Psoriasis, fungal infection.

∆∆ face: Psoriasis, contact dermatitis, rosacea.

∆∆ trunk: Psoriasis, pityriasis versicolor, fungal infection.

• Sebum production is normal, but the eruption often occurs in the sebaceous gland areas of the face, scalp, chest.
• Genetics + overgrowth of the commensal yeast Malassezia.
• Severe in some patients with HIV.

Clinical presentation

• Scalp and facial involvement: Excessive dandruff. Itchy scaly erythematous eruption affecting the nose, scalp margin, eyebrows, ears. Blepharitis (inflammation of eyelids) may occur. Most common in young males.
• Petaloid: A dry, scaly patch of eczema over the presternal area.
• Pityrosporum folliculitis: An erythematous follicular eruption with pustules or papules over the back.
• Flexural: Axillae, groins, submammary. Moist intertrigo (inflammation produced by chafing of adjacent areas of skin), often secondarily colonised by Candida albicans. Seen in the elderly (do not confuse with the similarly named infantile eruption).

Chillblains

• Inflamed and painful purple-pink swellings on the fingers, toes or ears that appear in response to cold.
• Result from an overcompensatory cold-induced vasoconstriction of cutaneous arterioles and venules.
• Usually affect women.
• Rx = Warm housing and clothing. Nifedipine may help.

Erythema ab igne

A reticulate, pigmented erythema.

Due to heat-induced damage - sitting before a fire, hot water bottles.

Livedo reticularis

- Marble-patterned cyanosis of the skin.

- Due to reduced arteriolar flow.

- Usually in women.

Causes:

• Physiological, i.e. cold-induced. Revesible.
• Vasculitis, e.g. SLE, PAN.
• Hyperviscosity due to cryoglobulinaemia or polycythaemia.
• Sneddon syndrome - livedo reticularis with cerebrovascular disease and circulating antiphosphlipid antibodies.

Treatment is aimed at the underlying disease.

Koebner phenomenon

Source = Wikipedia

Koebner phenomenon = skin lesions appearing on lines of trauma. It may result from either linear exposure or linear irritation.

Linear exposure:

• Molluscum contagiosum (auto-inoculation)
• Warts (auto-inoculation)
• Toxicodendron dermatitis (e.g. poison ivy... linear from brushing against plant).

Linear irritation, e.g. scratching or surgical wound:

• Psoriasis*
• Eczema*
• Lichen planus*
• Vitiligo*
• Lichen nitidus
• Lichen sclerosus
• Pityriasis rubra pilaris
• Keratosis follicularis
• Elastosis perforans serpiginosa.

*4 most common causes of Koebner phenomenon = PELV

The Koebner phenomenon was named after a rather eccentric, renowned German dermatologist, Heinrich Koebner (1838–1904). Koebner is best known for his work in mycology. Here is one story to illustrate his intense nature: in a medical meeting he proudly exhibited on his arms and chest three different fungus infections, which he self-inoculated in order to prove the infectiousness of the organisms he was studying.