logo Psoriasis case challenge

Scaly skin diseases

Psoriasis case challenge

A 19-year old student presents with extensive red scaly plaques on her scalp, ears, forehead, neck, back, abdomen, arms and legs. For the last two years, she has had patchy scaling in her scalp, which she has managed by shampooing daily with an anti-dandruff shampoo. A month ago, she developed a sore throat, for which she was treated with penicillin. The current rash developed a week or two after this. It is mildly itchy.

Which one of the following diagnoses is least likely? *! Atopic dermatitis * Pityriasis rosea * Discoid eczema * Psoriasis Explanation: The least likely diagnosis is atopic dermatitis, which nearly always starts in early childhood, is very itchy and predominantly affects flexures. Pityriasis rosea, discoid eczema and psoriasis may appear similar at times. However, pityriasis rosea and discoid eczema rarely affect the scalp. Explanation: The patient has psoriasis. What is the likely precipitating factor? * Psychological stress * Penicillin prescribed for tonsillitis * Rheumatic fever *! Streptococcal superantigens The development of small plaques of psoriasis following streptococcal tonsillitis is known as: * Koeberised psoriasis *! Acute guttate psoriasis * Erythrodermic psoriasis * Chronic plaque psoriasis

This patient has had a post-streptococcal flare of psoriasis, but her plaques are larger than guttate (“tear drop”). Preceding scalp psoriasis indicates that she may develop chronic plaques on trunk and limbs.

Read more about psoriasis on DermNet.

What concerns might the patient have? Short answer:

Her concerns may include:

  • Whether psoriasis is infectious (it is not)
  • Whether it is curable (post-streptococcal psoriasis remits completely in some patients)
  • Whether psoriasis is caused by her diet (it is not)
  • Genetic factors (her father has psoriasis)
  • Symptom control: psoriasis may be mildly to severely itchy and sometimes painful because of fissuring
  • Embarrassment due to psoriatic plaques on her face and arms and scale on her clothing
  • Effect on sport: communal changing rooms, inability to hide the plaques
  • Effect on social activities: going to the beach, upcoming ball
  • Effect on relationships: at work, at college, boyfriend
  • Effect on work (she has a part-time job at a food outlet)
  • Mood changes (anger, reactive depression): she may be having difficulty sleeping or concentrating on her studies
Which of the following medications are suitable for this patient on this occasion: # Cyclosporin 250mg bd # Prednisone 20mg od # Tretinoin cream bd #! Calcipotriol ointment bd

The dermatologist prescribed the following:

  • Coal tar/salicylic acid ointment to be applied to the scalp daily, an hour before washing with a medicated shampoo
  • Betamethasone valerate cream for plaques on face and ears at night
  • Calcipotriol ointment to plaques on trunk and limbs twice daily
  • Moisturising lotion as required for itch and dryness.
What concerns might she have about treatment? Short answer:

Her concerns may include:

  • The treatment sounds very tedious and time consuming
  • The expense: the minimum cost of the 5 prescribed items with full Drug Tariff subsidy is $15 if she has a Community Services card, but could be much more. The visits to her doctor / specialist and to the phototherapy clinic may also prove expensive.
  • Tar cream is malodorous
  • She has been told that steroid cream is dangerous and does not want to use this
  • The calcipotriol ointment is thick and may stain her clothing
  • Uncertainty that treatment will prove effective.
Select the maximum quantity of calcipotriol ointment you should prescribe for one month: * 30g * 100g *! 400g * 1000g Explanation: No more than 100g of calcipotriol should be applied per week (i.e. 400g per month) as larger quantities have been associated with hypercalciuria and hypercalcaemia.

Calcipotriol ointment resulted in thinner, less scaly plaques. However, the patient stopped applying calcipotriol after 4 weeks because she disliked its greasiness and considered it ineffective.

How much betamethasone valerate cream should be prescribed for her face for one month? *! 30g * 100g * 400g * 1000g Explanation: The smallest tube size for betamethasone valerate cream available in New Zealand is 30g, which is adequate to apply to the entire body surface once or twice, or to the entire face twice daily for about ten days. Topical steroids should be applied once or twice daily as a thin smear on the plaques and not on normal skin. The smallest tube size should be adequate for this patient in the first instance, but if psoriasis persists she may require repeat prescriptions.

The facial psoriasis cleared with betamethasone cream within 2 weeks, but relapsed as soon as she discontinued it. The patient was told that after the first two weeks she should only apply the betamethasone cream to her face at weekends.

Why is it best on the long term to avoid daily applications of betamethasone cream to facial skin? # Betamethasone valerate cream is expensive #! Topical steroids may result in tachyphylaxis # Betamethasone valerate cream may cause atopic dermatitis #! Topical steroids may cause adverse effects Explanation: Betamethasone valerate is a potent topical steroid. It is inexpensive and fully subsidised on the New Zealand Pharmaceutical Schedule ($1.20 for 30g, 2004). Mild topical steroids such as hydrocortisone are usually effective for facial atopic dermatitis, but more potent products are required to control psoriasis. Topical steroids do not result in remission of psoriasis so ongoing treatment is required. “Pulse” treatment with potent topical steroids may be effective and is less likely than daily treatment to cause tachyphylaxis and adverse effects.

Select the adverse effect of corticosteroids that best describes each image:

* Periorificial dermatitis * Striae atrophicae * Skin fragility *! Purpura Explanation: Steroid purpura in patient with atopic dermatitis, who has applied potent topical steroids daily for some years. She rubs at her itchy skin incessantly – note linear shape of purpura. * Periorificial dermatitis *! Striae atrophicae * Skin fragility * Purpura Explanation: Marked abdominal striae following pregnancy in 17-year-old patient with psoriasis. She had applied excessive quantities of ultrapotent topical steroid for many months. *! Periorificial dermatitis * Striae atrophicae * Skin fragility * Purpura Explanation: Periorificial dermatitis due to inadvertent application of topical steroid prescribed for psoriasis on her hands. * Periorificial dermatitis * Striae atrophicae *! Skin fragility * Purpura Explanation: Skin tearing and purpura following minor shear force in an elderly patient who has been taking oral prednisone for the last year. Rarely, topical steroids may have similar effect.

The young lady with psoriasis is referred to the local phototherapy clinic for narrow-band UVB treatment. She is asked to attend three times weekly to a maximum of 40 treatments.

Read more about phototherapy on DermNet.

Which of the following are short-term risks of phototherapy? #! Phototoxicity # Basal cell carcinoma #! Keratitis #! Koebnerised psoriasis Which of the following are long-term risks of phototherapy? #! Squamous cell carcinoma #! Cataract # Polymorphous light eruption # Vitiligo Which of the following skin conditions may be treated with phototherapy? #! Psoriasis #! Atopic eczema #! Vitiligo #! Pruritus #! Polymorphous light eruption #! Cutaneous T-cell lymphoma.

The patient’s concerns about phototherapy include the length of waiting list, fitting treatment into her timetable, transport and parking. She also was fearful of burning and developing skin cancer.

She missed several appointments for treatment and was frequently late. The sixth exposure resulted in patchy redness and discomfort 8-12 hours after treatment (a sunburn-like reaction). The phototoxic symptoms settled within a couple of days. She was tearful and angry when she attended her next appointment, frustrated by lack of progress and the "unfairness of it all".

Regarding phototherapy, which is the best advice for her? * Stop treatment because it is ineffective * Reduce treatment frequency to once a week *! Attend three times weekly as scheduled * Increase to five times weekly Explanation: UVB phototherapy results in 90% clearance of psoriasis in 75% patients, when delivered three to five times weekly on 10 - 40 occasions. Most patients are treated three times weekly because more frequent treatments result in scheduling difficulties and more interruptions by phototoxic episodes. Less frequent treatments rarely prove successful.
The image above shows the appearance after ten treatments with phototherapy. She has developed: *! Post-inflammatory hypopigmentation * Post-inflammatory hyperpigmentation * Koebner reaction * Scarring Explanation: Psoriasis sometimes resolves leaving pale macules (post-inflammatory hypopigmentation), whether it has cleared spontaneously or as a result of treatment, including phototherapy. It is not due to trauma (Koebner). In time, affected skin nearly always reverts to its normal colour. Post-inflammatory hyperpigmentation is less common. Psoriasis does not result in scarring (a fibrotic process in which there is increased collagen formation).

Luckily, narrowband UVB phototherapy proved effective. She was discharged from the clinic after 24 treatments. She had persistent scalp scaling, which she managed with twice weekly applications of tar ointment washed out using tar shampoo.