Psoriasis

Psoriasis, a chronic autoimmune inflammatory skin condition, often presents with varying symptoms. In Black patients, it’s crucial for family medicine physicians to take a thorough history, as the presentation of psoriasis can differ from that seen in other racial or ethnic groups.

• Symptom Onset: Patients will commonly report the gradual appearance of red, raised, scaly patches on the skin. Psoriasis can be localized or widespread, commonly affecting areas like the elbows, knees, scalp, and lower back.

• Itching (Pruritus): Most psoriasis patients experience itching, although pruritus may be less pronounced in Black patients compared to other groups. Itching can be a significant indicator of flare-ups.

• Family History: A family history of psoriasis or other autoimmune disorders (e.g., rheumatoid arthritis) can increase a patient's risk of developing psoriasis, as it is often genetically predisposed (HLA-Cw6 gene association).

• Comorbidities: Psoriasis in Black patients may be associated with comorbidities like metabolic syndrome, hypertension, diabetes, and cardiovascular disease. These conditions can worsen psoriasis and complicate treatment.

• Triggers: Common triggers for psoriasis flare-ups include stress, infections (especially streptococcal infections), and medications such as beta-blockers or lithium.

• Previous Treatments: Inquire about past treatment efforts, including topical corticosteroids and over-the-counter psoriasis treatments, as this helps inform future management strategies.

When examining Black patients with psoriasis, it's important to note that the clinical appearance may differ due to skin pigmentation. Psoriasis typically presents with the following signs:

• Plaque Psoriasis: This common type presents as well-defined, erythematous (red) plaques covered with silvery-white scales. However, in darker skin tones, erythema may be less obvious, with the plaques appearing darker brown or violaceous.

• Scalp Involvement: Psoriasis of the scalp can be more difficult to distinguish from seborrheic dermatitis in Black patients, presenting as dandruff-like flaking or thicker, scaly plaques.

• Inverse Psoriasis: Found in areas like the groin, underarms, and beneath the breasts, inverse psoriasis appears as smooth, shiny, red patches without significant scaling.

• Nail Psoriasis: Psoriasis may also affect the nails, causing pitting, discoloration, or onycholysis (nail separation).

• Guttate Psoriasis: Characterized by small, drop-shaped lesions, often triggered by infections like strep throat.

• Flexural Psoriasis: This form typically affects areas of skin folds (e.g., underarms, groin, beneath the breasts) and appears as shiny, erythematous patches without scales.
  
  Crucial Note for Darker Skin Tones

• Diagnosis Mimicry: Scalp psoriasis in Black patients is frequently misdiagnosed as Seborrheic Dermatitis. Psoriasis plaques are typically thicker and better defined.

• Post-Inflammatory Changes: As plaques resolve, they almost always leave Post-Inflammatory Hyperpigmentation (PIH) or Hypopigmentation. These pigmentary changes can be more distressing to the patient than the scales themselves.

• Prevalence Data: While historically thought to be less common, recent data indicates that the prevalence of psoriasis in Black populations is approximately 1.3% to 1.5%, compared to roughly 2.5% to 3.6% in White populations. However, Black patients often present with more extensive body surface area (BSA) involvement at the time of diagnosis.

Management is stratified by the Body Surface Area (BSA) affected and the impact on quality of life.

1. Topical Treatments (Mild to Moderate / Localized)

• Topical Corticosteroids: * Agents: Clobetasol propionate 0.05% (Very High Potency) or Betamethasone dipropionate 0.05% (High Potency).

  • Dosage: Apply a thin layer BID for 2–4 weeks.

  • Safety: Transition to "weekend-only" application or lower potency (Hydrocortisone 1%) for maintenance to prevent skin atrophy and PIH.

• Vitamin D Analogues: 

  • Agent: Calcipotriene (Dovonex). Often used as a steroid-sparing agent or in combination (e.g., Enstilar foam).

  • Dosage: Apply BID. Helps inhibit keratinocyte proliferation.

• Coal Tar: Effective for scalp scaling. Apply at bedtime; warn patient about staining and odor.

2. Phototherapy

• Narrowband UVB (NB-UVB):

  • Protocol: 2–3 sessions per week for 20–30 treatments.

  • Note: In darker skin (Fitzpatrick IV-VI), higher initial doses of UV light are often required to penetrate the melanin barrier effectively.

3. Systemic & Biologic Treatments (Moderate to Severe)

• Methotrexate: 

  • Dosage: 7.5–15 mg once weekly (titrated up to 25 mg). Co-administer with Folic Acid 5 mg to reduce GI side effects. Requires baseline CBC and LFTs.

• Cyclosporine: 

  • Dosage: 2.5 mg/kg/day (divided BID). Used as a "rescue" therapy for severe flares; limited to 3–6 months due to nephrotoxicity risk.

• Biologics (Targeted Therapy):

  • Etanercept (TNF-alpha): 50 mg twice weekly for 12 weeks, then weekly.

  • Ustekinumab (IL-12/23): 45 mg (90 mg if >100 kg) at week 0, 4, then every 12 weeks.

  • Secukinumab (IL-17A): 300 mg at weeks 0, 1, 2, 3, 4, then monthly.

4. Lifestyle & Comorbidity Management

• Weight & Diet: Weight loss can improve the efficacy of systemic treatments. Recommend a heart-healthy diet to manage cardiovascular risk.

• Smoking Cessation: Essential, as smoking is a primary driver of treatment resistance and palmoplantar flares.

• DermNet NZ – Psoriasis in Skin of Color: https://dermnetnz.org/topics/psoriasis-in-skin-of-colour

• Journal of Clinical and Aesthetic Dermatology – Psoriasis Management in African Americans (2023 update).

• National Psoriasis Foundation – Treatment Guidelines.