What are the different categories of skin disorders and their typical first‑line treatments?

Categories of Skin Disorders and First-Line Treatments

Skin disorders are best categorized by their underlying immune response patterns and pathophysiological mechanisms, with treatment selection based on disease severity, distribution, and specific molecular signatures rather than purely descriptive classifications.

Major Categories and Treatment Approaches

Inflammatory/Immune-Mediated Disorders

Psoriasis (Type 3, Psoriasiform Pattern)

• Topical corticosteroids remain first-line therapy for localized disease 1
• Topical vitamin D3 analogs (calcipotriene) are equally effective as medium-potency steroids without steroid side effects, though doses exceeding 100 g/week can induce hypercalcemia 1
• For severe cases requiring systemic therapy, methotrexate has been traditional, but tumor necrosis factor inhibitors and other biologic agents are now standard 1
• Narrowband UV-B light is first-line for children and pregnant women when topical therapy is insufficient 1

Eczema/Atopic Dermatitis (Type 2a, Eczematous Pattern)

• Topical corticosteroids are initial treatment 1
• For steroid-sparing approaches, calcineurin inhibitors (tacrolimus preferred over pimecrolimus for adults and children >2 years) are first choice 1
• Diluted bleach baths can delay need for systemic management 1
• When systemic therapy is required, oral cyclosporine is appropriate, though severe cases often require oral steroids 1

Acne Vulgaris

• Topical benzoyl peroxide and topical/systemic antibiotics are standard first-line treatments 1
• Oral contraceptives are effective for appropriate candidates 1
• Oral isotretinoin is the most effective treatment for severe or refractory cases 1

Cutaneous Lymphomas

Mycosis Fungoides (Early Stage)

• Stage-adjusted conservative approach with skin-directed therapies is recommended 2
• Topical corticosteroids, PUVA (psoralen plus UVA), topical mechlorethamine (HN2) or BCNU are first-line 2
• Radiation therapy with electron beam or soft X-rays for localized forms 2
• Total skin electron beam therapy (TSEBT) at lower doses (10-12 Gy) preferred over traditional 30-36 Gy due to fewer side effects and opportunity for re-treatment 2

Mycosis Fungoides (Advanced Stage)

• Combined topical and systemic therapy: PUVA with systemic retinoids or recombinant interferon-α 2
• Multi-agent chemotherapy only indicated for effaced lymph nodes, visceral involvement (stage IV), or widespread tumor stage uncontrolled by skin-targeted therapies 2

Sézary Syndrome

• Systemic treatment is required as this is a leukemic process by definition 2
• Extracorporeal photopheresis (ECP) alone or combined with other modalities is suggested as treatment of choice, with overall response rates 30-80% 2
• Low-dose alemtuzumab (10 mg subcutaneous, 3 times weekly for 12 weeks), single-agent chemotherapy (gemcitabine, PEGylated liposomal doxorubicin), or mogulizumab for blood involvement are second-line 2

Primary Cutaneous CD30+ Lymphoproliferative Disorders

• Radiotherapy (20 Gy total dose) is first choice for solitary or localized C-ALCL lesions 2
• Low-dose methotrexate (5-20 mg/week) for multifocal lesions or cosmetically disturbing lymphomatoid papulosis 2
• Brentuximab vedotin (BV) for refractory multifocal disease or extracutaneous involvement 2

Low-Grade Cutaneous B-Cell Lymphomas

• If Borrelia burgdorferi DNA identified, initial therapeutic trial with doxycycline 100 mg twice daily for 3 weeks 2
• Radiotherapy or surgical excision for solitary lesions 2
• Rituximab only when CD20 expression histologically confirmed 2

Primary Cutaneous Diffuse Large B-Cell Lymphoma, Leg Type

• R-CHOP is first-line treatment 2
• Radiation therapy for solitary lesions 2

Inherited Disorders

Congenital Ichthyoses

• Topical agents are essential first-line treatment for all patients 2
• Keratolytics (urea ≥10%, alpha-hydroxyacids 5-12%, propylene glycol >20%, salicylic acid >2%) are superior to emollients alone for removing scales 2
• Urea is most frequently used, with concentrations up to 20% (or 40% for localized thick areas) 2
• Apply once or twice daily, taper based on response 2
• Emollients should be applied at least twice daily for all ichthyoses 2
• Avoid keratolytics on face, flexures, and fissured areas due to irritation risk 2

Inflammatory Bowel Disease-Associated Cutaneous Manifestations

Pyoderma Gangrenosum

• Immunosuppression is the mainstay of treatment with rapid healing as the therapeutic goal 2
• Systemic corticosteroids traditionally considered first-line 2
• Infliximab should be considered if rapid response to corticosteroids cannot be achieved, particularly effective in short-duration PG (<12 weeks with >90% response rate) 2
• Intravenous ciclosporin and oral/intravenous tacrolimus reserved for refractory cases 2
• Topical tacrolimus is an alternative for localized disease 2

Erythema Nodosum

• Typically occurs during active UC and resolves with disease control 2
• Treatment directed at underlying IBD activity 2

Behavioral/Psychiatric Skin Disorders

Dermatillomania (Skin Picking Disorder)

• Cognitive-behavioral therapy (CBT) with habit reversal training is first-line treatment 3
• CBT should incorporate awareness training, competing response development, and self-monitoring tools 3
• Family involvement crucial, especially for younger patients 3
• SSRIs are second-line for ages 12-18 years with moderate-to-severe functional impairment who haven't responded to CBT 3
• N-Acetylcysteine 1200-2400 mg/day in divided doses is well-established with minimal side effects 3

Subcutaneous Panniculitis-Like T-Cell Lymphoma

• Systemic steroids or other immunosuppressive agents (ciclosporin, methotrexate) are first choice without hemophagocytic syndrome 2
• Radiotherapy with electrons for solitary lesions 2
• Multi-agent chemotherapy only for progressive disease unresponsive to immunosuppression or presence of hemophagocytic syndrome 2

Extranodal NK/T-Cell Lymphoma, Nasal Type

• Combined modality treatment with L-asparaginase containing chemotherapy (SMILE regimen) plus radiotherapy for localized disease is preferred 2
• Radiotherapy alone only for small solitary lesions in older/frail patients unable to tolerate intensive chemotherapy 2

Critical Pitfalls to Avoid

• Do not use multi-agent chemotherapy for early-stage cutaneous lymphomas—it is only indicated for advanced disease with nodal/visceral involvement or rapidly progressive skin disease 2
• Avoid prolonged systemic corticosteroid use in psoriasis and eczema—transition to steroid-sparing agents (calcineurin inhibitors, biologics) to prevent long-term toxicity 1
• Do not exceed 100 g/week of calcipotriene due to hypercalcemia risk 1
• Avoid keratolytics on facial, flexural, or fissured skin in ichthyosis patients due to severe irritation 2
• Screen for self-harm and suicidal ideation at every visit in dermatillomania patients, as approximately half report self-harm 3
• Assess for Borrelia burgdorferi before initiating immunosuppression in low-grade cutaneous B-cell lymphomas, as antibiotic therapy may be curative 2
• Monitor for hemophagocytic syndrome in subcutaneous panniculitis-like T-cell lymphoma—5-year survival drops from 91% to 46% when present, requiring immediate aggressive intervention 2