What is the diagnosis and treatment for a patient with a plaque-like rash due to prolonged excessive scratching?

Lichen Simplex Chronicus (Plaque-Like Rash from Chronic Scratching)

The diagnosis is lichen simplex chronicus (LSC), a localized form of neurodermatitis resulting from chronic scratching, and treatment requires breaking the itch-scratch cycle through potent topical corticosteroids combined with antihistamines and behavioral modification. 1

Diagnosis

The clinical diagnosis is based on:

• Presence of thickened, lichenified plaques with accentuated skin markings in areas accessible to scratching 1
• History of chronic scratching or rubbing lasting at least 6 weeks, which is the defining feature distinguishing this from acute dermatitis 1, 2
• Intense pruritus that drives the repetitive scratching behavior, creating a self-perpetuating itch-scratch cycle 2, 3
• Common locations include the nape of neck, ankles, wrists, and anogenital region—areas easily reached for scratching 1

Key Differential Considerations

If nodular lesions develop rather than flat plaques, consider prurigo nodularis (PN), which represents a more severe manifestation requiring different management 4, 2. PN is characterized by firm, hyperkeratotic nodules rather than flat lichenified plaques 2, 3.

Rule out underlying triggers including:

• Atopic dermatitis (look for flexural involvement, personal/family history of atopy) 1
• Contact dermatitis (assess for new exposures to irritants or allergens) 1
• Psoriasis (look for silvery scale, nail pitting, other body sites involved) 1
• Secondary bacterial infection (crusting, weeping, honey-colored exudate) 1

Treatment Algorithm

First-Line Therapy: Break the Itch-Scratch Cycle

Topical corticosteroids are the cornerstone of treatment 1:

• For body sites: Apply Class I (very potent) topical corticosteroid such as clobetasol propionate 0.05% or betamethasone dipropionate ointment twice daily 1
• For facial/intertriginous areas: Use Class V-VI (low-moderate potency) corticosteroid such as hydrocortisone 2.5% or desonide to avoid atrophy 1
• Duration: Continue until lichenification resolves to normal skin texture, typically 2-4 weeks, then taper 1
• Monitoring: Regular clinical review is essential; no unsupervised repeat prescriptions should be provided 1

Oral antihistamines to reduce pruritus and break the cycle 1:

• Non-sedating options: Cetirizine or loratadine 10 mg daily for daytime use 1
• Sedating option: Hydroxyzine 10-25 mg at bedtime to address nocturnal scratching and improve sleep 1

Adjunctive Measures

Emollients should be applied liberally and frequently 1:

• Use cream or ointment-based, fragrance-free products to restore skin barrier function 1
• Apply immediately after bathing while skin is still damp 1

Behavioral modification is critical 1:

• Keep nails trimmed short to minimize trauma from scratching 1
• Cover affected areas with occlusive dressings or clothing to prevent unconscious scratching 1
• Patient education about the itch-scratch cycle and importance of avoiding scratching 1

Second-Line Options for Refractory Cases

If inadequate response after 4-6 weeks of first-line therapy 1:

Calcineurin inhibitors for sensitive areas or steroid-refractory disease 1, 5:

• Pimecrolimus 1% cream or tacrolimus ointment applied twice daily 1, 5
• Particularly useful for facial, genital, or intertriginous involvement where corticosteroid atrophy is a concern 1
• Important caveat: Should only be used on areas with active eczematous changes, not as maintenance therapy 5

Intralesional corticosteroids for thick, resistant plaques 4:

• Triamcinolone acetonide 5-10 mg/mL injected directly into lichenified plaques 4

Phototherapy (UVB or PUVA) may be helpful in selected patients with widespread involvement 1

Critical Management Pitfalls

Do not use topical corticosteroids indefinitely 1:

• No more than 100 g of moderately potent preparation should be used per month 1
• There should be periods each year when alternative treatments are employed 1
• Very potent or potent preparations should be under dermatological supervision 1

Address secondary bacterial infection promptly 1:

• Deterioration in previously stable disease may indicate Staphylococcus aureus superinfection 1
• Send bacterial swabs if crusting, weeping, or honey-colored exudate present 1
• Treat with appropriate oral antibiotics if infection confirmed 1

Recognize when nodular transformation occurs 4, 2:

• If firm nodules develop instead of flat plaques, the diagnosis shifts to prurigo nodularis requiring more aggressive multimodal therapy 4, 2
• PN requires addressing both neural and immunologic components with systemic therapies 2, 3

Patient education is paramount 1:

• Adequate time for explanation about the chronic nature of the condition and the itch-scratch cycle is essential 1
• Demonstrate proper application technique for topical medications 1
• Provide written information to reinforce verbal instructions 1