What are the presentation and treatment options for Pityriasis lichenoides chronica (PLC)?

Pityriasis Lichenoides Chronica: Presentation and Treatment

Clinical Presentation

Pityriasis lichenoides chronica (PLC) presents as a gradual eruption of very small red-to-brown flat maculopapules with characteristic mica-like scale, following a relapsing course with long periods of remission. 1

Key Clinical Features

• Lesion morphology: Small red-to-brown flat maculopapules covered with fine, mica-like scale that distinguishes PLC from the more acute PLEVA variant 1
• Distribution: Lesions typically appear in a generalized pattern across the trunk and extremities 1
• Disease course: PLC demonstrates a significantly longer time course compared to PLEVA, with disease duration of at least 78 ± 48 months versus 35 ± 35 months for PLEVA 2
• Residual changes: Approximately 43% of patients with active PLC develop persistent pigmentary alterations (hyper/hypopigmentation) that can last at least 35 ± 20 months, independent of race 2
• Age of onset: Predominantly affects children and young adults, with mean age at onset of 12 years (median 8 years) 2

Important Diagnostic Considerations

• Histopathology: Shows dermal wedge-shaped lymphocytic infiltrate, epidermal spongiosis, parakeratosis, and variable keratinocyte necrosis, though PLC demonstrates more subtle histological features compared to PLEVA 1
• Long-term persistence: At long-term follow-up, 82% of PLC patients had active disease, indicating the chronic relapsing nature of this condition 2
• Benign prognosis: No progression to lymphomatoid papulosis or cutaneous T-cell lymphoma has been documented in long-term follow-up studies 2

Treatment Algorithm

First-Line Treatment

High-potency topical corticosteroids (clobetasol propionate 0.05%) applied twice daily for 2-3 months with gradual tapering should be initiated as first-line therapy. 3

• Apply to affected areas twice daily for 2-3 months, followed by gradual tapering to prevent rebound flares 3
• Patients should wash hands thoroughly after application to avoid inadvertent spread to sensitive areas 3
• Critical caveat: Use cautiously in pediatric patients, who represent the majority of PLC cases, due to risks of cutaneous atrophy, adrenal suppression, and hypopigmentation 3
• Response rates with topical corticosteroids are approximately 27%, which is modest compared to other modalities 2

Second-Line Treatment: Phototherapy

Narrow-band UVB phototherapy is recommended as the most effective second-line treatment, with clearance rates of 70-100%. 4

• Narrow-band UVB shows efficacy similar to PUVA but with a better safety profile 4
• Phototherapy demonstrated a 47% response rate in long-term follow-up studies, making it the most effective treatment modality 2
• Alternative phototherapy options include broadband UVB, UVA1, or PUVA, with comparable clearance rates between 70-100% 4
• Important consideration: Regular follow-up at 3 months is necessary to assess treatment response and monitor for adverse effects 3

Third-Line Treatment: Systemic Therapies

For refractory cases, oral erythromycin (clearance rates 66-83%) or low-dose methotrexate (clearance up to 100%) should be considered. 4

Oral Erythromycin

• Clearance rates range between 66-83% 4
• Can be combined with topical corticosteroids for enhanced efficacy 4
• Response rate of approximately 25% in long-term studies 2

Low-Dose Methotrexate

• Shows clearance rates up to 100%, though evidence comes from small, dated studies 4
• Should be reserved for severe, treatment-refractory cases 4

Alternative Systemic Option: Bromelain

• Oral bromelain (40 mg three times daily for 1 month, then 40 mg twice daily for 1 month, then 40 mg daily for 1 month) achieved complete clinical recovery in all treated patients 5
• Two of eight patients experienced relapse 5-6 months after therapy cessation but responded to repeat treatment 5
• Efficacy may relate to anti-inflammatory, immunomodulatory, and/or anti-viral properties 5

Critical Clinical Pitfalls

• Inadequate treatment duration: PLC requires prolonged therapy given its chronic relapsing nature; short treatment courses often result in recurrence 2
• Failure to taper corticosteroids: Abrupt discontinuation leads to rebound flares; gradual tapering over 3 weeks is essential 3
• Unrealistic expectations: Treatment response is often limited, particularly for PLC compared to PLEVA, with many patients experiencing persistent disease despite therapy 2
• Overlooking heliotherapy: Natural sunlight exposure showed a 33% response rate and represents a cost-effective adjunctive option 2
• Monitoring for progression: While rare, regular follow-up is necessary to ensure no progression to more serious conditions, though no cases of lymphoma transformation have been documented 2