Introduction

Lichen planus pigmentosus (LPP) is a rare dermatologic variant of lichen planus that creates substantial cosmetic distress to patients and remains a therapeutic challenge for dermatologists.

We report a case of a patient with recalcitrant LPP who had a remarkable response to isotretinoin therapy.

Case report

A 46-year-old woman with medical history notable for hypertension presented to the dermatology clinic with diffuse discoloration of her face and neck. Five years prior, she noticed a new onset of dark patches on her face and neck after a few hours of unprotected sun exposure. She also felt mild burning and itching in the affected area. Medications at the time included chlorthalidone.

Physical examination found hyperpigmented, gray patches diffusely on the face, sparing the nasolabial fold and infraorbital area, extending to the neck with clear demarcation from adjacent unaffected skin areas.

The patient began treatment on isotretinoin, 20 mg daily, as the next course of treatment. By 2 months on treatment, improvement in hyperpigmentation was observed, and stabilization of disease, with no new LPP eruptions, was achieved by 3 months. By 9 months of treatment, the patient had dramatically improved from her pretreatment appearance with near-complete resolution of her bluish gray dyschromia in both her facial and body lesions equally. Her minimal residual dyschromia was brown in color. Additionally, the patients satisfaction in her cosmetic appearance had significantly improved. At 1 year from treatment initiation, the patient continued to take isotretinoin, tapered down to 20 mg every other day. She had no new lesions and her residual dyschromia of prior lesions continued to fade. Low-dose isotretinoin treatment has been well tolerated with only mild, typical adverse effects of xerosis and cheilitis.

Discussion

LPP commonly presents in women with insidious onset during the third to fifth decade of life and often with a prolonged clinical course. Primary morphology of LPP is blue-grey-black–pigmented macules and patches commonly distributed in photo-exposed areas. Histologic features of LPP include pigment incontinence, perivascular lymphocytic infiltrate, and basal cell vacuolar degeneration. Our patients clinico-histopathologic features were consistent with a diagnosis of LPP.

Notably, this study excluded patients with systemic therapy attempted within 3 months of enrollment and does not describe prior treatment trials of included patients. Mechanistically, isotretinoin therapy may achieve clinical efficacy in active LPP through anti-inflammatory and immune-modulating effects.

However, further investigation is needed to specifically elucidate the mechanism of action both generally in dermatologic conditions and specifically in LPP.

Our case uniquely shows an important clinical outcome from isotretinoin therapy for LPP late in its course as well as after several prior treatment failures and/or minimally responsive results. Future prospective studies are needed to investigate clinical efficacy for recalcitrant, widespread, or late-presenting LPP, as isotretinoin may be an effective treatment option for these patients.

Suggested Reading

1. A clinico-demographic study of 344 patients with lichen planus pigmentosus seen in a tertiary care center in India over an 8-year period. Int J Dermatol. 2020; 59: 245-252
2. A global consensus statement on ashy dermatosis, erythema dyschromicumperstans, lichen planus pigmentosus, idiopathic eruptive macular pigmentation, and Riehl’s melanosis. Int J Dermatol. 2019; 58: 263-272
3. Low-dose oral isotretinoin therapy in lichen planus pigmentosus: an open-label non-randomized prospective pilot study. Int J Dermatol. 2016; 55: 1048-1054
4. Systemic isotretinoin therapy normalizes exaggerated TLR-2-mediated innate immune responses in acne patients. J Invest Dermatol. 2012; 132: 2198-2205