Meryeme Boutaarourt

Mohammed VI University Hospital of Tangier, Morocco

Abstract Title: Erythema dyschromicum perstans: Contribution of histo-dermoscopy correlation

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Introduction: Erythema dyschromicum perstans (EDP), also known as ashy dermatosis, is a rare pigmentary disorder predominantly reported in individuals with darker skin types. Its pathophysiology remains poorly understood, involving lichenoid pigmentary incontinence and a possible genetic susceptibility (HLA-DR4). Classically, EDP presents as symmetrical slate-gray macules distributed over the trunk and extremities. The isolated facial form, which is exceptional, represents a diagnostic challenge and is often confused with other causes of facial hyperpigmentation. This highlights the relevance of our observation, which emphasizes the importance of recognizing this entity in order to avoid diagnostic and therapeutic errors.

Observation: This is a 46-year-old woman with no significant past medical history and no relevant medication use, who presented with asymptomatic facial hyperpigmentation that had been progressively evolving over one year, in a context of preserved general condition. The history revealed no excessive sun exposure, no use of depigmenting agents, and no prior inflammatory eruption. Clinical examination showed ill-defined brownish-gray patches, predominantly affecting the left cheek and mandibular area, without inflammatory signs or scaling. The remainder of the cutaneous examination was unremarkable. Dermoscopic evaluation revealed gray-brown dots on a homogeneous pigmented background. A skin biopsy was performed, and histopathological examination demonstrated epidermal thinning with hyperorthokeratosis, basal layer vacuolar alteration, and a perivascular and peri-adnexal lymphocytic and melanophagic inflammatory infiltrate in the dermis, consistent with erythema dyschromicum perstans. Management included strict photoprotection and initiation of topical tacrolimus. Clinical stabilization was achieved after three months of treatment.

Discussion: Erythema dyschromicum perstans, also known as ashy dermatosis, is a rare pigmentary disorder, typically involving the trunk, with isolated facial involvement being exceptional and a source of diagnostic confusion. Its pathophysiology is based on a chronic lichenoid reaction associated with pigmentary incontinence and dermal melanin deposition. Clinically, it presents as asymptomatic brownish-gray macules, with differential diagnoses including melasma, post-inflammatory hyperpigmentation, lichen planus pigmentosus, and pigmented contact dermatitis. Dermoscopy, although not specific, provides valuable support; it typically reveals homogeneous gray-brown pigmentation or a diffuse bluish veil, corresponding to dermal melanin, and helps to exclude certain epidermal conditions such as melasma. Skin biopsy remains essential, demonstrating pigmentary incontinence with dermal melanophages and a mild lymphocytic infiltrate, without features suggestive of lichen planus pigmentosus or pigmented eczema. Thus, histo-dermoscopic correlation plays a central role in diagnosis: dermoscopy guides the diagnostic approach, while histology confirms and further characterizes the nature of the infiltrate and pigmentation. This integrated approach helps avoid diagnostic errors, particularly in atypical presentations such as isolated facial involvement. Management remains challenging, with variable efficacy of topical agents (tacrolimus, corticosteroids, depigmenting agents), systemic therapies, and laser treatments. In this case, stabilization was achieved with topical tacrolimus and strict photoprotection.

Conclusion: This case highlights an atypical presentation of erythema dyschromicum perstans, confined exclusively to the face, in a patient with no identifiable triggering factor. It underscores the importance of considering this entity in any case of persistent unexplained facial hyperpigmentation, as well as the value of dermoscopy combined with skin biopsy in confirming the diagnosis.