Abstract Number: 45

Making sense of acquired macular hyperpigmentation of uncertain aetiology

P. Kumarasinghe

Meeting: 2016 Dermcoll

Session Information

Date: -

Session Title: Pigmentary Disorders Symposium

Session Time: -

Macular pigmentation of the skin without an identifiable cause (macular pigmentation of uncertain aetiology/MPUA) is not an uncommon dilemma in clinical dermatol- ogy. Visible patches of hyperpigmentation can be distress- ing to the patient. It is more obvious in the Fitzpatrick skin Types III-V. Ashy dermatosis, erythema dyschromicum per- stans, lichen planus pigmentosus, idiopathic eruptive mac- ular pigmentation and Riehl’s melanosis are some terms that have been used to describe these cases. However the literature is confusing as there has not been a consensus on the use of the terms. One of the main problems is that the histopathology is rather nonspecific with dermal mela- nophages (give rise to the ashy grey colour) and sparse dermal lymphocytic infiltrates. Interface dermatitis is seen in some cases, but not in all. The histopathology can be indistinguishable from post inflammatory hyperpigmenta- tion, burnt out lichen planus, graft versus host reactions, fixed drug eruptions and several other conditions. It is very important to rule out various forms of drug induced hyper- pigmentations, frictional melanoses, macular amyloidosis, endocrine causes etc. in diffuse and patchy acquired pig- mentations.

It is best to consider various causes that can lead to macu- lar pigmentation of uncertain aetiology(MPUA) in a rational way before labelling as ashy dermatosis, LPP, EDP, Riehl’s melanosis or IEMP. Various causes of acquired patchy pigmentation and a rational approach to diagnosing and managing these difficult cases will be dis- cussed.