Mucinoses of the skin are a group of disorders sharing accumulation of mucin in the skin or hair follicles. Postinflammatory hyperpigmentation, with pigmentary incontinence, is due to loss of melanin from epidermal basal cells and its accumulation in dermal macrophages.Methods
We describe clinicopathologic features of two patients presenting with the association of pigmentary incontinence with an unusual diffuse, band-like dermal deposition of mucin, clinically presenting with reticular pigmented macular lesions.Results
Two patients were observed with asymptomatic, persistent, reticular, pigmented patches located in the flexures, thighs, neck and back. Histology showed melanophages with a diffuse, band-like dermal deposition of mucin, an increased number of fibroblasts, a slight T-cell infiltrate and scattered mast cells. Blood markers of lupus erythematosus were negative.Conclusions
These findings may draw attention to pigmentary disorders such as lichen planus pigmentosus, erythema dyschromicum perstans, pigmentatio maculos eruptiva idiopathica, dermatopathia pigmentosa reticularis, prurigo pigmentosa and frictional melanosis. None of these entities, however, includes mucin deposition among its microscopic features. Macules were not preceded by erythema or any other lesions. We suggest that our cases could belong to group II of Rongioletti and Rebora's classification, i.e. they could be cases of secondary mucin deposition in postinflammatory hyperpigmentation, possibly in an unusual form of lichen planus pigmentosus or, less likely, frictional melanosis.