Answer of Dermatopathology Case 47

Porokeratosis of Mibelli

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Abstract:

Mibelli revisited: a case of type 2 segmental porokeratosis from 1893. J Am Acad Dermatol.2010 Jan;62(1):136-8. Epub 2009 Jul 25.

In autosomal dominant skin disorders, a pronounced mosaic involvement may sometimes be found to be superimposed on the ordinary nonsegmental lesions. Such "type 2 segmental manifestation" reflects loss of heterozygosity occurring at an early developmental stage, giving rise to a cell clone that lacks the corresponding wild-type allele. Here, this genetic concept is applied to an unusual case of plaque-type porokeratosis of Mibelli (PM) as published in 1893 by Vittorio Mibelli in the International Atlas of Rare Skin Diseases. The right forearm and hand of the 21-year-old patient showed a pronounced linear porokeratosis that had developed since the age of 2 years. Moreover, nonsegmental lesions of PM involved both hands and forearms as well as the face and the neck, having first been noticed at the age of 7 years. Two siblings and the father were likewise affected with PM. Hence, Mibelli's case from 1893 meets all of the criteria of a type 2 segmental manifestation of an autosomal dominant skin disorder. Recognizing such cases of superimposed segmental involvement may help elucidate the molecular basis of PM.

Hyperkeratotic variant of porokeratosis Mibelli with dermal amyloid deposits. J Dermatol.2010 May;37(5):475-9.

We report a case of hyperkeratotic variant of porokeratosis Mibelli with dermal amyloid deposits. A 66-year-old man presented with multiple brownish keratotic lesions on the lower extremities, a verrucous nodule on the third toe of the left foot and brownish verrucous plaques on the buttocks for several years. Histopathological examination of the hyperkeratotic plaque in the right gluteal region revealed extreme hyperkeratosis and cornoid lamella. In the papillary dermis, there were prominent eosinophilic amorphous materials which were positive to Dylon staining. Treatment with oral etretinate resulted in a remission of the skin lesions in this case.

Porokeratosis Mibelli gigantea: case report and literature review. Hautarzt. 1999; 50(6):435-8.

Porokeratos of Mibelli is a rare inherited disorder of epidermal keratinization, whose pathogenesis is not fully understood. The common clinical feature is a erythematous plaque surrounded by a hyperkeratotic border. The histopathologic hallmark is a parakeratotic cornoid lamella. An unusual case of porokeratosis gigantea, a morphological variant of classical porokeratosis of Mibelli, is reported. The pathogenesis, taking in account especially the clonal hypothesis and premalignant nature of porokeratosis, is discussed.

Porokeratosis of Mibelli. Overview and review of the literature.Acta Derm Venereol.1997 May;77(3):207-13.

Porokeratosis of Mibelli is an uncommon dermatosis, which may be associated with immunosuppression and may undergo malignant transformation. Due to the wide range of clinical presentations, numerous classifications have evolved, resulting in some confusion. This article examines the classification and presentation of porokeratosis and, in particular, reviews the association with immunosuppression.