|Year : 1993 | Volume
| Issue : 4 | Page : 210-212
Linear porokeratosis of mibelli
MV Shenoy, K Venkateswaran Sri, BSN Reddy, Garg
M V Shenoy
Source of Support: None, Conflict of Interest: None
An unusual case of linear porokeratosis manifesting unilaterally in a 25 year old male patient is reported for rarity and clinical interest.
|How to cite this article:|
Shenoy M V, Sri K V, Reddy B, Garg. Linear porokeratosis of mibelli. Indian J Dermatol Venereol Leprol 1993;59:210-2
| Introduction|| |
Porokeratosis of Mibelli (PM) is an autosomal dominant genodermatosis with variable penetrance, characterised by a defective keratinization that histopathologically manifests as a stack of closely packed parakeratotic cells traversing the stratum corneum- the cornoid lamella.  Since the original description of this entity in 1893 by Mibelli, various other forms of this disease have been described. These are the disseminated superficial actinic porokeratosis of Chernosky and Freeman (DSAP);  porokeratosis plantaris palmaris et disseminata of Guss et al (PPPD); sub porokeratosis punctata palmaris et plantaris of Brown (PPPP);  linear porokeratosis-Rhabari et al  sand reticulate porokeratosis of Helfman et al. sub Among these variants the linear porokeratosis is considered to be rare.
| Case Report|| |
A 25-year-old male patient presented with a 2'/ 2 year history of slowly progressive asymptomatic violaceous skin lesions over the right half of the body. The lesions initially started over the right knee and gradually extended both upwards and downwards over the affected limb in a linear fashion and later to the abdomen, chest and upper limb on the right side. Cutaneous examination revealed multiple hyperpigmented violaceous keratotic papules and plaques arranged unilaterally over the lower limb, abdomen, chest and upper limb on the right side. Some of the - papules were discrete while others had confluenced to from annular plaques. In majority of the lesions the border was raised and the center was atrophic and partially depressed [Figure - 1] Close examination of the lesions especially the annular ones revealed a characteristic groove traversing the margins. In addition a linear verrucous plaque 3 x 2 cm size was present over the dorsal aspect of the right great toe encroaching the nail plate [Figure - 2] Rest of the skin and systemic examination did not reveal any abnormality.
Histological examination of the biopsy taken from the lesions over the arm and over right great toe on H & E staining showed characteristic parakeratotic column of cells (cornoid lamella) traversing the stratum corneum, with underlying epidermis showing absence of granular layer and dissolution of basal cells. Lymphocytic infiltrate was seen in the upper dermis corresponding to the cornoid lamella.
| Comments|| |
A striking similarity was noted on clinical appearance of the lesions over the upper limb and abdomen to lichen planus and the verrucous plaque over the right great toe to linear epidermal naevus in our patient but the presence of cornoid lamella on histopathological examination left no doubt about the diagnous of PM.
PM is believed to be an autosomal dominant genodermatosis with varying degree of penetrability. However isolated cases may occur due to mutation similar to the patient described herein. Various theories about the pathogenesis of this disorder have been described in the literature. Reed and Leone  postulated that the lesions arise in a clone of epidermal cells which can be seen as vacuolated cells underlying the cornoid lamella. This clone of cells spreads laterally with a growth rate more rapid than the resisting epithelial cells so that a fold on groove is formed at the point of pressure as the lesions spreads through the epidermis.
The abnormalities in the dermis underlying cornoid lamella have been suggested to be important in the pathogenesis of PM. Chromosomal instability has been found in cultured fibroblasts from the lesional skin.  Actinic radiation, aging, trauma and infection are believed to trigger the disease in a genetically predisposed individual. Reddy et al  proposed an interesting theory of the role of female hormones in preventing the development of porokeratosis in females of reproductive age group. While describing two cases of linear PM, Warren et al  reported that the linear lesions may represent a somatic gene mutation in embryonic life rather than Koebner's phenomenon.
In conclusion, it may be considered that linear PM originates from an abnormal clone of epidermal cells carrying the porokeratosis trait arranged along a dermatomal distribution early in embryonic life. The exact event which triggers the area to develop clinical lesions may not be obvious in all cases.
| References|| |
|1.||Reed RJ, Leone P. Porokeratosis - mutant clonal keratosis of the epidermis. Arch Dermatol 1970; 101: 340-7. [PUBMED] |
|2.||Chernosky ME, Freeman RG. Disseminated superficial actinic porokeratosis. Arch Dermatol 1967' 96: 611-24. |
|3.||Guss SB,Osburn RA, Lutzner MA. Porokeratosis plantaris, palmaris et disseminata, a third type of porokeratosis. Arch Dermatol 1971; 104: 366-73. |
|4.||Brown F. Punctate keratoderma. Arch Dermatol 1971; 104: 682-3. |
|5.||Rahbari H, Cordero AA, Meregan AH. Linear porokeratosis a distinctive clinical variant of porokeratosis of Mibelli. Arch Dermatol 1974; 109: 526-8. |
|6.||Helfman RJ, Poulos EG. Reticulated porokeratosis. Arch Dermatol 1985; 121: 1542-3. , |
|7.||Wolff Schreiner EC. Porokeratosis. In: Dermatology in General Medicine (Fitzapatrick TB, Eisen AZ, Klaus Woff, eds). 3rd edn. McGraw Hill, 534-40. |
|8.||Reddy BSN, Singh G. Porokeratosis of Mibelli. Ind J Dermatol Venereol Leprol 1982; 48: 287-8. |
|9.||Warren G, Eyre MG. Linear Porokeratosis. Arch Dermatol 1972; 105: 426-9. |
[Figure - 1], [Figure - 2]