CLINICAL HISTORY:

Signs and symptoms:  Occasional pruritus

Previous Treatment:  Super-high potency topical steroids

Other information:  past medical history was significant for an allogeneic bone marrow transplant for acute myelogenous leukemia; family history was non-contributory; he was taking no medications at the time of presentation

PHYSICAL EXAM:

Five discrete round plaques with central clearing and a peripheral keratotic ridge, ranging in size from 1.5 cm to 3.0 cm, on the extremities, were identified. Four similar lesions ere identified on the shaft of the penis and two hyperpigmented prurigo-like nodules were on his abdomen and right hand. Palms and soles were spared. (Fig 1 and Fig 2)

LABORATORY TESTS:

None

DERMATOHISTOPATHOLOGY:

Within the cornified layer an elongated column of parakeratosis coming off the epidermis at a forty-five degree angle is seen. Underneath the column of parakeratosis, there is an absent granular layer, and focally, dyskeratotic and large keratinocytes with hyperchromatic nuclei are present. The epidermis shows uniform, mild psoriasiform hyperplasia. Within the dermis, there is a superficial perivascular lymphohistiocytic infiltrate. (Fig 3 and Fig 4)

DIFFERENTIAL DIAGNOSIS:

1.   Graft vs Host Disease
2.   Disseminated Superficial Porokeratosis
3.   Porokeratosis of Mibelli
4.   Acrokeratosis Verruciformis
5.   Elastosis Perforans Serpiginosa

SCROLL DOWN FOR ANSWER AND DISCUSSION.

CORRECT DIAGNOSIS:

Porokeratosis of Mibelli

DISCUSSION:

Porokeratosis is a disorder of keratinization characterized histologically by the presence of a cornoid lamella. It was first described by Mibelli in 1893. Today, five clinical variants exist: (1) classic porokeratosis of Mibelli, (2) disseminated superficial (DSP) and disseminated superficial actinic porokeratosis (DSAP), (3) porokeratosis palmaris et plantaris disseminata (PPPD), (4) linear, and (5) punctate porokeratosis.

Clinically, lesions start as small, brownish, keratotic papules, which slowly enlarge forming irregular, annular plaques with a well-demarcated, raised hyperkeratotic border. The center of the lesion is usually atrophic. Lesions can range in size from a few millimeters to several centimeters. Usually, only a few lesions are present and they can present anywhere. However, they are typically found on acral areas of the extremities, thighs, and perigenital region. Lesions can spread by koebnerization.

Onset of porokeratosis of Mibelli is during childhood and males are more often affected than females. Familial studies suggest an autosomal dominant mode of inheritance. Lesions usually increase in size and number over time and tend to be asymptomatic.

Histologically, porokeratosis of Mibelli is characterized by a prominent cornoid lamella- a thin column of parakeratotic cells that extend through the surrounding orthokeratotic stratum corneum. Other features include an absent or decreased granular zone beneath the column of parakeratosis, vacuolated and/or dyskeratotic cells in the spinous layer, epidermal hyperplasia, and dilated capillaries associated with a moderately dense lymphohistiocytic infiltrate in the papillary dermis.

The etiology of porokeratosis is unknown. To some investigators, the cornoid lamella represents a defect in cornification. Others proposed that porokeratosis of Mibelli could be related to a mutant cellular clone of epithelial cells in the epidermis, and that the cornoid lamella represents the boundary between the abnormal clonal population and the normal epithelium.

Acquired immune deficiency is frequently found as a prelude to the development of porokeratosis and can account for up to 50% of new cases. Specifically, the reported incidence of porokeratosis occurring after organ transplant ranges from 0.34%-11%. The majority of patients developed disseminated superficial porokeratosis.

Although the pathogenesis of PK is unknown, it was for many years viewed as a benign entity. However, several cases of malignancy arising in lesions of porokeratosis were reported. The potential for malignancy has not been well defined and the risk of malignant transformation is unknown. However, authors have reported malignant degeneration in ~10%. The most commonly reported malignant lesions include Bowen’s disease, SCC, and rarely BCC. Malignant lesions have been reported to arise in larger, extremity lesions. Older patients and those with longstanding disease are at increased risk.

In spite of a poorly defined pathogenesis, porokeratosis displays a potential for malignancy and, at the minimum, careful observation is warranted.

TREATMENT:

Actual treatment for this patient:
Smaller lesions were treated via cryotherapy with liquid nitrogen. Larger lesions were initially treated with Tazarotene 0.1% cream bid. However, topical treatment with 5-FU is planned if lesions are unresponsive to tazarotene.

Other Treatment options:
Treatment options include excision, cryotherapy, electrodessication, dermabrasion, CO2 laser, 585 PDL, keratolytics, topical 5-FU, topical 5% imiquimod, topical diclofenac sodium, oral and topical retinoids. Patients should also avoid radiationd, immunosuppression, and excessive UV exposure.

REFERENCES:

1. Kanitakis Jean, et al. Porokeratosis in Organ Transplant Recipients. JAAD. 2001; 44(1)

2. Raychaudhuri SP, Smoller BR. Porokeratosis in immunosuppressed and nonimmunosuppressed patients. Int J Dermatol. 1992; 31:781-2

3. Reed RJ Leone P. Porokeratosis a mutant clonal keratosis of the epidermis. I. Histogenesis. Arch Dermatol 1970;101:340

4. Rio B et al. Disseminated superficial porokeratosis after autologous bone marrow transplant. Bone Marrow Transplant. 1997; (19) 77-79

5. Sasson M, Krain AD. Porokeratosis and Cutaneous Malignancy. A Review. Dermatol Surg 1996;22:339-342

6. Wade TR, Ackerman AB. Cornoid lamellation: A histologic reaction pattern. Am J Dermatopathol 1980;2:5-15

Additional Comment:

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