Page 60 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 2-33 Integumentary System

POROKERATOSIS

The porokeratoses are a group of benign epidermal
proliferations. The most common and best-described Disseminated superficial
clinical variants include disseminated superficial actinic actinic porokeratosis (DSAP).
porokeratosis (DSAP), porokeratosis of Mibelli, poro- Thin patches with a thin rim of epidermal
keratosis palmaris et plantaris disseminata, and punctu- hyperkeratosis on sun-exposed skin
ate porokeratosis. The underlying disease state is the
same for all variants, as are the characteristic and diag-
nostic histopathological findings. There are many other
clinical variants that are infrequently seen.
Clinical Findings: Porokeratoses are typically inher-
ited in an autosomal dominant fashion. They manifest
beginning in the third to fourth decades of life and Types of Porokeratosis
are more common in sun-exposed areas. The lesions
can be minute to a few centimeters in diameter. They Disseminated superficial actinic porokeratosis (DSAP)
usually are 1- to 2-cm, thin, flesh-colored to slightly Porokeratosis palmaris et plantaris disseminata
pink or hyperpigmented patches with a characteristic Linear porokeratosis
hyperkeratotic surrounding rim. This rim encompasses Punctate porokeratosis
the entire lesion and is almost pathognomonic for Porokeratosis of Mibelli (solitary porokeratosis)
porokeratosis.
The DSAP form is the most common and most easily
recognized clinical variant. Patients present with a
family history of similar skin growths. The lesions are
almost entirely located in sun-exposed regions of the
body. Patients who have had more ultraviolet light
exposure over their lifetime are more likely to have
multiple and more noticeable lesions. Most porokera-
toses are asymptomatic, and patients typically present
because of the appearance of the lesions and the fact
that they continue to develop more lesions over time.
Most lesions are flesh colored to slightly pink or red.
Some can be frankly inflamed, with redness and crust-
ing. Transformation into squamous cell carcinoma has
been reported. and patients should be counseled to be
reevaluated if they develop growths or ulcerations
within the porokeratosis. The lesions of DSAP are
much more likely to affect the skin on the extremities
than the facial skin.
The porokeratosis of Mibelli is a solitary lesion, or
a group of lesions with a linear array that have an
identical morphology of a thin patch with a thin
hyperkeratotic rim. They may occur anywhere on the
body. Low power. An atrophic epidermis with a scant High power. The cornoid lamella is made
Porokeratosis palmaris et plantaris disseminata is a amount of dermal inflammation is seen. A peri- of compacted stratum corneum. It overlies
unique variant that affects the skin of the palms and pherally located cornoid lamella is appreciated. an area that has lost its granular cell layer.
soles initially and then can disseminate into a general- The cornoid lamella is oriented with its
ized pattern. The lesions of the palms and soles can be distal ends pointing inward.
tender. This variant is also inherited in an autosomal
dominant manner. The lesions begin on the palms and
soles during the third to fourth decades of life and
slowly spread to other areas of the skin in a generalized taking chronic immunosuppressive medications (e.g., seen. The area can be atrophic or acanthotic. It is
pattern. after solid organ transplantation) and in those infected not uncommon to see an inflammatory infiltrate
Punctate porokeratosis of the palms and soles is a rare with the human immunodeficiency virus. This is indi- underneath the lesion, composed predominantly of
clinical variant that is localized to the palms and soles. rect evidence that chronic immunosuppression may lymphocytes.
The lesions tend to be 0.5 to 1 cm in diameter and have lead to a lack of tumor surveillance and the develop- Treatment: Treatment is difficult and often unsuc-
a well-defined rim of hyperkeratosis. Occasionally, they ment of porokeratosis. cessful for widespread areas such as those involved in
can be mistaken for plantar warts. Histology: On biopsy, the hallmark of porokeratosis DSAP. Sun protection and sunscreen use are recom-
Pathogenesis: The pathogenesis of porokeratosis, no is recognition of the cornoid lamella. The cornoid mended. Solitary lesions can be removed surgically.
matter which variant, is believed to be an abnormality lamella is the pathological representation of the hyper- Multiple disseminated lesions can be ablated with
of keratinocyte proliferation. A clonal expansion of the keratotic peripheral rim of tissue seen on clinical carbon dioxide laser ablation, 5-fluorouracil, or derm-
abnormal keratinocytes leads to development of the examination. The cornoid lamella is positioned at an abrasion. These therapies are not always effective and
expanding rim of hyperkeratotic tissue. This rim of angle away from the center of the lesion. The granular may be associated with scarring. It is imperative to
hyperkeratosis is recognized histopathologically as the cell layer underneath the cornoid lamella is often continue to monitor these patients with routine skin
cornoid lamella. No genetic defect has been identified. absent or severely thinned. The appearance of the examinations, because porokeratoses have a potential
Porokeratosis is more commonly found in patients center of the lesion is dependent on the clinical variant for malignant degeneration.

46 THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS