Porokeratosis

What is Porokeratosis?

Porokeratosis is a medical condition in which the process of keratinization is affected and disrupted. The patient presents patches of atrophy on the skin, these having distinctive clinical and histopathological features. The most distinctive feature is the border surrounding the patch, this being obviously hyperkeratotic. This border is also known as the cornoid lamella. Porokeratosis has more than just one clinical variant and you will find them presented below. Also, keep in mind that squamous cell carcinoma can develop within porokeratosis patches.

These are the most common forms of porokeratosis:

Classic porokeratosis of Mibelli
Disseminated superficial actinic porokeratosis (there is also a non-actinic variant identified)
Linear porokeratosis
Disseminated plantar and palmar porokeratosis
Punctate porokeratosis

Less common forms include:

Porokeratosis ptychotropica (verrucous variant, localized on the buttocks)
Porokeratoma (also known as porokeratotic acanthoma)
Porokeratotic adnexal ostial nevus (rare congenital disorder)
Pruritic papular porokeratosis

Porokeratosis Symptoms

The symptoms of porokeratosis depends on the actual form of the skin condition:

Classic porokeratosis of Mibelli

Small lesion located on extremities (more common) or in the genital area or mucous membrane (less common).
These lesions do not cause other symptoms in the majority of cases.
In some patients, mild itchiness may occur.
Lesions expand gradually but slowly over the course of years.
In immunosuppressed adults, lesions can appear and go through a rapid growth period.
Diameter of several cm (medical literature depicts cases of giant lesions, up to 20 cm in diameter).
Center of the lesion can suffer from modification of pigmentation (hyper or hypo).
In some cases, the center of the lesion presents scales. It can also be atrophic or characterized by the absence of hair.
Hyperkeratotic patches might also be present on the skin.

Disseminated superficial actinic porokeratosis

Multiple macules present on the arms and legs (distal extensor surface)
Presence of cornoid lamella
No lesions on the palms and soles
In some patients, facial lesions may occur
Hyperkeratotic patches might also be present in some cases
Lesions usually asymptomatic
Itchiness or burning sensation may accompany the lesions in certain cases
The non-actinic variant presents a generalized distribution of the lesions

Linear porokeratosis

Red or brown patches on the skin (unilateral)
Keratotic papules or plaques (linear distribution)
The distribution is along the embryonic lines of Blaschko
Less common – bilateral or generalized distribution
High risk of malignancy degeneration

Disseminated plantar and palmar porokeratosis

Areas affected – palms and soles
Generalized distribution or along the embryonic lines of Blaschko
Usually asymptomatic
May present itchiness or tenderness to palpation
Discomfort when walking in plantar lesions

Punctate porokeratosis

Multiple keratotic papules
Presence of cornoid lamella
Areas affected – palms and soles.

Causes of Porokeratosis

These are the most common causes and risk factors that lead to porokeratosis:

Genetic inheritance
Exposure to artificial ultraviolet light and prolonged exposure to the sun
Deficiency of the immune system
Renal transplants
Radiation therapy
Chemical and thermal burns
Dialysis
Photodynamic therapy
Cancer

Treatment

As there are so many different types of porokeratosis and they can all manifest differently in various patients, it should come as no surprise that the treatment of this condition is highly particularized. When prescribing a certain treatment, the doctor will take into consideration how spread the lesions are on the skin, where they are located and what are the risks of them becoming cancerous. However, apart from treatment, the patient will be recommended to avoid sun exposure, to use high SPF sunscreen when going out and to come to regular check ups so as any signs of cancer can be immediately identified.

These are the most common courses of treatment for porokeratosis:

Topical 5-fluorouracil – improves the symptoms and induces remission of all forms of porokeratosis.
Analogues of D3 vitamin – these are administered as topical treatments as well, being especially recommended for the disseminated superficial actinic porokeratosis. Two of the most recommended choices are calcipotriol and tacalcitol.
Anti-inflammatory creams, such as diclofenac, might also be used for the disseminated superficial actinic porokeratosis.
Modulators of the immune system – these are administered as topical treatments and the most recommended choice is imiquimod cream. This treatment is especially recommended for the classic form of porokeratosis (Mibelli).
Retinoids
- Topical retinoids are recommended in the cases of porokeratosis where the cornoid lamella is present. They can reduce the level of excessive keratosis and reduce this distinctive border of the lesion. However, these are not recommended to be taken for prolonged periods of time, as they can have serious side-effects on one’s health.
- Oral retinoids are recommended only in severe cases of porokeratosis, where there is an increased risk for malignancy degeneration.