Porokeratosis - two cases
Figure 1 - Patient A
Dermatology is a fascinating subject with a catalogue of different skin conditions we occasionally observe in the podiatry clinic. In this blog, coincidence meant that podiatrist Hazel Finlay (of Essential Footcare in Dumfries and Galloway) and I, came across two patients with different types of the same disease. Consequently, we compared notes and thought it would make an interesting blog.
A 73-year-old female presented to her podiatrist with small asymptomatic, annular lesions with brown edges on her leg (see figures 1 and 2). Under the dermatoscope the lesion demonstrated a discrete area with a defined keratotic border (figure 3). Medically she was fit and well with hypertension well controlled with nifedipine. Previously in 2017, she underwent cholecystectomy and hysterectomy and afterwards noted the gradual development of the lesions. She denied any history of excessive sun exposure in the past.
Figure 2 - Patient A
Figure 3 - Patient A. Lesion under dermatoscope showing cornoid lamella
A 63-year-old woman attended her first podiatry appointment with foot pain. Upon examination, it was noted she had multiple raised papular lesions across the anterior surface of both tibiae (figure 4, 5 and 6). These had previously been diagnosed by a dermatologist as disseminated superficial actinic porokeratosis (DSAP). She was undergoing regular laser treatment with a private dermatologist abroad as no treatment was available locally within the National Health Service.
Figure 4 - Patient B
Figure 5 - Patient B
Figure 6 - Patient B. Lesion under dermoscopy
Following a referral by the treating podiatrist, back to her GP, she was subsequently seen by the local dermatology service. She was treated with cryotherapy, retinol cream and emollients to all of the lesions, which are now healing (pictured in figure 7 and 8 below).
Figure 7 & 8 - Patient B after treatment
Porokeratosis is an uncommon group of skin disorders that are characterised by abnormal keratinization. Visually, lesions of porokeratosis are discrete annular plaques with a raised hyperkeratotic margin. On close inspection, using the dermatoscope, the edge demonstrates a groove within it visible as a thin white border or double track (figure 3) . Histologically, it is characterised by a feature known as the “cornoid lamella” - a column of stacked parakeratotic cells (those retaining their nucleus) extending through the stratum corneum. Lesions can be solitary or multiple and localised or disseminated. Around 10% of patients will develop malignancy within the lesions  - See figure 7.
There are several types of the condition which are summarised in the table below:
Table 1 : Types of Porokeratosis
Figure 9 - Squamous Cell Carcinoma developing in a porokeratotic lesion. (Lee et al.,)
Treatment for patients with porokeratosis is not usually necessary, although patients with the DSAP sub-type may benefit from sun protection advice. An array of treatments have been carried out with varying levels of success including keratolytics like salicylic acid, topical retinoids, topical 5-Fluorouracil, imiquimod cream, lasers and photodynamic therapy. Emollients may help improve the visual appearance of lesions and patients should be advised of the risks of malignancy within lesions and report any changes promptly.
Figure 10 - Giant porokeratosis arising on the sole of the foot (Koley et al., 2020)
Figures 11, 12 and 13 - Plantar Porokeratosis of Mantoux (Udare et al., 2016)
Declaration: Patient permission was given for use of their case histories and images.
1. Errichetti, E., Dermoscopy of Inflammatory Dermatoses (Inflammoscopy): An Up-to-Date Overview. Dermatology practical & conceptual, 2019. 9(3): p. 169-180.
2. Koley, S., S.M. Hassan, and S. Saha, Giant Porokeratosis: Report of Three Cases. Indian dermatology online journal, 2020. 11(6): p. 983-987.
3. Novice, T., M. Nakamura, and Y. Helfrich, The Malignancy Potential of Porokeratosis: A Single-Center Retrospective Study. Cureus, 2021. 13(2): p. e13083-e13083.
4. Udare, S. and K. Hemmady, Clinical and dermatoscopic features of porokeratosis palmaris et plantaris. Indian dermatology online journal, 2016. 7(4): p. 290-292.
5. James, W.D., et al., Andrews Disease of the Skin. 2020, London: Elsevier.