Human papillomavirus is a type of virus that has a high prevalence in the feet of athletes. As our colleagues from the World Academy of Podiatric Science (WAPS) point out, the correct nomenclature for this pathology in podiatry is plantar wart and it has two differentiated phases that are key for its identification with thermography.

It is a viral infection caused by the human papillomavirus or HPV, which lodges in the superficial layers of the skin. Plantar warts have an annual incidence of 14% in the general population, and somewhat higher, up to 27%, in the population that uses common showers such as athletes (Witchey et al. 2018; Johnson et al. 1995)

The papillomavirus is so present in athletes because its transmission is by direct contact in areas with wounds or cracks, where the virus accesses for its proliferation. For this reason, athletes who walk barefoot in high-traffic areas, such as collective showers or pool areas, have a higher risk of contracting the virus, as with tinea pedis or athlete's foot.

“In hot places and where the humidity is high, such as in a team locker room, it is very easy to get HPV, especially if you walk barefoot,” warns Dr. Antonio Gómez Bernal from the World Academy of Podiatric Science (WAPS) podiatry education platform.

Identification of the moment of infection with papillomavirus.

The human papillomavirus presents two phases in its infection process: productive or active phase and latent phase. Depending on the tropism of the tissue, as well as its clinical manifestations, Guzmán-López et al. (2010) classify HPV into three different clinicopathological groups: cutaneous, epidermodysplasia verruciformis, and mucosal, as described in Table 1:

Table 1. Classification of diseases caused by HPV. Extracted from Guzmán-López et al. (2010)

The pathophysiology of HPV infection is the adhesion of intact virions to squamous epithelial cells, from which two types of infections can occur: productive or latent.

• In the productive or active phase, viral replication takes place mainly in already differentiated squamous cells, that is, in the intermediate and superficial layers of the squamous epithelium, where intense DNA replication activity occurs. This intense activity, where the virus will try to replicate, causes a greater activation of the metabolism in that area.
• In latent-type infection, infection occurs predominantly in immature cells (basal or metaplastic cells) of the squamous epithelium. The viral DNA, which does not replicate, remains inside the cell in an episomal form. Morphological changes are negligible, which implies that viral detection is carried out only through molecular methods.

As for its appearance, the colleagues at Podoactiva explain to us in this post that it is similar to a cauliflower and that there is no uniformity in terms of its size, since it depends on the extent of the injury and how old it is. In addition, black dots usually appear, due to the vascularization of the virus, which can bleed if a delamination is performed.

Thermography as an ally for human papillomavirus identification

The hypothesis of the ThermoHuman team in collaboration with Dr. Antonio Gómez Bernal, podiatrist at Podoactiva, is that in the active phase the metabolism helps to nourish and reproduce the virus, so thermography can help us identify it thanks to its hyperthermic pattern. However, in the latent phase, the cell has no activity, so the pattern will be normothermic. In Figure 1, we can see a patient with HPV in the active phase:

Figure 1. Thermal and digital images of papilloma (HPV) located on the heel of the right foot with a very characteristic and localized hyperthermic circular shape (Thermal and digital images taken by Ismael Fernández Cuevas, ThermoHuman)

In the active phase of the papilloma, vascularization is decisive for proliferation, since the virus obtains greater irrigation to get nourished and grow. Greater vascularization implies a localized hyperthermic pattern, where the metabolism is more active and the virus is growing. In these stages, referral to a podiatrist, as Podoactiva professionals tell us, is crucial for your treatment.

In the latent phase, the vascularization of the region is practically non-existent, the virus remains without replicating and the thermal pattern that we find is normothermic. These results are preliminary in the relationship of thermography with the human papilloma virus in the feet of athletes.

Once the plantar wart has been identified, the estimated prognosis for its resolution, although it depends on the type of treatment, the extension and age of the virus and the patient's collaboration, ranges from one day to two years. If surgical treatment is performed, the

wart disappears successfully in almost all cases on the same day of the intervention. While, if laser thermal burns are performed, the process usually takes 6 to 8 weeks. In exceptional cases, such as immunosuppressed patients, the treatment period will be longer, but in the worst case, it should resolve within two years (Witchey et al. 2018).

A clinical case of papilloma in a professional soccer player and its resolution

We present the clinical case of a professional soccer player who was identified by thermography with a papilloma (mosaic type) on the heel of his left foot. Until the moment of the thermogram, the player was not aware of the existence of the papillomavirus, because there was no pain or discomfort associated.

However, and as can be seen in the images in Figure 2, the papilloma, both in the thermogram and in the digital image, showed a highly developed appearance. The thermal alarm was reported to the medical staff, who prematurely referred him to a specialist for treatment.

Figure 2. Thermal and digital images of the papilloma in its first evaluation. Property of ThermoHuman.

In the thermal image, we can observe a clear hyperthermia in the left foot that is corroborated by the software data, showing an asymmetry of 4.47ºC in the affected region.

The treatment consisted of an invasive approach and lasted for more than 7 months, during which the expert performed chemical burns with nitric acid and periodic delamination, on a monthly basis.

In cases like this one, recovery is very slow and requires special care since it can cause discomfort associated with the treatment, which in the case of soccer players or athletes can be especially bothersome because it is located on the sole of the foot. In addition, the team must be notified, so that the necessary measures are taken in order to prevent the spread to other players.

Figure 3 shows the evolution of the asymmetries in the avatars, as well as the thermal images and the evolution graph. We can see how throughout those seven months, the treatment was effective and the asymmetry gradually decreased.

Figure 3. Avatars with the average temperature asymmetries, thermograms and evolution of the asymmetries of the medial heel of the foot, illustrating the evolution of the papilloma treatment from the initial asymmetry of 4.47ºC to 0.31ºC. Images analyzed with ThermoHuman software.

Another clinical case of papilloma in a professional soccer player and its resolution

On this occasion, we present a very interesting case study: the differentiation of the three types of hyperthermic asymmetries that can occur in a thermographic image, through the clinical analysis of the specialist in podiatry (Figure 4). Together with a clinical assessment and complemented with other technologies, such as pressure platforms, they can help the specialist to assess the patient in the best way.

This is a player with discomfort in his right sesamoid. When the clinical examination is carried out, a hyperkeratosis is observed in that region, but in addition, black marks are detected on the heel, characteristics of the papilloma, which the player was unaware of.

When the thermographic image is performed, three types of hyperthermic asymmetries can be seen:

1. In the sesamoid region there is a hyperthermic asymmetry, produced by hyperkeratosis and because it is an area with greater pressure during walking.
2. In the region of the plantar fascia, as a result of the type of gait that overloads the sesamoid due to blockage of the sagittal plane, there is greater work that increases the temperature of the region, producing a hyperthermic asymmetry. This could be the origin of a plantar fasciopathy, as well described by Dr. Antonio Gómez Bernal in his article on fasciitis and thermography (Gómez-Bernal et al. 2021).
3. In the region where the papillomavirus is located, we observe a hyperthermic asymmetry due to the infection.

Figure 4. Digital image, thermogram and avatar of a soccer player with different asymmetries produced by: hyperkeratosis, greater mechanical load and papillomas. (Property of ThermoHuman)

Conclusions

Infrared thermography is confirmed as a useful and objective tool to support the diagnosis of human papillomavirus (HPV). As we have shown in previous cases with support in emergency triage in the identification of appendicitis, diagnosis support of neuropathies that can be confused with plantar fasciitis or to rule out major complications such as the case of patella fracture, can be very useful to support professionals in their clinical diagnosis processes, opening new lines of research to relate thermography with podiatry.

References

Gómez-Bernal A, Fernández-Cuevas I, Alfaro-Santafé J, Pérez-Morcillo A, Almenar-Arasanz A. Uso de la termografía infrarroja para determinar el perfil térmico de la planta del pie en pacientes con fasciopatía plantar: estudio transversal. Rev Esp Pod 2021; 32(2): 93-98

Guzmán-López S, Barboza-Quintana O, González-Ramírez RA. Biología del Virus del Papiloma Humano y técnicas de diagnóstico. Medicina universitaria. 2010;12(49):231-38.

Johnson LW. Communal showers and the risk of plantar warts. J Fam Pract. 1995 Feb;40(2):136-8.

Witchey DJ, Witchey NB, Roth-Kauffman MM, Kauffman MK. Plantar Warts: Epidemiology, Pathophysiology, and Clinical Management. J Am Osteopath Assoc. 2018 Feb 1;118(2):92-105.

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