A 72-year-old male, originally from the Dominican Republic and residing in Spain since 2014, attends a specialised clinic for sexually transmitted infections (STIs) in the Community of Madrid, referred from Primary Care for ulcerated and painful lesions in the genital region of four days' evolution. He lives with his wife, who has no symptoms, and reports no history of sexually transmitted infections, recent risky sexual relations, or drug use or pre-exposure prophylaxis (PrEP).
Physical examination reveals grouped erythematous papules at the base of the penis, scrotum and groin, along with confluent, raised, annular ulcerated plaques located on the dorsum of the penis (Fig. 1). Additionally, a single, exudative, ulcerated plaque is identified in the posterior region of the penis. No palpable inguinal lymphadenopathy, oral mucosal involvement, or internal genitalia involvement were detected. There is no fever, urethral discharge, or general malaise.
A sample is taken for genital ulcer PCR (Allplex™ Genital Ulcer Assay, Seegene) and specific PCR for Monkeypox virus (Monkeypox Virus Real Time PCR Kit, Bioperfectus). Serological testing for HIV, syphilis (RPR, TPHA) and hepatitis B, C and A viruses is performed using automated chemiluminescence immunoassay (CLIA) platforms ARCHITECT® (Abbott). Given the morphology, location and pain of the lesions, the initial suspicion was of herpes simplex virus (HSV) infection, which is why empiric treatment was prescribed with valacyclovir 1 g every 12 h for 10 days, along with topical antiseptic care.
Clinical course and diagnosisAfter waiting for the microbiological results, the PCR of the vesicular contents was positive for the varicella-zoster virus (VZV). Serologies for human immunodeficiency virus (HIV), syphilis (RPR, TPHA) and hepatitis C virus were negative, except for the total anti-core antibody (Anti-HBc) which was positive (22.38 IU/L), with HBsAg and anti-HBs negative, in a probable context of resolved infection. The general analysis showed a complete haemogram without significant alterations, except for iron deficiency anaemia (haemoglobin 11.4 g/dL, MCV 75 fL, ferritin 9 ng/mL). No signs of immunosuppression were observed. Biochemistry, as well as the lipid and renal profile, showed values within normal limits.
The antiviral treatment was adjusted to valacyclovir 1 g every 8 h for 10 days. In the clinical review performed five days after the initial diagnosis, new vesicular lesions were observed distributed metamerically and unilaterally in the perineum and right gluteus, corresponding to the sacral dermatomes S2–S3. This clinical evolution reinforced the previously established microbiological diagnosis.
Among the lesions initially observed, an exudative ulcerated plaque in the posterior region of the penis stood out (Fig. 2), which showed improvement after treatment, accompanied by a progressive decrease in pain, with favourable evolution of the rest of the lesions (Fig. 3). No signs of post-herpetic neuralgia were identified. Given the detected iron deficiency anaemia, treatment with oral iron supplements was initiated.
Herpes zoster corresponds to the reactivation of the varicella-zoster virus (VZV)1 from the sensory ganglia, typically manifesting in the distribution of a dermatome. Although it is more common in immunocompromised subjects, it can appear in elderly immunocompetent patients, as in this case.
Involvement of the sacral dermatome (S2–S3) can lead to painful vesicular lesions on the penis, scrotum, thigh, and gluteal region, which could point to a sexually transmitted infection. This presentation can lead to diagnostic error, especially if other lesions outside the genital area are not recognised. It is crucial to make a differential diagnosis between VZV and herpes simplex virus type 2 (HSV-2), as both can present with painful vesicular lesions in the genital region. HSV-2 usually affects the genital mucosa bilaterally, while VZV follows a metameric and unilateral distribution.2 Furthermore, antiviral treatment requires different dosage and duration guidelines, and the risk of complications such as post-herpetic neuralgia is characteristic mainly of VZV.3
Molecular biology techniques are a key tool for aetiological diagnosis in herpetic lesions, as they allow early differentiation with high sensitivity and specificity between VZV and herpes simplex virus (HSV-1 and HSV-2).
This case underscores the importance of having accessible molecular microbiological diagnostic techniques, which help to avoid diagnostic delays, therapeutic errors, and unnecessary complications. Furthermore, it reinforces the value of vaccination in older adults as an effective preventive measure to reduce the incidence and complications of herpes zoster.
Ethical considerationsThis study corresponds to a clinical case and did not require approval from an ethics committee. Informed consent was obtained from the subject for publication of the information and images.
Informed consentThe authors declare that they have the informed consent of the patients for the publication of images and of the article for scientific purposes.
Declaration of Generative AI and AI-assisted technologies in the writing processThe authors declare that no artificial intelligence tools have been used.
FundingThe authors declare that they received no funding to conduct this study.
None.
All authors have contributed substantially to this work, participating in the drafting of the article, the review of its contents, and the final approval of the version that is submitted.
