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What caused a 37-year-old man to develop a large nodule on the underside of his penis, and painful, swollen inguinal lymph nodes? That's the question Fabrice Bouscarat, MD, of Bichat-Claude Bernard Hospital in Paris, and colleagues had to answer, as they reported in .

On admission to hospital, the patient said the nodule developed 1 week earlier, shortly after he and his regular male partner had engaged in unprotected insertive anal intercourse. Within a few days, the bump on his penis had turned into an open, festering sore. At the same time, he developed a fever.

"Clinical examination revealed a large genital nodule on a very firm indurated tumoral base under the frenulum, with painful bilateral inguinal lymphadenopathies, foreskin edema, and lymphangitis of the penile shaft," Bouscarat and team noted. There was no evidence of any other lesions on his skin or mucosa.

The patient's medical history included a daily treatment regimen of emtricitabine and tenofovir (Descovy, Truvada) as pre-exposure prophylaxis for HIV.

The patient was started on treatment with amoxicillin/clavulanic acid, based on suspicion of potential bacterial lymphangitis.

Clinicians obtained swabs from the patient's throat and the ulcerated nodule and sent them for analysis. Polymerase chain reaction (PCR) assays of swabs were performed for several possible conditions, including mpox virus, herpes simplex virus (HSV), and varicella-zoster virus.

Findings of the PCR assays of samples from both the genital lesion and throat indicated that the patient did not have HSV or varicella-zoster virus. However, they proved to be positive for mpox (cycle threshold [Ct] 23 and 39, respectively).

Results of blood tests were negative for HIV and syphilis. Clinicians discharged the patient to home, with instructions to remain in isolation and undergo follow-up assessments daily.

Over the following 2 weeks, they noted increasing swelling of the patient's foreskin and shaft with transient worsening of his lymphangitis and phimosis.

The patient's fever had resolved by day 12. However, he developed two vesicles, one on his left hand and the other on his right foot.

On day 14, the team repeated blood tests and obtained swabs of the patient's throat, and the lesions on his penis, hand, and foot. Mpox PCR assay results were negative for the throat and blood samples, slightly positive for the cutaneous lesions (Ct 35), and still highly positive for the genital primary lesion (Ct 18), Bouscarat and colleagues noted.

On day 28, they said that with the exception of the genital lesion, the vesicles on his hand and foot had healed completely. The nodule on his penis had receded to some degree, although there was persistent ulceration, and PCR genital test results remained positive (Ct 32) for mpox.

The nodule regressed completely over the course of the following 3 weeks.

Discussion

Characteristic features of the classic form of mpox infection include transmission primarily within families, and a course of progression from a prodromal stage to a phase of eruption on the face and extremities marked by centrifugal distribution.

"The typical evolution is characterized by the occurrence of vesicles or pustules with secondary umbilication, erosions, and crusts," Bouscarat's group explained.

The recently reported new clinical-epidemiologic form of mpox differs from the classic form in several ways, they noted. They cited an of 54 patients with no links to mpox-endemic areas who attended sexual health clinics in London from May 14-25, 2022 (when mpox infections began to be reported worldwide). All self-identified as men who have sex with men, and all infections involved skin lesions, of which 94% were anogenital; the lesions occurred in more than one site in 89% of those affected.

Two other studies of mpox virus infection have reported that 11.2% have presented with a solitary lesion, and 10.8% with a as the only skin manifestation. Bouscarat and colleagues noted that this "highlights the risk of misdiagnosis with other sexually transmitted infections."

Immunocompromised individuals with a viral infection may be especially likely to present with chronic pseudotumors, the authors said. Although tumor-like lesions have occurred in the presence of HSV infections, other human-transmitted poxvirus infections such as have rarely involved acute or subacute pyogenic granuloma-like nodules, they wrote.

"To our knowledge, pseudotumoral lesions have not been described as an initial manifestation of MP [mpox] virus infection and should be added to the clinical spectrum," Bouscarat and co-authors concluded. of the early presentations of this latest form of epidemic mpox virus is "fundamental" to accurate and timely diagnosis.

Along with early diagnosis, isolation of infected individuals and counseling regarding post-exposure prevention with vaccination for partners are vital to avoid the spread of the virus and to contain the epidemic, they added.

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