Mpox (Monkeypox) with atypical clinical presentation and distinctive dermoscopic findings

Dear Editor, Mpox (formerly known as monkeypox), a zoonotic disease caused by the monkeypox virus, has caused recent global outbreaks.[1,2] The initial clinical presentation of mpox may manifest with nonspecific symptoms, which may result in delayed diagnosis. Herein, we report a case of mpox with an atypical clinical presentation and the “rising sun” sign observed on dermoscopy. A 44-year-old Taiwanese man, who has sex with men (MSM), presented with a 1-week history of fever, headache, sore throat, and left neck pain and a 4-day history of itchy rash on the limbs. His medical history includes human immunodeficiency virus (HIV) infection, which is being managed with emtricitabine/rilpivirine/tenofovir/alafenamide. He had recently received a diagnosis of acute tonsillitis at the otolaryngology clinic and was treated with amoxicillin/clavulanic acid. However, the symptoms did not improve, and a few vesiculopustular lesions developed on the distal parts of the limbs, starting from the left palm and progressing to the left forearm and legs. Physical examination showed exudative and swollen left tonsil, tender left cervical lymphadenopathy, and asynchronous skin lesions comprising crusted lesions on the left palm and forearm and pustules with perilesional erythema on the left hand and legs [Figure 1a-f]. Polarized dermoscopic examination revealed homogeneous brownish coloration for the left palm-crusted lesion, brown-to-red central crust with peripheral erythema for the left forearm-crusted lesion, and central homogeneous yellow area surrounded by bright erythematous halo (resembling “rising sun”) for pustules on the left hand and legs [Figure 2a-f]. The torso and anogenital region were spared.Figure 1: Clinical images. (a) Swollen left tonsil with whitish-yellow exudate was noted on examination of the oral cavity. (b and c) Crusted lesions on the left palm and forearm. (d-f) Pustules with perilesional erythema on the left hand, ankle, and bilateral knees.Figure 2: Polarized dermoscopic images. (a) Homogeneous brownish coloration for the left palm-crusted lesion. (b) Brown-to-red central crust with peripheral erythema for the left forearm-crusted lesion. (c-e) Central homogeneous yellow area surrounded by bright erythematous halo for pustules, resembling “rising sun,” on the left hand, ankle, and knee. (f) Homogeneous yellow coloration with a central crust and mild peripheral erythema for the pustule on the right knee.Travel and contact history revealed that the patient had not traveled abroad recently but had engaged in unprotected oral sex with another man 2 weeks before the onset of the symptoms. Laboratory analysis revealed leukocytosis (13610/ul), elevated C-reactive protein level (15.49 mg/L), and a normal CD4 cell count (1003 cells/mm3). The HIV viral load was undetectable. Serological tests for herpes simplex virus (HSV), varicella-zoster virus, and syphilis were negative. Due to suspicion of mpox based on clinical features and epidemiologic criteria, real-time polymerase chain reaction tests on viral swabs from the pharynx and vesiculopustular fluid were conducted. The results confirmed the diagnosis of mpox (the cycle threshold (Ct) values were 36 and 24, respectively). He was then admitted to a negative pressure isolation room, and supportive care was provided. No new-onset vesiculopustular lesions were seen thereafter. All skin lesions had become crusted 2 weeks after admission, and the patient was discharged. Mpox is characterized by a prodromal phase of fever, constitutional symptoms, and lymphadenopathy, followed by an eruptive phase of centrifugally evolving macules, papules, vesiculopustules, crusted lesions, or ulcers, which can present simultaneously or at different stages of evolution.[1–4] The most frequently affected cutaneous areas include the anogenital area, followed by the trunk/limbs, face, and palms/soles.[1,2] Mucosal lesions occurred in approximately 41% of patients, mostly presented in the anogenital area.[1] Oropharyngeal symptoms, such as oral or tonsillar lesions and pharyngitis, as presenting symptoms are uncommon, observed in only 5% of patients.[1] Mpox is mainly transmitted through sexual close contact with infected individuals, especially MSM.[1,2,5,6] In our patient, the prodromal symptoms of sore throat with left cervical lymphadenopathy may suggest that the virus enters oral epithelial cells through receptive oral sexual exposure and then replicates in the cervical lymph nodes with subsequent hematogenous dissemination to develop skin lesions. This may explain the reasons for sparing the anogenital area (the most common site) and initial presentation mimicking acute tonsillitis. Cutaneous manifestations occur in 95% of patients with mpox.[1] The number of skin lesions ranges from a few to hundreds, which may increase over time.[1–3] In this patient, the number of skin lesions was scarce and the first lesion arose on the palm (the least common site), thus posing a diagnostic challenge to clinicians. Some diseases may present similar acrally distributed or widespread vesiculopustular eruptions and should be considered differential diagnoses. These include hand-foot-and-mouth disease, orf disease, pompholyx, palmoplantar pustulosis, HSV infection, varicella, syphilis, and nodular scabies.[2,3,5,7] The dermoscopic features of mpox have been previously reported, including diffuse bright white structureless area for vesiculopustular lesions and yellow-to-brown central umbilication/crust surrounded by bright whitish structureless halo for umbilicated pustules or crusted lesions.[4,5] In this patient, we propose that the distinctive dermoscopic “rising sun” sign for the pustules of mpox, characterized by a central homogeneous yellow area surrounded by a bright erythematous halo, is a potential diagnostic hallmark for mpox, as this pattern does not appear in other vesiculobullous disorders.[8] This case highlights that the initial clinical presentation of mpox may be atypical. The detection of centrifugal asynchronous skin lesions with lymphadenopathy and the characteristic dermoscopic “rising sun” sign for pustules may assist the diagnosis. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed. Data availability statement Data sharing is not applicable to this article as no datasets were generated or analyzed during the current study. Financial support and sponsorship Nil. Conflicts of interest Prof. Cheng-Che E. Lan and Prof. Stephen Chu-Sung Hu, editorial board members at Dermatologica Sinica, had no roles in the peer review process of or decision to publish this article. The other authors declared no conflicts of interest in writing this paper.