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Mpox: Dermatology registry data pinpoints unique signs



Data from a dermatology monkeypox (mpox) registry reveal that patients struck during the 2022 worldwide outbreak experienced two nontraditional findings: Skin lesions that frequently appeared before systemic illness and a much lower overall numbers of lesions.

“Just these two findings alone show how important it is to remain clinically vigilant as dermatologists,” Esther Freeman, MD, PhD, director of global health dermatology at Massachusetts General Hospital, Boston, said in an interview. She is the corresponding author of the study, which analyzed 101 mpox cases from 13 countries and was published online on in the Journal of the American Academy of Dermatology.

Colorized transmission electron micrograph of monkeypox particles (pink) found within an infected cell (green), cultured in the laboratory. Image captured and color-enhanced. NIAID

“Mpox appeared to manifest differently than in previous outbreaks with morphologic and clinical evolutions much different than previously reported in endemic and prior outbreaks,” added Dr. Freeman. “Dermatologists should continue to keep mpox on the differential as it continues to circulate at low levels in the population and is a mimicker of many other common skin diseases.”

According to the Centers for Disease Control and Prevention, as of Jan. 20, 2023, there have been 30,061 cases of mpox in the United States during the outbreak that began in 2022; 23 people died. Worldwide, the number of cases neared 85,000.

Esther Freeman, MD, PhD, Director, Global Health Dermatology, Massachusetts General Hospital, Boston, and associate professor of dermatology, Harvard Medical School, Boston

Dr. Esther Freeman

Most of the affected cases were among gay, bisexual, and other men who have sex with men. A vaccination effort began last summer, and the number of cases soon plummeted. The national daily case count in January has been in the single digits.

For the new report, dermatologists tracked cases via the American Academy of Dermatology/International League of Dermatologic Societies (AAD/ILDS) Dermatology COVID-19, Monkeypox (mpox), and Emerging Infections Registry. The new report includes data about cases entered from Aug. 4 to Nov. 13. Of these cases, 97% were male, median age was 35 years, 62% were White, 20% were Hispanic, and 11% were Black.

Just over half (54%) of patients reported skin lesions as the first sign of disease, while others had signs such as fever (16%) and malaise (9%). “This is a sharp contrast to endemic or prior outbreaks in which a ‘flu-like’ prodrome preceded lesions,” Dr. Freeman said. “Dermatologists should be aware that patients may come in with mpox skin lesions as their only initial symptoms.”

In contrast to past outbreaks where patients may have had dozens or hundreds of lesions, 20% had only 1 lesion, while 52% had 2-5 lesions, and 20% had 6-20 lesions. “There may be only a few lesions, so index of suspicion needs to be high,” Dr. Freeman said.

According to the study, “the most common skin lesion morphologies and secondary characteristics reported included papules, vesicles/blisters, pustules, erosions/ulcers and crust/scabs.” Dr. Freeman cautioned that “lesions may not go through the ‘typical’ progression from papule to pustule. The initial lesion could even be an ulceration or a crust. For dermatologists, this means you need to have a high index of suspicion, especially if you see a new onset lesion in the groin or perianal area, though they can also start elsewhere.”

She added that “the lesion you see on exam could be a classic pustule/pseudopustule, but it might not be – it could be a small perianal erosion or ulceration. If you have any concern it could be mpox, it’s a good idea to test by PCR.”


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