Monkeypox can 'masquerade' as other conditions, with wide range of symptom severity

As global outbreaks of monkeypox made headlines, Dr. Antoine Cloutier-Blais's Montreal clinic began seeing patients with unusual — and often painful — bodily lesions.

By early June, the family physician and his colleagues had treated around 15 patients with confirmed infections, out of the roughly 100 lab-confirmed cases reported so far in Quebec. People with suspected infections soon started showing up to the clinic on a near-daily basis.

Cloutier-Blais began to notice some interesting trends.

The pox lesions, he found, weren't presenting exactly like what he'd seen in photos circulating online of people infected in parts of Africa, where the virus had been found for decades. 

"Lesions are much smaller and usually very much localized," he said, adding there's also a "very wide spectrum of different kinds of presentations."

In some cases, lesions are showing up on or inside various bodily areas, including patients' mouths, genitals or anal region, sometimes spreading to the limbs or torso or popping up across the entire body.

But for other patients, visible symptoms have been far more subtle — even just a single mark on the skin.

Medical experts in multiple countries are noticing similar patterns. In this unprecedented outbreak — which is offering many global clinicians their first real-world experience with this disease — there's a clear range in severity, from classic full-body rashes requiring hospital stays and pain medication, all the way to instances where monkeypox presents as a mild infection that may be easy to miss or easy to confuse with other conditions.

And while these infections are typically treatable, there's also growing concern this virus could spread into vulnerable populations at a higher risk of life-threatening disease.

Monkeypox often shows up as a flu-like illness, featuring symptoms like fever, chills, and muscle stiffness that can predate the telltale lesions.

Yet, for recent patients in the U.S., the emergence of a rash was often the first warning sign that they were sick. 

"In these new cases, what we're hearing is that those [pre-rash] symptoms might be really mild or not even noticed at all," said Dr. Agam Rao, medical officer of the U.S. Centers for Disease Control and Prevention's Poxvirus and Rabies Branch, during an interview with the medical journal JAMA.

For clinicians unfamiliar with the virus, it may also be hard to differentiate some monkeypox infections from chickenpox — or certain sexually transmitted infections like herpes and syphilis.

"Monkeypox can masquerade as other conditions," said Dr. Rosamund Lewis, a Canadian physician and the technical lead at the World Health Organization (WHO) for the monkeypox outbreak.