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when a patient walks into the outpatient clinic, a wrapped red line suddenly grows on his ankle?

immediately afterwards, the treating doctor was shocked to discover:this crooked and creeping "thread" is alive and is constantly crawling inside the skin...

the moving "red line"

in the clinic, a 7-year-old child was a little restless in front of the doctor - there was a "red line" on his left ankle, accompanied by severe itching.

this "red line" suddenly appeared in just 3 days.

3 days ago, the child suffered from sudden severe itching on his left ankle, accompanied by scratching, and a vague "scratch" appeared on the itchy area;by the next day, the itching sensation had not subsided, and the originally vague "scratches" seemed to be alive, gradually becoming more obvious and red, turning into a dark red line that completely wrapped around the ankle.

the "red line" on the child's ankle, source: reference 2

after careful inspection, the doctor found that this "red line" accompanied by itching extended from the upper surface and inner side of the left foot to the sole. the surrounding skin was slightly edematous, but there was no tenderness.

according to the description of the family, the child had not been bitten by insects or animals recently, and the affected area was indeed smooth with no signs of bites. the doctor ruled out an inflammatory reaction caused by insect bites.in addition, the child in front of him had a rosy complexion, was fully vaccinated, and had no swollen lymph nodes throughout his body. the auxiliary examination results returned later also showed that the complete blood cell count was normal, and there were no abnormalities in various system examinations.

at a loss, the doctor returned to the original point: severe itching and mysterious red lines, all of which started 3 days ago. so i asked the child again carefully about the details of his life that day.

the family members began to carefully recall the child's itinerary. when they mentioned that the child had played barefoot with his companions on the beach near their home that day, the doctor immediately became alert: "playing barefoot on the beach?"

it turned out that the patient's family lived on the outskirts of the city, surrounded by a small unattended beach. adults didn't care, but it was a paradise for local children.the beach is littered with garbage and no one cleans it regularly. occasionally, you can see some excrement from cats, dogs and other animals...

at this point, the treatment team suddenly understood the child’s diagnosis: cutaneous larvae migrans (clm).

larva "map" discovered over a hundred years ago

clm is a zoonotic disease caused by hookworm larvae. the main hosts of hookworms are dogs, cats and other animals, where they develop and grow into adult worms in their small intestines. when the feces of hookworm-infected animals is buried in the soil, the eggs can develop into larvae in 2 to 9 days.

when humans happen to step on or touch contaminated soil, the sharp heads of hookworm larvae can penetrate the top layer of skin and burrow into human skin.

the morphology of adult hookworms and their comparison with matchsticks (the larvae are smaller), source: references 1 and 3

"clm is a relatively rare skin disease, mainly caused by the larvae of certain nematodes, flukes or tapeworms that are parasitic in cats, dogs and other animals, which invade human skin and migrate." feng xinyu, associate researcher at shanghai jiao tong university school of medicine, said, hookworm disease is endemic worldwide and is widely distributed in tropical and subtropical regions.

"in our country, except for a few northwest regions, all other provinces are endemic due to ancylostoma americanus and ancylostoma duodenale."

patients with clm typically present with progressive itching and a map-like erythematous creeping rash.this is because after hookworm larvae enter human skin, they will move under the skin and form tunnels, constantly causing inflammatory reactions and forming single or multiple traces, which can move up to 1cm per day.

map-shaped erythematous creeping rash, source: reference 1

according to previous literature reports, clm has been discovered by the medical community for more than 100 years. the most common symptoms among patients are foot lesions caused by stepping on contaminated soil like the child who was treated this time, but it may also be possible. affects any other part of the body such as the buttocks, thighs, abdomen, or tongue, etc.

"hookworm cases are still reported in some areas of my country, and unlike other parasitic diseases where the disease is mainly transmitted through the mouth, the main route of infection for hookworm is through the skin."li tong, chief physician of the department of infectious diseases at beijing you'an hospital affiliated to capital medical university, once said that especially in rural areas, children are prone to infection through skin contact with pollutants.

a medical team once reported a case of extensive truncal clm in a 9-month-old baby in bmj. the baby developed itching and slowly progressing snake-like linear lesions on the abdomen and chest. the baby suffered from daily drying of clothes on the grass and contact with contaminated soil. lead to.

source: bmj, reference 4

clinically, although clm has horrific symptoms, it is usually a self-limiting disease—the hookworm larvae are unable to fully penetrate the skin. larvae that cannot enter human muscle tissue or intestines cannot continue to develop into adult worms in the stratum corneum of the skin and eventually die. patients often recover within 5 to 6 weeks.

but for most patients, intense itching and skin lesions severely interfere with daily activities.if individual patients are not treated promptly, they may develop secondary infections, joint pain, fever, and a weakened immune system. dr. li tongzeng believes: “when encountering typical skin manifestations during consultation, you need to be more vigilant and pay attention to the patient’s epidemiological history.”

in this case, the treatment team gave the child oral albendazole for 3 days, and added antihistamines to relieve the itching. after one week, the child's itching disappeared and the lesions began to subside. the follow-up period of 6 weeks thereafter also continued. maintain medication and eventually recover.