Bizarre patient: Fluorescent blue pimples on child’s skull

A 6-year-old boy comes to a dermatology clinic with his parents. The scene takes place in Hangzhou, China.. The child does not stop scratching his head and for good reason, he has had a skin rash on his face and on his back for more than three months. skull. The itching are so intense that he is losing his hair in patches. At first glance, it only seems to suffer froma skin condition such as eczema where the psoriasis.

But two signs lead doctors on another track. The boy has the lymph nodes located just behind the ears swollen, a sign that it is an infection. But above all, the pimples that dot his skull glow fluorescent blue when observed under the light UV. There is no doubt about the diagnosis: the boy has capillary ringworm (Tinea capitis). It remains to discover the microorganism who originated it.

On the left, the blue pimples on the child’s scalp and on the right, the microscopic fungus responsible for his condition. © Tingting Wang and para. NEJM

A little fungus in the hair

A small sample of hair dipped in hydroxide potassium will reveal the culprit. The sample is passed under a light microscope and the doctors observe small blue organisms, segmented in the shape of worms. It is not a bacterium or a parasite but of thehypha ofa microscopic fungus from the dermaphyte family: Microsporum canis. L’species is confirmed by molecular biology tests.

As its name suggests, Microsporum canis infect the dogs, but also cats and other pets. the mushroom is responsible for 90% of cases of ringworm contracted by our four-legged friends. Animals contaminate humans, especially children under 12, through direct contact or via fungus-carrying hairs. Mr. canis attacks the keratin which forms the hair, thus causing a alopecia sometimes irreversible. L’inflammation local that it provokes assaults theepidermis which peels.

The young patient was therefore infected by a contaminated animal, but his family does not have any pets. On the other hand, he could have been in contact with a dog during a stay in the countryside a few months earlier and which coincided with the appearance of the first symptoms. Dermatophytosis can be treated with molecules antifungals – here terbinafine orally and in topical cream – which prevent the synthesis of the main constituent of plasma membrane of the fungus, which is essential for its survival. All’s well that ends well for the young patient since six weeks of treatment allowed him to get rid of the infection and he did not relapse.