This month’s news from across the specialty
What’s hot
July 1, 2024
In this monthly column, members of the DermWorld Editorial Advisory Workgroup identify exciting news from across the specialty.
Is topical 5-fluorouracil toxic to our pets? The answer is yes, as explained by Young et al in their JAAD article ‘5-fluorouracil toxicosis in our pets: a review and recommendations’ (doi:10.1016/j.jaad.2023.12.058). Commonly prescribed for at-home treatment of actinic keratoses in a 40g tube, 5-FU may be left in areas accessible to pets. As dermatologists, we may fail to educate our patients about this risk. The most common form of ingestion is biting of the tubes, but licking of the tubes and of patients’ arms can also result in toxicity. Mechanism of toxicosis results from 5-FU’s ability to disrupt DNA replication and repair. Clinical symptoms may occur within 30 minutes of ingestion, and include seizures, vomiting, and bloody diarrhea indicative of gastrointestinal hemorrhage. How much 5-FU would a pet have to ingest? A small, medium, and large-sized pet would only have to ingest 1.2g, 5g, and 10g, respectively, to reach lethal doses. Pet fatalities due to 5-FU have increased over the recent years and are very likely underreported. The authors recommend that we inform our patients of the risk and instruct them to store their tubes away in safe places in order to prevent accidental exposures.
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Erythema marginatum is classically associated with rheumatic fever — a delayed sequela of Streptococcus pyogenes infection (JAAD Int. 2024. April 18;16:75-6). Erythema marginatum is classified as one of the major criteria in the diagnosis of rheumatic fever, seen in <6% of cases.
Urticaria affects 15-25% of the population at some point in their lifetime and is often associated with a bacterial or a viral infection. Streptococcal infection is reported as the cause of 17% of urticaria cases in children — the population most affected by rheumatic fever. The paucity of cases of erythema marginatum reported with rheumatic fever is most likely due to the indistinguishable presentations between erythema marginatum and urticaria, a common occurrence secondary to streptococcal infection. Erythema marginatum and urticaria are both characterized as a transient, migratory, annular, and polycyclic, erythematous eruption. While some describe the defining feature between erythema marginatum and urticaria to be the absence or presence of pruritus, respectively, this is not universal, as cases of erythema marginatum with pruritus have been described and cases of urticaria without pruritus are not uncommon. Histopathology of both conditions demonstrates a sparse superficial perivascular lymphocytic infiltrate with interstitial neutrophils and eosinophils.
The diagnosis of erythema marginatum is rarely discussed as a diagnostic consideration today due to the rarity of rheumatic fever but is merely accepted as a distinct cutaneous eruption still present in most modern textbooks. Since there are no clinical or histopathologic characteristics specific to either diagnosis that allow for differentiation, it is likely that erythema marginatum and urticaria are the same entity.
The presence of eosinophils in a skin biopsy often prompts the thought of an allergic reaction. In contrast, for non-allergic cutaneous reactions, we expect the absence of eosinophils. Unfortunately, the presence or absence of this beautiful bilobed cell with shiny red granules may not always be so important. Two recent articles in dermatopathology collected data from the existing literature on eosinophils in inflammatory dermatoses. A systematic review examined the presence of eosinophils in psoriasis. Eosinophils were detected in approximately half of the published cases of psoriasis in variable quantities (doi: 10.1111/cup.14604). Sanchez et al studied this cell in traditionally eosinophil-poor skin diseases (Am J Dermatopathol. 2023. 45: 820-1). They found the presence of increased eosinophils in psoriasis, pityriasis rubra pilaris, lichen sclerosus, hypertrophic lichen planus, and oral lichen planus. All authors concluded that the presence of tissue eosinophilia alone should not be used to exclude one of these inflammatory conditions.
More What’s Hot!
Check out more What’s Hot columns from the DermWorld Editorial Advisory Workgroup.
My professional relationship with measles has been exclusively adjectival. I’ve seen plenty of “morbilliform” — that is, measles-like — rashes, but not measles itself.
That could change.
In 2000, measles in the U.S. was declared eliminated, meaning there were no locally acquired cases, just “imported” cases among persons visiting the U.S. (When a disease is eradicated, by contrast, there are no cases worldwide — think smallpox.) Two prolonged outbreaks in 2019, among under-vaccinated communities in New York, however, prompted CDC to review measles cases since then.
From January 2020 through March 2024, 338 cases were reported — 13 in 2020, 170 in 2021, 121 in 2022, and 58 in 2023. The 97 cases reported from January through March 2024 represent more than a 17-fold increase compared with the mean number of first-quarter cases during the prior three years.
Patient median age was three years (range 0-64 years), and nearly 60% occurred in people 19 years old or younger. Nearly 70% were unvaccinated, and nearly 25% had unknown vaccination. Some 96% of U.S. cases were associated with imported measles; of those, 61% occurred among U.S. residents who were unvaccinated (although eligible for vaccination) or had unknown vaccination status.
Measles in the U.S. is technically still considered eliminated but increases in measles incidence globally combined with decreasing vaccination coverage in the U.S. and elsewhere threatens that status. While public health agencies focus on increasing vaccination rates and ensuring adequate disease surveillance, clinicians should be vigilant for morbilliform rashes that are truly measles.
