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To the Editor: The letter by Herbert et al. (Feb. 22 issue) 1 explores persistent false positive results on SARS-CoV-2 rapid antigen tests but overlooks various factors, such as interfering substances and testing conditions. 2 Structural similarities between pathogens such as dengue virus and SARS-CoV-2 imply potential cross-reactivity. 3 The potential for IgM cross-reactivity with rheumatoid factor–positive serum samples was observed in blood tests used to detect IgM SARS-CoV-2 by means of gold immunochromatographic and enzyme-linked immunosorbent assays. 4 SARS-CoV-2 rapid antigen tests differ from antibody tests, with the former identifying SARS-CoV-2 viral proteins and the latter detecting human IgM SARS-CoV-2 antibodies. Thus, the . . .

Caplan syndrome is a rare disorder characterized by the coexistence of pneumoconiosis and rheumatoid arthritis (RA), primarily observed in individuals with silica or coal dust exposure. Data on disease behavior in the context of incomplete or irregular immunosuppressive therapy remain limited. This case report describes a 56-year-old man with a history of mixed dust exposure and smoking who presented with recurrent fever, chest pain, and polyarthralgia. Despite being diagnosed and treated for pulmonary tuberculosis and cryptococcosis, his respiratory and articular symptoms persisted. Serological tests revealed persistently elevated rheumatoid factor (RF) and anticitrullinated peptide antibody (ACPA), while a lung biopsy demonstrated chronic inflammation with carbon deposition, confirming Caplan syndrome. Retrospective analysis indicated that elevations of RF and ACPA preceded observable radiological and pathological changes. Notably, inflammatory markers continued to rise significantly even after infections were controlled and despite only episodic glucocorticoid use. This case highlights the importance of early serological monitoring and comprehensive management in high-risk patients and underscores that, rather than being viewed merely as complications, infections in autoimmune contexts should be recognized as potential triggers and aggravators of immune dysregulation, warranting heightened vigilance in both diagnosis and management.

We analyzed the serum from COVID-19 patients and vaccinated subjects, and found that the specific IgA titer level could be used to assist COVID-19 diagnosis, especially in China.We analyzed the serum from COVID-19 patients and vaccinated subjects, and found that the specific IgA titer level could be used to assist COVID-19 diagnosis, especially in China.

Glasgow Coma Scale 15, blood pressure 135/84 mm/Hg, heart rate 107/min, respiratory rate 23/min, and oxygen saturation 88% in room air. [...]serological tests should be conducted in each patient showing high liver enzymes and the coexistence of the two diseases simultaneously. Footnotes Authorship Contributions Design: S.S.Y., F.K.B., Data Collection or Processing: S.S.Y., F.K.B., Analysis or Interpretation: S.S.Y., F.K.B., Literature Search: S.S.Y., F.K.B., Writing: S.S.Y., F.K.B. Conflict of Interest: No conflict of interest was declared by the authors. Gastrointestinal manifestations of SARS-CoV-2 infection and virus load in fecal samples from the Hong Kong cohort and systematic review and meta-analysis.

Descending necrotizing mediastinitis (DNM) is a severe, life-threatening disease with a high mortality rate resulting from sepsis or other complications. DNM can also be a rare and severe complication of Epstein–Barr virus (EBV) infection in adolescents and young adults but has never been reported in a pre-school child. A 4-year-old girl was admitted to our hospital with a 2-day history of fever and chest pain. Computed tomography (CT) revealed a right sided pleural effusion, fluid collection in the retropharyngeal and mediastinal areas, cervical lymphadenopathy, and marked hepatosplenomegaly. She was diagnosed with empyema, retropharyngeal abscess, and mediastinitis. To improve her dyspnea, a chest tube was inserted, and antibiotic treatment was initiated. Her condition improved temporarily, but on day 5 in our hospital, she developed a fever again. A repeat CT scan showed exacerbation of fluid retention in the retropharyngeal area and the mediastinum, for which she underwent drainage and debridement of necrotic tissue in the retropharynx and mediastinum. The presence of cervical lymphadenopathy and marked hepatosplenomegaly suggested the involvement of EBV. Serological tests for EBV revealed primary EBV infection at the time of the DNM onset. Finally, she was diagnosed with DNM following primary EBV infection. At follow-up 1 year later, she was doing well. The risk of DNM should be recognized in patients, even pre-school aged children, with primary EBV infection.

Canine heartworm disease is a life-threatening disease caused by and is prevalent in Brazil. The standard drug for its treatment, melarsomine dihydrochloride, is a fast-killing organic arsenical chemotherapeutic agent not approved in Brazil. Therefore, an alternative strategy, such as macrocyclic lactone in combination with a tetracycline antibiotic, has to be used. The alternative method is a long-term therapy that could lead to compliance issues during treatment. The aim of this case report is to present a preliminary assessment on the efficacy and safety of an off-label biannual administration of slow-release moxidectin (0.5 mg/kg every 6 months), which is formulated for annual administration (0.5 mg/kg annually). This overdose was chosen to test if moxidectin serum levels could be maintained high enough to harm the worms. It was administered to a 4-year-old female dog in combination with a 30-day doxycycline course. The second dose of moxidectin was administered approximately a week before she gave birth to three healthy puppies. Microfilariae were not detected on day 180 of treatment. Serological tests showed that the worms were eliminated, as two negative antigen tests were obtained 6 months apart (at day 180 and day 360 of treatment). Therefore, the off-label biannual use of moxidectin in combination with doxycycline was effective in eliminating in 360 days and was harmless for the pregnant dog and her offspring, suggesting that this strategy is promising. Although these results are encouraging, further studies are needed to confirm safety and efficacy issues.

The presence of Onchocerca guturosa in cattle is responsible for lesions similar to those observed in cases suspected of brucellosis, however, Onchocerca sp. is not a trade barrier, although it is also responsible for economic losses due to the removal of the affected parts of the carcasses. Brucella sp. is a zoonotic agent transmitted to humans through the consumption of contaminated animal products, the contact with infected animals and the handling of carcasses. This agent is also responsible for non-tariff trade barriers. Cervical bursitis is Brucella sp. suggestive lesions in bovine carcasses that requires laboratory tests to confirm the diagnosis. The objective of this study was to record the co-infection of Brucella abortus and Onchocerca sp. as a first report of co-infection of these two agents in the same lesion. The sample constituted of a nuchal bursitis in the cervical ligament, a suggestive lesion common to these two agents, submitted to histopathology and Brucella spp. isolation in the Brucellosis reference laboratory of the Brazilian Ministry of Agriculture, Livestock and Food Supply. Brucellosis serological diagnosis were also performed in the animal’s serum sample. B. abortus was isolated from the lesion and filarid nematode structures were identified in histopathology. All serological tests were positive for brucellosis. Further studies are needed, however, to understand the co-infection by Onchocerca sp. and B. abortus .