Hypersensitivity Reactions Associated With Zoonotic Human Sporotrichosis Followed at a Medical Mycology Service in Northeastern Brazil

Zoonotic sporotrichosis has been an emerging disease in the state of Ceará since 2022, with a significant increase in cases over the past two years. Hypersensitivity reactions occur in up to 8% of patients and are observed particularly in milder and localized forms. This study aimed to report sporotrichosis cases that evolved with immunoreactivity manifestations among patients followed at a Medical Mycology Service in Ceará. A cross-sectional study conducted from January 2024 to May 2025. Patients with sporotrichosis diagnosed by microbiological or clinical-epidemiological criteria and presenting signs and symptoms compatible with immunoreactivity manifestations were included. Data were collected through medical record review. Descriptive analysis was performed using EPI INFO software (version 7.2.6.0). Of the 46 sporotrichosis cases identified during the study period, eight (17%) patients presented clinical manifestations of immunoreactivity. Most patients were female (n = 6), with a median age of 50.5 years. Clinical forms included fixed cutaneous (n = 4) and lymphocutaneous (n = 4). All patients had contact with infected cats, including bites (n = 1), scratches (n = 4), and household contact without reported bites or scratches (n = 3). Cutaneous immunoreactive manifestations included erythema nodosum (n = 4), erythema multiforme (n = 3), and one undefined reaction. Additionally, two patients developed bilateral arthritis involving large and small joints. Only one patient with erythema multiforme required hospitalization. Most cases (n = 6) were diagnosed based on clinical-epidemiological criteria. Two patients had Sporothrix brasiliensis isolated from skin tissue fragments. Four patients were treated with corticosteroids, and three experienced spontaneous remission of immunoreactivity. Antifungal treatment duration ranged from 2 to 4 months. The frequency of immunoreactivity manifestations identified at the studied center was higher than that reported in the literature. However, the low rate of fungal isolation in cultures may hinder disease recognition. Further studies are needed to better understand this phenomenon, which has been increasingly observed in Ceará.