Backgrounds:

Pyrexia of unknown origin (PUO) in children remains a clinical challenge. Despite improvements in diagnostic and management approaches, the aetiology of >50% of cases is unknown. We describe our experience of PUO before and during the COVID-19 pandemic.

Methods

Anonymised data from referrals to paediatric infectious disease (PID) services were collected retrospectively between 01/01/2019 – 31/12/2021. Pyrexia of unknown origin was defined as undifferentiated fever for ≥7 days.

Results:

66 patients with PUO were referred over the study period (4.2% of referrals). The majority were from paediatric wards (92.4%), with the remainder from intensive care units (3%), general practitioners (1.5%) and emergency departments (1.5%). 40 (60.6%) were managed locally and of these 5 had PID follow-up, 21 (31.8%) were transferred to our center, 5 (7.6%) were transferred to another tertiary hospital (for services not available at our center e.g. cardiology/rheumatology).

Details of 17 transfers are available in Table 1. The median age was 4 years (IQR 2-9), 10 (59%) were females and 2 (12%) had serious co-morbidities. Identified causes included: infection 5/17 (29%), inflammatory 4/17 (24%) and malignancy 1/17 (0.06%). In 7/17 (41%) no aetiology was found. Of the 45 cases not transferred to our center, identified causes included: infection 3/45 (6.7%), inflammatory 3/45 (6.7%) and multisystem inflammatory syndrome in children (MIS-C) 1/45 (2.2%), with no cause identified in 38/45 (84%).

Conclusions/Learning Points:

Reassuringly, the majority of the persistent fevers in children resolve, even without a specific diagnosis. Of note, there has not been an increase in PUO cases during the COVID-19 pandemic. Finally, in cases where the cause of PUO is identified, infective and inflammatory conditions are most common, highlighting the importance for joint management with rheumatology.