Phalangeal microgeodic syndrome: a paediatric case series.

We present the clinical and radiological characteristics of phalangeal microgeodic syndrome in a cluster of five children during the second peak of COVID-19 pandemic in the UK. Each child presented with phalangeal swelling and erythema, prompting a comprehensive multi-disciplinary team review to analyse the clinical presentation, blood test results and imaging. The cohort's average age was 14.1 years, ranging from 10.4 to 16.6 years, with two girls and three boys. Four children experienced phalangeal involvement in the hands, whilst one was affected solely in the feet. A rheumatological work-up was performed for all. Hand X-rays performed on three children revealed distinct radiographic features like microgeodes, subperiosteal bone resorption and rarefaction in two cases. However, further MRI showed extensive changes closely correlated with the clinical signs of cutaneous vasculopathic rashes. The MRI abnormalities were notable, encompassing marrow oedema primarily affecting metaphyses and epiphyses, displaying broad transition zones. Soft tissue swelling and cortical erosions were also observed. These MRI features proved more pathognomonic in the acute clinical context. The study concluded that phalangeal microgeodic syndrome, characterised by digital swelling and erythema, might not be adequately assessed by plain X-rays. The more comprehensive MRI features, including marrow oedema and soft tissue abnormalities, appeared to be more indicative in diagnosing the condition. Considering the rarity of this syndrome and its temporal association with the COVID-19 pandemic, the study hypothesised that COVID-related thrombophilia and immune-mediated vasculopathy might act as crucial triggers for the active bony manifestations seen in this syndrome. KEY POINTS: • PMS is a rare, predominantly paediatric condition, of unknown aetiology which affects the digits. • Laboratory investigations are generally negative; however, in the appropriate clinical context, the X-ray findings of microgeodes and pattern of bone marrow oedema seen on MRI are pathognomonic. • Considering the rarity of PMS and temporal association with the COVID-19 pandemic, COVID vasculopathy may represent a previously unrecognised aetiology for PMS.