A diagnostic challenge: misdiagnosing Blau syndrome as juvenile dermatomyositis in a pediatric patient

INTRODUCTION: Blau syndrome (BS) and juvenile dermatomyositis (JDM) are distinct conditions with different pathophysiological mechanisms. Accurate diagnosis of BS can be challenging due to overlapping clinical features with other inflammatory conditions. This case is being reported to highlight a pediatric case initially diagnosed with JDM, and subsequently found to have BS through genetic testing. CASE PRESENTATION: We present the case of a 4-year-old Arab male initially diagnosed with JDM based on skin manifestations, negative histology for another disease, and no other clinical features suggestive of an alternate diagnosis. However, subsequent symptoms suggestive of BS emerged, leading to genetic testing confirmation of BS, marking the second reported case in the region. This unique clinical scenario highlights the challenges in diagnosing BS and the potential for misinterpretation of the skin rash as JDM. Accurate differentiation between these conditions is crucial to guide appropriate management and prevent delays in treatment. DISCUSSION: The diagnostic process for JDM involves clinical evaluation, laboratory investigations, imaging, and biopsy findings. However, muscle biopsy may yield false-negative results. BS has been misdiagnosed as other conditions, such as Kawasaki disease and juvenile idiopathic arthritis, due to overlapping clinical features. This case highlights the significance of a thorough diagnostic strategy for BS that takes into account any potentially negative histopathology findings. A precise diagnosis is essential since misdiagnosis can result in inadequate or delayed therapy. CONCLUSION: The diverse presentation of the skin rash in BS can pose difficulties for physicians in distinguishing it from other pediatric rheumatological conditions, such as JDM.