<section><h2>Spot Dx — What's causing this swollen eyelid?</h2><p><b>Kaitlyn, 14 years old, presents with two weeks of painless left eyelid swelling. She saw another GP a week ago who prescribed flucloxacillin 500mg qid, but the swelling has worsened. She denies recent trauma. She is generally well, with no systemic symptoms, no past history of note or allergies. She does not use glasses, but vision on the left has become blurry. On examination, she is afebrile. Uncorrected visual acuity is 6/60 on the left and 6/5 on the right. Pupils are equal and reactive. The eyelid is minimally tender and the affected area fluctuant. The orbit appears inferiorly and laterally displaced, and upgaze is restricted. </b></p></section><section><h2>Correct!</h2><p><p>The answer is <b>d.</b> <b style="color: inherit; font-size: 18px; letter-spacing: 0px;">Orbital rhabdomyosarcoma.</b></p><p><span style="color: inherit; font-size: 18px; background-color: transparent; letter-spacing: 0px;">Although infection is the most likely cause of an orbital mass, some key features point away from orbital/preseptal cellulitis and towards malignancy in this case.[1] </span><span style="color: inherit; font-size: 18px; letter-spacing: 0px; background-color: transparent;">These include the absence of ocular discomfort or pain, chemosis, fever or systemic symptoms, which are typical of these infectious causes.[1,2] </span></p><p><span style="color: inherit; font-size: 18px; background-color: transparent; letter-spacing: 0px;">The lack of response to appropriate antibiotics is also a clue to a potential non-infectious cause, although could be due to an atypical or drug-resistant causative organism. Rhabdomyosarcoma is the most common primary orbital malignancy in children, typically presenting in those aged 0-14.[1,3]</span></p><p><span style="color: inherit; font-size: 18px; background-color: transparent; letter-spacing: 0px;">Around 70% of orbital rhabdomyosarcomas are located superiorly or superionasally, leading to downward and lateral globe displacement. They typically present as a rapidly enlarging, painless mass, which may also be associated with ptosis, proptosis and chemosis. Urgent ophthalmological review and orbital imaging is warranted.</span></p><h4><b>Outcome</b></h4><p>CT findings are in keeping with ocular rhabdomyoscaroma, with no sign of local invasion. Excision biopsy confirms the diagnosis. There is no metastatic disease on staging. Kaitlyn is treated with chemoradiotherapy, with good response and retains visual function. There is no evidence of disease recurrence in five years of follow-up.</p></p></section><section><h3>Oops! You got the wrong answer.</h3><p><p><b>Re-read the history and click 'Retake' to try again:</b></p><p>Kaitlyn, 14 years old, presents with two weeks of painless left eyelid swelling. She saw another GP a week ago who prescribed flucloxacillin 500mg qid, but the swelling has worsened. She denies recent trauma. She is generally well, with no systemic symptoms, no past history of note or allergies. She does not use glasses, but vision on the left has become blurry. On examination, she is afebrile. Uncorrected visual acuity is 6/60 on the left and 6/5 on the right. Pupils are equal and reactive. The eyelid is minimally tender and the affected area fluctuant. The orbit appears inferiorly and laterally displaced, and upgaze is restricted. <b><br></b></p></p></section><section><h2>What is the most likely diagnosis?</h2></section>