Popliteal artery entrapment syndrome is an important, albeit infrequent, cause of severe disability among young adults and athletes with anomalous anatomic relationships of the musculotendinous structures surrounding the popliteal artery. We report a case where duplex ultrasonography and dynamic magnetic resonance arteriography was used to diagnose popliteal artery entrapment. We used a posterior surgical approach to give the best view of the anatomic structures compressing the popliteal artery. Compression had not yet damaged the arterial wall, therefore operative decompression of the artery by resection of the aberrant muscle was sufficient. The result was complete recovery, with absence of symptoms and with patency verified by Doppler examination. We conclude that emergency physicians who encounter young patients with progressive lower limb arterial insufficiency should be aware of the possibility of popliteal artery entrapment. Early diagnosis using physical examination, history taking, and imaging is necessary. The treatment of choice is surgical correction to achieve normal anatomy within the popliteal fossa.

We report the first fatality caused by novel influenza A (H1N1) infection despite having the diagnosis confirmed and being given antiviral treatment after hospitalisation. This patient was also the first with influenza A (H1N1) to be supported with extracorporeal membrane oxygenation in Hong Kong. Although extracorporeal membrane oxygenation is an effective means of supporting patients with refractory hypoxaemia on high mechanical ventilatory support, it is labour-intensive and technically demanding. We also discuss the challenges faced when managing this case.

Kearns-Sayre syndrome is a rare disorder often caused by mitochondrial DNA rearrangement. The most commonly reported mitochondrial DNA deletion is 4977 bp in size spanning nucleotides 8469 and 13447. The clinical signs of Kearns-Sayre syndrome include chronic progressive external ophthalmoplegia, retinitis pigmentosa, heart block and cerebellar ataxia, as well as other heterogeneous manifestations including neuromuscular problems and endocrine disorders. Cardiac conduction defects can develop insidiously, leading to sudden death sometimes if not promptly recognised. This report focuses on the diagnosis of Kearns- Sayre syndrome in a Chinese girl who presented initially with short stature, delayed puberty, insidious onset of ptosis and later with typical features of Kearns-Sayre syndrome including complete heart block. Genetic analysis disclosed a novel 7.2 kilobases deletion in muscle tissue. Mitochondrial diseases have heterogeneous phenotypes and mutational analysis has proven to be an effective tool for confirming the diagnosis.

Hereditary spastic paraplegias are a heterogeneous group of chronic central motor system disorders, characterised by progressive lower limb spasticity. Hereditary spastic paraplegia is clinically classified into pure and complicated forms, by the absence or presence of additional neurological or extra-neurological features. Hereditary spastic paraplegias follow all modes of inheritance and the pure-form autosomal dominant type is the one most commonly reported. Spastic paraplegia 4, autosomal dominant (SPG4, MIM#182601) and spastic paraplegia 3, autosomal dominant (SPG3A, MIM#182600), account for most autosomal dominant hereditary spastic paraplegias. Using DNA mutation analysis, the authors identified an SPG3A missense mutation (p.R239C) in a Chinese family where three members have early-onset pure spastic paraplegia. To our knowledge, this is the first report of a gene mutation in hereditary spastic paraplegias in our locality. DNA-based diagnosis plays a key role in the early diagnosis of familial hereditary spastic paraplegias.

Orbital vascular malformations usually present with proptosis. We report a case where a patient with an orbital venous malformation presented with enophthalmos. Since many underlying orbital pathologies, including orbital metastases, can cause enophthalmos, it is important to investigate patients properly. Computed tomographic imaging of the orbit remains the most useful tool in the management of patients with enophthalmos.