The "reversed halo" sign in pneumonococcal pneumonia: a review with a case report.

The "reversed halo" sign (RHS) is a distinct radiological sign representing a focal rounded area of ground-glass opacity surrounded by a more or less complete ring of consolidation. Initially, it was reported in two cases of cryptogenic organizing pneumonia and was considered to be relatively specific of the disease. Since then, it has been reported in a wide variety of clinical entities, thus reducing its specificity. We describe the reversed halo sign in a case of pneumonococcal pneumonia. To the best of our knowledge, this is the first report in English literature. The presence of the "reversed halo" sign during the resolution phase of pneumonococcal pneumonia has serious implications. First, it further reduces its specificity. Second, it opens new areas of research regarding its significance in cases of cryptogenic organizing pneumonia.

A rare cause of dysphagia--aberrant right subclavian artery (ARSA).

Aberrant Right Subclavian Artery (ARSA) is a rare vascular anomaly. It is though the most frequent anomaly involving the aortic arch, being present in about 1% of the general population. We present a case of a 71 year old male with symptoms of chronic cough and dysphagia. He was referred to our clinic for further evaluation of a mediastinal mass. A second Computed Tomography of the thorax was performed, this time with the use of i.v. contrast. The latter examination confirmed the diagnosis (ARSA), sparing the patient of invasive and potentially life threatening diagnostic procedures (invasive angiography, mediastinoscopy). This case highlights the significant pitfalls regarding the mediastinal evaluation, especially when i.v. contrast is not used. The majority of the mediastinal structures are vessels. Vessels abnormalities should be included in the differential diagnosis of a mediastinal mass.

A 77 year old male with peripheral eosinophilia, pulmonary infiltrates and a small pleural effusion.

The presence of peripheral eosinophilia with lung infiltrates poses a diagnostic challenge for the clinician. The differential diagnosis includes a wide spectrum of diseases. In some of them (for example vasculitis, lymphoma) eosinophilic pneumonia represents just another "symptom" and not the final diagnosis. A thorough diagnostic procedure is required to examine all related clinical entities in order to establish a firm diagnosis. In particular, Idiopathic Chronic Eosinophilic Pneumonia (ICEP) is a rare disorder. In the majority of cases, it is characterized by peripheral eosinophilia, lung infiltrates, bronchoalveolar lavage eosinophilia (above 25%), exclusion of other possible causes and last but not least an impressive improvement under steroid therapy. Relapses are common but they do not seem to be related with ICEP associated mortality.

NMR studies on truncated sequences of human telomeric DNA: observation of a novel A-tetrad.

The structure of the telomeric DNA has been a subject of extensive investigation in recent years due to the realization that it has important functional roles to play in vivo and the observations that truncated telomeric sequences exhibit a great variety of 3D structures in aqueous solutions. In this context, we describe here NMR structural studies on two truncated human telomeric DNA sequences, d-AG(3)T and d-TAG(3)T in solutions containing K(+)ions. The G(3)stretches in both the oligonucleotides were seen to form parallel-stranded quadruplexes. However, the AG(3)segment as a whole, had different structural characteristics. The structure of d-AG(3)T revealed the formation of a novel A-tetrad, which was not seen in d-TAG(3)T. The A's in the tetrad had syn glycosidic conformation as opposed to the anti conformation of the G's in the G-tetrads. The A-tetrad stacked well over the adjacent G-tetrad and the twist angle at this step was smaller in d-AG(3)T than in d-TAG(3)T. These observations are expected to be significant from the point of view of structural diversity and recognition in telomeres.