Antithrombin III deficiency: decreased synthesis of a biochemically normal molecule

A 29-yr-old white female has suffered from recurrent venous thromboses over the last 12 yr. Plasma antithrombin III (AT-III) levels were 48% of normal by immunoelectrophoresis and 56% by chromogenic assay. Three of four siblings and the father had similar AT-III levels without associated venous thromboses. Heparin-Sepharose chromatography demonstrated normal behavior of the patient's AT-III. Her purified AT- III could not be distinguished from AT-III purified from a normal control either by SDS polyacrylamide gel electrophoresis or by crossed immunoelectrophoresis, and the heparin cofactor activity and the progressive antithrombin activity of both AT-III samples were identical. Turnover studies were made in the patient using her own purified AT-III labeled with 131I, (*I). The results did not differ significantly from studies made with autologous *I-AT-III in two normal control women. Her fractional breakdown rate of 0.54 total plasma AT- III per day compared with 0.45 and 0.52 in the controls. These studies indicate that the patient synthesizes a normal AT-III molecule at half normal rates.     

MR imaging in infants with airway obstruction: preliminary observations

Magnetic resonance (MR) imaging of the trachea and main bronchi was performed in seven infants (aged 3-15 months) with symptoms of airway obstruction. Diagnoses made clinically, radiologically, and by transnasal flexible fiberoptic endoscopy included vascular ring (one patient), tracheal compression by the innominate artery (five patients), and tracheomalacia (one patient). MR images in sagittal and axial sections clearly demonstrated tracheal compression at the level of the innominate artery in three infants and tracheal narrowing due to a vascular ring in one patient. The other three patients had airway narrowing apparently unrelated to aberrant vascular structures on MR images. The appearance of the airways on MR images corresponded closely to endoscopic observations. It is concluded that MR imaging is capable of demonstrating airway obstruction in infants and delineating any relationship to major mediastinal blood vessels.