REVIEW ARTICLE Mounier-Kuhn syndrome a case study M J Trollip MMedRad(Ó) PO Box, 1695, Heidelberg, 1438 Clinical information A 21-year-old male presented to the casualty department complaining of swelling of both feet for 2 weeks and persistent headache. On further inquiry he also reported a 3-year his- tory of coughing and a course of treat- ment for tuberculosis during the 6 months immediately preceding this presentation. On examination the patient was found to be dyspnoeic and orthop- noeic with a productive cough and abdominal distension. Anaemia, peripheral oedema and digital club- bing were also noted as well as cyanosis which improved on oxygen. Urinalysis revealed no abnormality. He was apyrexial (36°C), awake and fully oriented. Respiratory system A tachypnoea of 26/min was noted. Bilateral basal crepitations were found and an area of bronchial breathing, dull to percussion, in the left base. No respiratory distress was present. Cardiovascular system The patient's blood pressure was 113/73 mmHg and pulse 120 bpm. A hyperdynamic circulation was found with a loud SI, right ventricular S3 gallop and loud P2. Suspected bruits of mitral and tricuspid valve incom- petence were noted. Jugular venous pressure was raised. The apex of the heart was displaced laterally into the 6th intercostal space. Abdomen Examination revealed ascites and liver enlargement of 2 cm. No rebound tenderness was present. A vasculitic skin rash could be seen over most of the torso and legs. Radiological examination Chest X-ray A grossly dilatated appearance of the trachea and main bronchi was observed. The right lung field showed an interstitial infiltrate including Kerley B lines, and also confluent shadowing in the perihilar areas and upper lobe. Bronchiectatic changes could be seen in the right lower zone. Right apical pleural thickening was present (Fig. I). On the left, lower lobe bronchiec- tasis and volume loss were noted with compensatory hyperinflation of the upper lobe. Blunting of the left costophrenic angle was present with some Kerley B lines. Enlargement of the cardiac shadow was also present 12 SA JOURNAL OF RADIOLOGY • March 2002 Fig. I. The grossly dilated trachea and main bronchi are clearly seen with bronchiectatic changes in the right lower zone. The heart is also enlarged. with prominence of upper-lobe vas- culature. CT chest - high resolution and mediastinal cuts Tracheobronchial ectasia was again observed. The trachea measured 4.13 x 4.65 cm in diameter, while mainstem bronchial dilatation of 2.19 cm and 2.00 cm were noted on the right and left side respectively (Fig.2). Thymic hyperplasia and right jugular prominence could also be seen. The rest of the mediastinum and both hilar regions were felt to be normal. Fig. 2. Marked ectasia of the trachea is clearly seen. Ground-glass infiltrates suggest underlying mfect/on. REVIE\tV ARTICLE A pleural effusion had formed on the right. Volume loss on the left resulted in ipsilateral cardiac shift. Both upper lobes and the middle lobe showed ground-glass infiltrates. Bronchiectasis was confirmed bilater- ally in the peri -hilar regions and bases. Advanced fibrotic changes were seen in the left lower lobe, causing 'shaggi- ness' of the pleuro-pericardial sur- faces. A confident diagnosis of tracheo- bronchomegaly (Mounier-Kuhn syndrome) was made. Complications of acute and chronic infection includ- ed visible pneumonitis, bronchiectasis and fibrosis. Thymic hyperplasia was likely reactive, due to repeated infec- tions. Cardiac ultrasound examination A massive right ventricle was found with enlargement of the right atrium. Mild tricuspid incompetence was demonstrated with an increased pressure gradient. A pulmonary pres- sure of 70 mmHg was measured, indi- cating severe pulmonary hyperten- sion. Final diagnosis 1. Mounier-Kuhn syndrome (tra- cheobronchomegaly), complicated by: (i) pneumonia; (ii) bronchiectasis and fibrosis; and (iii) cor pulmonale with tricuspid incompetence. 2. Hyperplasia of the thymus due to chronic infection. The patient was treated with Lasix, Berotec inhalations, Ciprobay and physiotherapy. Discussion Tracheobronchomegaly was origi- nally recognised at autopsy by Czyhlaz in 1897, but the first clinical descrip- tion by Mounier- Kuhn was given in 1932.1,2 Mounier-Kuhn syndrome pri- marilyaffects the supporting struc- tures of the trachea and major bronchi, weakening them and leading to ectasia. Bronchi abruptly revert to normal by the 4th to 5th divisions.' The syndrome is characterised by marked ectasia of the trachea and main bronchi, bronchiectasis and repeated lower respiratory tract infec- tions.' Presentation is typically during the 3rd or 4th decade, with a prepon- derance in males of African -American origin." A familial tendency is observed with an autosomal resessive inheritance pattern.' Tracheobronchomegaly is the underlying cause in virtually all observed instances of tracheal dilata- tion. It is regarded as a primary dys- plasia rather than a complication of recurrent infection; this is in keeping with the acute transition to normal calibre bronchi." Symptoms include recurrent respiratory infections, chronic productive cough and exer- tional dyspnoea.' Weakness of proxi- mal airway walls results in flaccidity and collapse, ineffective cough, reten- tion of mucus and consequently, repeated infections.' As the cartilagenous rings of the trachea and larger bronchi dilate, the intervening soft tissues bulge out- ward, forming diverticular, extralumi- nal protrusions of the air column. These lesions are best seen on the lat- eral chest view. In severe cases, associ- ated tracheobronchomalacia leads to proximal airway collapse during expi- ration. The increase in tracheal diameter can be pronounced as in this case or subtle enough to be easily over- 100ked.4,5 Widening of the trachea beyond 30 mm or mainstem bronchial diameters over 20 mm on the right or 18 mm on the left indicate tracheobronchomegaly,' Peri-hilar emphysema and bullae can also be found (Fig. 3).4 Secondary tracheobronchomegaly has been described in patients with Ehlers-Danlos syndrome, Marfan syndrome, Kenny-Caffey syndrome, Brachmann-de Lange syndrome, con- nective tissue diseases, ankylosing spondylitis, long-chain deposition disease and following prolonged ven- tilation in premature infants. Other sources give a shorter differential for Fig. 3. The trachea measured 4.13 x 4.65 em in diameter while mainstem bronchial dilatation of 2.19 em and 2.00 em were noted on the right and left side respectively. 13 SA JOURNAL OF RADIOLOGY • March 2002 REVIE\N ARTICLE tracheobronchomegaly, consisting of Mounier-Kuhn syndrome, Ehlers- Danlos syndrome, cutis laxa and relapsing polychondritis." Tracheal stenting has proved of great benefit in patients with advanced stages of Mounier-Kuhn disease (Fig. 4).4 Summary Measurement of the dilated tra- chea on a chest X-ray can make the diagnosis of tracheobronchomegaly. Normal tracheal diameter on a pos- tera-anterior radiograph is 20 mm, with a standard deviation of 2 mm. In cases of tracheobronchomegaly the Fig. 4. Bilateral basal bronchiectasis with left lower lobe fibrosis causing 'shagginess' of the pleuro- pericardial surfaces, measurement exceeds three standard deviations. A tracheal diameter of more than 25 mm is consistent with the diagnosis of tracheobronchorne- galy,' References ). Ker JA, Prinsloo H, Tracheobronchomegaly associated with recurrent pneumonia, Trop Doet 2000; 30: 242 -243. 2, Dee PM, Chest case of the day. Tracheobronchomegaly - the Mounier-Kahn syndrome, Am J Roentgenoll996; 167(1): 235, 238. 3, Dahnert W. Radiology Review Manual, 4th ed. Baltimore: Williams and Wilkins, 1999:443. 4. Blake MA, Clarke PD, Fenlon HM. Thoracic case of the day. Mounier- Kuhn syndrome (tra- cheobronchomegaly). Am J Roentgenol 1999; 173: 822, 824 - 825. 5, Choplin RH, Wehunt WD, Theros EG, Diffuse lesions of the trachea, Semin Roentgenol1983; 18: 38-50, Imaging of Diseases of the Chest 3/e Peter Armstrong, Alan G. Wilson, Paul Dee and David M. Hansell This comprehensive resource covers all imaging aspects of the lungs, the pleura and the mediastinum and integrates all available imaging modalities, Both common and uncommon disorders are included, whilst the logical, clinical organisation of the text allows for fast, efficient access to the information you require. Reviews of the second edition "Never has a 'point source' on focused imaging managed to be so thoroughly concise and complete.i.lt belongs in every radiology resident's personal llbrary.Jvtarvetoua" Radiology "Few single-volume textbooks on thoracic imaging can compare with this book" American Journal of Roentgenology "The writing is straightforward and succinct with careful attention to detail. "The illustrations are uniformly excellent and well chosen" Clinical Radiology April 2000, hardback, 1056 pp, 1 800 illustrations Mosby, R3 050r-------~------------------------------4 Features ORDERS SA Medical Association Private Bag X1, Pinelands 7430. Tel (021) 530-6527 Fax (021) 531-4126 E-mail: fpalm@samedical.org Please allow 4 weeks for delivery. Prices subject to foreign exchange fluctuations. • Includes all you need to know in one convenient single-volume resource, • Written clearly and concisely by renowned authors from the UK and USA, • Multi-modality coverage ensures that all the modalities applicable to thoracic imaging are included. • Includes nearly 2 000 high-quality images and illustrations - an image bank that covers a wide variety of cases. • Chapters are organised by diseases and disorders, allowing for fast navigation through the text. • Chapter outlines, Summary tables and Key points boxes summarise the most important information. 14 SA JOURNAL OF RADIOLOGY • March 2002 mailto:fpalm@samedical.org