Respiratory Medicine CME (2009) 2, 86e91

CASE REPORT

Mounier-Kuhn syndrome and tracheopathiaosteoplastica in the same patient withrespiratory insufficiency

Ines Zendah a,*, Imen Aissa a, Soumaya Darouas a, Amel Khattab a, MajedBeji b, Habib Ghedira a

a Department of Pneumology I, Abderrahmene Mami Hospital of Pneumology, 2080 Tunis, Tunisiab Department of Pneumology, La Rabta Hospital, 1007 Tunis, Tunisia

Received 16 August 2008; accepted 15 October 2008

KEYWORDSMounier-Kuhnsyndrome;Tracheobronchomegaly;Tracheopathiaosteoplastica;Respiratoryinsufficiency

* Corresponding author. Tel.: þ216 9184.

E-mail address: ines_zen@yahoo.f

1755-0017/$34 ª 2008 Elsevier Ltd. Adoi:10.1016/j.rmedc.2008.10.013

Summary

Mounier-Kuhn syndrome (MKS) or tracheobronchomegaly, and tracheopathia osteoplastica (TO)are rare diseases. MKS is a clinical entity characterized by abnormal dilatation of the tracheaand main bronchi. TO is a clinical and pathologic condition characterized by multiple submu-cosal cartilaginous and osseous nodules lining the upper respiratory tract. Some people withMKS manifest recurrent pneumonia or chronic cough with sputum production, hemoptysis ordyspnea. Occasionally, it is found in asymptomatic individuals. CT scan imaging is the key toolfor the diagnosis when showing a dilatation of the trachea and main bronchi. TO is usuallybenign and asymptomatic, frequently diagnosed incidentally during intubation. Flexible fiber-optic bronchoscopy and laryngoscopy are the key diagnostic tools which typically demonstrateirregular spicules of submucosal bone and cartilage projecting into the tracheobronchial lumenand causing various degrees of airway obstruction. When this aspect is found bronchial biopsyis not mandatory. We report the case of a 26-year-old man with features of both MKS and TOwho presented a previous history of productive cough, recurrent pneumonia and dyspnea;admitted for pulmonary infection resulting in a respiratory insufficiency. MKS was diagnosedby CT scan and TO by fiberoptic bronchoscopy. To our knowledge, this is the first time thesepathologies are reported in the same patient, and our patient is the second one having MKSwho presented with respiratory insufficiency.ª 2008 Elsevier Ltd. All rights reserved.

860 2362; fax: þ216 71 821

r (I. Zendah).

ll rights reserved.

Figure 1 Chest X ray film. Increase in the diameter of thetrachea and of the main bronchi, diffuse and bilateral bron-chial shadows and multiple bilateral nodules.

Mounier-Kuhn syndrome and tracheopathia osteoplastica 87

Introduction

Mounier-Kuhn syndrome (MKS) or tracheobronchomegaly isa clinical entity characterized by abnormal dilatation of thetrachea and main bronchi. Tracheopathia osteoplastica(TO) is a clinical and pathologic, usually benign conditioncharacterized by multiple submucosal cartilaginous andosseous nodules of various sizes lining the upper respiratorytract.1,2 Both of the two pathologies are rare.

Tracheobronchomegaly is an unusual cause of recurrentchest infections often with persistent, productive cough.TO is usually an incidental finding on chest imaging studies,especially computed tomography (CT) scanning.

We report a case of an association of both pathologies ina patient with a previous history of recurrent pneumonia,productive cough and exertional dyspnea, who presentedwith a respiratory insufficiency due to a respiratoryinfection.

The association of these diseases has not been reportedas yet to our knowledge and only one patient with MKSpresenting with respiratory insufficiency has been reportedin the literature.

In some patients recurrent bronchial or parenchymalinfections, dyspnea or other recurrent symptoms that donot respond to treatment should alert the physician tosome anatomical factors among which are MKS and TO, asthey can result in difficulty in eradicating the cause of therecurrent respiratory disorders.

Case report

A 26-year-old man, non-smoker, presenting a 2-year-history of productive cough, recurrent pneumonia andexertional dyspnea, was admitted to our departmentbecause he presented 10 days prior a worsening dyspneaand cough associated with fever.

The patient had parental consanguinity. He had a pasthistory of meningitis resulting in mental retardation andbilateral hypoacousia.

His physical examination revealed a fever at 38.5 �C,a heart rate at 110 beats/min, a respiratory rate at 26cycles/min, intercostal retraction and bilateral crackles.

Blood gas analysis whilst breathing air showed thefollowing results: pH 7.4, PaO2 52.2 mmHg, PaCO2

24.7 mmHg, HCO3� 15.6 mmol/l and SaO2 85%.

Chest X ray film showed thoracic distension, significantincrease in the diameter of the trachea and of the mainbronchi, elevated diaphragmatic cupala, diffuse and bilat-eral bronchial shadows and multiple bilateral nodules(Figure 1).

White blood cell count was elevated at 20.700 � 109/l,CRP elevated at 144 mg/ml and sedimentation rateelevated at 98/110 mm.

Acid fast bacilli were absent from the sputum. Pseudo-monas aeruginosa and Haemophilus influenzae were iso-lated in the sputum culture. They were sensitive to all thetested antibiotics.

The diagnosis of hypoxemic pulmonary infection withprobable bronchiectasis was made and the patient startedbeing treated with intravenous ceftazidime 3 g per day for15 days in combination with gentamycin 160 mg for 5 days.

The patient also underwent bronchial drainage and nasaloxygen was administered for the hypoxemia.

Flexible bronchoscopy revealed an abnormal tracheaflattened anteroposteriorly with multiple whitish osteo-cartilaginous nodules protruding into the tracheal lumeninvolving the anterolateral wall. Posterior trachealmembrane was spared. The entire trachea and the rightmain bronchi were involved. They were of hard consistencywhen grasped with biopsy forceps. They extended from theproximal portion of the trachea to the proximal part of theright main bronchus, leading to a narrowing of the first thirdpart of the trachea by almost 40%. These formations sparedthe posterior face of the trachea (Figure 2). The bronchialbiopsy done twice was superficial. Histopathologicalexamination showed a superficial respiratory epithelium.The diagnosis of TO was therefore made.

Chest CT scan revealed an enlarged trachea in its lowercervical and thoracic portions with a sagittal trachealdiameter reaching 30 cm. The anterior wall was thin withmultiple calcified densities protruding into the anterior andlateral walls, resulting in an irregular shape of the trachealcontour. The posterior wall was thin with multiple diver-ticula but without the nodules. This enlargement continuedto the main, lobar and segmental bronchi which had thinwalls. The nodules were located evenly in the mainbronchi. The carina was elevated. There was a right apicalconsolidation with paraseptal emphysema. Both lowerlobes had mosaic perfusion. There was ground-glass hazi-ness in the lingula. A small left pneumothorax was noted(Figure 3). The CT aspect made the diagnosis of MKS andconfirmed its association to TO. Respiratory functional testsrevealed a restrictive syndrome. No similar cases have beenseen in the family.

Figure 2 Flexible bronchoscopy. Trachea flattened ante-roposteriorly, multiple whitish osteocartilaginous nodulesprotruding into the tracheal lumen involving the anterolateralwall and sparing the posterior face of the trachea.

88 I. Zendah et al.

Over the first three days, fever disappeared. After a fewdays biological findings and blood gas analysis valuesreverted to within the normal limits. The patient was dis-charged and advised to return regularly to the clinic forfollow-up. Symptomatic measures will be prescribedwhenever necessary.

Discussion

Our patient has the features of two unusual conditions: MKSand TO. Although first recognized at post-mortem exami-nation by Czyhlarz in 18973 and latterly described byMounier-Kuhn in 19324 the term tracheobronchomegalyderives from the review of Katz et al in 1962.5 The diseaseremains rare. Himalstein and Gallagher,6 however, founda 1% prevalence in a series including 500 bronchograms.Most cases of tracheobronchomegaly probably are under-diagnosed. This disease is defined as a transverse and

Figure 3 Chest CT scan. Enlarged mainstem bronchi withnodules.

sagittal tracheal diameter exceeding 25 and 27 mmrespectively.7 Men are more often affected than women.

TO is a disorder detected in approximately 1 in 2000patients who undergo bronchoscopy and usually manifestsin the sixth to seventh decades of life with no sexualpredominance.8

MKS is due to atrophy or absence of the longitudinalelastic fibers and the smooth muscles that form itswalls.9,10 The longitudinal elastic fibers of the trachea andthe main bronchi are severely atrophied and the muscularismucosa is thick. These abnormalities result in dilatation ofthe membranous and cartilaginous portions of the tracheaand main bronchi. The most important respiratory impair-ment in patients with MKS is the total collapse of theairways during expiration.7,9 In our patient, however, therewas no obstructive syndrome but a restrictive one. This isprobably explained by the fact that the collapse of theairways is not important enough to cause an obstructivesyndrome and the restrictive syndrome is probably due tothe bronchiectasis. This increased compliance of the chestwall results in protrusions of the musculomembranoustissue between the cartilaginous rings. In our patient theprotrusions were too hard and macroscopically typical ofa TO.

With the impairment of the cough reflex and of themucociliary defense mechanism, the airways are extremelywidened and weakened, which causes mucus accumulation,recurrent pneumonia, bronchiectasis, emphysema andfibrosis.7,9,11,12

As for TO, it is postulated that the cough results froma combination of factors, including turbulent airflow,increased airway sensitivity, and impaired ciliary clear-ance.13 In our patient presenting with MKS and TO manymechanisms may be associated to cause cough and there-fore bronchial and parenchymal infection, which explainsthe presence of bronchiectasis.

The cause of the MKS is still unknown but it is thought tohave an acquired origin because of the extreme rarity ofthe disease and its association with chronic respiratoryinfections and delayed onset. Moreover, it has been sug-gested that this disease may be caused by barotrauma inneonates who received intensive ventilatory and oxygensupport.14 Cigarette smoke and air pollution may also bethe physiopathologic explanation of the disease.12

However, a genetic link is also suggested because MKS wasreported in siblings, in association with EhlerseDanlossyndrome and with cutis laxa. The association with thesepathologies may suggest a congenital defect in connectivetissue as the basis for tracheobronchomegaly; most cases,however, presented in the third or the fourth decade oreven in later decades of life and showed no evidence ofother connective tissue disorders.15,16

Tracheobronchomegaly was reported to be also associ-ated with duplication of the distal trachea, double carina,tracheal trifurcation, and with a congenitally shortabnormal right upper-lobe bronchus.17e19 One case ofassociation to the KennyeCaffey syndrome has beenreported (dwarfism, normal intelligence, thickened bonecortices with small medullary cavities, ocular abnormali-ties, and transient hypocalcemia).20 Our patient presentsa mental retardation which would be another associativefactor to the disease but in his case it seems to be rather

Mounier-Kuhn syndrome and tracheopathia osteoplastica 89

due to the meningitis that he had presented. An autosomalrecessive pattern of inheritance has been suggested fromstudies in one family.21

The cause of TO is also still unknown. Some authors,22

however, present the theory of neoplastic lesions arisingdirectly from the cartilaginous rings or local trauma of thetrachea with resultant osseous, cartilaginous metaplasia,chronic infection, congenital anomalies, chronic inflam-mation, metabolic abnormalities, mechanical and chemicalirritation and genetics.23 Recently, a familial case has beenrecorded involving both mother and daughter.8 We wouldlike to emphasize that among the chronic inflammationscaused by MKS in our patient, as far as we know this is thefirst case in which MKS and TO coexist.

In both MKS and TO, inheritance has been suggested. Ourpatient presents a consanguinity which increases theoccurrence of hereditary diseases, making it probable thatboth pathologies are hereditary in this patient. However,the probability of having two hereditary diseases is poor inthe same patient and no similar cases were described in ourpatient’s family.

The symptoms of MKS are not specific and may mimicchronic bronchitis or bronchiectasis. Some people manifestrecurrent pneumonia or chronic cough with sputumproduction, hemoptysis or dyspnea.12,15 Occasionally, it isfound in asymptomatic individuals.

TO is usually benign and asymptomatic, frequentlydiagnosed incidentally during intubation, bronchoscopy orCT performed for other reasons.1,24,25 Although manypatients are asymptomatic, progressive growth of thenodules may lead to dyspnea, stridor, hoarseness, coughand dysphagia caused by the narrowing of the airwaylumen. Hemoptysis may occur if the underlying mucosaulcerates. Distal bronchial lesions may result in atelectasisand wheezing. In our patient fiberoptic bronchoscopyrevealed that the nodules caused an important narrowingof the trachea, which explains the cough and dyspneapresented by him.

In fact, accurate diagnosis of TO can be challengingbecause of the nonspecific nature of the symptoms. TO is ingeneral a relatively benign and a slowly progressivedisease, and this partly explains the low incidence ofreports.26Although some clinical signs of TO may be presentat diagnosis, it is usually an incidental finding on chestimaging studies, CT being the imaging modality of choice inthis entity.27 To our knowledge this is the second case of TOpresenting with respiratory insufficiency.28

Diagnosis of MKS depends on the demonstration of thecharacteristically large trachea and proximal bronchi byplain radiography, CT or magnetic resonance imaging(MRI).13,29 Radiologic findings of an irregular air columnreflect the ‘‘corrugated’’ effect that is produced whenredundant mucosa prolapses through the tracheal rings,and CT scan reveals these abnormalities better than chestradiographs.7 In our patient, the diagnosis was overlookedon plain radiography as it revealed an enlarged trachealsilhouette. However, its significance was not appreciateduntil CT scanning revealed the diameter of the tracheaallowing the diagnosis of tracheobronchomegaly.

The thoracic CT shows in cases of MKS greatly dilatedtrachea and right main bronchi with an abrupt transition toa normal caliber of the peripheral airways and protrusion of

redundant musculomembranous tissue between the carti-laginous rings, resulting in an irregularly corrugated orscalloped appearance of the air columns and sometimesbronchiectasis.12,30 Parenchymal consolidation may also beencountered.16

In TO, characteristic CT imaging findings consist ofmultiple calcified or uncalcified densities protruding intothe anterior and lateral walls of the trachea, resulting inirregular shape of the tracheal contour and decreasedfrontal diameter.24,28,31 CT imaging may also show potentialcomplications, including post-obstructive collapse, bron-chiectasis and pneumonia.25 In our patient, CT scan showeda dilatation of the trachea and main bronchi in relation withMKS and densities of the trachea and main bronchi inrelation with TO. Parenchymal complications were alsoseen.

MRI, with its high resolution, can help better than CTscan for the diagnosis of TO by better defining the submu-cosal nodules, the sparing of the tracheal posterior wall,and the extent of the tracheal thickening to the bronchi onthe coronal planes.29,32 But it is less sensitive than CT fordemonstrating the punctiform calcifications in the submu-cosal nodules and the potential complications such as lobarcollapse and post-obstructive bronchiectasis.29

In MKS, flexible fiberoptic bronchoscopy may show flat-tened trachea and cartilaginous nodules.16 In TO, flexiblefiberoptic bronchoscopy and laryngoscopy are the keydiagnostic tools which typically demonstrate irregularspicules of submucosal bone and cartilage projecting intothe tracheobronchial lumen and causing various degrees ofairway obstruction. The posterior pars membranacea isspared.13,27 As the lesions arise from the cartilaginoussupporting rings of the airway, endoscopic anomalies mayinvolve the entire trachea and mainstem bronchi.23,27 Onlyareas of the respiratory tree with underlying cartilage areaffected. Endoscopic features of TO are typical andpathognomonic. These lesions are typically hard and theirbiopsy is difficult; consequently, the diagnosis is oftenmade from the visual appearance alone such as in the caseof our patient.33,34 Histological examination of the nodulesis nonspecific, but it usually reveals cartilaginous, osseousand fibrous tissue.25,27 Occasionally, marrow is present inthe new bone; however, the marrow is typically nothematopoietic.35

Expiratory studies may reveal obstructive syndrome inMKS11,12,36,37 and usually show no abnormality or anobstructive pattern in TO.38,39

MKS may be confused with WilliamseCampbellsyndrome, a rare form of congenital cystic bronchiectasisthat results from a deficiency of cartilage in the fourth- tosixth-order bronchi. Although both diseases can result insignificant bronchiectasis, patients with WilliamseCamp-bell syndrome have normal-caliber trachea and mainbronchi.37 Predominant enlargement of the central bronchior central bronchiectasis may also be seen in allergicbronchopulmonary aspergillosis and cystic fibrosis. Allergicbronchopulmonary aspergillosis usually occurs in asthmaticpatients showing a response to Aspergillus antigens andpresenting large mucoid impactions, as well as fleetingperipheral air-space opacities.

TO may also be confused with many other diseases,resulting in a delay of the diagnosis,this being more due to

90 I. Zendah et al.

the fact that TO is rarer than the other differential diag-noses. In TO distal bronchial lesions by generating wheezingoften lead to a misdiagnosis of asthma or bronchitis.

The differential diagnosis of multiple nodules within thetracheobronchial tree includes amyloidosis, endobronchialsarcoidosis, squamous papillomatosis, relapsing poly-chondritis, calcified tuberculosis and neoplasia. Theseentities should be specially considered in cases of posteriorwall involvement.24,34

MKS requires symptomatic treatment and antibioticswhen an infectious complication requires it.

Treatment modalities of TO include relief of symptoms.The tracheal diameter can be increased by means of a rigidbronchoscope, allowing the use of laser or forceps, whichrelieves the symptoms.27 Stent placement and even radia-tion therapy can be useful.2 Surgical excision of theinvolved trachea is reserved for severe obstruction of thelumen by the nodules.40

Conclusion

MKS and TO are rare diseases. Their symptoms are notspecific. The diagnosis is made by CT scan for MKS and byfiberoptic bronchoscopy for TO. Recurrent respiratorysymptoms should make physicians think of TO and MKSamong the possible etiologies. However, these diseases aremuch more rare than the other ones, which can lead toa misdiagnosis and the resulting recurrent symptoms. Thesymptoms are unspecific. The diagnosis of MKS relies on CTscan and that of TO on flexible bronchoscopy. The treat-ment is symptomatic in the case of MKS and may sometimesbe surgical or by means of a rigid bronchoscope in the caseof TO.

Conflict of interest statement

None of the authors have a conflict of interest to declare inrelation to this work.

Ethics statement

The work has been approved by the appropriate ethicalcommittees related to the institution in which it was per-formed and the patient’s parents accepted the publicationof the case report (we could not have the patient’sagreement as he has mental retardation).

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