Medical Image of the Month: Mounier-Kuhn Syndrome

Figure 1. AP chest x-ray showing significant tracheomegaly (diameter 30.8 mm), bilateral interstitial infiltrates with dense consolidation more at the lower lobes (left>right).

Figure 2. Axial thoracic CT in lung windows (A-D) and soft tissue windows (E-F). Sagittal CT in soft tissue windows (G-H). A: tracheal diameters in 2 dimensions (coronal 30.4 mm, sagittal 37.6 mm), para-septal emphysema (yellow arrows). B: showing tracheomegaly (23.2 x 34.3 mm) and para-septal emphysema changes (yellow arrows. C: enlarged mainstem bronchi diameters (right mainstem 22.3 x 30.6 mm, left mainstem 24.4 x 16.0 mm). In addition to central bronchiectatic changes (red arrows), left lower lobe consolidative changes (blue arrow). D: dense left lower lobe consolidation and para-septal emphysema. E: Significant tracheomegaly (31.5 x 41.a mm) and dilated esophagus (orange arrow). F: Significant tracheomegaly and dilated esophagus.

Figure 3. A: Sagittal CT scan (soft tissue window) showing significant tracheomegaly (sagittal diameter 35.8 mm). B: Sagittal CT chest (lung window) showing significant tracheomegaly, multiple tracheal diverticuli (green arrows) on the upper posterior tracheal wall.

Figure 4. Pulmonary function testing.

A 52-year-old non-smoking, Caucasian male patient with a past medical history of reported chronic obstructive pulmonary disease (COPD), recurrent lower respiratory tract infections, prior history of pneumothorax, and dysphagia presented with fevers and shortness of breathing associated with a productive cough for one week. Clinically, he was mildly tachypneic and chest auscultation revealed crackles bilaterally - more prominent at the left base. A chest radiograph (Figure 1) showed bilateral lower lobe pulmonary opacities (left more than right). Computed tomography (CT) of the chest demonstrated airspace disease in the lower lobes in addition to significant tracheobronchomegaly along with paraseptal emphysema and central bronchiectatic changes (Figures 2 and 3). Upper posterior tracheal wall diverticulae were also noted (Figure 3). Serum α₁-antitrypsin level and serum immunoglobulins, including IgE levels, were normal. Our patient declined performing diagnostic bronchoscopy. He had a pulmonary function test performed few months prior to his hospital admission which showed combined mild obstructive/restrictive pattern (Figure 4). He responded well to empiric antibiotics and chest percussion therapy. He was discharged in stable condition.

Discussion

On the basis of above findings, a diagnosis of Mounier-Kuhn syndrome complicated by pneumonia was made. The syndrome was first described by P. Mounier-Kuhn in 1932 (1). The diagnosis is usually made when the tracheal diameter is greater than 3 cm on a CT chest (measured 2 cm above the aortic arch) (2). Other diagnostic criteria include a mainstem bronchial diameter of 20-24 mm (right) and 15-23 mm (left) (3). Our patient’s tracheal diameter was around 37 mm. Both mainstem bronchi were dilated.

The abnormal tracheobronchial dilatation in this syndrome is attributed to atrophy of the muscular and elastic tissues in the tracheal and the bronchial walls (3). Hence, in addition to tracheobronchomegaly, these patients can also develop tracheal diverticulosis along with varicose and cystic bronchiectasis (3). These patients usually present in the 3rd or 4th decade of life with nonspecific respiratory symptoms including recurrent bronchitis and subsequently end up being misdiagnosed with COPD (3).

Three subtypes of this syndrome had been described. Subtype 1 has symmetric dilation of the trachea and mainstem bronchi. Subtype 2 demonstrates tracheal dilation and tracheal diverticula. Subtype 3 has diverticular and saccular structures extending to the level of the distal bronchi (3). Our patient likely fits subtype 3 of this syndrome. Overall, treatment is supportive - usually with antibiotics, physiotherapy and postural drainage. In rare instances, tracheal stenting has been used (4). Special consideration should be taken post intubation as achieving good cuff seal can be potentially challenging.

Dysphagia has not been well documented in this syndrome and could be a coincidental finding in our case. However, theoretically, the etiology of this patient’s dysphagia could be secondary to extrinsic compression of the anterior esophageal wall by his markedly dilated trachea. Historically, he underwent multiple esophageal dilatations and at least one Botox injection over the last 5 years without any significant improvement.

Abdulmonam Ali MD and Naga S. Sirikonda MD

Pulmonary and Critical Care

Good Samaritan Hospital

Mount Vernon, Illinois

References

1. Mounier-Kuhn P. "Dilatation de la trachee: constatations, radiographiques et bronchoscopies." Lyon Med. 1932;150:106-9.
2. Menon B, Aggarwal B, Iqbal A. Mounier-Kuhn syndrome: report of 8 cases of tracheobronchomegaly with associated complications. South Med J. 2008;101(1):83-7. [CrossRef] [PubMed]
3. Falconer M, Collins DR, Feeney J, Torreggiani WC. Mounier-Kuhn syndrome in an older patient. Age Ageing. 2008;37(1):115-6. [CrossRef] [PubMed]
4. Schwartz M, Rossoff L. Tracheobronchomegaly. Chest 1994;106(5):1589-90. [CrossRef] [PubMed]

Cite as: Ali A, Sirikonda NS. Medical image of the month: Mounier-Kuhn syndrome. Southwest J Pulm Crit Care. 2019;19(2):73-5. doi: https://doi.org/10.13175/swjpcc044-19 PDF 

Medical Image of the Week: Diffuse Pulmonary Ossification

 

Figure 1. Scout view from a high-resolution CT (HRCT) in this patient, demonstrating predominantly peripheral coarse interstitial thickening, with architectural distortion. Multiple calcific densities are associated with the interstitial abnormality.

Figure 2. A: High resolution CT axial image, 1 mm slice thickness, “lung windows”, bone algorithm. (Window width, 2500 HU; level, 500 H). Extensive peripheral/subpleural predominant reticulation and superimposed net-like, branching, and highly attenuating structures (dendriform configuration) are nicely depicted. Some coexisting less than 4 mm nodules are deposited predominantly in the areas of reticulation. B: Corresponding mediastinal window.

An 84-year-old man with a twelve-year history of interstitial lung disease with indolent course was referred for a new oxygen requirement. He had previously been diagnosed with usual interstitial pneumonia associated with occupational exposures. Over the previous six-months he became breathless with minimal activity. During this interval he had lost nearly 40 pounds. He had worked in uranium mining and had a mere four-pack-year smoking history. In his free time, he was an artisan and engaged in woodworking, metal craft and stonework. He was hypoxic with exertion and notably cachectic. His clinic exam was significant for grade 1 clubbing and soft inspiratory crackles that were audible at the bilateral bases. Pulmonary function testing demonstrated a restrictive ventilatory defect with severe reduction in diffusion capacity. A chest radiograph was followed by high resolution computed tomography (HRCT) with representative images shown in Figures 1 and 2. A diagnosis of diffuse pulmonary ossification (DPO) associated with UIP was made.

Pulmonary ossification indicates bone tissue formation; this in contrast to the deposition of calcium salts in pulmonary calcification. The pathogenesis is uncertain as most patients have no derangements in serum calcium and phosphorus levels. Transforming growth factor-β, implicated in idiopathic pulmonary fibrosis, is also thought to stimulate chondrocytes and osteoblasts in DPO. Other associated chemokines include bone morphogenic protein, and interleukins 1 and 4.

Patients with DPO may be minimally symptomatic or have significant disease to the level of respiratory failure. The diagnosis is most often made by a surgical biopsy or at the time of autopsy. Nodular and dendriform histologic types are described; the latter of which develops in areas of interstitial fibrosis. The nodular form often follows longstanding pulmonary venous congestion from cardiovascular disorders. Chest radiography is insensitive for diagnosis and may only demonstrate an interstitial pattern. Calcification is generally only seen once HRCT is obtained. ^99mTc-methylene diphosphonate (Tc-MDP) nuclear medicine scanning will also detect the presence of pulmonary ossification. Imaging-wise, the differential diagnosis for DPO, is restricted. Pulmonary alveolar microlithiasis could potentially be confused with DPO. The intra-alveolar accumulation of innumerable minute calculi called microliths are generally much smaller, usually less than 2 mm, with a uniform size and distribution throughout the lungs (‘sandpaper” appearance). At a later phase the number and volume of the calcific deposits increases and becomes more granular. The distribution follows the interlobular septa or bronchovascular bundles and can be confused with DPO. Previous granulomatous disease may have a somewhat similar appearance. However, the density per area unit of the calcific deposits tends to be much less, and the distribution is more random and not necessarily associated with underlying abnormal/ fibrosing tissue. There is a strong association between DPO and IPF, when compared with nonspecific interstitial pneumonia (NSIP) and chronic hypersensitivity pneumonitis. This may improve diagnostic specificity in patients with IPF.

Therapy with calcium binding agents, chelation, and corticosteroids has been disappointing, and there is currently no proven treatment.

Steven Sears DO¹, Bhupinder Natt MD¹, and Diana Palacio MD²

¹Division of Pulmonary, Critical Care, Allergy and Sleep and ² Department of Medical Imaging

University of Arizona College of Medicine. Tucson, AZ USA

References

1. Chai JL, Patz EF. CT of the lung: patterns of calcification and other high-attenuation abnormalities. AJR AM J Roegenol. 194;152:1063-6.[CrossRef] [PubMed]
2. Fried ED, Godwin TA. Extensive diffuse pulmonary ossification. Chest. 1992;102:1614-5. [CrossRef] [PubMed]
3. Chan ED, Morales DV, Welsh CH, McDermott MT, Schwarz MI. Calcium deposition with or without bone formation in the lung. Am J Respir Crit Care Med. 2002;165:1654-69. [CrossRef] [PubMed]
4. Schwarz MI, King TE. Interstitial lung disease 3rd ed. Hamilton, Ontario: B.C Decker, 1998.
5. Fernández-Bussy S, Labarca G, Pires Y, Díaz JC, Caviedes I. Dendriform pulmonary ossification. Respir Care. 2015 Apr;60(4):e64-7. [CrossRef] [PubMed]
6. Egashira R, Jacob J, Kokosi MA, Brun AL, Rice A, Nicholson AG, Wells AU, Hansell DM. Diffuse pulmonary ossification in fibrosing interstitial lung diseases: prevalence and associations. Radiology. 2017 Jul;284(1):255-63. [CrossRef] [PubMed]
7. Castellana G, Castellana G, Gentile M, Castellana R, Resta O. Pulmonary alveolar microlithiasis: review of the 1022 cases reported worldwide. Eur Respir Rev. 2015 Dec;24(138):607-20. [CrossRef] [PubMed]

Cite as: Sears S, Natt B, Palacio D. Medical image of the week: diffuse pulmonary ossification. Southwest J Pulm Crit Care. 2019;19(2):65-7. doi: https://doi.org/10.13175/swjpcc028-19 PDF