Ann Thorac Surg 2001;71:2009-2011
© 2001 The Society of Thoracic Surgeons
Case report
Rare clinical diagnosis of dendriform pulmonary ossification
Jana M. Jaderborg, MDa,
Robert F. Dunton, MDa
a Department of Surgery, The University of Kansas School of Medicine-Wichita, Wichita, Kansas, USA
Accepted for publication April 10, 2000.
Address reprint requests to Dr Dunton, 3311 E Murdock, Wichita, KS 67208
e-mail: rdunton{at}kscable.com
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Abstract
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Dendriform pulmonary ossification, defined as "widespread heterotopic bone formation within the lungs," is a rare entity, which is usually diagnosed upon post-mortem examination. The case of a 43-year-old man with dendriform pulmonary ossification is presented. In this patient’s case, thoracoscopic biopsy was an excellent diagnostic modality for identifying dendriform pulmonary ossification. Although this entity has been reported rarely, with improved technology and survival we might expect its prevalence to increase.
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Introduction
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Diffuse pulmonary ossification is a rare entity, diagnosed almost exclusively on postmortem examination [1]. There are two recognized types of diffuse pulmonary ossification: nodular and dendriform [2, 3]. Dendriform pulmonary ossification is usually confined to areas of alveolar septal fibrosis and appears as small bone spicules with marrow. Less than 100 cases have been reported since Luschka first reported it in 1856 [4]. Patients are generally asymptomatic, but when symptomatic, diffuse pulmonary ossification is usually associated with other pulmonary diseases such as interstitial pneumonia, fibrosis, or bronchiectasis [3].
A 43-year-old man presented to his family physician with a complaint of intermittent fevers up to 38°C the prior week. He initially denied any history of dyspnea, hemoptysis, chest pain, or cough; however, on further questioning admitted to increasing dyspnea on exertion and a dry, nonproductive cough associated with lying down. He was diagnosed with interstitial pneumonia 2 years previously. At that time, he experienced a 3-week history of intermittent fevers, which resolved after oral antibiotics. He reported treatment for pneumonia as a child and placement of a tracheostomy for long-term airway management. Physical examination was normal except for clubbing of the fingertips bilaterally and an old tracheostomy scar. Chest auscultation was normal. Chest roentgenogram revealed coarse reticulonodular markings in bilateral mid-to-lower lung fields consistent with interstitial pneumonitis (Fig 1).
Persistent pulmonary symptoms prompted diagnostic bronchoscopy. Biopsies and lavage of right middle and lower lobe bronchi were obtained. Pathology revealed chronic inflammation. Pulmonary function tests revealed a mild small airway obstructive ventilatory defect. He had slightly decreased lung volumes although he maintained normal diffusion capacity. Since these results were inconclusive, thoracoscopy was performed. There were innumerable tiny white nodules over the entire lung surface and, on palpation with instruments, the lung felt boggy with a gritty surface. As the lung deflated, it was noted to have a "coral reef" appearance (Fig 2). Wedge biopsies were taken from the lingula and lower lobe, and the tissue was friable. Frozen sections revealed areas of calcification. The patient recovered without complication.
After decalcification, final pathology revealed bone fragments with fatty marrow spaces with a "dendriform or tree-like growth pattern" (Fig 3). Based on the findings of branching dendriform bone structure in the interstitial pulmonary spaces and presence of fatty marrow, the patient was diagnosed with dendriform pulmonary ossification.
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Fig 3. Decalcified specimen (x 400) demonstrating lung tissue (left), demineralized bone (center), and cellular marrow (right).
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Patient follow-up includes pulmonary surveillance with yearly pulmonary function tests and chest roentgenograms. He continues to have some dyspnea, especially with exertion and while lying down.
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Comment
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Dendriform pulmonary ossification is found in patients with some form of chronic pulmonary fibrosis. The linear spicules are located in the interstitium or alveolar septa and arranged in a twig-like pattern [5]. Müller and colleagues describe these spicules as 2 to 8 mm in diameter, exhibiting regular dichotomous branching at angles of 60° to 70° every 2 cm [6]. The bony spicules do not penetrate the alveolar space; they do contain fatty and sometimes cellular marrow [7]. It usually affects older men and can be associated clinically with cystic fibrosis, histoplasmosis, amyloidosis, and chronic abscess [2]. Diagnosis of this disease is usually made on postmortem examination, not clinically.
The pathophysiology of dendriform pulmonary ossification is unclear, but review of surgical literature indicates that fibrosis of any cause is the precursor to its development [2]. Attempts have been made to attribute the branching ossifications to bronchial, vascular, or lymphatic anatomic structures within the lung tissue without success [6]. The branching ossification’s correlate with the structural pattern of interstitial connective tissue of the normal lung, which, in chronic pulmonary fibrosis, becomes more prominent. Microscopically, the transition from fibrosis to bone has been clearly documented. The theorized etiologic basis for this includes initiation of ossification by a chronic anoxic and acidic environment stimulating fibroblast metaplasia to osteoblasts [2]. It is well-known that fibroblasts can undergo metaplasia to osteoblasts in other tissues, promoted by an acidic and anoxic environment. This kind of milieu has been documented in 24- to 48-hour-old wounds, and may be present in healing lung tissue. In a patient with multiple episodes of pneumonia or other lung disease leading to scarring, an anoxic, acidic environment may be created and lead to this kind of transformation.
With the advent of mechanical ventilation and improved patient care skills, an inevitable increase in survivors of chronic lung diseases will occur. Hence, the prevalence of dendriform pulmonary ossification may increase in coming years. Thoracoscopic biopsy enhances the procurement of tissue to establish a clinical diagnosis. Treatment options are not well established, largely due to the lack of clinical diagnoses. In this case, pulmonary surveillance with annual pulmonary function tests and chest roentgenograms is recommended for surveillance.
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References
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Popelka C.G., Kleinerman J. Diffuse pulmonary ossification. Arch Intern Med 1977;137:523-525.[Abstract/Free Full Text]
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Lushka H. Verastigte knochenbildung im parenchym der lung. Virchows Arch 1856;10:500-505.
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Jacobs A.N., Neitzschman H.R., Nice C.M., Jr Metaplastic bone formation in the lung. Am J Roentgenol Radium Ther Nucl Med 1973;118:344-346.[Medline]
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Dail D.H., Hammar S.P. Metabolic and other diseases. In: Dail D.H., Hammar S.P., eds. Pulmonary pathology, 2nd ed. New York: Springer-Verlag, 1994:730-736.
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Abstract
Introduction
