Pulmonary veno-occlusive disease: a misnomer?

Clinical features of canine pulmonary veno-occlusive disease and pulmonary capillary hemangiomatosis

Background

Histologic features of pulmonary veno‐occlusive disease (PVOD) and pulmonary capillary hemangiomatosis (PCH) have been described in dogs but without a thorough clinical description.

Objectives

To report the clinical features, diagnostics, treatment, and outcome of dogs with histologic evidence of PVOD and PCH.

Animals

Fifteen pet dogs meeting histopathologic criteria of PVOD (occlusive remodeling of small‐sized to medium‐sized pulmonary veins) or PCH (alveolar capillary proliferation and congestion), or both.

Methods

Medical records of dogs with PVOD and PCH identified based on histopathologic features between 2003 and 2017 were retrospectively reviewed.

Results

Fifteen dogs met inclusion criteria of a histologic diagnosis of PVOD or PCH or both. Dogs were older (median 11 years) with no apparent breed or sex predisposition. Dogs presented with acute clinical signs (median 3 days), usually respiratory distress. Thoracic radiography (available in 10 dogs) revealed right cardiomegaly and patchy or diffuse interstitial to alveolar patterns, with 9 dogs having a normal left cardiac silhouette. In 5 dogs tested, pulmonary arterial hypertension (PAH) was documented. In all 3 dogs, thoracic computed tomography scans showed pulmonary arterial enlargement and perivascular diffuse nodular ground‐glass opacities. Ten of 15 dogs died within 1 day; median survival was 3 days.

Conclusions and Clinical Importance

In dogs with PAH, the inability to document left‐sided congestive heart failure and failure to identify another cause of signs of respiratory disease should increase suspicion for PVOD and PCH. With increased awareness of PVOD and PCH by clinicians and pathologists, dogs with compatible clinicopathologic features should be evaluated for these pulmonary vascular disorders.

Interstitial Lung Disease in Children Made Easier…Well, Almost

Interstitial lung disease (ILD) in pediatric patients is different from that in adults, with a vast array of pathologic conditions unique to childhood, varied modes of presentation, and a different range of radiologic appearances. Although rare, childhood ILD (chILD) is associated with significant morbidity and mortality, most notably in conditions of disordered surfactant function, with respiratory failure in 100% of neonates with surfactant protein B dysfunction and 100% mortality without lung transplantation. The authors present a summary of lung development and anatomy, followed by an organized approach, using the structure and nomenclature of the 2013 update to the chILD Research Network classification system, to aid radiologic diagnosis of chILD. Index radiologic cases with contemporaneous histopathologic findings illustrate a summary of recent imaging studies covering the full spectrum of chILD. chILD is best grouped by age at presentation from infancy (diffuse developmental disorders, lung growth abnormalities, specific conditions of unknown origin, surfactant dysfunction mutations) to later childhood (disorders of the normal host, disorders related to systemic disease processes, disorders related to immunocompromise). Appreciation of the temporal division of chILD into infant and later childhood onset, along with a sound understanding of pulmonary organogenesis and surfactant homeostasis, will aid in providing useful insight into this important group of pediatric conditions. Application of secondary lobular anatomy to interpretation of thin-section computed tomographic images is pivotal to understanding patterns of ILD and will aid in selecting and narrowing a differential diagnosis. ^©RSNA, 2017.

Pulmonary Veno-Occlusive Disease

Pulmonary hypertension is a well-known though poorly characterized disease in veterinary medicine. In humans, pulmonary veno-occlusive disease (PVOD) is a rare cause of severe pulmonary hypertension with a mean survival time of 2 years without lung transplantation. Eleven adult dogs (5 males, 6 females; median age 10.5 years, representing various breeds) were examined following the development of severe respiratory signs. Lungs of affected animals were evaluated morphologically and with immunohistochemistry for alpha smooth muscle actin, desmin, CD31, CD3, CD20, and CD204. All dogs had pulmonary lesions consistent with PVOD, consisting of occlusive remodeling of small- to medium-sized pulmonary veins, foci of pulmonary capillary hemangiomatosis (PCH), and accumulation of hemosiderophages; 6 of 11 dogs had substantial pulmonary arterial medial and intimal thickening. Ultrastructural examination and immunohistochemistry showed that smooth muscle cells contributed to the venous occlusion. Increased expression of CD31 was evident in regions of PCH indicating increased numbers of endothelial cells in these foci. Spindle cells strongly expressing alpha smooth muscle actin and desmin co-localized with foci of PCH; similar cells were present but less intensely labeled elsewhere in non-PCH alveoli. B cells and macrophages, detected by immunohistochemistry, were not co-localized with the venous lesions of canine PVOD; small numbers of CD3-positive T cells were occasionally in and around the wall of remodeled veins. These findings indicate a condition in dogs with clinically severe respiratory disease and pathologic features resembling human PVOD, including foci of pulmonary venous remodeling and PCH.