INTRODUCTION:DIPNECH is an extremely rare pulmonary lesion, with less than fifty reported cases in the literature. It has predilection for non-smoking middle age females, with predominant obstructive ventilatory defect and an associated histological evidence of bronchiolitis. High resolution chest CT scan shows multiple small pulmonary nodules with mosaic perfusion suggestive of small airway disease. There is unfortunately very little that we know about this disease in regards to management and prognosis.
CASE PRESENTATION:This is a 57 year-old lifetime non-smoker female, with a ten-year history of unexplained dry cough, wheezes and dyspnea. She has been labeled with asthma because of evidence of obstructive ventilatory defect with reversibility; however she had poor response to maximal therapy including trials of oral corticosteroids. CT of the chest showed multiple bilateral sub-centimeter nodules with bilateral tracheobronchial calcifications. The nodules were followed for more than two years without significant change in size. Spirometry showed moderately severe obstructive ventilatory defect with variable bronchodilator response, mildly reduced diffusing capacity and evidence of air trapping. Bronchoscopic random transbronchial biopsies of the right upper lobe showed chronic bronchiolitis with peribronchial fibrosis, and pulmonary tumourlet. CT guided biopsy of the dominant left lower lobe nodule showed carcinoid tumor based on its size of 9mm. Twenty four hour urine collection for 5-hydroxyindoleacetic acid (5-HIAA) and an octreotide nuclear scan to further evaluate carcinoid syndrome were both negative. The diagnosis of DIPNECH was made based on the stability, diffuse nature of the nodules and histological evidence of characteristic neuroendocrine cell proliferation in two different lobes one of which was on random transbronchial biopsy.
DISCUSSIONS:DIPNICH comprises a generalized proliferation of scattered neuroendocrine cells, small nodules or a linear proliferation of pulmonary neuroendocrine cells. These proliferations are superficial to the basement membrane and confined to the bronchial and bronchiolar epithelium. When there is extension of neuroendocrine cells beyond the basement membrane, the proliferations are termed tumourlets, which can be localized or diffuse.Nodules of more than 5 mm in diameter are classified as carcinoid tumors; they are usually single masses although they can be associated with DIPNECH. DIPNECH is thought to be a primary proliferative process, which can be associated with constrictive obliterative bronchiolitis. Those cells are known to produce potentially fibrogenic cytokines such as bombesin. Before making this diagnosis, reactive neuroendocrine cell hyperplasia to chronic lung conditions such as cystic fibrosis, and chronic obstructive pulmonary disease should be ruled out. Presentation of DIPNECH is either symptomatic with a slow but progressive obstructive airway illness, or incidental on biopsy specimens of tumor related lung resection. Lung function studies are most commonly obstructive; hence most of these patients are mistakenly diagnosed with asthma with average of 8.6 years before the correct diagnosis is made. Typical HRCT findings include evidence of small airways obstruction in the form of mosaicism and the coexistence of multiple pulmonary nodules. Most patients with DIPNECH have indolent and non-progressive course, with 83% of patients with symptoms being alive at 5 years. Watchful waiting for these patients is the rule. Progressive disease with deteriorating flow indices have been described especially when it is associated with constrictive bronchiolitis. For these patients the drug of choice is classically corticosteroids.
CONCLUSION:In conclusion, DIPNECH is characterized by mosaic perfusion due to air trapping, airway wall thickening, and small nodules on high resolution CT scans. Because of airway obstructive physiology and small diffuse pulmonary nodules that have relative stability, DIPNECH is usually mislabeled as asthma for an average of 8.6 years before diagnosis is made. Very little is known about management and prognosis of DIPNECH, which is pathologically considered a preinvasive condition for pulmonary tumorlets and carcinoid tumors.
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