Micronodular pattern of organizing pneumonia

Abstract

Rationale:Organizing pneumonia (OP) is a clinicopathological entity characterized by granulation tissue plugs in the lumen of small airways, alveolar ducts, and alveoli. OP can be cryptogenic (primary) (COP) or secondary to various lung injuries.Patient concerns:We report the case of a 38-year-old male smoker with COP presenting in the form of diffuse micronodules on computed tomography (CT) scan and describe the clinical, radiological, and functional characteristics of micronodular pattern of organizing pneumonia (MNOP) based on a review of the literature including 14 cases.Patients were younger (36.3 ± 15.5 years) than those with the classical form of OP. The clinical presentation was subacute in all cases with a mean duration of symptoms before admission of 14.5 ± 13.2 days. The radiological pattern was characterized by centrilobular nodules and “bud-in-tree” sign in 86.7% of patients. The diagnosis was based on histological examination of transbronchial (28.6%) or surgical biopsies (71.4%).Diagnosis:An associated condition was identified in 65% of cases and included illicit substance abuse (44.5%), myeloproliferative disease (33.5%), and infections (22%).Outcomes:Steroid therapy was effective in all patients with improvement of symptoms and documented radiologic resolution. No relapse was recorded.Lessons:MNOP should be recognized and distinguished from other diagnoses, mainly infectious bronchiolitis and disseminated tumor, as it requires early specific steroid therapy.

Hashimoto's thyroiditis‑induced cryptogenic organizing pneumonia: A case report

“…The current clinical treatment of COP is still based on corticosteroid therapy, and 65–80% of patients with COP achieve complete clinical and pathological remission after corticosteroid therapy. Although COP responds well to corticosteroids, it may be prone to relapse following treatment (23,24). COP may be induced by numerous factors, including viral infections and autoimmune diseases, but its pathogenesis remains incompletely understood and warrants further study.…”

Reply to Takimoto: Micronodular Pattern of Organizing Pneumonia or Hypersensitivity Pneumonia Induced by an Immune Checkpoint Inhibitor?

“…If these features are not detected, a surgical lung biopsy should be considered; however, small biopsy specimens are sufficient for diagnosis. In addition, the prevalence of a micronodular pattern of OP (MNOP) on radiological series is estimated to range from 10% to 24%; 4 however, the prevalence of a diffuse pattern in the total lung field of MNOP is rare. 4,5 CT pattern resembling HP has occasionally been observed in patients with immune checkpoint inhibitor (ICI)-induced pneumonia and described as centrilobular nodules, Copyright © 2020 by the American Thoracic Society bronchiolitis-like appearance, and tree-in-bud micronodularity; 6 however, the manifestation of diffuse pattern in the total lung fields of patients with ICI-induced pneumonia is rare.…”

“…If these features are not detected, a surgical lung biopsy should be considered; however, small biopsy specimens are sufficient for diagnosis. In addition, the prevalence of a micronodular pattern of OP on radiological series is estimated to range from 10% to 24% ( 4 ); however, the prevalence of a diffuse pattern in the total lung field of micronodular pattern of OP is rare ( 4 , 5 ).…”

Micronodular Pattern of Organizing Pneumonia or Hypersensitivity Pneumonia Induced by an Immune Checkpoint Inhibitor?

“…OP, cryptogenic or secondary, is a clinicopathological entity characterized by granulation tissue plugs in the lumen of small airways, alveolar ducts, and alveoli. An unusual radiological presentation corresponding to diffuse micronodular pattern mimicking miliary lung infiltration has been reported, and the prevalence of this micronodular pattern of OP (MNOP) in radiological series is estimated to range from 10% to 24% ( 2 , 3 ). The typical MNOP on CT imaging is widespread lung micronodules without diffuse ground-glass opacities, airspace consolidation, or cavitation.…”

“…In large series of OP, the histological diagnosis was obtained on TBB specimens from 31% to 67% of cases. Importantly, most cases of MNOP were diagnosed by surgical lung biopsy ( 2 ). Regarding HP, the meta-analysis of 11 studies on TBB revealed a diagnostic yield of 64.3% ( 6 ).…”