Fungal infections in immunocompetent patients-even those with intrathecal drug delivery pumps (ITDDPs)-are exceedingly rare. This is the first report of Trichosporon arachnoiditis in a patient with an ITDDP. The patient presented with falls and progressive lower extremity weakness. Imaging showed a compressive lesion, for which the patient was taken for exploration and decompression. Cultures grew Trichosporon and pathology showed fungus consistent with Aspergillus The patient's recovery was complicated by respiratory failure requiring re-intubation secondary to an exacerbation of myasthenia gravis. Additionally, the patient developed cholestatic hepatotoxicity from voriconazole requiring biliary sphincterotomy and replacement of voriconazole. ITDDPs pose a significant risk of infection, and although fungal arachnoiditis is rare, it should be considered in the differential diagnosis in this patient population.

Hypersensitivity pneumonitis (HP) is classified into fibrotic and nonfibrotic phenotypes. Rarely, nonfibrotic HP presents radiologically with multiple cysts. Histologically, nonfibrotic HP is characterized by cellular interstitial pneumonia, cellular bronchiolitis, and poorly formed non-necrotizing granulomas; however, the histopathological features and mechanisms underlying cyst formation remain poorly understood. We report a rare case of cyst-predominant nonfibrotic HP. A 42-year-old woman underwent pulmonary surgery for enigmatic lung cysts complicated by spontaneous pneumothorax. Histological examination revealed subpleural cystic lesions mimicking those of Birt-Hogg-Dubé syndrome and an absence of cellular interstitial pneumonia, a feature considered mandatory in current HP guidelines. Despite this, the presence of cellular bronchiolitis, microgranulomas, and supportive clinical findings led to a diagnosis of nonfibrotic HP following multidisciplinary discussion. This case underscores a significant diagnostic pitfall, as cyst-predominant nonfibrotic HP may be overlooked by clinicians and pathologists and misdiagnosed as Birt-Hogg-Dubé syndrome or other cystic lung diseases.

Usual interstitial pneumonia (UIP) is a common pattern in fibrotic lung diseases characterized by distinctive radiological and histopathological features. UIP is associated with various underlying causes including idiopathic UIP, i.e. idiopathic pulmonary fibrosis (IPF), and secondary UIP, e.g. connective tissue disease-associated interstitial lung diseases (CTD-ILDs) and fibrotic hypersensitivity pneumonia (fHP). Previous work suggests radiological UIP patterns have strong correlations with overall poor prognosis. This review synthesizes current knowledge on the diverse entities of fibrotic lung diseases presenting with the UIP pattern. This review also highlights previous studies in biomarker searching of IPF and secondary UIP. A number of biomarkers associated with disease diagnosis are summarized, providing new insights for clinicians in disease differentiation. Finally, this review emphasizes the future directions of differential diagnosis through radiology- and blood- biomarkers with the integration of artificial intelligence (AI).