Contrast Sensitivity Impairment in Diabetic Retinopathy: Clinical and Structural Correlates.

Crystal-Storing Histiocytosis (CSH) is an exceptionally rare disorder characterised by the intracytoplasmic accumulation of crystallised materials, most commonly immunoglobulin, within histiocytes []. More than 95% of reported cases are associated with lymphoproliferative or plasma cell disorders (LP-PCDs) including multiple myeloma, plasmacytoma, and low-grade B-cell lymphomas []. Less frequently, CSH has been described in association with autoimmune disease, chronic infection, occupational exposure or medication use, often involving non-immunoglobulin crystalline material [,]. CSH may present in a generalised form, involving multiple organs or in a localised form confined to a single anatomical region []. Pulmonary CSH represents a rare subtype of the localised form with fewer than 30 English-language clinicopathological cases identified. Most published cases of Pulmonary CSH are associated with either LP-PCD or other identifiable secondary conditions [,]. To the best of our knowledge, only one prior English-language clinicopathological case has been reported without an identifiable associated condition []. Here, we report a rare case of pulmonary CSH presenting as multiple pulmonary lesions initially suspected to represent lung cancer. The diagnosis of pulmonary CSH was established histologically following surgical resection, with no evidence of an associated LP-PCD or alternative underlying condition despite extensive evaluation. The patient has undergone over a decade of longitudinal clinical, biochemical and radiological surveillance, providing unique insight into the long-term natural history and radiological evolution of this rare entity. To contextualise our findings, we also present a narrative review of published cases of localised pulmonary CSH.