Ophthalmic histiocytic lesions (diseases of the L group): A multicenter clinicopathological study of 18 cases and review of literature Tariq Alzahem 1,2,3 * , Hind M Alkatan 1,2,4 * , Azza MY Maktabi 5 , Naif Alsulaiman 6 and Antonio Augusto V Cruz 7 Abstract Introduction: Langerhans cell histiocytosis (LCH) and Erdheim–Chester disease (ECD) are rare histiocytic disorders in the L (Langerhans) group diseases. They range from self-limited benign diseases to lethal disseminated forms. Methods: This retrospective study was conducted in 3 tertiary hospitals in Saudi Arabia and Brazil. Histopathological records were searched for all patients diagnosed with ocular and periocular histiocytic disorders from January 1993 to December 2018. Histopathological slides and medical files were reviewed for data collection and simple analysis of demographics, clinical manifestations, and management. The relevant literature is reviewed. Results: Twenty-two eyes of 18 patients with biopsy-proven histiocytic disorders in the L group were included. Female- to-male ratio was 1.25:1. Average age at presentation was 14 years (range, 1–54). LCH was diagnosed in 14 eyes, while eight eyes had ECD. All LCH cases were unilateral and confined to the bone as cases of eosinophilic granuloma (EG), while patients with ECD were bilateral. Commonest presentations in EG and ECD were eyelid swelling (85.7%) and periocular xanthomas (75%), respectively. Orbit was involved in 100% of EG cases, with bony erosion in 54.5%. Relevant systemic involvement was found in 100% of ECD and 21% of EG cases. Surgical intervention was needed in 16 of the 22 eyes (72.7%). All EG and 25% of patients with ECD required surgical excision. Conclusions: Histiocytic disorders are a rare group of diseases, including the L group. Relevant systemic associations require specific and selective therapy. A high clinical index and multidisciplinary collaboration are essential for the proper evaluation and management of these patients. Keywords Histiocytes, Langerhans cell histiocytosis (LCH), Eosinophilic granuloma, Erdheim-Chester disease (ECD), Touton giant cell Date received: 3 November 2021; accepted: 21 June 2022 1 Ophthalmology Department, College of Medicine, King Saud University, Riyadh, Saudi Arabia 2 King Saud University Medical City, King Saud University, Riyadh, Saudi Arabia 3 Vitreoretinal Division, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia 4 Pathology and Laboratory Medicine Department, College of Medicine, King Saud University, Riyadh, Saudi Arabia 5 Pathology and Laboratory Medicine Department, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia 6 Oculoplastics Division, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia 7 Ophthalmology Department, School of Medicine of Ribeirão-Preto, University of São Paulo, São Paulo, Brazil *The first 2 authors contributed equally to the manuscript. Corresponding author: Hind M Alkatan, Department of Ophthalmology, College of Medicine, King Saud University, Riyadh 11362, Saudi Arabia. Emails: hkatan@ksu.edu.sa, hindkatan@yahoo.com Original research article European Journal of Ophthalmology 1–11 © The Author(s) 2022 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/11206721221113431 journals.sagepub.com/home/ejo