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Introduction: Infestation with Pediculus species, or common lice, is frequently diagnosed in the emergency department (ED). Because lice ingest human blood, prolonged and heavy infestation can plausibly lead to iron deficiency anemia. Severe anemia attributable to lice infestation has infrequently been reported to date. Our objective in this study was to retrospectively review cases of lice-related anemia at a single public hospital to identify risk factors and associated demographic and clinical features of this disease process. Methods: We screened the medical records for patients presenting to the ED of an urban public hospital between 2016–2024 for the diagnoses of lice infestation and severe anemia (hemoglobin < 7 grams per deciliter (g/dL). Cases were reviewed for clinical and demographic characteristics. Results: A total of 932 patients were diagnosed with pediculosis infestation in the ED during the study period; 332 (35.6%) of those patients had a complete blood count obtained by the treating team. Thirty-seven cases of severe anemia were identified (3.9% of total pediculosis cases, 11.1% of those for whom a complete blood count was obtained); 84% were microcytic, indicating iron deficiency anemia. Twenty-five patients (68%) were undomiciled, and nine patients (24%) were shelter domiciled. Twenty-three patients (62%) had comorbid psychiatric diagnoses, and 21 (51%) had substance use disorders. The median hemoglobin was 4.4 g/dL (range 2.4-6.9 g/dL). Thirty patients (81%) were admitted to a medical floor and seven patients (19%) to an intensive care unit, each with a comorbid primary condition. Conclusion: In this cohort, anemia secondary to lice infestation was seen in patients with unstable housing, substance use disorders, and psychiatric disease. Most patients were hemodynamically stable, consistent with the proposed mechanism of chronic blood loss. The prevalence of this condition may be higher than previously noted among this vulnerable population. Emergency physicians should be aware of this rare but potentially serious disease process.

INTRODUCTION/BACKGROUND:Infestation with Pediculus species, or common lice, is frequently diagnosed in the emergency department (ED). Because lice ingest human blood, prolonged and heavy infestation can plausibly lead to iron deficiency anemia. Severe anemia attributable to lice infestation has infrequently been reported to date. Our objective in this study was to retrospectively review cases of lice-related anemia at a single public hospital to identify risk factors and associated demographic and clinical features of this disease process. METHODS:We screened the medical records for patients presenting to the ED of an urban public hospital between 2016-2024 for the diagnoses of lice infestation and severe anemia (hemoglobin < 7 grams per deciliter (g/dL). Cases were reviewed for clinical and demographic characteristics. RESULTS:A total of 932 patients were diagnosed with pediculosis infestation in the ED during the study period; 332 (35.6%) of those patients had a complete blood count obtained by the treating team. Thirty-seven cases of severe anemia were identified (3.9% of total pediculosis cases, 11.1% of those for whom a complete blood count was obtained); 84% were microcytic, indicating iron deficiency anemia. Twenty-five patients (68%) were undomiciled, and nine patients (24%) were shelter domiciled. Twenty-three patients (62%) had comorbid psychiatric diagnoses, and 21 (51%) had substance use disorders. The median hemoglobin was 4.4 g/dL (range 2.4-6.9 g/dL). Thirty patients (81%) were admitted to a medical floor and seven patients (19%) to an intensive care unit, each with a comorbid primary condition. CONCLUSION/CONCLUSIONS:In this cohort, anemia secondary to lice infestation was seen in patients with unstable housing, substance use disorders, and psychiatric disease. Most patients were hemodynamically stable, consistent with the proposed mechanism of chronic blood loss. The prevalence of this condition may be higher than previously noted among this vulnerable population. Emergency physicians should be aware of this rare but potentially serious disease process.