Skin Lesions Mimicking Mosquito Bites as the Initial Presentation of Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma

We report the case of a 60-year-old man who initially presented in October 2021 with a history of recurrent itchy skin lesions across exposed areas of his body such as the neck and extremities. As per history and clinical examination, the lesions were initially interpreted as an insect bite reaction for which the patient was provided with symptomatic treatment. Despite the treatment, the patient continued to experience recurrent skin lesions. Histopathologic exam of a skin biopsy showed eosinophil-rich superficial and deep inflammatory infiltrates which supported the diagnosis of a cutaneous reaction to an insect bite or another hypersensitivity-type reaction which further made the diagnosis challenging. In 2024, he developed systemic symptoms such as dizziness, vomiting, and generalized lymphadenopathy. Laboratory tests revealed significant leukocytosis with persistent lymphocytosis, mild anemia, and thrombocytopenia. A peripheral smear was done and showed mature lymphocytosis with smudge cells. Flow cytometry identified a clonal B-cell population expressing CD5, CD23, CD200, and lambda light-chain reaction, supporting a diagnosis of chronic lymphocytic leukemia. Positron emission tomography-computed tomography (PET-CT) demonstrated hypermetabolic lymphadenopathy above and below the diaphragm and hepatosplenomegaly. Cutaneous manifestations resembling different benign dermatologic conditions, such as an insect bite reaction, may rarely precede systemic symptoms of an underlying hematologic malignancy. This case emphasizes the significance of reassessment and follow-up in patients with recurrent and evolving dermatological findings.