Blood film examination for vacuolated lymphocytes in the diagnosis of metabolic disorders; retrospective experience of more than 2,500 cases from a single centre.

BACKGROUND A range of metabolic diseases can result in abnormal accumulation of metabolic byproducts, resulting in abnormal lymphocyte cytoplasmic vacuolation, identifiable on routine blood film examination. AIMS This study retrospectively examines the usefulness of blood film examination for vacuolated lymphocytes in a specialist paediatric pathology department in relation to patient's age and presentation. It also describes specific diagnostic features in relation to specific classes of metabolic disease. METHODS Retrospective review of a histopathology database to identify all blood films examined for the detection of vacuolated lymphocytes during a 15 year period (1989-2004). RESULTS In total, 2,550 blood films were investigated. The median age at submission was 2 years (range, birth to 88), and>90% of samples were from children<18 years. The most common indications were developmental delay/regression, ataxia, seizures, and cardiomyopathy. Vacuolated lymphocytes were identified in 156 films (6.1%). The frequency of vacuolated lymphocytes varied with clinical presentation, with ophthalmic indications having the highest positive rate (40%). In cases with vacuolated lymphocytes, a wide range of underlying metabolic diagnoses was apparent, the most common being juvenile neuronal ceroid lipofuscinosis and acid maltase deficiency, which accounted for more than half of the diagnoses. CONCLUSIONS The examination of blood films for lymphocyte vacuolation is clinically useful in patients with a history suggestive of metabolic disease. The test is cheap, rapid, minimally invasive, and provides first line screening, with some findings indicating clues to a specific underlying diagnosis.