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

Abstract

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.

Figure 1

Histograms showing the age distributions at the time of submission of blood film examination in (A) all 2550 cases and (B) those aged 18 or less (2318 patients; 91%).

Figure 2

Photomicrographs of blood films submitted for examination for the presence of vacuolated lymphocytes. (A) Routine May-Grunwald-Giemsa stained blood film showing two lymphocytes with many large bold vacuoles, such as are seen in GM1 gangliosidosis, and juvenile Batten’s disease. (B) Routine May-Grunwald-Giemsa stained blood film showing a lymphocyte with discrete small vacuoles seen in Pompe’s disease and adult acid maltase deficiency. (C) Periodic acid Schiff (PAS) stained blood film showing a lymphocyte with PAS positive inclusions in Pompe’s disease and adult acid maltase deficiency. (D) Toluidine blue stained blood film showing metachromatic cytoplasmic inclusions in a lymphocyte. (E) Enzyme histochemical demonstration of β galactosidase in a blood film showing normal enzyme activity in a lymphocyte and eosinophil but negative activity in a neutrophil. (F) Enzyme histochemical demonstration of β galactosidase in a blood film showing absent enzyme activity in a lymphocyte and a granulocyte seen in GM1 gangliosidosis and galactosialidosis.

Figure 3

Low power image of a blood film, illustrating the correct area in which to look for the presence of vacuolated lymphocytes (arrow), and (inset) high power photomicrograph demonstrating a small lymphocyte and monocyte (May-Grunwald-Giemsa staining; original magnification, ×400).