OBJECTIVELysosomal storage diseases are a group of inherited disorders caused by deficiency of lysosomal enzymes or structural components. The manifestations of lysosomal storage diseases are complicated due to different enzyme deficiency. It has been reported that a range of metabolic diseases resulting in abnormal accumulation of metabolic byproducts may exhibit abnormal cytoplasmic vacuolation of lymphocytes. The aim of this study was to elicit the usefulness of vacuolated peripheral lymphocytes detection in screening and diagnosis of lysosomal storage diseases.

METHODClinical data of 42 patients who underwent microscopic and electron microscopic examination of peripheral blood specimens in our department were retrospectively evaluated between January 2008 and December 2009.

RESULTForty-two patients with the suspected lysosomal storage diseases were included, these patients presented with motor and developmental retardation and/or regression. Seizure occurred in 32 patients. Hepatosplenomegaly were found in 4 patients. Three patients presented with declined visual acuity. Atrophy and/or abnormal signals were detected on cranial CT/MRI images in 24 patients. Blood biochemical tests were normal. Serum levels of ammonia, lactic acid and pyruvate were normal. Serum amino acid profiles and urinary organic acid profiles were normal. Serum fatty acid profiles were normal. Vacuolated lymphocytes were detected on microscopic examination of blood film in 14 patients, and 8 of these patients were confirmed to have lysosomal storage disease. Curvilinear body was found on electronic microscopic examination of peripheral lymphocytes specimens in 4 patients, confirming the diagnosis of neuronal ceroid lipofuscinosis. In 3 of these 4 patients, curvilinear body were also found on electronic microscopic examination of skin and/or muscle specimens. Enzyme analysis confirmed the diagnosis of metachromatic leukodystrophy in one patient and Pompe's disease in another patient. Typical pathological changes were found on the examination of bone marrow in 2 patients with normal acid sphingomyelinase activity. So the patients were diagnosed with Niemann-Pick disease type C. The diagnosis of other 6 patients with vacuolated lymphocytes was unknown.

CONCLUSIONBecause of its usefulness and minimal invasiveness, vacuolated peripheral lymphocytes examination should be a screening test for lysosomal storage disease. As for patients with suspected neuronal ceroid lipofuscinosis, electron microscopic examination of peripheral lymphocyte specimens may provide specific clues to the final diagnosis.