Avoiding Pitfalls in Ultrastructural Evaluation of Peripheral Blood Leukocyte Buffy Coats for Metabolic Inclusion Disease
John Hicks, Eric Wartchow, Gary Mierau. Baylor College of Medicine & Texas Children's Hospital, Houston, TX; Children's Hospital Colorado, Aurora, CO
Background: Ultrastructural examination of leukocytes within buffy coats prepared from peripheral blood samples is often performed in diagnostic electron microscopy laboratories for evaluation in children with suspected metabolic inclusion disease. Identification of characteristic inclusions by electron microscopy can guide appropriate metabolic disease genetic testing. There are certain ultrastructural features that may be misinterpreted as metabolic inclusions and result in a possible misdiagnosis.
Design: The pathology archives of a pediatric hospital were accessed over a 5 year period to identified ultrastructural inclusions in leukocytes from buffy coats that mimic metabolic disease inclusions and represent potential pitfalls in diagnosis. Buffy coats from 35 patients were identified as having ultrastructural inclusions that possess ultrastructural inclusions that mimic metabolic disease inclusions. The majority of the children were under 2 years of age (75%) with an age range from 1 month to 7 years, and had clinical signs and symptoms concerning for metabolic inclusions diseases (most commonly neuronal ceroid lipofuscinosis [NCL]).
Results: Analysis of the electron microscopic digital images revealed 3 types of inclusions that may mimic metabolic inclusion disease. The most common was tubular arrays within the cytoplasm of lymphocytes (22/35). These tubular arrays may mimic certain forms of NCL; however, the tubular arrays are typically associated with natural killer cells (NK cells). Tubular reticular inclusions (TRIs)were identified in 9 cases. TRIs are associated with autoimmune disease (systemic lupus erythematosus), immunocomprised and immunosuppressed states, and viral infections. Myelin figures were seen in 12 cases, sometimes in cases also with tubular arrays and TRIs. These figures represent degradation products of cell and cytoplasmic membranes.
Conclusions: Identifying cytoplasmic inclusions in peripheral blood leukocytes that may mimic metabolic inclusion disease is important to avoid misdiagnosis of children with suspected metabolic disease and avoidance of unnecessary, inappropriate and expensive genetic testing, Ultrastructural examination of peripheral blood leukocytes in buffy coats provides an initial screening process that assists the clinician in decision making in selecting definitive diagnostic tests.
Monday, March 4, 2013 9:15 AM
Proffered Papers: Section H1, Monday Morning