Childhood T-cell acute lymphoblastic leukaemia expressing "Ia-like" antigen:" a case report.

A 4-year-old girl presenting with vomiting, abdominal pain, and renal failure was found to have gross hepatosplenomegaly, a renal mass, and bilateral pleural effusions. A diagnosis of acute lymphoblastic leukaemia (ALL) was suggested by a peripheral white cell count (WCC) of 119,000 x 10(6)mm3, 57% blasts, 22% lymphocytes, and confirmed by bone marrow examination. Lymphocyte surface marker studies at diagnosis enabled classification as a T-ALL, with a significant proportion of the T cells also bearing receptors for the third component of complement (C3). Seventy-two percent of the peripheral blood mononuclear cells reacted with anti-Ia monoclonal antibody (FMC44), and a smaller proportion (25%) carried receptors for the Fc portion of IgG. The T-classification of this ALL was verified at central nervous system (CNS) relapse and at a subsequent nodal relapse. Double-marker studies on cells from the infiltrated lymph node prepared in suspension confirmed the presence of Ia-positive T cells. The Ia marker is usually a useful discriminant between T and non-T cells in normal and ALL cell populations. The case described here highlights the need for a panel of markers to be used in classification of childhood ALL and supports the suggestion that there is a distinct subtype of Ia-positive T-ALL.