High LDH cannot be used as sole indicator of haemolysis in DHF since significant elevations of LDH, AST and CK are usual findings in severe dengue cases due to ischemic tissue injury. Higher indirect than direct bilirubin in dengue fever was reported in only 15% of cases in India, suggesting that dengue fever cases with this finding may indicate some haemolysis, as in our patient. Our case developed a positive direct Coombs’ test differing from other cases that were Coombs’ negative. Dengue virus may alter antigens on red blood cell membranes and cross-react with antibody directed against the virus; there may be different immune-related mechanisms by which antibodies are directed at antigens developed on RBC membranes by various dengue virus serotypes. The pathophysiology of thrombocytopenia and leucopenia in dengue fever is poorly understood, but hypotheses such as depression of bone marrow, direct invasion of virus in monocytes and plateletsand increased consumption and destruction, have been proposed, with red blood cells possibly being relatively resistant to viral invasion. Our patient did have leucopenia. In the study by Malathesha et al. 5, leucopenia was seen in 27.6% of cases, lymphocytosis (>45%) in 66%, monocytosis (>10%) in 84.6%, basophilia (>2%) in 52.9%, and 44.4% had platelet counts below 50×10?/L.
Dengue fever with early alterations of biochemical markers such as high LDH, CK, and AST, lower levels of albumin, total cholesterol, and triglycerides can predict severe dengue disease 6. Additionally, rise of LDH, CK and AST (Table 2) are not only predictors of severe dengue, but may also be biochemical features of rhabdomyolysis 12,13. In our case, there was no clinical symptoms or signs to suggest rhabdomyolysis The renal profile was normal. The clinical picture was dominated by marked pallor, jaundice and reticulocytosis. With the sudden anaemia and prolonged APTT, disseminated intravascular coagulopathy was considered, but ultimately thought to be unlikely as the peripheral blood film showed evidence of haemolysis without evidence of microangiopathic features,prothrombin time (PT) and fibrinogen were also normal. Although dengue fever is characterized by either single or multiple cytopenias (thrombocytopenia and/or leucopenia), similar features in peripheral blood film can be seen in bacterial sepsis and other viraemias. Prolongation of APTT may help to differentiate dengue from surgical causes of abdominal pain especially acute appendicitis 7. The abdominal pain of dengue is commonly relieved by fluid replacement. Prolongation of APTT with normal prothrombin time, a characteristic feature of severe dengue 10,11, is thought to be due to imbalance between intrinsic and extrinsic factors in the coagulation systems 10.