LAUSR

Dear editor Paroxysmal cold hemoglobinuria (PCH) is a rare type of cold mediated autoimmune hemolytic anemia (AIHA) causing intravascular hemolysis and hemoglobinuria typically after exposure to cold. It is mediated by donath landsteiner (DL) antibodies (Abs) directed against the P antigen on the RBC surface. DLAb is an IgG Ab encountered after a viral illness or immunization as an acute form in young children and in chronic form in some hematological malignancies and tertiary syphillis (of historical importance only) in adults [1–3]. There are reports of parvo-virus and respiratory syncytial virus (RSV) associated PCH in adults [4,5]. DLAb has a strong affinity for RBCs and remains attached to them even at core body temperatures where it activates the initiator classical as well as terminal complement pathways leading to red blood cell (RBC) lysis. DLAb does not disintegrate and is capable of binding to new RBCs unlike the complement which is consumed with each hemolytic event. This nature of DLAb results in certain spurious results on hemogram like extremely low RBC count, MCV exceeding linearity which mimic other types of AIHA and often mislead the pathologists and clinicians. However there are certain pathological findings and tests as discussed and explained in detail below that can help us reach the correct diagnosis. There are several reported cases where the erythrogram shows spurious results owing to IgM autoantibody [6–8]. The index case is different beacuse here the offender is a IgG biphasic hemolysin which causes paroxysmal hemoglobinuria.