Diagnostic difficulties in a patient with paroxysmal cold haemoglobinuria and acute kidney injury

Paroxysmal cold haemoglobinuria (PCH) is a form of autoimmune haemolytic anaemia (AIHA) characterised by a sudden onset of haemoglobinuria, either spontaneously or following exposure to cold. In children, it is commonly seen following a viral illness or after immunisation. Diagnosis of PCH is confirmed by a positive Donath Landsteiner (DL) test in which biphasic haemolysins are detected. However, in a real clinical setting, the serological diagnosis of PCH is not always easy. PCH can cause tubular renal injury, which in turn can lead to renal impairment. We describe a case of a two-year-old boy who was admitted to the hospital with pallor, jaundice, dehydration, and dark urine. Two weeks before admission, the child had an upper respiratory tract infection. Laboratory tests showed severe anaemia (haemoglobin 4.5g/dl, haematocrit 11.5%, LDH 8525 U/l), hyperbilirubinaemia (104 μmol/l), haemoglobinuria, and acute kidney injury: GFR 43.9 ml/min/1.73 m² (grade 2 according to Acute Kidney Injury Network). The direct antiglobulin test was positive for C3c and C3d complement components. The diagnosis of PCH was confirmed by the presence of biphasic antibodies in a DL test on the third day of hospitalisation. The patient received supportive treatment.