[en] We report the case of a 2.5-month-old infant with severe anaemia discovered fortuitously during an acute febrile illness. The patient was admitted because of a septic arthritis of the knee. Initial biology showed a 3.5 g/dl haemoglobin concentration. The anaemia was microcytic and hypochromic, with obvious haemolysis and reticulocytosis. Standard analysis was not contributive. Further investigations allowed the diagnosis of elliptocytosis. The patient was treated by antibiotics, orthopaedic measures and iterative transfusions. Now, 18 months from the initial episode, she is in good health. With this history, we discuss the clinical process facing severe anaemia during infancy and review the particularities of such uncommon congenital anaemia. Elliptocytosis is a haemolytic anaemia caused by congenital anomalies of the erythrocyte membrane. Diagnosis requires morphological studies of the red blood cells on peripheral blood smear. The disease is often overlooked by membrane protein electrophoresis. The condition is heterogeneous concerning clinical, biochemical and genetic aspects. Most of the cases are linked to mutations of the alpha-spectrin gene, in autoassociation regions. Search of spectrin and protein 4.1 genes mutations can confirm the diagnosis but is not routinely performed.