Atypical haemolytic uraemic syndrome (aHUS), unlike typical HUS is due to complement dysregulation. At least one abnormality of the complement system can be identified in 70% of patients. aHUS is associated with a poor prognosis with 25% mortality and 50% progress to end-stage renal disease. Genetic abnormalities in the complement system, proteins including CFH, CFI, CFB, C3, CFHR1/3 and MCP (CD46) lead to uncontrolled complement activation in aHUS. We presented the second reported case of aHUS associated with a heterozygous c.191G > T mutation in exon 2 of MCP who responded rapidly to plasma exchange.