Atypical presentation of atypical haemolytic uraemic syndrome

A 17-year-old girl presented with fever, myalgia, vomiting for 1 month and oliguria and dyspnoea for 4 days. She was tachycardic,hypertensive, with pedal oedema and decreased breath sounds. She had high serum creatinine (3 mg/dL), anaemia, thrombocytopenia, leucocytosis and eosinophilia with schistocytes. Lactate dehydrogenase, transaminases were high, with low haptoglobin and high ferritin (5269 ng/mL). Complement C3/C4 and fibrinogen were normal. Urinalysis showed large blood and protein and stool studies were negative. Her ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) was normal. Kidney biopsy showed acute interstitial nephritis (AIN) in addition to thrombotic angiopathy. The differentials - haemolytic uraemic syndrome (HUS), thrombotic thrombocytopenia (TTP) and haemophagocytic lymphohistiocytosis (HLH) were ruled out. Her genetic testing was abnormal for large CFHR1-CFHR3 homozygous deletion and heterozygous missense variant in exon 2 of DGKE making the diagnosis of atypical HUS. She received eculizumab and was discharged on oral steroids for AIN and biweekly eculizumab infusions with excellent recovery.