Atypical hemolytic uremic syndrome: a pediatric case report

Background. Atypical hemolytic uremic syndrome (aHUS) is an extremely rare but life-threatening di­s­order in children since it may cause acute kidney injury. Patients with aHUS are at risk of recurrence. Hence, in this paper, we present a case of a 9-year-old boy with aHUS relapse. The child was admitted to the emergency department on the fifth day of illness with main complaints of facial puffiness and decreased urine output. Based on the medical history, the patient developed the second episode of aHUS after 6 years of complete recovery from the first episode. There was no preceding diarrheal illness, instead, the clinical manifestation of both aHUS episodes was triggered by a respiratory tract infection. The results of diagnostic studies performed during the first episode of aHUS were as follows: stool tests for Esche­richia coli and Shiga toxins were negative; a complement assay showed no abnormalities; ADAMTS13 activity and anti-complement factor H antibodies were normal. The results of the kidney ultrasonography and biopsy were consistent with the diagnosis. Family history was remarkable for aHUS in a younger sibling confirmed by molecular genetic testing, in particular, a pathogenic variant in the CD46/MCP (membrane cofactor protein) gene in the heterozygous state has been identified. Physical examination revealed paleness, facial swelling, moderate hypertension, and oliguria. Laboratory findings demonstrated hemolytic anemia, thrombocytopenia, significant azotemia, a severe reduction in the glomerular filtration rate, a high level of aspartate aminotransferase, insignificant electrolyte imbalance, and proteinuria. Supportive treatment included fluid and electrolyte management, fresh frozen plasma, furosemide, and dexamethasone. The child commenced acute hemodialysis due to severe acute kidney injury. Conclusions. A recurrence of aHUS is characterized by severe renal failure requiring acute hemodialysis. Viral infections are potential triggers of aHUS. A relapsing course of the disease and a family history of aHUS indicate the importance of genetic screening, as familial aHUS should be considered.