BACKGROUND: Hemolytic uremic syndrome (HUS) can be categorized as primary (typical or atypical) or secondary (with a coexisting diseases). Typical HUS usually means shiga-toxin-medicated and thrombotic thrombocytopenic purpura. Secondary HUS is often initiated by coexisting diseases or conditions such as infections, transplantation, cancer, and autoimmune disease. Atypical HUS (aHUS) is usually induced by genetic mutations of one or several complement-regulating genes and associated with dysregulated complement activation. In the era of compliment-inhibiting therapy, early recognition of aHUS is important for patient prognosis. However, compliment-inhibiting therapy is not always beneficial in patients with secondary HUS.

CASE REPORT: We present a case of a 49-year-old woman with aHUS, which was caused by a novel genetic point mutation of complement factor H gene (p.Gly1110Ala) mimicking secondary HUS with scleroderma. Instead of administering eculizumab treatment for C5 polymorphism, the patient was successfully treated with mycophenolate mofetil.

CONCLUSIONS: HUS has complex and mixed etiologies and requires genetic testing. Attention should be paid to new point mutations in aHUS.

Keywords: Hemolytic-Uremic Syndrome, Mutation, Scleroderma, Diffuse, Atypical Hemolytic Uremic Syndrome, Complement Factor H, Mycophenolic Acid, Point Mutation, Scleroderma, Systemic