What is the immediate management for a 31-year-old male with acute gum bleeding, epistaxis, severe thrombocytopenia, and suspected atypical Hemolytic Uremic Syndrome (aHUS)?

Immediate Management of Suspected Atypical HUS with Acute Bleeding

Initiate eculizumab (900 mg IV weekly × 4 weeks, then 1200 mg at week 5, then 1200 mg every 2 weeks) immediately upon suspicion of aHUS without waiting for confirmatory genetic testing or ADAMTS13 results, as delays increase morbidity and mortality. 1, 2

Critical First Steps (Within Hours)

Immediate Hematology Consultation

• Obtain urgent hematology consultation as delay in identification is associated with increased mortality and morbidity 3
• Stabilize critical organ dysfunction while initiating complement inhibitor therapy 4

Urgent Diagnostic Testing (Do Not Delay Treatment)

• Order ADAMTS13 activity level immediately to exclude thrombotic thrombocytopenic purpura (TTP), as ADAMTS13 <10 IU/dL indicates TTP requiring plasma exchange instead 5, 1
• Obtain stool testing for Shiga toxin-producing E. coli (STEC) to exclude typical HUS, which requires only supportive care 5, 1
• Confirm microangiopathic hemolytic anemia with peripheral blood smear showing >1% schistocytes 5, 1
• Measure LDH, haptoglobin, indirect bilirubin, and reticulocyte count to confirm hemolysis 3
• Check complement levels (C3, C4, CH50) and anti-complement antibodies 1, 4
• Obtain creatinine and urinalysis for hematuria/proteinuria to assess renal involvement 5, 4

Complement Inhibitor Therapy (First-Line Treatment)

Eculizumab Dosing for Adults

• 900 mg IV weekly for 4 weeks 2
• 1200 mg IV at week 5 (one week after fourth dose) 2
• 1200 mg IV every 2 weeks thereafter for at least 6 months 1, 2
• Administer doses within 2 days of scheduled time points 2

Mandatory Meningococcal Prophylaxis

• Vaccinate against meningococcal serogroups A, C, W, Y, and B at least 2 weeks before first eculizumab dose if possible 2
• If urgent therapy cannot be delayed, provide antibacterial prophylaxis immediately and vaccinate as soon as possible 2
• Inform patient that vaccination does not eliminate meningococcal infection risk 2
• Provide Patient Safety Card to carry at all times during and for 3 months after treatment 2

Supportive Management

Transfusion Strategy

• Transfuse red blood cells only for symptomatic anemia or to achieve hemoglobin 7-8 g/dL in stable patients 3, 4
• Transfuse minimum number of RBC units necessary to relieve symptoms 3
• Avoid platelet transfusions unless life-threatening bleeding occurs, as they may worsen thrombotic microangiopathy 1, 4
• For this patient with acute gum bleeding and epistaxis, assess severity: if bleeding is not life-threatening, withhold platelet transfusion 1, 4

Additional Supportive Measures

• Provide folic acid 1 mg daily supplementation 3
• Monitor for acute kidney injury and consider renal replacement therapy if indicated 4, 6

Monitoring Response to Therapy

Laboratory Monitoring Schedule

• Monitor complete blood count every 2-4 weeks until doses stabilized 4
• Assess platelet count normalization (target >150,000/mm³) 4
• Monitor LDH normalization and disappearance of schistocytes to confirm resolution of hemolysis 4
• Track serum creatinine for stabilization or improvement in renal function 4

Critical Pitfalls to Avoid

Do Not Delay Treatment

• Never wait for genetic testing results before initiating eculizumab, as genetic mutations are identified in only 50-60% of aHUS cases 1, 4
• Do not wait for ADAMTS13 results if aHUS is strongly suspected and STEC-HUS is excluded 1

Avoid Premature Discontinuation

• Do not discontinue eculizumab prematurely, as this carries 10-20% risk of relapse with potential renal failure 4
• If eculizumab is discontinued, monitor patient for at least 12 weeks for TMA complications 2

Transfusion Caution

• Do not transfuse platelets prophylactically, as this can worsen microangiopathic thrombosis 1, 4
• Discuss with blood bank team before any transfusions that patient has possible complement-mediated TMA 3

Special Considerations for This Patient

Bleeding Management

• The acute gum bleeding and epistaxis with severe thrombocytopenia require careful assessment 3
• Apply local hemostatic measures (nasal packing, topical thrombin) before considering platelet transfusion 1
• Reserve platelet transfusion only if bleeding becomes life-threatening (intracranial hemorrhage, massive GI bleeding) 1, 4

Genetic Testing (After Treatment Initiation)

• Order next-generation sequencing of complement genes (CFH, CFHR1-5, C3, CD46, CFI, THBD, DGKE, CFB) 3, 1
• Provide genetic counseling once diagnosis confirmed due to possible genetic transmission 3

Long-Term Planning

• Maintain eculizumab therapy indefinitely unless thorough risk assessment performed 4
• Monitor for signs of relapse including clinical presentation, laboratory data, and proteinuria 3, 4
• Counsel patient about increased infection risk, particularly encapsulated bacteria 2