22 Oct 2020

10/8/20: atypical HUS

PGY3 Chris Vo presented a case of a 73 y/o F with history of hypertension who was brought in by her husband to the hospital with complaints of abdominal pain, fatigue, and bloody diarrhea for the past 4-5 days.  Patient recently returned from Puerto Vallarta, MX 2 days ago, where she ate various local restaurants.  Husband reports that she has become increasingly lethargic and more confused.   She reports additional nausea but denies fevers, chills or vomiting.  Home medications include amlodipine.  Lives in San Gabriel, CA.  Denies tobacco use, drinks 1 glass of win a day, no drug use.

Vitals: T 36.8, HR 77, RR 21, BP 122/70, O2 sat 99% 2L NC

Physical Exam significant for normal cardiac and pulm exam, abdomen diffusely tender to palpation, scattered ecchymoses on L arm, A&Ox3 but inappropriately answering questions, inconsistently following commands.

CBC: WBC 5.8> Hb 10.1/Hct 30.8 <Plt 94 (MCV 93.2, RDW 13.8%)

CMP:

Na 132/K 3.5/Cl 99/HCO3 23/BUN 43/Cr 1.3 <Glucose 110 (baseline Cr 0.6)

ALP 74>T.protein 5.3/Albumin 2.7/AST 25/ALT 17/Tbili 2.4/Dbili 0.7

Coags: PT 10, INR 1

Infectious workup was significant for positive stool culture for E. coli producing shigella toxin.

Renal workup did not reveal much significance on urinalysis.

Hematology workup revealed peripheral smear with schistocytes, haptoglobin <10, elevated LDH at 977, elevated DDimer, normal fibrinogen, and negative Coombs test.  ADAMTS13 was at 43% (measured during plasma exchange).

Diagnosis was made initially concerning for HUS; however, when the patient did not improve with supportive therapy or plasma exchange, the diagnosis shifted to atypical HUS.

Treatment: The patient initially was treated at outside hospital with supportive therapy with improvement in her bloody diarrhea.  However, on hospital day 8, her mental status acutely worsened with negative findings of stroke on imaging.  Given the schistocytes seen on the peripheral smear along with the thrombocytopenia, initial diagnosis was TTP vs HUS.  She was transferred to the ICU for plasma exchange x 9 days along with 3 days of solumedrol.  Given no improvement, the patient was transferred to Norris in which the diagnosis was shifted more towards atypical HUS given that the patient has not improved clinically on prior treatment.  She was started on eculizumab and on hospital day 3 at Norris an by hospital day 6 at Norris, she has had significant improvement in her mental status and was discharged with clinic follow up.

Teaching points:

  1. Thrombotic microangiopathy (TMA) is a pathology that results in thrombosis in capillaries and arterioles, due to an endothelial injury.  Primary TMA syndromes include TTP and HUS.
  2. Hemolytic uremic syndrome (HUS) is characterized by the simultaneous developed of nonimmune hemolytic anemia, thrombocytopenia and acute renal failure.
  3. In aHUS, a genetic or sporadic insult causes dysfunction in the complement cascade leading to complement deposition on endothelial cells, thickening of arterioles and capillaries and endothelial swelling and detachment.
  4. Treatment included supportive care, plasma exchange and anti-C5 monoclonal antibodies such as Eculizumab.

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