Hemolytic uremic syndrome (HUS) is a thrombotic microangiopathy (TMA) affecting the kidneys. Compared with typical HUS due to an infection from shiga toxin-producing <i>Escherichia coli</i>, atypical HUS involves a genetic or acquired dysregulation of the complement alternative pathway. In the presence of a mutation in a complement gene, a second trigger is often necessary for the development of the disease. We report a case of a 54-year-old female, with a past medical history of pulmonary tuberculosis, who was admitted to the emergency service with general malaise and reduction in urine output, 5 days after vaccination with ChAdOx1 nCoV-19. Laboratory results revealed microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Given the clinical picture of TMA, plasma exchange (PEX) was immediately started, along with hemodialysis. Complementary laboratory workup for TMA excluded thrombotic thrombocytopenic purpura and secondary causes. Complement study revealed normal levels of factors H, B, and I, normal activity of the alternate pathway, and absence of anti-factor H antibodies. Genetic study of complement did not show pathogenic variants in the 12 genes analyzed, but revealed a deletion in gene CFHR3/CFHR1 in homozygosity. Our patient completed 10 sessions of PEX, followed by eculizumab, with both clinical and laboratorial improvement. Actually, given the short time lapse between vaccination with ChAdOx1 nCoV-19 and the clinical manifestations, we believe that vaccine was the trigger for the presentation of aHUS in this particular case.

IntroductionCases of central diabetes insipidus (CDI) have been reported after COVID-19 infection, with hypophysitis being the most likely cause. COVID-19 vaccines potential adverse effects may mimetize some of these complications.Case ReportWoman 37 years old, with rheumatoid arthritis under adalimumab (40 mg twice a month) since December 2018. She was in her usual state of health when she has received the second dose of BNT162b2 mRNA COVID-19 vaccine (June 2021). Seven days later, she started reporting intense thirst and polyuria and consulted her family physician.Blood Analysiscreatinine 0.7 mg/dL, glucose 95mg/dL, Na+ 141mEq/L, K+ 3.9 mEq/L, TSH 3.8 mcUI/L (0.38-5.33), FT4 0.9 ng/dL (0.6-1.1), cortisol 215.4 nmol/L (185-624), ACTH 21.9 pg/mL (6- 48), FSH 4.76 UI/L, LH5.62 UI/L, estradiol 323 pmol/L, IGF1 74.8 ng/mL (88-209), PRL 24.7mcg/L (3.3-26.7) osmolality 298.2 mOs/Kg (250- 325); Urine analysis: volume 10200 mL/24h, osmolality 75 mOs/Kg (300-900), density 1.002. On water restriction test: 0’ – Serum osmolality 308.8mOsm/Kg vs. urine osmolality 61.0 mOsm/Kg; 60’ - urine osmolality 102 mOsm/Kg; urine osmolality 1 h after desmopressine was 511mOsm/kg. MRI revealed no abnormal signs consistent with hypophysitis except for the loss of the posterior pituitary bright spot on T1 weighted imaging. Diagnosis of CDI was assumed, and started therapy with desmopressine. A report of potential adverse effect was addressed to national health authorities.ConclusionIn hypophysitis MRI often shows loss of posterior pituitary bright spot on T1 weighted imaging, pituitary enlargement or stalk thickening but those findings were not present in this patient. To the best of our knowledge, CDI has never been reported following administration of a COVID-19 vaccine.

Introduction Generalized immunization against COVID19 has become the cornerstone in prevention of associated severe acute respiratory syndrome. Maintenance dialysis patients (MDP) are at higher risk of both exposure and mortality from the disease. Efficacy and security of BNT162b2 vaccine is well documented for the general population, but not in MDP, particularly in peritoneal dialysis (PD) patients. This study aims to compare humoral response between HD and PD patients. Materials and Methods Observational prospective study including MDP on HD or PD program from a Portuguese middle-sized Nephrology Center, who received BNT162b2. Specific anti-Spike IgG was measured as arbitrary units per milliliter (AU/mL) on two separate occasions: 3 weeks after the first dose and 3 weeks after the second. The two modality groups were compared both for absolute value and number of non-responders (NR) after both inoculations. Demographic data was also obtained and compared. Results Of 73 patients enrolled, 67 were eligible for the final study: 42 HD and 25 PD patients. PD group developed significantly higher antibody titers both after first (Med 5.44 vs 0.99; p<0.01) and second dose (Med 170.43 vs 65.81; p<0.01). HD status was associated with non-responding after the first dose (Phi=0.383; p<0.01), but not after the second one (p=0.08). Age, Charlson Comorbidity Index and dialysis vintage were lower in the PD group (p<0.01; p=0.02; p<0.01, respectively). Conclusion This study demonstrated a better humoral response to immunization with BNT162b2 in PD patients, when comparing to HD patients, after both inoculations. Both groups showed substantial humoral response after just one dose of the vaccine. Older age and higher comorbidity burden may explain the relative immunogenicity deficit, probably in a superior degree comparing with age matched healthy population.

Introduction: Maintenance dialysis patients (MDP) are at higher risk of exposure with increased mortality from COVID-19 with generalized immunization becoming the cornerstone in prevention. This study aims to compare humoral response between hemodialysis (HD) and peritoneal dialysis (PD) patients. Materials and Methods: Observational prospective study following HD and PD programs from a Portuguese Center receiving BNT162b2 vaccine. Specific anti-Spike IgG quantification to compare both for absolute value and nonresponders (NR) between modalities and against risk factors. Results: Of 67 MDP, 42 were HD and 25 PD patients. PD developed higher antibody titers after both first (median 5.44 vs. 0.99 AU/ml, p < 0.01) and second dose (median 170.43 vs. 65.81 AU/ml; p < 0.01). HD associated with NR after the first dose (p < 0.01). Conclusion:This study demonstrated improved humoral immunogenicity with BNT162b2 in PD compared to HD patients. These differences are attributed to comorbidity burden and age differences, rather than dialysis modality.

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