Immunodeficiency: Complement disorders.

The complement system is an important component of innate and adaptive immunity that consists of three activation pathways. The classic complement pathway plays a role in humoral immunity, whereas the alternative and lectin pathways augment the innate response. Impairment, deficiency, or overactivation of any of the known 50 complement proteins may lead to increased susceptibility to infection with encapsulated organisms, autoimmunity, hereditary angioedema, or thrombosis, depending on the affected protein. Classic pathway defects result from deficiencies of complement proteins C1q, C1r, C1s, C2, and C4, and typically manifest with features of systemic lupus erythematosus and infections with encapsulated organisms. Alternative pathway defects due to deficiencies of factor B, factor D, and properdin may present with increased susceptibility to Neisseria infections. Lectin pathway defects, including Mannose-binding protein-associated serine protease 2 (MASP2) and ficolin 3, may be asymptomatic or lead to pyogenic infections and autoimmunity. Complement protein C3 is common to all pathways, deficiency of which predisposes patients to severe frequent infections and glomerulonephritis. Deficiencies in factor H and factor I, which regulate the alternative pathway, may lead to hemolytic uremic syndrome. Disseminated Neisseria infections result from terminal pathway defects (i.e., C5, C6, C7, C8, and C9). Diagnosis of complement deficiencies involves screening with functional assays (i.e., total complement activity [CH50], alternative complement pathway activity [AH50], enzyme-linked immunosorbent assay [ELISA]) followed by measurement of individual complement factors by immunoassay. Management of complement deficiencies requires a comprehensive and individualized approach with special attention to vaccination against encapsulated bacteria, consideration of prophylactic antibiotics, treatment of comorbid autoimmunity, and close surveillance.

Secondary Syphilis Presentation and Urticarial Eruption After Moderna COVID-19 Vaccination.

The diversity of the cutaneous manifestations of syphilis and the ability of the spirochete to evade diagnosis have been well documented by medical literature. However, what triggers the onset of secondary syphilis is not yet clear because of difficulties studying the bacterium. Our case describes the onset of a heterogeneous rash (or coexisting rashes) that presented the day after vaccination with the Moderna mRNA-1273 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine. The potential etiologies of the patient's rash: A vaccine reaction, reactivation of chronic spontaneous urticaria, or a physical sign of syphilis itself are then reviewed. The potential for the Moderna coronavirus disease 2019 (COVID-19) vaccine to be the catalyst of this patient's cutaneous manifestations of his immune system responses is also hypothesized.

Ruptured Abdominal Aortic Aneurysm Presenting as Septic Shock.

A patient presented to the emergency department with undifferentiated shock 4 days after discharge from a hospitalization for a lower gastrointestinal bleed. The patient fulfilled 4/4 of the Systemic Inflammatory Response Syndrome criteria and 3/3 of the quick Sequential Organ Failure Assessment criteria on presentation to the emergency department, notably, without a localized source of infection and no localizing symptoms. After admission, the patient's hemoglobin was found to have dropped more than expected after intravenous (IV) fluid administration, suggesting a potential alternative or concurrent etiology of the patient's shock state. A digital rectal and focused assessment with sonography in trauma exam were performed and negative. The patient was then diagnosed with a ruptured infrarenal abdominal aortic aneurysm contained in the retroperitoneum by repeat point-of-care ultrasound. The patient was hemodynamically stabilized and taken for emergent grafting without confirmatory imaging. The patient was later found to also have 4/4 blood cultures positive with methicillin-sensitive Staphylococcus aureus associated with an aortic valvular vegetation and a mycotic aneurysm which contributed to the abdominal aortic aneurysm rupture. This case supports the use of comprehensive point-of-care ultrasound imaging to more rapidly and more definitively differentiate types of shock and etiologies of a shock state which can lead to more timely changes in management and improvement in outcomes.