Differential Diagnosis for Febrile Illness with Low C3, Low C4, and Renal Dysfunction
Single Most Likely Diagnosis
- Post-Streptococcal Glomerulonephritis (PSGN): This condition is characterized by a febrile illness, low levels of complement components C3 and C4, and renal dysfunction, often following a streptococcal infection. The combination of these symptoms makes PSGN a leading candidate for the diagnosis.
Other Likely Diagnoses
- Systemic Lupus Erythematosus (SLE): SLE can present with a wide range of symptoms, including febrile illness, renal dysfunction, and low levels of C3 and C4 due to immune complex deposition. It is a common cause of complement level abnormalities and renal issues in the context of a systemic illness.
- Membranoproliferative Glomerulonephritis (MPGN): MPGN is a type of glomerulonephritis that can lead to low levels of complement, particularly C3, and is associated with renal dysfunction. It can be idiopathic or secondary to other conditions, including infections and autoimmune diseases.
- Shiga Toxin-producing E. coli (STEC) Infection: Certain strains of E. coli can cause a severe illness characterized by hemolytic uremic syndrome (HUS), which includes renal dysfunction. While complement levels are not always low, the severity of the illness and potential for renal failure make it a consideration.
Do Not Miss Diagnoses
- Meningococcemia: This is a life-threatening infection caused by Neisseria meningitidis. It can present with a febrile illness, and while renal dysfunction and low complement levels are not universal, the disease's rapid progression and high mortality rate make it crucial not to miss.
- Thrombotic Thrombocytopenic Purpura (TTP) or Hemolytic Uremic Syndrome (HUS): Both conditions can lead to renal dysfunction and have a high mortality rate if not promptly treated. While they might not directly cause low C3 and C4 levels, their severity and potential for multi-organ failure necessitate consideration.
- Sepsis: Sepsis from any cause can lead to renal dysfunction and has a high mortality rate. Complement levels might be affected in severe infections, and the condition's urgency makes it a "do not miss" diagnosis.
Rare Diagnoses
- Atypical Hemolytic Uremic Syndrome (aHUS): This is a rare condition characterized by the formation of blood clots in small blood vessels throughout the body, leading to renal failure. Complement levels, particularly C3, might be low due to genetic mutations affecting the complement system.
- Dense Deposit Disease (DDD): Also known as Membranoproliferative Glomerulonephritis Type II, DDD is a rare autoimmune disease that affects the kidneys and can lead to low levels of complement, particularly C3.
- C3 Glomerulopathy: This is a group of rare diseases characterized by the accumulation of C3 in the glomeruli, leading to renal dysfunction. It can present with persistently low C3 levels and is often associated with genetic abnormalities in the complement pathway.