2025 – PAGE 114 – ALLERGY & IMMUNOLOGY

CONDITIONS WITH LOW COMPLEMENT LEVEL

Conditions where low complement levels are found include the following:

• • POSTSTREPTOCOCCAL GLOMERULONEPHRITIS (PSGN)
  • SYSTEMIC LUPUS ERYTHEMATOSUS (SLE)
  • CRYOGLOBULINEMIA
  • HEPATITIS C (because it actually can cause cryoglobulinemia)
  • MEMBRANOPROLIFERATIVE GLOMERULONEPHRITIS (MPGN)
  • MULTIPLE MYELOMA
  • SJOGREN’S SYNDROME

MNEMONIC: This mnemonic is meant to help you remember which diseases are associated with LOW COMPLEMENT on lab testing. Keep in mind that it is not specific enough to differentiate between low C3 versus low C3 and C4, etc. Details on these specific diseases are found elsewhere.

• Imagine you’re at a circus and they ask for a personal item. You hand them a compliment card you plan to mail to your favorite restaurant. It’s in an envelope with a STRIPED POSTAGE STAMP on it. In a magician’s hand, it suddenly starts BURNING UP and flames are shooting off of it. The magician then throws the burning compliment card through a LOOP OF FIRE at a CRYING GREEN GOBLIN that has two NIPPLE-RINGS SHAPED LIKE C’S. The GOBLIN gets angry and becomes monstrously huge. He approaches the audience and stomps on a group of visiting MEMBERS OF PARLIAMENT wearing gray wigs who were quietly watching the show. The only way to appease the green goblin is to keep giving him green M&M’s until his CHEEKS/PAROTIDS are so full that they are ready to pop!
  • STRIPED POSTAGE STAMP = POSTSTREPTOCCCAL GLOMERULONEPHRITIS (PSGN)
  • BURNING UP = Reminder that complement is DECREASED in these diseases
  • LOOP OF FIRE = SYSTEMIC LUPUS ERYTHEMATOSUS (SLE)
  • CRYING GREEN GOBLIN = CRYOGLOBULINEMIA
  • NIPPLE-RINGS SHAPED LIKE C’S = HEPATITIS C (Hep C can cause cryoglobulinemia)
  • MEMBERS OF PARLIAMENT = MEMBRANOPROLIFERATIVE GLOMERULONEPHRITIS (MPGN)
  • M&M’s = MULTIPLE MYELOMA
  • FULL CHEEKS/PAROTIDS = SJOGREN’S SYNDROME

PEARLS:

• LEUKEMIA AND LYMPHOMA are two other causes of DECREASED complement levels.
• NORMAL COMPLEMENT levels are found in IGA VASCULITIS, IGA NEPHROPATHY, RAPIDLY PROGRESSIVE GLOMERULONEPHRITIS (RPGN, not MPGN), and HEMOLYTIC UREMIC SYNDROME.

NEUTROPHIL DISORDERS/PHAGOCYTIC ISSUES

NEUTROPENIA DEFINITIONS

Neutropenia is defined as follows:

• 0–12 MONTHS: ANC of < 1000/μl
• After 12 months: ANC of < 1500/μl. An ANC of < 1500 = Mild, < 1000 = Moderate, < 500 = Severe.
• PEARL: For the pediatric boards, there is a STRONG association between NEUTROPENIA and MUCOSAL ULCERATIONS. This could be due to an immunodeficiency in the patient or during a time of aplasia resulting in pancytopenia.