2025 – PAGE 107 – ALLERGY & IMMUNOLOGY
CD4 CELL
CD4 cells = Helper T cells
MNEMONIC: CD4 = Helper = “Hel4er” T cells. Just replace the p with a 4 (or, if you prefer, “4elper T cells”).
CD8 CELL
CD8 cells = Cytotoxic T cells
NEUTROPENIA
Neutropenia is defined as an ANC < 1000 for children less than 1 year of age, and < 1500 for older children. For the boards, there is a STRONG association with MUCOSAL ULCERATIONS. MUCOSAL ULCERATIONS = NEUTROPENIA. The patient may have a genetic immunodeficiency, or possibly a low ANC due to aplasia. (Is the patient pancytopenic?)
- Mild neutropenia: ANC < 1500
- Moderate neutropenia: ANC < 1000
- Severe neutropenia: ANC < 500.
PEARL: A key point to remember is that an 11-month-old with an ANC of 1050 is NOT neutropenic.
PEARLS/MNEMONICS FOR BRUTON’S, SCID, AND HYPER-IGM
- PEARL: This table summarizes a few KEY findings from some of the disorders you’re about to see.
| LAD/TONSILS | PCP PNA | LYMPHOPENIA | |
| Bruton’s | NO | NO | |
| SCID | NO | YES | YES |
| Hyper-IgM | PRESENT | YES | |
| DiGeorge | YES |
* MNEMONICS: The disorders will be discussed in more detail. Memorize the following mnemonic in the meantime. ABSENT NODES/SMALL TONSILS: “SMOOTH neck/face and oropharynx without any bumps.” The smooth neck/face represents a LACK OF LYMPHADENOPATHY on exam. The “oropharynx without any bumps” represents a LACK OF TONSILS.
- BRUTON’S: “Use BRUT aftershave so you can have a SMOOTH face/neck!” Now imagine the most muscular man you know using BRUT aftershave. He has a SMOOTH face/neck (no LAD or tonsils on exam), but he also cut himself. He’s bleeding and starts to cry because he’s been too macho to establish care with a PCP. HE DOES NOT HAVE A PCP = PCP pneumonia is NOT seen in Bruton’s Agammaglobulinemia.
- SEVERE COMBINED IMMUNODEFICIENCY = SCID: “You can SCID across SMOOTH surfaces, like a curvy and SMOOTH NECK.”
PNEUMOCYSTIS CARINII PNEUMONIA (PCP)
PNEUMOCYSTIS CARINII PNEUMONIA (PCP) = PNEUMOCYSTIS JAROVECI PNEUMONIA = FOUND IN Hyper IgM and SCID (but not BRUTons).
MNEMONIC: Imagine a super HYPER naked preschooler running all over the gravel schoolyard. He’s being chased by the teacher when he SCIDS. He does a running split and destroys his NADS/NODES. His mommy has to come and take him to his established PCP to get checked out…and maybe to rule out ADHD. J The destruction of the NADS kind of represents a LACK of lymph NODES (goNADS or goNODES or noNODES). This child DOES have a PCP, which means he IS susceptible to getting PCP/PJP.