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 +0  (nbme22#5)

I think this was referring to reverse transcriptase, and the only two viruses I knew that used them were HepB and HIV/retroviruses. Given the context I picked HIV/retroviruses which are SS + sense. This was kind of weird though since the virus was “new” ... but I’ve learned that “new” usually means very little on these tests.

yotsubato  "New" means made up fantasyland virus
yotsubato  Also Hep B is a ssDNA virus that goes to RNA, then is reverse transcribed to dsDNA

 +4  (nbme23#31)

I’m going to say it’s X linked agammaglobulinemia rather than SCID, but the difference between these two are tiny but this is why I think it’s the former:

  • Boy (increased risk but both BA and SCID are x linked)
  • Recurrent bacterial infections but don’t mention diarrhea or thrush which is in SCID
  • Timeline is after 6 months, so the mother’s antibodies wore off.

SCID should be immediately because they just don’t have the IL2 receptors. CVID shows up when they’re 20-40 years old. You get absent germinal centers in both. No mention of absent thymic shadow which is in SCID.

placebo079  “Uniformly” low is also a clue; in CVID they are not.
tea-cats-biscuits  This makes sense, though what really threw me off was that in Classic Bruton’s Agammaglobulinemia there’s near-zero B counts though (or at least that’s what FA and UTD says, “Absent B cells in peripheral blood” FA 116, 2018). The Q says the leukocyte count was normal though. Wouldn’t the leukocyte count include lymphocytes in the differential? And wouldn’t lymphocytes be low due to the near complete lack of B cells in peripheral circulation if it was BA?
partybrockk  @tea-cats-biscuits Bruton’s is a failure of B cells to /MATURE/. So you get normal lymphocyte counts, decreased levels of immunoglobulins, and absent germinal centers.
tea-cats-biscuits  @partybrockk That makes sense to me, but I keep getting hung up on how that’s not what either FA or UTD says about the classic lab findings of XLA. UTD specifically says this: “Laboratory findings include hypogammaglobulinemia/agammaglobulinemia, deficient antibody responses to immunizations, and absent or markedly reduced B cells in the blood,” and I previously quoted FA. I suppose it doesn’t really matter, but it’s definitely a bit frustrating unless I’m missing something about how absent B cells in the blood wouldn’t correlate to a decreased lymphocyte count ...
temmy  please correct me if i am wrong cos i might be but my logic was there is decreases immunoglobulin uniformly meaning the B cells are uniformly absent and since they develop in the germinal center, the germinal center will be absent.
almondbreeze  Picked 'decreased # of CD4 lymphocytes'.. ->Both CD4 and CD8 T lymphocytes were affected; the decrease was most pronounced for naïve T cells. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1809006/)

Subcomments ...

Kid probably had cholera -- giving Na+ and glucose takes advantage of sodium-glucose cotransporter thereby replenishing electrolytes and energy.

hipster_do  To add on to the diarrhea kid -- SGLT1 is the Na-glucose symporter and it facilitates movement of water into the enterocytes. Water loves to follow sodium around, I think sodium over other electrolytes purely because sodium is generally the highest concentration electrolyte. +1