Random Step 1 notes

Here goes for some random notes related to questions that I'm doing for the Step 1 exam.

Leigh disease: mitochondrial disorder also known as subacute necrotising encephalomyelopathy. Specific defect is cytochrome oxidase. Particularly affects muscle and brain, patients present in early adulthood, have progressive intellectual deterioriation, weakness, ataxia and siezures, then die within a few years. I'm not quite sure why they wait so long to present... but I'm not overly bothered either and am too lazy to look it up further!

Tuberculin test: aka PPD. Injection of small amount of tuberculin under the skin. If there's a delayed type IV hypersensitivity reaction, with tissue damage mediated by macrophages that are stimulated by previously sensitised CD4+ T-memory cells - which in turn are recognising the antigen presented by the macrophages.

Hypersensitivity is one that I always get confused by... I found a good mnemonic somewhere (that I've now lost and don't precisely remember) which refers to the ACID test:

Ok, so it's not perfect, but it's a start! Type II hypersensitivity can be subdivided into non-cytotoxic and cytotoxic (T-cell mediated). But there's a bit of an overlap between types II and III, apparently...

... onto salivary mucus formation. Most mucus is medial, meaning sublingual ('l' is also higher up the alphabet than 'm', and therefore comes first), then submandibular, then parotid glands, in order of percentage mucus-producing tissues.

Anyway, I'm done for today. Way too many distractions and need to do something other than stare at a computer screen for a while (although, gotta say that reading the MMC farce as it goes on is kind of amusing). More tomorrow, perhaps, or in the next few days.