Ok, I have this character idea, but part of it is a negative quality that is not covered in the rules (as far as I've found so far). For SR4

I want a human character with dwarfism. I need the negative quality. Thought maybe the fine folks here can help me out.

just make a human character that is only 1.5m tall and be done with it?

I would simply state that "dwarfism" just makes you a dwarf, as in the realio-dealio as found in SR. The changes brought on by the "whatevertheycallit"...y'know the magic coming back thingy (you can see how much I care about or for the backstory, huh?)... helped change and/or remove some of the pre-existing genetic conditions to fit the new meta-types. Just an option, of course.

That said, with dwarves not being all that uncommon, I would place them at a -5 BP flaw unless they have a particularly disadvantaged version of dwarfism. There are already SR markets on a much larger scale than today for "dwarfgearz" and, to be frank, the character would probably be catered to on a much better scale than today. Buses and cars configured to help them get aboard, etc so the impact on their life would be dramatically reduced.

I didn't think about the fact that having real dwarves would mean that a human with dwarfism would not stand out so much, and not but hampered. I think maybe the -5 bp flaw would be something my game master would go for. I don't care about getting a lot of bp from it, it's more for flavor reasons.

Depends on the type of dwarfism. 25 BP to actually be a Dwarf is a pretty sweet deal. You can always drop another 10 BP to bump your Edge and just try to convince people you're just a short Human, or take the Human-Looking quality.

If it's simply skeletal dwarfism, the movement and gear sizing penalties should be enough. I'd say that cybertechnology can offset many of the other physical problems, possibly without even affecting Essence. A 5 point flaw with the usual backstory expectations, 10 for an awakened character if your GM thinks the surgery should cost Essence.

If it's a variety that affects the organs or cartilage, you're looking at some serious impairment without prohibitively expensive bioware treatments (like penalties to all physical attributes). Probably worth 10 to 20 points. Keep in mind, this puts a bit of pressure on the GM to help you come up with appropriate modifiers and what it would take to offset them. Dwarfism can be crippling.

The social effects of either are pure fluff, and not worth additional BP. Metahumans don't get discounts for racism, neither should you.

Dwarf Poser?

If it was me, I'd cobble it together from other qualities, (Infirm, for example, if the condition is profound enough), along with simply buying lower ratings of certain attributes.

I didn't buy my physical abilities very high (but wasn't planning out it anyway), and I got meta-dwarf speed and item size limitations for 5 bp. It turned out alright in the end. I'm happy with my character and the gm is too.