My sister-in-law has only a couple of months to live without help.  If
I give her a kidney would that stop the Calciphylaxis?  I am O+ and
she is O with Rh negative factor.  Could that work?

Hi - I'm sorry to hear about your sister-in-law.

No one really understands the mechanism of calciphylaxis - it almost
exclusively occurs in individuals with end-stage renal failure,
although not all with ESRF will develop calciphylaxis (in fact, very
few).  It is thought that calciphlyaxis requires the high calcium and
phosphate levels found in patients with renal failure along with a an
inciting, inflammatory event - for some people this appears to be a
severe infection, or sepsis, in others the insult appears to come from
the drugs used to suppress the immune system (or from the infections
that result from these drugs I suspect) during an organ transplant. 
Kidney transplanation is thought to be a contributing factor towards
the development of calciphylaxis rather than a treatment for this
disorder, so I think that the answer would be no, that a transplant
would not help her.  Additionally, transplanted organs need to be very
close matches of many factors in addition to the ABO and Rh blood
types (which you gave above), and a mismatch at the Rh factor would
likely be a problem.

Best wishes.

synarchy

Sodium Thiosulfate is an IV drug treatment that has helped some
people.  Parathyroidectomy has also helped some or a drug to suppress
PTH hormone