Peruvian Pasos and Paso Finos are different breeds.
They share ancestors 400 years ago, but each breed developped separately and their gaits are quite different also.
BUT:  
There used to be a registry called the: "American Paso Fino Association."
This registry allowed Peruvian Pasos to be crossed with Paso Finos and still be registered.  Rumours has it that this registry is dissolved.

The "Paso Fino Horse Association" in Florida has never allowed the two breeds to be crossed, and all my horses are registered with this association.  
DSLD (Degenerative Suspensory Ligament Desmitis) is a newly recognized disease and so far had been reported in horses of many breeds.
---Pre purchase vet exams and flexion tests are always recommended!
And with genetic diseases cropping up everywhere, it's always a good idea to look at the soundness of sire and dam!

DSLD - the controversy:

This dreadful disease involves the gradual degeneration of ligaments and connective tissue.  There is no cure.  A flexion test of the joints as done in a pre- purchase exam WILL reveal any problem with this disease.  It is passed on through genetics.  So far all agree.

Research says that it affects many breeds, including Quarter Horses, European Warmbloods, Thoroughbreds and Standartbreds, and Paso Finos, besides Peruvian Pasos.
Research claims that there is
NO HIGHER INCIDENCE OF DSLD IN PERUVIAN PASOS THAN IN THE OTHER BREEDS.

Other articles claim that research showed that there is indeed a difference, that Peruvian Pasos get it at an earlier age and without being objected to stressful exercise.
What drew the attention to the disease to start with was without doubt the fact that some Peruvian Pasos were having troubles with severe lameness. 
Many of these were bred for extreme smoothness and had a conformation that included very long and almost vertical pasterns.  

DSLD is a disease that presents the dropping of the pasterns as a SYMPTOM, ---- meaning many horses with the disease did not have dropped pasterns and open angles (post legged) to start with, --- it developped as a result of the disease.

So what some say is that these are two different worries:
--- A breakdown of some horses that have a conformation of extremely long, low pasterns.
---A genetic disease that affects the horse to the point where it might have to be put down, that often has symptoms of dropping pasterns and increasingly open angles in the hock and stifle, as the leg straightens to adjust to being longer with  fetlocks that are closer to the ground.

Read and decide for yourself, the links are at the bottom:

 www.dsld.org   ( Link to the "not for profit" organization that researches the disease)

DSLD - Degenerative Suspensory Ligament Desmitis "  (Link to article in "Conquistador" magazine),