Multicystic bone disease (Gorham-Stout syndrome) in a spider monkey (Ateles geoffroyi )

In April 2000, a 2.5-year-old pet female Geoffroyi's spider monkey presented for reduced activity, a subdued demeanor, and boney enlargement involving both radii.

On further examination, polyostotic bone cysts were identified involving many of the tubular bones and were identified radiographically. Microscopic examination of a bone biopsy revealed hemorrhage and other characteristics typical of an aneurysmal bone cyst. In addition, excessive osteoclasia was noted, in association with fibrotic areas rather than with Howship's lacunae as expected from a growing animal.

These findings were consistent with Gorham-Stout syndrome, a rare condition reported previously in ∼175 human cases and in a dog at necropsy. The diet history and further testing suggested a negative calcium balance. Treatment included the administration of bis-phosphonates, which appeared to bring about marked improvement. Almost 8 years later (November 2008), radiographs were again taken and suggested some resolution of bone cysts, primarily those in the legs.

This represents the first reported case and a potential therapy for this rare condition in a non-human primate.