What was that?
It was the tarsal (ankle) and metatarsal (foot) bones of a dog’s leg. But why are they so funky?
These bones are affected by Marie’s disease, or hypertrophic pulmonary osteoarthropathy (people like Marie’s disease because it’s shorter and rhymes). It is characterised by clubbing of the fingers and toes, and inflammation of the bony surfaces (periostitis) and joints (arthritis).
As you might realise from the name, it is often associated with lung conditions, especially lung tumours. So the whole name breaks down to: hyper = over, trophy = growth, pulmonary = lungs, osteo = bones, artho = joints, and pathy = badness. Phew!
Aside from lung tumours, other diseases can also cause hypertrophic osteoarthropathy, although for some reason they are mainly problems that affect the chest. No-one is 100% sure how exactly chest problems mess with the bones, but there are several theories.
Longstanding irritation and inflammation to any tissue can cause mineralisation, so it is thought perhaps the blood supply to bone is somehow disrupted which would lead to swelling and inflammation. There is a large nerve running through the chest — the vagus nerve — which has many branches and, among other things, tells the blood vessels how ‘open’ (or dilated) they should be. Perhaps diseases in the chest affect this nerve, in turn causing the blood vessels elsewhere to open up fully and blood to pool, eventually resulting in inflammation and irritation. Another idea is that hormones (or hormone-like substances) might be produced as a by-product of disease, signalling the bones to overgrow.
Pierre Marie and his mate Eugen von Bamberger (probably not actually friends) are credited with first describing the disease. However, about 2500 years ago Hippocrates also recognised clubbed fingers and toes, and signs of hypertrophic pulmonary osteoarthropathy have been found in human remains from his time.