Getting to the bottom of an exotic disease

Patient A is a 62 year-old woman who is a carrier for Fragile X syndrome (she has had 3/5 Fragile X sons) who is otherwise healthy except middle ear disease with hearing loss and vestibular dysfunction, a mild tremor in her hands and pain with decreased sensation and in her feet. She comes into neurology clinic because she is worried that she may have a very rare manifestation of carrying the Fragile X mutation that presents as ataxia and tremor. She is armed with literature printed out from the internet from a Fragile X website and was told by a friend or hers who works in health care that she should have some tests run to determine if her neurological symptoms are due to the X. Her physical exam confirms the tremor, mild sensory loss in her feet, and balance problems with walking but is not ataxic.

She has been seen by half a dozen doctors, none of whom have given her a diagnosis. She has been taking medications to help with the pain in her legs - this is called neuropathic pain because it is pain generated by damage to the nerve itself, unlike normal pain that is due to damage from tissue. Neuropathic pain is notoriously difficult to treat and she has tried all the medications at some point, but only with moderate relief. However, this is not really why she has come to the clinic. She has come because she wants an answer to her neurological symptoms - the balance problems, the tremor, and the neuropathology in her feet. She is typical of many patients who have unclear or unknown causes of their ailments. Unfortunately, there is nothing that modern medicine will be able to do for her - I know this right away. A patient bouncing from doctor to doctor in search of diagnosis is a familiar pattern and it almost always means that the disease is idiopathic and there is no cure, and only treatment of symptoms at best.

My preceptor tells her that he wants to check her for diabetes, hypothyrodism, and some nutritional deficiencies. She expresses some dissatisfaction with this approach because she states she has had these tests done in the past; she is convinced she is not diabetic. We explain to her that it is best to rule out reversible and common causes of neuropathy before running down the path of an uncommon, exotic disease that will be expense to diagnose. Even her balance problems are much more likely explained by her ear disease than the Fragile X. But she possessed by the idea of having Fragile X carrier ataxia-tremor although it is rare (even in carriers). Finally my preceptor gives in and orders the $2000 MRI that would make the diagnosis. This frustrates me not only because it is a senseless waste of health care resources, but because it feeds patient A's fantasy about her disease. This was a wasted chance to inform her about the logic of medical decision making. The key point that my preceptor did not convey was that even if she did have the Fragile X syndrome it would not change anything - there is no treatment one way or another. Sure, it is nice to know if you got a disease or not, but in this case if that knowledge does not affect prognosis or treatment, then the expense of reaching the exotic diagnosis should fall on the patient (not their insurer).

A side note - yesterday I complained about specialists being expensive. This is another case in point. A good (primary care) doctor would have eliminate several possible diagnoses from a good history and physical exam, then ordering studies (imaging, lab tests, etc.) to confirm or rule out the top 1-3 diagnoses. My preceptor, a neurologist, took a shotgun approach by ordering a a battery of tests to rule out all the competing diagnoses, including many obscure, rare causes of neuropathy. I think this is pretty typical of how specialists work, and it makes sense on occasion, say when the patient has already been worked up for common causes with simple, inexpensive tests. Still a question I am always asking is why order this study if it is not going to change what we do?