Alkaptonuria is an autosomal recessive disease that is a result of abnormal phenylalanine and tyrosine metabolism, characterized by excretion of large amounts of homogentisic acid (aka alkapton) in the urine, hence alkaptonuria. The circulating HGA causes significant damage to all classes of cartilage (ergo damage to joints and heart valves), leads to kidney stones and a characteristic calcification of the annulus of the intervertebral disks which leads to a syndrome similar to bamboo spine.
It generally is either noted in infancy with discoloration of the urine, or, if undetected then, in the late thirties or early forties, when accumulation of the pigment begins to stain the sclera or, in advanced cases, the tendons. It also can declare itself, as in this case, by chromhidrosis. It can be excreted in the sweat glands of the face, the axillae or the areola.
Now, to the nitty gritty. I gave you all clues that the meds were not the problem. I also mentioned she had a stone cold normal examination, including her axillae which were normal as pumpkin pie. That implied her sclerae were normal. All this means we are catching her on the front end of the clinical expression of her disease. For two bonus points, which two countries are noted for high incidences of alkaptonuria. Finally, and most critically, I mentioned (in a separate email, which should have told you it was very, very important) she was in her late thirties.
Which question should you ask her? Most importantly, you should ask her about dark urine, which she denies. My next question, which was answered with a "how the hell did you know that?" look was, did she have back problems. In fact, she had just gone to a back doc the week before and had her MRI the day before I saw her. She was sitting rigidly straight, as if she were HLA B-27 incarnate.
Labs? Urine HGA and a CBC, to chase down the rare bleeding diathesis. If, for some reason, she were negative on the HGA, I would then start looking at heavy metal assays (trying to link the chromhidrosis with the tremor).