Your symptoms can be due to polyneuropathy. Following are the causes of polyneuropathy (many times cause it is not known);
2) An underactive thyroid gland
4) Thiamine deficiency
5) Vitamin B 12 deficiency (pernicious anemia)
6) Vitamin B 6 (pyridoxine) taken in excessive amounts
7) Drugs, medications, herbs
8) Autoimmune diseases
9) Heavy metals such as lead and mercury.
Following investigations are done (many of which had been done for you);
1) Electromyography/nerve conduction studies (EMG/NCS)
2) MRI of the spine and brain
3) blood glucose and glycosylated hemoglobin
4) serum B12 level with methylmalonic acid (with or without homocysteine),
5) serum protein electrophoresis
6) Anti-nuclear antibody
7) Lyme testing
8) Rheumatoid factor
9) Sjogren's syndrome testing (Anti-Ro, Anti-La Antibodies)
Skin and nerve biopsy may be needed / recommended after the results of these investigations
Please feel free for your follow up questions.
I would be happy to assist you further, if you need any more information.
You are very welcome.
A recurrent lung and knee problem is more pointer towards autoimmune disorders. Steroids do help in autoimmune disorders. A skin and nerve biopsy will rule out or rule in the neuropathy and may indicate the type. It is easier than a spinal tap and less hazardous. Chronic Inflammatory Demyelinating Polyradiculoneuropathy can be one of the possibility. The other diagnosis to look for would be;
Systemic Lupus Erythematosus
Again the biopsy of the skin and nerve can be a clinching evidence. Blood and urine immunoelectrophoresis if not done also would be helpful. You may get an EMG which is non invasive and can give you a crucial direction for the diagnosis. Otherwise a spinal tap would be next step and mandatory.
It is privilege assisting you.
You are most welcome.
Skin and nerve biopsy are done from the area which has maximum symptoms. Leg would be likely area in your case for the biopsy. This needs only a local anesthesia and is an out patient minor procedure. Not all neuropathies we discussed are autoimmune. SLE and vasculitis are autoimmune.