Hello, I'M NOT A DR. Reading your story, esp. with the coughing I would suggest your husband see a 'PULMONARY" specialist. He can do a bronchial scope to see the type of bacteria he has in his lungs from coughing , SINCE HIS MEDS ARE NOT WORKING, NEXT IS PULMONARY.
Keep me posted, I too have a cough ...and would like to know how your husband is progressing...
BEST OF HEALTH, BLESSINGS,
Might sound daft but has he been tested for food allergies? I know my father in law had similar symptoms to your husband, he used to get regular colds/flu like symptoms, hives/ large cysts all over his arms and legs, blisters in his mouth, rashes up his neck and face........the list was endless. We found out later that he had candida of the blood! It means an incredibly difficult and very strict diet with NOTHING processed and you literally have to cut out everything but a month on the diet and he saw such an improvement. Might be worth a look in to it. He was misdiagnosed so many times and it took years until someone suggested this to us. Hope it helps or that you do find a cure for him.
Have you seen an Infectious Disease Specialist, or asked your PCP about viral agents that may be responsible for your husband's symptoms? Occasionally exposure to a pathogen will trigger a sort of "immune cascade" in which the body begins fighting a virus that hasn't been active for years, decades even, or a virus reactivates, as seen with Shingles (varicella zoster virus (VZV)). If autoimmune markers have been tested for and nothing stands out, viral titer loads and inflammation markers would be my next step for diagnostics.
See:
Galley HF, Webster NR. The immuno-inflammatory cascade. Br J Anaesth. 1996 Jul;77(1):11-6. Review. PubMed PMID: 8703619.
Low-dose naltrexone is being found to be helpful for several of these autoimmune diseases. It is not covered by insurance, and has to be mixed by a compounding pharmacy. It costs around $30 to $40 a month. If he takes prednisone, it could replace the prednisone and not have the side effects. All of this assumes that his doctor will prescribe it though.
With so many autoimmune diseases, make sure he is tested for Celiac disease. Try stopping dairy. He could substitute almond milk if he isn't allergic to nuts. He could supplement with magnesium and vitamin D for some pain relief.