An LDN site (The Low Dose Naltrexone Homepage) claims that LDN is effective in treating these conditions:
Bladder Cancer, Breast Cancer, Carcinoid, Colon & Rectal Cancer, Liver Cancer, Glioblastoma, Lung Cancer (Non-Small Cell), Lymphocytic Leukemia (chronic), Lymphoma (Hodgkin’s and Non-Hodgkin’s), Malignant Melanoma, Multiple Myeloma, Neuroblastoma, Ovarian Cancer, Ovarian Cancer, Pancreatic Cancer, Prostate Cancer (untreated), Renal Cell Carcinoma, Throat Cancer, Uterine Cancer,ALS (Lou Gehrig’s Disease), Alzheimer’s Disease, Ankylosing Spondylitis, Autism Spectrum Disorders, Behcet’s Disease, Celiac Disease, Chronic Fatigue Syndrome, CREST syndrome, Crohn’s Disease, Emphysema (COPD), Endometriosis, Fibromyalgia, HIV/AIDS, Irritable Bowel Syndrome (IBS), Multiple Sclerosis (MS), Parkinson’s Disease, Pemphigoid, Primary Lateral Sclerosis (PLS), Psoriasis, Rheumatoid Arthritis, Sarcoidosis, Scleroderma, Stiff Person Syndrome (SPS), Systemic Lupus (SLE), Transverse Myelitis, Ulcerative Colitis and Wegener’s Granulomatosis.

The site offers no independent support for any these claims.

In my view it is up to NT members to judge for themselves how plausible it is that Naltrexone, an opiate receptor antagonist, may be beneficial for such a vast array of health problems.

I'm a full body neuropathy patient and I've been on LDN for months now. This drug has made a difference between me not being able to cope being on this planet for one more day with this awful condition and me getting back a healthy chunk of my life. But that is just my personal experience. Mileage may vary. The side effect profile is low and this drug is cheap - about a dollar a day. It's not a panacea, but my doctor and nurse told me that it has helped many of their patients with pain and autoimmunity; therefore, I think it is worth considering.

Doctors like Pradeep Chopra are using it in their RSD patients to a very good success rate. I believe in a You Tube talk that he said 70% of his patients have a good response. He generally combines LDN with gabapentin. He has a small case study floating out on pub med.

http://www.painri.com/pradeep-chopra-md/

This paper gives a good overview of the proposed mechanisms of action (promotes T cell regulation and reduces central nervous system inflammation).

The use of low-dose naltrexone (LDN) as a novel anti-inflammatory treatment for chronic pain

This case study is behind a paywall, but it looks like they examine a patient that was prescribed LDN for SFN.

Off-Label, Low-Dose Naltrexone for Refractory Painful Diabetic Neuropathy | Pain Medicine