Jody, the lumbar plexus is basically like a loop of nerves where the anterior branchs of the lumbar nerves (L1-L4)come together - think of the cloverleaf on a major interstate where several different roads converge and branch off. So lumbar plexopathy is inflammation of that bundle of nerves. Meralgia Paresthetica sounds frightening, but it's just a medical way of describing thigh pain. It could be a result of the lumbar plexoplathy, or neuritis from lupus inflammation. Your rheumatologist would probably refer to this as LFCN - lateral femoral cutaneous neuropathy - or Bernhardt-Roth syndrome. It results from injury, disease, or compression of the LFC nerve, usually at the L2 or L3 nerve root. Sitting or standing for prolonged periods can make the symptoms worse, and moving or changing position may help.
I've had several different neuropathies - my neurologist groups them all under polyneuropathy, while my rheumatologist prefers mononeuritis multiplex. Neurontin may help - also physical therapy, massage, and gentle stretching exercises, I've also been treated with accupuncture and nerve blocks, and had a couple of nerves surgically decompressed. Oral steroids usually have little effect, although steroid injections idirectly into the surrounding muscle can help temporarily. Trigger point (or dry) injections also work for some people.
Is your doctor monitoring your blood sugar carefully? Because when all my neuropathy problems seemed to kick in, my blood sugar was normal when they tested it at the lab. My doctor was still concerned because neuropathies are so associated with diabetes, and we have a family history. So he did a special blood test - hemoglobin A1c - that gives an average of the amount of glucose in your blood over a period of months. That test showed I had been having periods of high blood sugar that hadn't been detected in my routine labwork. When I started trying to control my blood sugar very tightly - some (but not all) of the neuropathy symptoms improved.