Lupus causes a person to avoid being in the sunshine. Sunshine creates vitamin D3 in the body. If one avoids the sun, then one is more likely to be low in Vitamin D3, unless one takes a supplement or eats cod liver oil regularly. So thus Lupus can cause low Vitamin D3.
Can't answer the recurring sinus infection issue - but from a layman's point of view, if the body's immune system is so busy attacking itself that it reduces lymphocyte counts to below normal levels, then I can see how an opportunistic infection could become a chronic recurring infection. Great question for the Rheumatologst and the ENT.
Gluten & Sulfite Sensitivity, Multiple Food & Inhalant & Medication Allergies, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD (Lupus?), Osteoporosis, Anemia, Very Low Lymphocyte Counts (T-Cells & B-Cells), malabsorption/malnutrition, etc.
Meds: Pulmicort, Injectable Vitamin B12, Herbs, Nutritional Supplements, Essential Oils, Homeopathy.