Symphysis pubis dysfunction is more or less a symptom of pelvic girdle pain.
Prior to redefining pelvic girdle pain during pregnancy many medical journal would publish papers just concerned about naming the condition. It was agreed that the signs and symptoms were the same but terminology varied from Diastasis Symphysis Pubis (DSP) Symphysis, Symptom Giving Pelvic Girdle Relaxation, Symphyseal Shear, Symphysis Pubis Dysfunction, Physiological Pelvic Girdle Relaxation, Pelvic Arthropathy, Symphysiolysis, Pelvic Joint Syndrome, Superior Pubic Shear, Inferior Pubic Shear all occurring during pregnancy and/or postpartum - just to name a few. Within the last couple of years medical professional specializing in this area of obstetrics have realized that classifying the degree of pelvic girdle pain as mild, moderate or severe, that this would enable a clearer definition for basic information, diagnostics and epidemiology, and therapeutical interventions that then would be followed by treatment, patient education and support.
Hope this helps.