PURPOSE: The incidence of femoral localized periosteal thickening (LPT), which can precede atypical femoral fracture (AFF), is not low (1-10%) in Japanese patients with autoimmune inflammatory rheumatic diseases (AIRDs). We explored the associations between underlying AIRDs and the prevalence of LPT. METHODS: We conducted post-hoc analyses of two cohorts that included a total of 280 Japanese women, 105 of whom had AIRDs and had been taking bisphosphonate (BP) and prednisolone (PSL), and 175 of whom had rheumatoid arthritis (RA). RESULTS: LPT was detected in a total of 18 patients (6.4%) and three (1.1%) developed AFFs. RA was negatively correlated with LPT. A disease other than RA requiring glucocorticoid treatment, BP use ≥ 5 years, PSL use ≥ 7 years, and a PSL dose ≥ 5.5 mg/day were positively correlated with LPT. After adjusting for age, diabetes mellitus, and BP duration or daily PSL dose, RA was no longer associated with LPT. CONCLUSION: LPT in Japanese patients with AIRDs was associated with BP and glucocorticoid treatment rather than underlying AIRDs. When a PSL dose ≥ 5.5 mg/day is required long-term (typically combined with long-term BP treatment [≥ 5 years]), clinicians need to pay particular attention in case LPT and AFF, as well as glucocorticoid-induced osteoporosis.