Avoiding Open-Skull Biopsy in Osteomyelitis-Pachymeningitis with Severe Recurrent Temporal Swelling: An Experience of SAPHO syndrome with Increased Serum IgG4 and Its Literature Review.

Hypertrophic pachymeningitis is a rare disease associated with synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome. We recently treated a 20-year-old female who exhibited hypertrophic pachymeningitis accompanied by recurrent temporal swelling. Physical examination only revealed severe pain in the left temporal head with subcutaneous swelling; however, when we performed a lumbar puncture, we noticed that she also had tenderness in the right sacroiliac joint. Bone scintigraphy revealed the bull's head pattern, the typical findings of SAPHO syndrome. Moreover, it was noted the C-reactive protein, erythrocyte sedimentation rate, and interleukin-6, but not interleukin-4, were elevated during clinical worsening, which was compatible with the diagnosis of SAPHO syndrome. The controversial complication of immunoglobulin G subclass 4 (IgG4) syndrome has been debated due to the increased serum IgG4 at onset, which has been considered not contradictory to the diagnosis of SAPHO syndrome according to literature reviews. Considering the patient's recurrent course and specific radiological findings, we avoided the need for a biopsy to diagnose SAPHO syndrome and prioritized specific treatments such as anti-tumor necrosis factor antibody, resulted in stable condition. When hypertrophic pachymeningitis is encountered, a careful whole-body examination, in addition to biomarkers including IgG4, should be performed in order to differentiate it from SAPHO syndrome.