Periostitis Differential Diagnosis

Periostitis is an important finding on a musculoskeletal imaging study. It represents inflammation within the periosteum, a layer of connective tissue which surrounds bone. Various forms exist, which typically reflect the aggressiveness of the underlying process. No good mnemonic here (Roentgen Ray Reader referenced below has one, but it is quite long), but the major categories are:

	Disease	Notes
	Physiologic Periostitis	Appears around age 3 mos Resolves by 6 mos
	Caffey's Disease	Infantile cortical hyperostosis Involves mandible Occurs before 6 mos
	Arthritis	Typically psoriatic or reactive
	Pachydermioperiostitis	Autosomal dominant disorder Skin thickening
	Fluorosis	Symmetric Sclerotic bones
	Hypervitaminosis A
	Infection (Osteomyelitis)	Involucrum - thick irregular new bone that forms from periosteum Sequestra - avascular dead bone from cortical blood supply disruption
	Fractures	Can be seen in regular fractures or stress fractures
	Tumor	Osteosarcoma (Codman's triangle, sunburst) Ewing's sarcoma (Lamellated, hair-on-end) Chondroblastoma (age<20)
	Eosinophilic granuloma
	Hypertrophic Pulmonary Osteoarthropathy
	Venous stasis	Thick, undulating reaction Also see edema, phleboliths