Table 1.

Highlights the osteoarticular sites that are mostly affected by the main rheumatological diseases, along with other areas less commonly involved or not belonging to the musculoskeletal system. Furthermore, the main tissue alterations caused by each pathology are described, visible on the WB-MRI as zones of altered signals [2].

Disease	Most Commonly Involved Areas	Other Areas	General Radiological Features	WB-MRI DWI
AS	Sacroiliac and discovertebral joints	Peripheral enthesitis and thoracic wall joints	BME, bone erosions, bone sclerosis, and ankylosis DWI is able to highlight active inflammation areas with high b-values	It has greater resolution power compared to STIR sequences in detecting inflammatory lesions and in distinguishing them from degenerative ones.
Juvenile spondyloarthritis	Peripheral joints (lower-limb joints) and the enthesis	Sacroiliac and discovertebral joints	BME in proximity of the enthesis
Psoriatic arthritis	DIP and PIP joints (distal joints)	MCP/MTP and CMC/TMT joints (proximal joints)	Sinovitis and enthesitis; pencil-in-cup deformity
SAPHO	Sacroiliac and sterno-clavear regions, and the anterior chest wall	Extra-axial skeleton	Presence of chronic (fibroadipose involution) and active (BME) lesions
CRMO	Long-bones metaphysis, ankle, and calcaneus	Appendicular and axial skeletal	Non-specific signs of inflammation and relapsing-remitting lesions	DWI may be useful to distinguish malignancy from CRMO in the spine
Systemic sclerosis	Fingers, wrists, and ankles	Systemic disease: esophagus, skin, lungs, and kidneys	Synovitis, tenosynovitis, myositis, enthesitis, and fasciitis
Polymyalgia rheumatica	Pelvic and shoulder girdle	NA	Inflammation of peri-acetabular space and underneath the pubic symphysis
Polymyositis	Proximal limb muscles, symmetrical;	Swallowing and respiratory muscles	Inflammation of the affected muscles
Dermatomyositis	proximal limb muscles and skin symmetrical;	Swallowing and respiratory muscles	Inflammation of the affected muscles
IBM	distal muscles of the limbs, asymmetrical; and	Swallowing and respiratory muscles	Inflammation of the affected muscles
ASS	joints, entheses, and synoviums	Respiratory and limbs muscles	Inflammation of these structures
Eosinophilic fasciitis	Fasciae	Muscles and hypoderma close to the fascia	Inflammation with fibrosis and thickening of the fasciae
Sarcoidosis	Multifocal involvement of the axial skeleton	Systemic disease: lungs, eyes, hepato-splenic, and muscles	Presence of chronic and active lesions
Langerhans cell histiocytosis	Skull bones, upper limbs, and flat bones	Skin, endocrine system, and lungs	Coexistence of active and quiescent lesions
AVN	Epiphysis long bones	Joints of the knees, shoulders, ankles, wrist, hips, and jaw	Ischemic lesions
Hereditary ostechondromatosis	Flat bones or metaphysis of the long bones	NA	Multiple benign ostechondromas; signs of malignant transformation: growth of lesions after puberty or thickening of the cartilage hood
PFD	There is no preferential bone location	NA	Multifocal benign proliferation of bone-fibrous tissue inside the bone marrow space
Neurofibromatosis	Deformity of the orbit, facial bones, and spine	CNS and PNS	Nerve tumor that deforms adjacent structures