= RIBBING DISEASE

= autosomal recessive disorder of intramembranous ossification similar to progressive diaphyseal dysplasia

Age: after puberty, typically in middle-aged adults

• mild neuromuscular symptoms

Location: typically tibia / femur

Site: diaphyseal portion of long bones only

Distribution: either unilateral / asymmetric + asynchronous bilateral involvement of long bones

• cortical thickening of periosteal + endosteal surfaces
• epiphyses characteristically spared
• ± narrowing of medullary canal
• disease may progress slowly and then stabilize

DDx: progressive diaphyseal dysplasia (begins in childhood, severe neuromuscular symptoms, symmetric bilateral sclerosis of long bones, skull involved)