= DISH = FORESTIER DISEASE = ANKYLOSING HYPEROSTOSIS

= common ossifying diathesis characterized by bone proliferation at sites of tendinous + ligamentous attachment (enthesis)

Etiology:

1. may be caused by altered vitamin A metabolism (elevated plasma levels of unbound retinol)
2. long-term ingestion of retinoid derivatives for treatment of acne (eg, Accutane^®); ? hypertrophic variant of spondylosis deformans

Age:>50 years; M÷F = 3÷1

• pain, tenderness in extraspinal locations
• restricted motion of vertebral column
• hyperglycemia; positive HLA-B27 in 34%
• increased incidence of hyperostosis frontalis interna
• Spine
  Location: middle + lower thoracic >lower cervical >entire lumbar spine
  • flowing ossification of at least 4 contiguous vertebral bodies:
    • osteophytes located anteriorly + laterally on right side (not on left because of aortic pulsations)
    • osteophytes largest at level of intervertebral disk
    • radiolucency beneath deposited bone
  • disk spaces well preserved, no apophyseal ankylosis, no sacroiliitis
• Pelvis
• bridge across superior aspect of symphysis pubis
• ossification of iliolumbar + sacrotuberous + sacroiliac ligaments (high probability for presence of spinal DISH, DDx: fluorosis)
• “whiskering” at iliac crest, ischial tuberosity, trochanters
• broad osteophytes at lateral acetabular edge, inferior portions of sacroiliac joints
• Extremities
  • big heel spurs (on plantar + posterior surface of calcaneus)
  • spur of olecranon process of ulna
  • spur on anterior surface of patella
  • ossification of coracoclavicular ligament, patellar ligament, tibial tuberosity, interosseous membranes

Cx: postoperative heterotopic bone formation (hip)

DDx:

1. Fluorosis (increased skeletal density)
2. Acromegaly (posterior scalloping, skull features)
3. Hypoparathyroidism
4. X-linked hypophosphatemic vitamin D–resistant rickets
5. Ankylosing spondylitis (squaring of vertebral bodies, coarser syndesmophytes, sacroiliitis, apophyseal alteration)
6. Intervertebral osteochondrosis (vacuum phenomenon, vertebral body marginal sclerosis, decreased intervertebral disk height)