= LÉRI DISEASE [melos, Greek = limb; rhein, Greek = flow]

[André Léri (1875–1930), pupil of Joseph Babinski and Pierre Marie, president of French Ophthalmological Society]

= rare sporadic mixed sclerosing bone dysplasia with disturbances in endochondral + intramembranous ossification characteristically appearing as flowing hyperostosis

Age: usually occult until adulthood; slow chronic progressive course in adults; rapid progression in children

Cause: developmental error of intramembranous bone formation related to mutation in LEMD3 on chromosome 12q, which codes for an inner nuclear membrane protein responsible for inhibition of transforming growth factor b + bone morphogenic protein

Path: overproduction of bone matrix + increased angiogenesis

Associated with: osteopoikilosis, osteopathia striata, tumors / malformations of blood vessels (hemangioma, vascular nevi, glomus tumor, AVM, aneurysm, lymphedema, lymphangiectasia)

• often asymptomatic incidental finding
• severe pain + limited joint motion (bone may encroach on nerves, blood vessels, or joints) → ± joint contracture
• thickening + fibrosis of overlying skin (resembling scleroderma); muscle atrophy (frequent)
• Dermatofibrosis lenticularis disseminata (Buschke-Ollendorff syndrome) = asymptomatic small flesh-colored to yellow dermal papules / coalescent plaques (in 25%) on buttocks, trunk, arms, skin folds
  Age: usually in childhood; often during 1^st year of life
  Histo: connective tissue nevi with predominantly abnormal elastin / abnormal collagen

Location:

• common: in diaphysis of appendicular skeleton (lower >upper extremity); usually monomelic with at least two bones involved in dermatomal distribution (following spinal sensory nerve sclerotomes) / monostotic / polyostotic
• rare: in axial skeleton (skull, spine, ribs)

Site: entire cortex / limited to one side of cortex

Patterns: (1) osteoma-like, (2) myositis ossificans-like, (3) osteopathia striata-like, (4) classic dripping candle (5) mixed (overlap syndrome)

• cortical + medullary hyperostosis of single / multiple adjacent bones:
  • “dripping / flowing candle wax” sign = continuous / interrupted streaks / blotches of irregular cortical hyperostosis along tubular bone beginning at proximal end extending distally with slow progression
• may cross joint with joint fusion
• small opacities in scapula + hemipelvis (similar to osteopoikilosis)
• discrepant limb length
• flexion contractures of hip + knee
• genu valgum / varus
• dislocated patella
• ossified soft-tissue masses (27%)

DDx:

1. Osteopoikilosis (generalized)
2. Fibrous dysplasia (normal bone structure not lost, not as dense)
3. Engelmann disease
4. Hyperostosis of neurofibromatosis, tuberous sclerosis, hemangiomas
5. Osteoarthropathy