Syphilitic osteomyelitis
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syphilitic osteomyelitis Treponema pallidum bone
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PMID: 39385133
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syphilitic osteomyelitis clinical features pathology treatment tertiary syphilis
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Syphilitic Osteomyelitis
Syphilitic osteomyelitis is a rare manifestation of tertiary (late) syphilis, caused by the spirochete Treponema pallidum. Congenital syphilis also produces characteristic bone lesions in infants, though via a slightly different mechanism.
Etiology & Stage
- Causative organism: Treponema pallidum (gram-negative spirochete)
- Occurs in the tertiary stage of acquired syphilis (years after initial infection)
- Congenital form: transplacental transmission - affects neonates and infants
Bones Affected
Predominantly subcutaneous bones (i.e., bones with little soft-tissue coverage) are targeted:
- Tibia (most common)
- Sternum
- Clavicle
- Skull
- Ulna
It is characteristically a disease of the diaphysis - this distinguishes it from acute pyogenic osteomyelitis and Brodie's abscess (which begin in the metaphysis), and from osteoclastoma (epiphysis).
In congenital syphilis, the epiphyses and metaphyses of long tubular bones (humerus, radius, tibia) are affected symmetrically; rarely, atypical sites like the calcaneus may be involved (Guo & Zhang, 2024 - PMID 39385133).
Pathology
Two forms of bony pathology occur:
| Form | Description |
|---|---|
| Diffuse periostitis | Widespread periosteal thickening and new bone formation |
| Localized gumma | Focal granulomatous lesion within bone; may soften and liquefy |
The gumma may break down to form a typical syphilitic ulcer (a punched-out, indurated ulcer with a "wash-leather" slough at its base).
Clinical Features
- Pain - characteristically deep, boring, nocturnal pain (worse at night; this is a classical feature of syphilitic bone disease)
- Swelling - bone is palpably irregular and thickened
- Bony irregularity - felt on careful palpation of the affected bone
- Ulcer/sinus - if gumma breaks down
- Multiple lesions - lesions are often multiple, affecting more than one bone simultaneously
On general examination, look for other syphilitic stigmata (interstitial keratitis, Hutchinson's teeth, saddle nose, choroidoretinitis, tabes dorsalis, cardiovascular syphilis) and elicit history of syphilitic contact.
Investigations
| Investigation | Finding |
|---|---|
| X-ray | Periosteal thickening ("onion peel") OR punched-out translucent (lytic) areas surrounded by dense sclerosis; lesions often multiple |
| Serology | Positive Wassermann Reaction (W.R.) and Kahn test (older tests); modern: VDRL, RPR (non-treponemal); TPHA, FTA-ABS (treponemal) |
| Bone biopsy | Gummatous necrosis with plasma cell infiltrate; spirochetes on dark-field microscopy |
The hallmark radiological appearance is punched-out lytic areas in the midst of dense sclerosis with periosteal new bone formation.
Differential Diagnosis
Syphilitic osteomyelitis must be distinguished from (in the context of diaphyseal bone lesions):
- Chronic pyogenic osteomyelitis - history of acute onset, fever; organisms in pus on aspiration; negative serology
- Tuberculous osteomyelitis - affects ends of long bones/short bones; cold abscess; X-ray shows rarefaction and cavity formation; positive Mantoux
- Ewing's sarcoma - also a diaphyseal lesion, but in children/adolescents; "onion peel" periosteal reaction; high ESR; negative serology
- Multiple myeloma - also diaphyseal; older age; Bence Jones proteinuria; plasma cells on bone marrow biopsy
- Brodie's abscess - metaphyseal; central lytic lesion with sclerotic rim
(S Das A Manual on Clinical Surgery, 13th Edition)
Treatment
Penicillin remains the mainstay:
- Benzathine penicillin G 2.4 million units IM weekly x 3 doses (for tertiary/late syphilis)
- Doxycycline or ceftriaxone for penicillin-allergic patients
- If gumma has formed a syphilitic ulcer: local wound care in addition
- Congenital syphilitic osteomyelitis: aqueous crystalline penicillin G IV; surgical debridement if needed (as illustrated in the 2024 BMC Pediatrics case of calcaneal involvement)
With early diagnosis and appropriate antibiotic treatment, prognosis is excellent and bone remodeling/healing can be complete.
Key Distinguishing Points (Quick Summary)
| Feature | Syphilitic Osteomyelitis |
|---|---|
| Stage of syphilis | Tertiary (acquired); congenital (infants) |
| Bone segment | Diaphysis |
| Bones | Tibia, sternum, clavicle, skull, ulna |
| Pain character | Nocturnal boring pain |
| Pathology | Periostitis or gumma |
| X-ray | Punched-out lytic areas + dense sclerosis + periosteal thickening |
| Serology | VDRL/TPHA positive |
| Lesions | Often multiple |
Sources: S Das A Manual on Clinical Surgery, 13th Ed.; Bailey & Love's Short Practice of Surgery, 28th Ed.; Guo & Zhang, BMC Pediatrics 2024
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