Clubbing, Periostosis & Arthralgia (incl. Pachydermoperiostosis)
- The triad of clubbing, periostosis and arthralgia makes the diagnosis, not any single feature
- Primary HOA is pachydermoperiostosis, a genetic prostaglandin E2-pathway disorder with pachyderma and cutis verticis gyrata
- Secondary HOA is far commoner and paraneoplastic: new-onset HOA in an adult mandates a search for the cause, often in the chest
- Bone scan 'tramline' uptake is sensitive for early or radiographically occult periostosis
- Treat the cause: dealing with the tumour or the suppurative or cardiac disease often improves or resolves the HOA
- “Schamroth (window) sign: the diamond-shaped gap between apposed terminal phalanges is obliterated in clubbing
- “A normal chest radiograph does not exclude the cause: request CT of the chest
- “A bland, non-inflammatory joint aspirate supports HOA
The Syndrome & Its Two Forms
Hypertrophic osteoarthropathy (HOA) is a clinical syndrome of digital clubbing, periostosis (periosteal new-bone formation along the long bones) and arthralgia with joint effusions, often with painful swelling of the distal limbs. The diagnosis rests on recognising the triad rather than any single feature. It comes in two forms, and telling them apart decides what you do next.
Primary HOA. The hereditary form is pachydermoperiostosis (Touraine-Solente-Gole syndrome), a genetic disorder of the prostaglandin E2 degradation and transport pathway caused by HPGD or SLCO2A1 mutations. Besides clubbing and periostosis it produces pachyderma, thickened and furrowed facial and scalp skin, and cutis verticis gyrata, a corrugated thickening of the scalp. It is rare, typically presents in young men with a family history, and may be incomplete: clubbing and periostosis without florid skin changes.
Secondary HOA. This is the far commoner form, and clinically the more important to recognise, because it is a paraneoplastic or systemic marker. The skin changes of the primary form are usually absent. It is classically associated with:
- Intrathoracic malignancy, especially non-small-cell lung cancer and mesothelioma
- Suppurative lung disease: bronchiectasis, lung abscess, empyema, cystic fibrosis
- Cyanotic congenital heart disease, inflammatory bowel disease and chronic liver disease
The consequence. New-onset HOA in an adult, and especially new clubbing, mandates a search for an underlying, often pulmonary, cause.
- Primary (pachydermoperiostosis)
- Genetic (HPGD/SLCO2A1; PGE2 pathway)
- Secondary
- Paraneoplastic/systemic (lung cancer, suppurative lung disease, etc.)
- Primary (pachydermoperiostosis)
- Pachyderma + cutis verticis gyrata
- Secondary
- Usually absent
- Primary (pachydermoperiostosis)
- Young men; family history
- Secondary
- Adult with underlying disease
- Primary (pachydermoperiostosis)
- Rare
- Secondary
- Far commoner
- Primary (pachydermoperiostosis)
- Symptomatic; genetic counselling
- Secondary
- Find and treat the underlying cause (chest!)
Why Clubbing and Periostosis Happen: The Pathophysiology
One final common pathway. Primary and secondary HOA reach the same place by different routes. Both converge on excess PGE2 and a fibrovascular, growth-factor drive acting on the distal soft tissues and the periosteum.
Primary: a clearance defect. Pachydermoperiostosis is a loss of PGE2 clearance, and both culprit genes handle PGE2 breakdown. HPGD encodes 15-hydroxyprostaglandin dehydrogenase, the enzyme that degrades prostaglandins; SLCO2A1 encodes the prostaglandin transporter that carries PGE2 into cells for that degradation. Lose either and PGE2 accumulates systemically, acting on fibroblasts, osteoblasts and vessels to produce the clubbing, the periostosis and the skin changes.
Secondary: bypassing the lung filter. The lung normally filters out megakaryocytes and large platelet aggregates. With an intrathoracic tumour, a right-to-left shunt (cyanotic heart disease) or chronic suppurative lung disease, these clumps bypass the pulmonary filter and impact in the distal digital capillaries. There they release platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF), which drive fibrovascular proliferation, oedema and periosteal new bone, with COX-2 and PGE2 again the shared mediator.
What the mechanism explains. The unifying theme is PGE2 plus a VEGF/PDGF fibrovascular drive: failed clearance in primary disease, raised platelet-and-growth-factor production in secondary disease. It is why COX inhibitors and NSAIDs ease the bone pain, why the bone scan lights up the cortices ("tramline"), and why removing the tumour or treating the lung disease can reverse the HOA.
Defining and Assessing Clubbing
The definition. Clubbing is a bulbous enlargement of the distal digit from increased soft tissue at the nail bed, with loss of the normal nail-fold angle and increased nail-bed fluctuation. It evolves through recognised stages:
- Increased nail-bed fluctuation (a "floating nail")
- Loss of the nail-fold angle
- Increased nail curvature
- The drumstick digit
The objective signs. The Schamroth sign screens for clubbing, but clubbing has a precise definition and several objective bedside signs the examiner expects:
- Lovibond's angle, the profile nail-fold angle, is normally around 160 degrees and flattens to 180 degrees or more in clubbing
- The Schamroth (window) sign: apposing the dorsal surfaces of opposing terminal phalanges normally leaves a diamond-shaped gap, and in clubbing this window is obliterated
- The phalangeal depth ratio: the distal phalangeal depth is normally less than the interphalangeal depth and exceeds it in clubbing, a ratio greater than one
Why it matters. Clubbing can be the earliest and only feature, before florid periostosis. New clubbing in an adult is the trigger to investigate for the underlying, especially intrathoracic, cause of secondary HOA, so assessing it objectively rather than noting that the fingers "look clubbed" changes management.
Imaging
Radiographs. The hallmark is symmetric periosteal new bone along the diaphyses and metaphyses of the long bones: the tibia, fibula, radius and ulna. Look for it along the tubular bones of the forearm and hand as well as the tibia. The periostosis of primary HOA is identical in kind to that of the secondary form.
Bone scan. A radionuclide bone scan shows symmetric 'tramline' (double-stripe) cortical uptake along the long bones. It is sensitive for early or radiographically occult disease, and is often positive before radiographic changes are obvious.
Working It Up: What to Order, and What if the Chest Is Clear
"Search for the underlying cause" is the right instruction, but the orthopaedic surgeon who has just found symmetric periostitis needs to know what to request, and what to do when the obvious test comes back normal.
- 1Confirm the syndrome
Symmetric periosteal new bone on long-bone radiographs, plus clubbing assessed objectively (Lovibond angle, Schamroth window, phalangeal depth ratio), plus arthralgia.
Do not stop at 'periosteal reaction' on a report - look at the hands.
- 2Image the chest - CT, not just a radiograph
A chest radiograph is the first test but a normal film does NOT exclude the cause: a small peripheral adenocarcinoma or an early mesothelioma can be radiographically occult while producing florid HOA.
Most secondary HOA is explained here.
- 3If the chest is genuinely clear, widen the search
Echocardiography for cyanotic congenital heart disease and infective endocarditis; liver function and screening for chronic liver disease; symptom-directed assessment for inflammatory bowel disease and coeliac disease; thyroid function, since thyroid acropachy is the classic mimic.
These are the non-pulmonary causes the classic 'pulmonary osteoarthropathy' name obscures.
- 4Reconsider primary disease
A young man, an onset around adolescence, a family history, thickened furrowed facial skin or cutis verticis gyrata, and no underlying illness point to pachydermoperiostosis rather than a missed malignancy.
Genetic testing (HPGD, SLCO2A1) confirms it and stops a fruitless cancer hunt.
- 5If everything is negative
Do not simply discharge. HOA can PRECEDE the diagnosis of the underlying tumour, sometimes by months.
Arrange interval clinical review and repeat chest imaging rather than closing the episode.
The step most easily missed is the last. The syndrome is sometimes the first manifestation of the malignancy, so a negative initial screen buys surveillance rather than reassurance.
If you aspirate the joint. Effusions are part of the triad and a useful discriminator when the diagnosis is uncertain. The fluid in HOA is non-inflammatory: clear, viscous, with a low white cell count, unlike the turbid, high-cell-count fluid of an inflammatory or septic arthritis. A bland aspirate from a knee effusion in a patient with clubbing and periostitis supports HOA rather than pointing away from it.
Telling the Periosteal Reactions Apart
The radiologist's report will often say only "periosteal reaction", and the orthopaedic role is often to recognise the syndrome from exactly that finding. Symmetric periostitis has a short differential, and the discriminators are worth holding.
- Distribution and character
- Symmetric, smooth then layered periostitis of long-bone DIAPHYSES and metaphyses (tibia, fibula, radius, ulna); spares epiphyses
- The discriminator
- CLUBBING - and an underlying cause, usually intrathoracic
- Distribution and character
- HANDS and FEET - metacarpals, metatarsals and proximal phalanges; fluffy, spiculated, 'bubbly' periostitis
- The discriminator
- Graves disease with exophthalmos and pretibial myxoedema; typically painless
- Distribution and character
- Distal tibia and fibula, undulating
- The discriminator
- Chronic venous insufficiency, oedema, skin changes; no clubbing
- Distribution and character
- Undulating periostitis, often ulna and metatarsals; children
- The discriminator
- Excess intake history; no clubbing
- Distribution and character
- Mandible, clavicle, ulna in INFANTS under 6 months
- The discriminator
- Age and mandibular involvement are decisive
- Distribution and character
- Symmetric DIAPHYSEAL cortical thickening from both endosteal and periosteal surfaces
- The discriminator
- Progressive diaphyseal dysplasia with waddling gait, in childhood
- Distribution and character
- Symmetric long-bone periostitis
- The discriminator
- PGE1 infusion to maintain a patent ductus - the pharmacological proof of the mechanism
Also on the list. In children, physiological periostosis belongs in the differential. What is characteristic of HOA is the combination of clubbing, symmetric long-bone periostosis and arthralgia.
The prostaglandin row. Neonates given a prostaglandin infusion develop exactly this periostitis. It is as close to a human experiment as the field offers, and the strongest single argument that PGE2 drives the periosteal reaction. The paediatric hyperostoses are covered in Caffey Disease, Camurati-Engelmann Disease and Melorheostosis.
Management
Secondary HOA: treat the cause. Resection or treatment of the lung tumour, or control of the suppurative or cardiac disease, often improves or resolves the HOA. The single most important action in new-onset secondary HOA is to use the syndrome as the clue to find and treat the occult disease.
Symptomatic relief. NSAIDs help the arthralgia and bone pain. Agents acting on the prostaglandin pathway may help: bisphosphonates, and COX inhibitors in primary disease.
Primary HOA. Pachydermoperiostosis is managed symptomatically, with genetic counselling.
In its common secondary form, HOA is a messenger for an underlying disease, most importantly an intrathoracic malignancy. New-onset clubbing and symmetric long-bone periostosis with arthralgia in an adult should never be treated as an isolated musculoskeletal complaint. The exam and clinical error is to overlook the secondary form's role as a sign of occult, potentially serious, disease.
Mnemonics & Memory Aids
CPA
Hook:CPA = the HOA triad: Clubbing (check the Chest), Periostosis, Arthralgia. Secondary = paraneoplastic - find the cause.
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“An adult is referred with bilateral leg pain; radiographs show symmetric periosteal new bone along the tibiae, and you notice finger clubbing. What is the diagnosis and what must you do?”
The syndrome
- Triad: digital clubbing + periostosis + arthralgia/effusions
- Schamroth (window) sign screens for clubbing
- Recognise the triad, not just one feature
Primary vs secondary
- Primary = pachydermoperiostosis (genetic PGE2 pathway; pachyderma + cutis verticis gyrata; young men)
- Secondary (far commoner) = paraneoplastic/systemic marker
- Secondary causes: lung cancer/mesothelioma, suppurative lung disease, cyanotic heart disease, IBD, liver disease
Imaging
- Symmetric periosteal new bone of long-bone diaphyses/metaphyses
- Bone scan: symmetric 'tramline' cortical uptake (early/occult disease)
- Differential: thyroid acropachy, venous stasis periostitis, vitamin-A toxicity
Management
- Secondary: treat the underlying cause (often improves/resolves HOA) - SEARCH the chest
- Symptomatic: NSAIDs; bisphosphonates / prostaglandin-pathway agents
- Primary: symptomatic + genetic counselling
Evidence & Key Studies
Acquired digital clubbing as the incomplete form of pachydermoperiostosis (primary HOA)
- Reports two healthy young men with acquired digital clubbing as the incomplete form of pachydermoperiostosis (primary hypertrophic osteoarthropathy).
- Illustrates the clinical features relevant to recognition - clubbing, periostosis (periosteal thickening), the Schamroth sign, and the cutaneous features of pachydermoperiostosis (pachyderma/cutis verticis gyrata).
- Reinforces that primary HOA (pachydermoperiostosis) can present incompletely, primarily with clubbing and periostosis, in young men.
The recognition of primary hypertrophic osteoarthropathy as the incomplete form of pachydermoperiostosis (acquired clubbing, periostosis, the Schamroth sign and the cutaneous pachyderma/cutis verticis gyrata features) in young men comes from the cited Staunton and Chang report. The HOA triad, the prostaglandin-pathway genetics (HPGD/SLCO2A1), and - most importantly - the paraneoplastic nature of secondary HOA (its association with intrathoracic malignancy and suppurative lung disease, with management directed at the underlying cause) are standard, well-established teaching, as are the work-up sequence, the non-inflammatory effusion and the periosteal-reaction differential. (See also Caffey Disease, Camurati-Engelmann Disease, Melorheostosis and Plain Radiography Principles.)