What is Poncet’s disease?

What is Poncet's Disease?

Poncet's disease is a rare form of reactive arthritis that develops in patients with active tuberculosis at an extra-articular site, characterized by sterile polyarthritis or oligoarthritis that resolves completely with anti-tubercular treatment alone, without evidence of direct mycobacterial invasion of the joints. 1, 2

Clinical Characteristics

Joint Involvement Pattern

• Oligoarthritis is the most common presentation (seen in approximately 57% of cases), though polyarthritis also occurs frequently 3
• Ankle joints are most commonly affected, followed by other large joints 3
• The arthritis is characteristically non-erosive and non-deforming 3
• Joint symptoms can vary dramatically in duration, from as short as 3 days to as long as 6 years before diagnosis 3
• The pattern is typically additive polyarthritis affecting large joints 1

Associated Tuberculosis Sites

• Extrapulmonary tuberculosis is more common than pulmonary disease in Poncet's disease 3
• Lymph node tuberculosis is the most frequent extrapulmonary site 3
• Other sites include renal tuberculosis, elbow joint tuberculosis, and pulmonary tuberculosis 1, 4

Systemic Features

• Nearly half of patients (48%) present without systemic symptoms, making diagnosis challenging 3
• When present, systemic manifestations may include erythema nodosum 2, 5
• The arthritis may be accompanied by constitutional symptoms in some cases 2

Diagnostic Approach

Essential Diagnostic Features

• Mantoux test (tuberculin skin test) is positive in the vast majority of cases (81%) 3
• Synovial fluid analysis shows no direct bacillary invasion or mycobacterial organisms 1
• Evidence of active tuberculosis at an extra-articular site must be documented 2, 3

Proposed Diagnostic Criteria

Based on the largest case series, diagnostic criteria include 3:

• Two essential criteria: Active tuberculosis at an extra-articular site AND sterile arthritis
• Two major criteria: Non-erosive arthritis AND complete resolution with anti-tubercular treatment alone
• Three minor criteria: Positive tuberculin test, absence of other causes of arthritis, and oligoarticular pattern

Key Diagnostic Pitfall

Poncet's disease remains a diagnosis of exclusion 5. You must rule out:

• Direct tuberculous arthritis (usually monoarticular with mycobacterial invasion) 5
• Other causes of reactive arthritis 2
• Other inflammatory arthritides 3

Treatment and Prognosis

Therapeutic Response

• Resolution of arthritis occurs rapidly with anti-tubercular chemotherapy alone, typically within days to two months 1, 4, 2
• No additional immunosuppressive or anti-inflammatory therapy is required beyond standard anti-TB treatment 4, 5
• All patients treated with anti-tuberculous drugs in reported series achieved complete resolution of joint symptoms 3, 5

Clinical Course

• The arthritis resolves completely without residual joint damage or deformity 3
• Response to anti-TB therapy is so characteristic that lack of improvement should prompt reconsideration of the diagnosis 2

Pathophysiologic Considerations

Poncet's disease likely represents an immunopathogenic response to tuberculin antigens rather than direct infection, similar to the mechanism proposed for erythema nodosum in tuberculosis 5. This explains why:

• Joints remain sterile despite active TB elsewhere 1, 2
• The condition responds to anti-TB treatment without need for joint-directed therapy 4
• The arthritis pattern resembles other forms of reactive arthritis 2