Key clinical massage
Poncet’s disease is an acute onset reactive polyarthritis associated
with tuberculosis infection. Although uncommon, the diagnosis should be
considered among patients presenting with symmetrical polyarthritis in
tuberculosis-endemic regions.
Introduction
Sudan is one of the developing countries in which tuberculosis (TB) is
considered as a major health concern. In 2019, the World Health
Organization estimated that the number of new cases of TB in Sudan was
29,000 (1).
TB is a multisystemic disease that has the ability to affect any organ.
The skeletal system is involved in 1 to 3% of TB cases, and the spine
is the most commonly involved skeletal organ (2).
Poncet’s disease (also known as Tubercular rheumatism) is a rare form of
TB which usually manifest as symmetrical polyarthritis without evidence
of joint invasion by Mycobacterium tuberculosis (3). We present a case
report of Poncet’s disease as an initial presentation of tuberculosis in
an undiagnosed patient in Sudan.
Case presentation
A 38-year-old female presented to the referral clinic with bilateral
knee and wrist pain and swelling for one month. In addition, she
reported pain in the metacarpophalangeal joints of both hands with
associated morning stiffness. On further questioning, she reported
cough, fever, and night sweating for 3 months. According to Sudanese
Vaccination Protocol, she had a complete immunization status, including
the BCG vaccine. Family history of TB, autoimmune diseases, or
rheumatologic diseases was denied.
Her vital signs were: a temperature of 38.4°C, a respiratory rate of 19
cycles per minute, a pulse rate of 98 beats per minute, and an
SpO2 of 94%. On examination, she was found to be pale.
The rheumatologic examination revealed swelling and tenderness in both
knees, both wrists, and the metacarpophalangeal joints of both hands. To
add, further clinical examination (including a chest examination) was
unremarkable. The complete blood count (CBC) showed mild microcytic
hypochromic anemia with raised erythrocyte sedimentation rate (ESR) (85
mm) and C-reactive protein (CRP) (12 mg/L). The autoimmune workup was
negative (antinuclear antibody and rheumatoid factor). X-rays of her
affected joints were normal (no evidence of erosion).
Owing to her clinical picture and the prevalence of TB in Sudan, chest
x-ray (CXR) and Gene-Xpert test of sputum were performed. CXR showed
hilar lymphadenopathy, and the Gene-Xpert of sputum detected
mycobacterium tuberculosis.
Based on that, the anti-tuberculous therapy was started using the
following drug regimen: rifampicin, isoniazid, ethambutol, and
pyrazinamide. The four medications were used for two months, following
this period, the ESR and CRP returned to normal ranges. In addition,
rheumatologic symptoms were completely resolved. Following this, the
rifampicin and isoniazid were continued for 4 months. Adherence to
medication was emphasized and monitored during the management period.
Six months following the completion of the anti-tuberculous therapy, she
was in good health and showed complete resolution of symptoms.
Discussion
In this study, the patient presented with bilateral knee, wrist, and
metacarpophalangeal joint pain in addition to morning stiffness.
Although the presentation is typical for systemic rheumatological
diseases, the autoimmune work-up was negative, while the Gene-Xpert was
positive for tuberculosis. Lourenço et al reported a similar
presentation (4). In their case report, the patient experienced
asymmetrical oligoarthritis (knees and ankles) in addition to erythema
nodosum but these were not supported by the typical immunological
markers (4). This, accompanied by a positive interferon gamma release
assay test pointed towards the diagnosis of tuberculosis and
subsequently Poncet’s disease (PD) (4).
In an additional study conducted by Garg et al. among 18 patients with
acute inflammatory ankle arthritis, eight patients were diagnosed with
PD based on a positive Mantoux test and CT scan of the chest showing
mediastinal and/or paratracheal and/or unilateral hilar lymphadenopathy
with central necrosis (5). The accuracy of the results are questioned by
the lack of microbiological and histopathological confirmation however
it showcase the importance of including PD as a differential diagnosis
of acute ankle arthritis in tuberculosis-endemic regions (3).
Polyarthritis is the presenting feature in our case, consistent with
findings of the literature (5). Knees and ankles were the most commonly
involved joints followed by the wrists in a review by Ktroot et al (5).
while Knees followed by small joints of the hands particularly MCP
joints were the most commonly involved joints in a case series by
Abdulaziz et al (3).
An additional feature of Poncet’s disease found in this study is the
absence of joint erosion in the x-rays of the affected joints, as
Poncet’s is classically defined as an arthritis that develops in the
acute onset of tuberculosis and resolves following the commencement of
anti-tuberculosis medications, without causing joint destruction (5, 6).
This finding was also reported by Lourenço et al and Higashiguchi et al
(4,8).
A review of the literature showcases the historical association of PD
with extrapulmonary TB (9). However, from the description of 198 PD
cases in the literature, the site of TB infection was demonstrated in
96.5 % with 56.8% being extrapulmonary in nature (6). Another review
of 52 cases of PD reported an extrapulmonary site only in 48% of cases
(5). While an extended review of the literature from 2007 to 2012
reported the finding of an extrapulmonary infection in cases of PD to be
60% (3), and exceeding 70% in their own cohort of patients (3).
In this case, the arthritis resolved after 6 weeks of the commencement
of anti-tuberculous therapy. This finding is comparable to another study
which concluded that the clinical presentation of PD was short lived and
the arthritis subsided in an average of 51.6 days following the
initiation of therapy (6).