2.2 Extrapulmonary tuberculosis (EPTB)

Starting from a pulmonary localisation (primary infection), M. tuberculosis can spread to other organs during a silent phase, generally at the beginning of the infection (Chapter 1). Active TB can develop in many other parts of the body, in particular lymph nodes, meninges, vertebrae, joints, kidneys, genital organs and the abdominal cavity.

EPTB forms can develop at any age. Young children and HIV infected adults are more susceptible.

EPTB forms present with a variety of clinical characteristics. However, a common characteristic is the insidious evolution with gradual deterioration of the physical condition. Furthermore, there is a lack of response to symptomatic or non-tuberculosis anti-infective treatments. EPTB may be associated with a pulmonary localisation, which should be searched for when ever EPTB is diagnosed or suspected. Table 2.3, at the end of this chapter, summarizes the characteristics of EPTB.

2.2.1 Lymph node tuberculosis

Lymph node TB is a common presentation particularly in certain areas of Africa and Asia, where it represents up to 25% of TB cases3,4. This form is more common in children and HIVinfected patients.

The presentation of lymph node tuberculosis is non-inflammatory adenopathies, cold and painless, single or multiple, usually bilateral, evolving in a chronic mode towards softening and fistulisation. Cervical localisation is most frequent, ahead of axillary and mediastinal forms. They are associated with other localisation in 10 to 30% of cases.

Diagnosis is mainly clinical, however fine needle aspiration can be done if the diagnosis is in question (Chapter 3, Section 3.10).

Adenopathies usually disappear in less than 3 months after treatment initiation. Paradoxical reactions may be observed at the beginning of treatment (appearance of the lymph node getting worse with abscesses, fistulas or other lymph nodes appearing) and often a change in the treatment is not needed.

Differential diagnosis includes malignancies (lymphoma, leukaemia, ear/nose/throat tumours, Kaposi sarcoma) and other infections (bacterial, viral, non-tuberculosis mycobacteria, toxoplasmosis, HIV infection, syphilis, African trypanosomiasis).

2.2.2 Tuberculous meningitis

Meningitis due to tuberculosis is most common in children below 2 years of age5 and in HIV-infected adults. Headaches, irritability, fever, and an altered mental status accompany the
beginning of the disease, often in a variable manner, which is progressive in nature. The meningeal syndrome (stiff neck, hypotonia in infants, photophobia and headache) is present in most cases. Vomiting may be present. The impairment of the third cranial nerve is a sign that can accompany TB meningitis (oculomotor paralysis).

The main differential diagnoses are other forms of meningitis where the cerebrospinal fluid (CSF) is clear – viral/fungal meningitis or incompletely treated bacterial meningitis are the most common.

TB meningitis is a medical emergency, and any delay in diagnosis/treatment may result in irreversible neurological sequelae5.

2.2.3 Tuberculosis of bones and joints

Tuberculosis of bones and joints is mostly found in children, probably because of better vascularisation and oxygenation of osteo-articular structures during growth.

Arthritis: Often arthritis due to TB is a chronic monoarthritis, starting insidiously, with little or no pain and accompanied by joint destruction. The joints most often affected are the hips, knees, elbows and wrists. Half of the patients with TB arthritis have PTB at the same time.

Osteitis: This is the less frequent presentation of TB of the bones. It may be a primary osteitis or an osteitis complicating arthritis. It affects long bones and is occasionally accompanied by cold abscesses. Like arthritis, it is distinguished from common bacterial infections by the contrast of slight symptoms and the extent of destruction detected by radiography.

Spondylodiscitis (TB of the spine or Pott's disease): TB of the spine affects vertebrae and disks, bringing about destruction and deformation of the spine. A missed diagnosis of thoracic or cervical spinal TB can result in paralysis. Dorsal localisation is the most frequent followed by lumbar and lumbosacral areas. Localised pain may precede the appearance of the first radiological anomalies (destruction of an inter-vertebral disk) by several months. A para-vertebral cold abscess may accompany osteo-articulary lesions, yet neurological signs may complicate them.

The diagnosis is often made based on the clinical history and X-ray, as biopsy and culture is difficult to perform in resource-constrained settings. Deterioration of physical condition and prolonged and insidious clinical history of osteitis or arthritis are in favour of TB aetiology as opposed to bacterial osteomyelitis or brucellosis. The patient may have a history of not responding to broad-spectrum antibiotics.

2.2.4 Genitourinary tuberculosis

Renal involvement is frequent and may be asymptomatic for a lengthy period of time, with a slow development of genitourinary signs and symptoms including: dysuria, urinary frequency, nocturia, urgency, back and flank pain, abdominal pain, tenderness/swelling of the testes or epididymitis and haematuria. General physical condition is preserved most of the time with only about 20% of patients having constitutional symptoms6.

Diagnosis is suspected in the presence of pyuria (white blood cells in the urine) and microor macroscopic haematuria, which does not respond to broad-spectrum antibiotics. Examination of the urine aids in diagnosis (Chapter 3, Section 3.10).

In women, genital tract contamination can also happen by a haematogenous path. Abdominal pain, leucorrhoea and vaginal bleeding are variable, non-specific signs of genital tract tuberculosis. Extension may be found in the peritoneum with resulting ascites. The presenting complaint leading to the diagnosis of genitourinary disease is often sterility.

In men, genital localisation is secondary to renal localisation. It is manifested most often by epididymitis with scrotal pain.

2.2.5 Abdominal tuberculosis

Abdominal TB commonly presents as ascites resulting from the peritoneal localisation of the infection. The frequency of chronic ascites in tropical regions, with its many different causes, makes this relatively uncommon form of TB a common diagnostic challenge7. Diagnosis is assisted greatly by examination of the ascitic fluid via paracentesis (Chapter 3, Section 3.10).

Besides ascites, clinical symptoms are non-specific: abdominal pain, diarrhoea and constitutional symptoms (fever, night sweats, malaise, weight loss). The ascites may mask weight loss.

2.2.6 Tuberculous pleural effusion

TB pleural effusion by itself is often asymptomatic, especially if less than 300 ml. When the effusion is large, shortness of breath may be present. Sputum production and cough may only be present if there is also pulmonary involvement, which is common. Constitutional symptoms such as fever, weight loss, night sweats, anorexia and malaise may also be present.
This form of TB is more frequent in young adults8. Diagnosis is assisted by examination of the pleural fluid via paracentesis (Chapter 3, Section 3.10).

2.2.7 Tuberculous pericardial effusion

Clinical signs of a tuberculous pericardial effusion include: chest pain, shortness of breath, oedema of the lower limbs and sometimes ascites. The clinical examination may show pericardial friction rub, raised jugular pressure and tachycardia. The radiography and ultrasounds are key elements for diagnosis (Chapter 3, Section 3.7).

Pericardiocentesis may be necessary in the event of acute heart failure resulting in haemodynamic compromise. It must be performed by experienced personnel in wellequipped hospitals.

2.2.8 Cutaneous tuberculosis

The clinical presentation of cutaneous tuberculosis is chronic, painless, non-pathognomonic lesions, ranging from small papula and erythema to large tuberculomas. The diagnosis is based on culture from a biopsy9.