PHTHISIOLOGY

Lecture 5

CLINICAL FORMS OF TUBERCULOSIS:

Primary tuberculosisSecondary tuberculosis

Primary TB

The development of clinical TB will occur in 5%-10 % of primary infected persons.

The factors involved in increased risk of developing TB are those interfering directly with host immunity.

Factors that facilitate the development of TB disease

• Diseases and conditions that weaken immunity, such as malnutrition, alcoholism,

• advanced age, HIV/AIDS, diabetes, gastrectomy, chronic renal insufficiency, silicosis, paracoccidioidomycosis, leukemias, solid tumors, immunosuppressive drug

treatments

Primary TB in children

• 3.1 million children under 15 years of age are infected with TB worldwide.

• According to the World Health Organization (WHO), children with TB

represent 10 % to 20 % of all TB cases.

Primary TB in children

• The majority of these cases occur in low- income countries where the prevalence of

HIV/AIDS) is high

Primary TB in children

• children younger than five years old may develop disseminated TB in the form of miliary disease or tuberculous meningoencephalitis before the TST

result becomes positive.

Primary TB in children

A very high index of suspicion must be adopted when pediatric patients have a contact history.

Primary TB in children

• Children with asymptomatic infection usually have a positive TST result but do not

have any clinical or radiographic manifestations. These children may be

identified on a routine medical examination.

Primary TB in children

• TST following standard procedures is an important element for TB diagnosis in children.

• Sometimes these patients are identified by a positive TST that may be associated with allergic manifestations such as erythema nodosum and phlyctenular conjunctivitis.

Primary TB in children

• Erythema nodosum is a toxic allergic erythema with nodular lesions in the skin or under it, 2 to 3 cm large. These lesions are spontaneously painful and very painful under pressure, and are usually located bilaterally in feet and legs. It is usually accompanied by pharyngitis, fever and joint inflammation

• and is more frequent in girls over six years.

Primary TB in children

• Primary TB in childrenPhlyctenular conjunctivitis is an allergic keratoconjunctivitis characterized by

the presence of small vesicles that usually evolve to ulcers and resolve without

scars. associated to the phlyctenular conjunctivitis are photophobia and an excessive lacrimation

Primary TB in children

• Progression of the primary infectious complex may lead to enlargement of hilar and mediastinal lymph nodes with resultant bronchial collapse. Progressive primary TB may develop when primary focus cavitates and bacteria spread through contiguous bronchi.

Primary TB in children

• Lymphohematogenous dissemination, especially in young patients, may lead to miliary TB when caseous material reaches the bloodstream from a primary focus or a caseating metastatic focus in the wall of a pulmonary vein Tubercular meningoencephalitis

• may also result from hematogenous dissemination.

Primary TB in children

• Tubercular meningoencephalitis may also result from hematogenous

dissemination

Primary TB in children

• Endobronchial tuberculosis• This form of pulmonary TB occurs when the

infected lymph nodes erode into a bronchus. Enlargement of lymph nodes may result in signs suggestive of bronchial obstruction or hemidiaphragmatic paralysis.

• Dysphagia due to esophageal compression may be observed.

Primary TB in children

• Vocal cord paralysis may also occur as a result of local nerve compression.

• A partial or complete bronchial obstruction can also occur. Usually it is the result of deposition of caseous material within the lumen. Obstructive hyperaeration of a lobar segment or a complete lobe is less common in pediatric patients.

Primary TB in children

• Cavities, bronchiectasis and bullous emphysema are occasionally seen. Many older children are asymptomatic at he time of diagnosis. In general, however, children are more likely to present with wheezing, cough, fever, and anorexia as part of the symptoms.

Primary TB in children

• Persistent cough may be indicative of bronchial obstruction, while difficulty in

swallowing may result from esophageal compression. Hoarseness or difficult

breathing may suggest vocal cord paralysis.

Primary TB

• Adult primary TB is paucibacillary, practically non-contagious, difficult to diagnose.

and of variable severity in seriously immunodepressed patients

Secondary TB

• The existence of post-primary TB, also known as secondary TB, means that the

infection can progress after the development of an adequate specific immune response.

TB lesions in the upper right lung

SIMON’s foci in the left lung

Secondary TB

• This TB episode can develop in two ways: - by reactivation of the primary focus or - by inhalation of new bacilli (super infection)

Secondary TB

• Pulmonary TB is the most common form of post-primary disease

Secondary TB

• The response to bacillary multiplication provokes caseous necrosis that

eventually blends and progresses to liquefaction.

Secondary TB

• Tubercle bacilli find favorable conditions• for population growth after liquefaction of the

caseous necrosis and subsequent cavitation,• and may produce more than 108 bacilli per

cavity with a diameter of less than2 cm. • The development of tuberculous cavities in

the lung characterizes the postprimary TB

Secondary TB

• infectious material can spread through bronchi,

• resulting in the continuous production and elimination of sputum. The natural evolution

• of post-primary lesions in immunocompetent persons can lead to dissemination

• and death in about 50 % of cases, and to chronicity in about 25 % to 30 %.

Secondary TB

• Natural cure can also occur in 20 % to 25 % of cases, when the host immune response

is able to re-establish control of the disease

TB and HIV

• In HIV positive persons infected with the

tubercle bacillus, however, 7 % to 10 % will

develop active TB annually.

Parenchymal infiltrate in the upper left lung

Parenchymal infiltrate in the upper left lung

Lung infiltrate and cavitation in the upper lobe of the right lung (x-ray)

Lung infiltrate and cavitation in the upper lobe of the right lung (x-ray)

Lung infiltrate and cavitation in the upper lobe of the right lung (CT)

infiltrate and cavitation and in both upper lobes

Miliary TB in adults (chest X-ray)

Miliary TB in adults (CT)

Pleural involvement with no parenchymal lesion

Pleural involvement with upper lobe lung infiltrate

Lymph node tuberculosis

Cerebral TB: hydrocephaly, hypodense central

areas, and atrophic lesions.

Erithema nodosum and erithema induratum of Bazin.

Tuberculosis and HIV/AIDS

• Interactions between M. tuberculosis and HIV infection:

• results in the worsening of both pathologies. HIV promotes progression of M. tuberculosis latent infection to disease and, in turn,

• M. tuberculosis enhances HIV replication, accelerating the natural evolution of HIV infection

X-ray of a patient with HIV co-infection and 427 CD4+ cells/μL ;cavity images in both upper lobes

Patient with 23 CD4+ cells/μL: lower and medial lobe opacities with hilar and mediastinal lymph node compromise.

AIDS patient with 71 CD4+ cells/μL:

hematogenous dissemination of TB.

Figure 17-

AIDS and disseminated MDR-TB; CD4+ count of 23 cells/μL.

Lymphadenopathy in an AIDS

• Aspiration procedure of a cervical lymphadenopathy in an AIDS patient with

disseminated TB. The aspirate had a caseous aspect and was AFB smear

microscopy + (10AFB/field).

Lymphadenopathy in an AIDS

Kernig’s sign positive in the TB meningitis. The spinal fluid was positive for M. tuberculosis culture