Transcript Medical factors

Pulmonary tubercolosis
Dr Nawal N Binhasher
Assistant professor, Medical
consultant, Medical department
Epidemiology
The incidence of TB has been slowly rising
since the 1980s of the previous century
esp in eastern & southern Africa where
HIV is common.
 By the beginning of this century, there
were an estimated 8-9 million new cases
& 1.8 million people died of TB in 2000.
 With the present trend, 9-10 million new
cases of TB are expected in 1020.

Epidemiology
Across regions, sub-Saharan Africa has by far
the highest annual incidence rate ≈ 290/100,000
population, but Asia harbors the largest No of
cases.
 India, China, Indonesia, Bangladesh, & Pakistan
together account for over half the global burden.
 The most striking rises have been seen in subSaharan Africa & the former Soviet Union. These
rises offset the fall in cases No in other parts of
the world mainly west & central Europe, the
Americas, & the Middle East.

Epidemiology
Globally, ≈ 11% of TB cases are co- infected
with HIV, 38% of that in sub-Saharan Africa &
< 1% in china & India.

Risk Factors:
1. Geography (place & date of birth): as
mentioned above
2. Immunocompromise: mainly HIV/AIDS (&
others like: steroids, TNF –inhibitors, drug
injection abusers)
3. Medical factors, like: DM; 8 folds higher,
Cancer; esp hematological & head & neck ca,

Risk Factors
Celiac disease, ESRD, intestinal bypass or
gastrectomy, chronic malabsorption
syndromes, Cigarette smoking, Iron status: ↑
dietary Fe is associated with an ↑ risk of
pulmonary TB, Vitamin-D: an inverse


relationship between vit-D levels & both active
& latent TB infection has been shown in
several studies.
Low socioeconomic status (poverty).
Children & aging.
Pathophysiology
The disease is spread by airborne droplets,
containing MTB, inhaled & lodged in the distal
AW.
 MTB is taken up by alveolar macrophages in
which it replicates with spread via the lymphatics
to hilar LN & a few escape to blood stream.
These cells interact with T lymphocytes with the
development of cellular immunity that can be
demonstrated 3-8 wks after initial infect’n by a +
ve skin reaction to ID injection of protein from
tubercle bacilli (tuberculin).

Pathophysiology

The cell-mediated immunity leads to granuloma
formation (central caseation »» may completely
heal » many become calcified » 20% of these
contain dormant tubercle bacilli » reactivation
when host cellular immunity is depressed)