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Para-amino salicylic acid (PAS)


One of the earliest anti-tuberculosis drugs, it is still occasionally used for treating multi-drug resistant tuberculosis.

Paediatric TB

TB in children.

Paraparesis

Weakness in the lower limbs.

Paraplegia

Paralysis of the lower limbs.

Pathogen

A micro-organism able to cause disease. There are two types – obligate and facultative (or opportunist). 
PCR

See Polymerase Chain Reaction.

Percutaneous

The route of administration through or via the skin.

Pericardial effusion

Fluid accumulating in the pericardium – the bag in which the heart lies.

Pericarditis

Inflammation or infection of the pericardium – the bag in which the heart lies.  Tuberculous pericarditis is an uncommon and serious condition as scarring can interfere with the normal beating of the heart (constrictive pericarditis). For unknown reasons, it is particularly common in the Transkei where it was termed ‘Transkei heart’.

Peripheral neuropathy



Pins and needles in the fingers or toes.

Persister

See latent tuberculosis.

Phagocytosis

The ‘eating and digestion’ of micro-organisms by specialised cells of the immune system.  Some pathogens, including the tubercle bacillus, are resistant to digestion and thrive within these phagocytic cells. They are thus referred to as intracellular pathogens.

Phlyctenular conjunctivitis

Inflammation of the eye with itching or pain, excessive production of tears and sensitivity to light. It is most frequently seen in children with primary tuberculosis aged between 5 and 10 years and occurs more frequently in girls than in boys. Usually just one eye is affected. Small grey nodules are seen near the edge of the cornea and the adjacent area of the eye is reddened due to dilatation of blood vessels.  It usually clears up within a few days although it may recur.

Phthisis

Meaning wasting, an old term for tuberculosis.

Pleura

The membranes forming a sac or cavity in which the lungs lie.

Pleural effusion

Fluid accumulating in the pleural cavity.

Pleurisy

Inflammation of the pleura.

Point prevalence

The number of cases of a disease in a community at a given point in time.

Polymerase chain reaction

A technique for amplifying a few specific fragments of DNA in a clinical specimen to millions of fragments that are easily detectable. This method has the potential to detect tubercle bacilli in specimens within hours rather than weeks. Initial problems of sensitivity have been resolved but cost factors prevent its universal use.

Poncet’s disease

A form of arthritis, thought to be due to immune reactions, occurring in a small minority of patients with active tuberculosis.  It usually resolves when the underlying tuberculosis is successfully treated.

Post-primary tuberculosis

Tuberculosis occurring after a period of latency following initial infection (usually appearing three or more years after initial infection).  The usual site, irrespective of the site of the initial infection, is the apex of the lung and tissue necrosis leading to cavity formation is evident.

Pott’s disease

Spinal tuberculosis. Named after Sir Percival Pott, a surgeon at St. Bartholomew’s Hospital, London.

Prevalence


Prevalence is a measurement of all individuals affected by the disease at a particular time. This is distinct from incidence, which is is a measurement of the number of new individuals who contract a disease during a particular period of time.

Preventive therapy

Anti-tuberculosis drugs given to a person with latent tuberculosis, (usually indicated by a positive tuberculin reaction) to prevent the development of active disease. Therapy is usually based on isoniazid alone.

Primary complex, tuberculous

The initial lesion of tuberculosis, consisting of a lesion at the site of implantation of the bacilli (usually the lung but occasionally other sites) and in the lymph nodes draining that site.

Primary tuberculosis

Active tuberculosis following initial infection by the tubercle bacillus.

Primary drug resistance

Resistance as a result of infection of a patient by a strain of tubercle bacillus already resistant to one or more drugs.

Psoas Abscess

Abscess of the psoas muscle (a muscle that joins the backbone to the thigh).

Pulmonary tuberculosis

Tuberculosis of the lung. The most common form of tuberculosis. Pulmonary TB is the only form of TB that may be infectious.

Purified Protein Derivative (PPD)

A derivative of tuberculin prepared by harvesting precipitated proteins. It is less likely to give non-specific reactions than unpurified tuberculin.

Purulent

Containing or formed of pus.

Pyrazinamide

One of the first-line anti-tuberculosis drugs.

Pyridoxine

Vitamin B6.  This is often prescribed with anti-tuberculous drugs to prevent certain side effects of Isoniazid on the nervous system.

Pyuria

Producing urine which contains white blood cells.

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