Main Article: T.B

48 years old female live in Faisal, Giza. Complaining of shortness of breath, cough with sputum and chest pain radiating to shoulder in the left side, condition started one year ago with developing the clubbing of her both fingers and pain on both knee, both elbow joints pain with movement 5 month ago for the first time, in the hospital admitted on Thursday, February 22 , 2015. Dyspnea worsens with movement and relieve with rest, sputum more while patient lying on left side with no blood, hands become blue discoloration and palpitation with movement. Lying on right side is normal. The patient had fever at the beginning. Weight loss?, night fever? picture.

This patient has DD e.g. 1. Tuberculosis, 2. Bronchiectasis, Bronchogenic carcinoma and cystic fibrosis complicated with pleural effusion most probably. To understand the case read the article below.

Bacteria named Mycobacterium Tuberculosis lives in bovines animal, the talent  bacteria transfer into human since 1906 or later, mostly affect human lungs alveoli. Human immune system recognize the bacteria as foreign body, the immune system send the macrophages to attack the bacteria then macrophage engulfs the bacteria in order to kill the bacteria through toxic substances , in the same time the macrophage wants to present antigen of bacteria on the surface of macrophage that can be identified by T-lymphocytes and killed by together but unable  to present the antigen of bacteria due to presence of waxy mycolic acid capsule of bacteria  thus suppressed immunity. Another macrophage come to it and fused together form giant cell granuloma in order to prevent spreading of  the bacteria. Abnormal tissue necrosis inside macrophage with soft white cheese like material has been formed called caseous granuloma also cavities formation filled with caseous material that contains living bacteria that can be passed into bronchi through cavities. Through cough living bacteria can spread person to person as a droplets transmission. Bacterial infection cause fever, its a logic. Once fever, it let the patient to sweat to minimize the temperature; as body defense. But characters are night fever and night sweat with weight loss. Necrosis may come out with cough up blood. If chronic cough with above symptoms suggests the talent mycobacterium tuberculosis.

How to choose the investigations?
every disease has their own specific test to confirm the disease.
You choose the investigation from patient's complaint. Example, main complain is cough so the problem is in the lungs most probably, that is why you choose  the Chest X -ray specially for TB because of specific test for suspected TB case. Nodular shadow in the  upper zone on x-ray. Sputum culture and sensitivity test but it takes longer time to give result. Mantoux  tuberculin test for the risk people.
What is Tuberculin Skin Test?TB
It is a skin test to identify the M.Tuberculosis inside body. we inject the Purified Protein Derivative intradermally, if the site of injection become raised and indurated indicates the M.TB positive patient. But there are some exception. The skin is raised and indurated due to delay type hypersensitivity reaction due to presence of TB elsewhere in the body especially lungs.
What are the exceptions and why these exceptions  ?
1. Result of tuberculin skin test is positive means  the skin is raised and indurated. If  there is  raised skin and indurated  but no M. TB elsewhere in the body is called "False  positive test ", due to if patient have AIDS, very old age and malnutrition.
To remember forever, just think this way; test name is false positive so false equal wrong or No now if you combine it looked like "No  positive" equal Negative in meaning so No TB elsewhere in the body but skin is raised and indurated.
2. False Negative test, it is the opposite of false positive but reason is time difference between the first day of infection till 4 weeks, skin is not raised and indurated within 4 weeks of getting infected but after 4 weeks the skin is raised and indurated so the  TB  needs at least 4 weeks to become positive on tuberculin skin test. That is why it is not diagnostics.
Treatment : M. Tuberculosis has high lipid containing mycolic acid in cell wall, that is why needs multidrug regimen to kill the M. Tuberculosis. Treat  the underlying  cause first . In the TB case, cause is bacteria so antibiotics. Bacteria is very talent,  needs multidrug regimen and longer duration. Antibiotics are
1. Isoniazid 5 mg/kg/day with pyridoxine 10 mg/day.
2. Rifampicin 10 to 15 mg/kg/day
Both for 6 months and supplemented with pyrazinamide 25 mg to 30 mg for the first two months and
3. Streptomycin 10 to 15 mg/kg/day
4. Ethambutol 15 mg/kg/day.