Most common site for extrapulmonary tuberculosis is -

Ans. is 'a' i.e., Lymph nodes Tuberculosis* Tuberculosis may be pulmonary or extrapulmonary.Pulmonary tuberculosis* Pulmonary tuberculosis is classified into two types1) Primary tuberculosis# It is the initial infection by tubercular bacilli in a host and almost always begins in lung. It is mostly seen in children.# Inhaled tubercle bacilli is implanted in the distal air space of the lower part of upper lobe or upper part of lower lobe, close to pleura to form subpleural lesion. This area is about 1 to 1-5 cm with caseating necrosis is known as Ghon's focus. Due to early bactermia (bacillemia) seeding of tubercle bacilli may occur at apex to produce Simon's focus.# Primary complex or Ghon's complex of tuberculosis consists of 3 components : -i) Ghons focus (subpleural caseating lesion)ii) Caseating hilar lymph nodeiii) Draining lymphatics.* Ghon's focus is one of the component of Ghon's complex (primary complex).# Ghon's complex undergoes progressive fibrosis and calcification, detected radiologically and is called Ranke complex.# Cavity formation is unusual in primary TB.2) Post-primary tuberculosis# It is due to reactivation of latent infection or exogenous reinfection. It usually affects adults. Apical segment of upper lobe is affected, where PA02 is high, and lesion is called Puhl lesion. Lesions are large.# Lymph node involvement is uncommon. Cavity formation is common.# Infraclavicular lesion of secondary pulmonary TB in the apex of lung is called 'Assman's focus'.Important lesions in Pulmonary T.B.Primary TB* Ghon's focus: Primary subpleural lesion.* Simon's focus: Lesion in apex of lung due to seeding of bacilli in apex in early bacillemia.* Ghon's complex: Ghons focus plus hilar lymphadenopathy.* Ranke complex: Ghons complex with calcification in lymph nodes.Secondary TB* Phul's lesion : Lesion in the apex of lung in chronic pulmonary tuberculosis.* Assman's lesion: Infraclavicular lesion in the chronic pulmonary TB.Extrapulmonary tuberculosis* Most common site of extrapulmonary tuberculosis is lymph nodes. Other extrapulmonary sites of involvement are pleura, pericardium, meninges, brain, genitourinary system, GIT and skeletal system.* Miliary or disemminated tuberculosis (Miliary disease) refers to widespread dissemination of mycobacterium tuberculosis via hematogenous route.* Most common cutaneous manifestation of tuberculosis is lupus vulgaris (55%) followed by scrofuloderma (27%).