The Mantaux of a 40-year-old man who had presented with fever, weight loss and cough reads 18 x 19 mm. Sputum cytology is negative for AFB. What is the most likely condition?

All the given features (low-grade fever, cough and weight loss) above were ourable for pulmonary tuberculosis, and the fact that a sputum cytology doesn't negate the possibility for a detection of pulmonary tuberculosis. A negative PCR from a smear which is positive for acid fat bacilli makes diagnosis of tuberculosis highly unlikely. Cell culture identification of Mycobacterium tuberculosis and Mycobacterium bovis is required for diagnosis of tuberculosis. Ref: Siegenthaler's Differential Diagnosis in Internal Medicine By Walter Siegenthaler, 2007 ; Oxford Textbook of Medicine, Volume 1, By D. A. Warrell, Timothy M. Cox, John D. Fih, 2003, Page 560