Case Presentation:

A 50–year–old Caucasian male, known HIV, off Highly Active Antiretroviral Therapy (HAART) for 7 years, presented to the ED because of weakness. He gave a 2–week history of fever and productive cough, as well as poor appetite and a 50 lb weight loss for the past year. Relevant investigations: White cell count 2.9, hemoglobin 7.6 g/dl, Vitamin B12 59 pg/ml, prealbumin 5.2 mg/dl. HIV viral load 195,000, Absolute CD4 count 1.0. Computed Tomography (CT) chest revealed a 5.7 cm cystic/necrotic mass in the left lower lobe. He was placed in airborne isolation, started on HAART, Ampicillin/Sulbactam intravenously and nutritional supplementation, resulting in good clinical improvement. One of three Gram stains showed Gram–positive rods, so clarithromycin and trimethoprim–sulfamethoxazole (TMX) were added for empiric coverage of Rhodococcus Equi and Nocardia Asteroides. Three consecutive morning stains for Acid Fast Bacilli (AFB) were negative. He was discharged on Day 7 on amoxicillin/clavulanate, clarithromycin and TMX orally, but returned to hospital on Day 17 complaining of feeling unwell. CXR revealed progressive left lower lobe consolidation, new left hydropneumothorax necessitating tube thoracostomy. On Day 30, DNA probe of all three AFB cultures were positive for Mycobacterium Kansasii and he was converted to appropriate oral therapy.

Discussion:

The differential of cavitary lung disease in HIV is broad, commoner infective etiologies are: Pseudomonas aeruginosa, Nocardia asteroides, Rhodococcus equi, Mycobacterium Tuberculosis (M TB), Mycobacterium kansasii, and invasive pulmonary aspergillosis. Pneumocystis Jiroveci is one of the commoner causes of spontaneous pneumothorax, whilst this is rare for Mycobacterium Kansasii. Our case is also unique in that it is less common to see cavitary disease in patients with such low CD4 counts. Mycobacterium Kansasii is the second most common cause of non–tuberculous mycobacterial disease in HIV patients, after Mycobacterium Avium complex. It is typically seen in middle aged, Caucasian males with CD4 cell counts < 50. Typically diagnosed by culture, obtained from at least 2 consecutive early morning sputum samples, it can also be diagnosed rapidly and accurately by Polymerase chain Reaction (PCR). M Kansasii and M TB are clinically indistinguishable, and because M Kansasii does not require isolation, use of PCR may obviate the need for airborne precautions. Rifampin sensitive strains should be treated with Rifampin, Ethambutol and Isoniazid, for at least 12 months of culture negative sputum samples. For rifampin resistant patients, a three drug regimen should be used based on in vitro susceptibilities, including include clarithromycin or azithromycin, moxifloxacin, ethambutol, sulfamethoxazole.

Conclusions:

Physicians should consider M Kansasii in the appropriate clinical setting and consider PCR testing which may lead to earlier initiation of appropriate treatment in HIV patients with cavitary lung lesions.