HISTORY OF PRESENT ILLNESS
The patient is a 3-year-old boy with a history of asthma who presented with cough and chest pain. His illness began 2 weeks prior with left-sided chest pain with inspiration. The family had misplaced his baseline asthma medications. He was seen in the emergency department and felt to have musculoskeletal pain. His pain improved slightly, but he was brought back to the emergency department 8 days later with wheezing and rhinorrhea. He was described as having increased work of breathing and a significant cough. There was no fever. In the emergency department, he was felt to be in mild respiratory distress and was treated with prednisone and albuterol and then discharged. However, the following day, he developed blood streaked sputum evolving into a small volume of hemoptysis. He was brought back to the emergency department. There was no fever, chills, or weight loss.
The patient has a history of asthma for which he was hospitalized three times. His last admission was 3 years prior to this current presentation. His medications are albuterol which he receives twice a day and a fluticasone metered-dose inhaler that he has not received in several weeks.
T 37.2°C; P 70 bpm; RR 30/min; BP 108/52 mmHg; Oxygen saturation 99% in room air
In general, he was a well-appearing young boy in no acute distress. His physical examination was significant for a clear lung examination with no evidence of wheezes, rales, or rhonchi. The remainder of his physical examination was unremarkable.
Chest roentgenogram was obtained (Figure 4-6). Tuberculin skin test reaction was less than 5 mm.
FIGURE 4-6. Chest radiograph.
COURSE OF ILLNESS
He was initially started on a course of azithromycin for a presumed Mycoplasma pneumoniae infection. His chest pain continued, but his hemoptysis had resolved. With concern for his chest roentgenogram findings, a further diagnostic test was performed which revealed the diagnosis.
DISCUSSION CASE 4-4
Considering the patient’s medical history, the most common cause for his cough is likely to be asthma with a superimposed infectious process. His symptoms did appear to improve slightly with standard asthma therapy of bronchodilators and steroids. Allergic or sinus symptoms can also cause a significant cough in this age group. Similarly, one should inquire about a history of smoking or possible foreign body aspiration.
The hemoptysis in this case is not unusual in many of the processes described. It is important to try and establish that this is true hemoptysis and not hematemesis or bleeding from the nasal passages (Table 4-7). With true hemoptysis, the most common etiologies include cystic fibrosis, pneumonia, bronchiectasis, congenital heart disease, and tracheobronchitis. Finally, the hilar adenopathy noted on chest roentgenogram should alert one to pursue a more thorough investigation, with consideration to mycobacterial infections and granulomatous disorders.
TABLE 4-7. Hemoptysis versus hematemesis.
Chest radiograph revealed a right middle lobe infiltrate with right hilar adenopathy (Figure 4-6). Nasogastric aspirates were sent for acid fast bacilli (AFB) stain and cultures. AFB stain was negative but AFB culture revealed growth of mycobacterium avium-intracellulare. The diagnosis is a pulmonary infection with mycobacterium avium-intracellulare.
INCIDENCE AND EPIDEMIOLOGY
Nontuberculosis mycobacterium (NTM) are ubiquitous in the environment. They are found in soil, water, food, house dust, and domestic and wild animals. Human infection likely occurs with aspiration of aerosolized particles. Human-to-human transmission is not believed to occur.
It is difficult to determine the incidence of NTM infections as they are not a reportable disease to health authorities. Furthermore, symptoms are confused with Mycobacterium tuberculosis infections. It is also challenging to properly differentiate asymptomatic colonization from true infection. A positive culture for NTM does not always represent invasive disease. Moreover, interpretation of a single positive respiratory culture for MAI should take into account the possibility of environmental contamination.
The most common NTM organisms form the Mycobacterium avium complex (MAC) which consists of both M. avium and Mycobacterium intracellulare. Aside from patients with HIV, those with the greatest risk of becoming infected with pulmonary MAC are those patients with underlying lung disease. This includes patients with chronic obstructive pulmonary disease, chronic bronchitis, bronchiectasis, recurrent aspiration, and cystic fibrosis. However, reports of patients with no underlying lung disease and MAC infections have been reported. The southeastern part of the United States does appear to have a higher incidence of MAC infections.
Rarely, a patient will present with disseminated NTM infection. These patients should be investigated for an underlying immune deficiency, since patients with certain disorders such as IFN-γ receptor defects and IL-12 defects are highly susceptible to infections with NTM.
There are four major clinical syndromes of NTM infection that are most commonly seen in children: lymphadenitis, pulmonary infections, skin and soft tissue infections, and disseminated disease.
Pulmonary infections with NTM are rare in children, and are more often seen in the elderly. MAC is the most common NTM to cause pulmonary infections, but cases have been reported with Mycobacterium kansasii and Mycobacterium fortuitum as well. Symptoms are very similar to tuberculosis with a productive cough, fevers, and weight loss. Hemoptysis is less common, and is seen in less than 25% of patients with pulmonary MAC infections. It is rare for disease to disseminate beyond a pulmonary infection if the host is immunocompetent.
Wheezing is a common presenting symptom, and often hilar adenopathy leads to signs and symptoms of bronchial obstruction. It is common for these children to be evaluated for possible foreign body aspiration prior to the discovery of their NTM infection. On occasion, a child will have repeated illnesses with fever and cough and be diagnosed as having recurrent pneumonias.
NTM infections can only be diagnosed with a high degree of clinical suspicion. Diagnosis is based on isolating the organism in conjunction with appropriate clinical disease.
The following tests can be useful:
Blood tests. Complete blood counts, erythrocyte sedimentation rate, urinalysis, and serum chemistry tests are generally normal with NTM infections.
Sputum or gastric aspirate (mycobacterial culture and acid-fast stain.) Acid-fast stain of sputum and gastric aspirates are often negative in cases of NTM as the number of organisms may be quite small. Therefore, a negative AFB stain does not exclude the diagnosis of NTM infection. NTM can be grown from sputum and gastric aspirate culture, but results must be interpreted with caution, as asymptomatic patients may be colonized with NTM. Thus, clinical criteria have been developed requiring either radiographic evidence of disease with greater than one positive sputum samples, or reproducibility of positive cultures over the course of a year.
Purified protein derivation skin testing (PPD). Patients with MAC will generally have reactions of 0-10 mm. It is rare to see larger reactions. A positive PPD should never be considered diagnostic for NTM infection and a negative PPD should never eliminate the diagnosis.
Chest roentgenogram. This may reveal findings similar to infection with tuberculosis. Cavitary lesions are not uncommon, but are often smaller than with M. tuberculosis. Other radiographic presentations may include patchy, nodular infiltrates or even isolated pulmonary nodules. Hilar adenopathy may also be seen.
Bronchoscopy. Inadequate sputum samples are often obtained in children, and bronchoscopy may be indicated to obtain useful cultures. Adenopathy sufficiently large to cause bronchial obstruction can occur, and often bronchoscopy is performed in an attempt to rule out an anatomic etiology for the bronchial compression.
As the majority of NTM organisms are resistant in vitro to single drug therapy, combination therapy is, therefore, generally the rule. Treatment will often include isoniazid, rifampin, rifabutin, ethambutol, streptomycin, amikacin, azithromycin, or clarithromycin. For many patients, treatment regimens may extend for 18-24 months and specifically for at least 12 months after sputum cultures have become negative. Many of these medications have significant side effects and patients should be monitored closely. Side effects include but are not limited to the following: rifampin (hepatitis), rifabutin (uveitis especially when used with macrolide, hepatitis, polyarthralgias), ethambutol (retrobulbar neuritis manifest by decreased visual acuity or red-green color discrimination), amikacin (ototoxicity, nephrotoxicity), azithromycin (reversible hearing loss, GI upset), and clarithromycin (GI upset).
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