The case of an 11-year-old Croatian boy of Mediterranean origin with a history of asthma, dyspnea on exertion and chronic hypoxemia is presented. The patient was initially misdiagnosed with difficult-to-control asthma, based on his past medical history, persistent symptoms of dyspnea, reduced exercise tolerance, and several asthma exacerbations. CT angiography of the thorax showed two PAVM, one on each side of the lungs. A three-dimensional reconstruction of the patient's left lobe vascularization showed an AVM and an aneurism with a single feeding artery originating from the pulmonary artery, and a single draining vein. HHT clinical diagnosis was made by the presence of three Curaçao criteria (epistaxis, mucocutaneous telangiectases, and PAVM).
Many diseases mimic asthma and these alternate diagnoses should be considered, especially if asthma symptoms do not respond to treatment as expected. According to the American Thoracic Society workshop consensus for definition of refractory or severe asthma certain criteria are used for diagnosis. First, major characteristics: a) treatment with continuous or near continuous (>50% of year) oral corticosteroids; and b) need for treatment with high-dose inhaled corticosteroids. Second, minor characteristics: a) one or more asthma exacerbations per year; b) use of a daily short-acting β2-agonist because of asthma symptoms; c) airway obstruction (FEV1 <80% of predicted, diurnal peak expiratory flow variability of >20%); d) needing three or more oral corticosteroid courses per annum; e) a near-fatal asthma event in the past; f) deterioration with reduction in oral or intravenous steroid dose; and g) needs additional daily treatment with a controller medication such as a long-acting β2-agonist, leukotriene antagonist, or theophylline. Two major criteria, or one major criterion and two minor criteria must be met for diagnosis of difficult-to-control asthma. In general, difficult-to-control asthma can be divided into two subgroups: first, true difficult-to-control asthma requiring thorough diagnostic work-up and appropriate management by a specialist; and second, false difficult-to-control asthma which is only apparently difficult-to-control and is conditioned by different comorbidities. Four different conditions can be classified under false difficult-to-control asthma. First, incorrect diagnosis of asthma: congenital anomalies of upper airways, large airways obstruction, gastro-esophageal reflux, cystic fibrosis, bronchiectasis, cardiac disease, and hyperventilation syndrome. Second, asthma and comorbid conditions. Third, continued exposure to aggravating factors. Fourth, non-adherence to treatment, incorrect choice of inhalers, and poor inhaler technique.
PAVM are uncommon. According to an autopsy study by Sloan and Cooley in 1953, only three cases of PAVM were detected in 15,000 consecutive autopsies. The Mayo Clinic reported 194 cases of PAVM over 45 years, indicating an annual incidence of 4.3 cases per year.[7–9] PAVM may be acquired or congenital and approximately 70% of the cases of PAVM are associated with HHT. PAVM occurs twice as often in the female gender compared with the male gender.
PAVM can be either simple or complex. The simple type (80% of cases) consists of a single feeding segmental artery and a single draining vein, and the complex type (20% of cases) has two or more feeding arteries or draining veins.[12,13] More than half of the lesions are in the lower lung fields, followed by the middle lobes and then the upper lobes.[12,14] PAVM can be single or multiple in occurrence and the incidence of single PAVMs ranges from 42% to 74%.[8,9] In patients with HHT the PAVM are multiple (35% to 65%),[8,15,16] and usually associated with severe complication and infection. The study of Bosher et al. found that 25% of patients had bilateral disease. Our patient had two simple PAVMs, one on each side of the lungs.
Approximately 72% of patients with PAVM have symptoms referable to PAVM or underlying HHT. Symptoms related to PAVM often develop between the fourth and sixth decades of life when the shunted blood exceeds 25% of total blood volume.[6,19,20] Symptoms of HHT commonly become noticeable before the age of 20 (for example, epistaxis, skin telangiectases).[21,22] Dyspnea on exertion is the most common complaint in patients with PAVM and it is seen in about half of patients.[15,23,24] Other symptoms attributable to PAVM include the following: hemoptysis (in approximately 10% of patients), chest pain (6%), finger clubbing (20%), cyanosis (18%) and thoracic murmurs (3%). Our patient had dyspnea on exertion with chronic hypoxia and he was resistant to conventional asthma therapy. Thoracic murmur was revealed on physical examination.
Orthodeoxia is a decrease in partial pressure of oxygen in arterial blood (PaO2) or SaO2 that occurs when one assumes an upright position from the supine position. The fraction of cardiac output that shunts right-to-left circulation is elevated in patients with PAVM; normal values are less than 5%. The shunt fraction is most accurately assessed by using the 100% oxygen method, which involves the measurement of PaO2 and SaO2 after the patient breathes 100% oxygen for 15 to 20 minutes. A shunt fraction of more than 5% has a sensitivity of 87.5% and a specificity of 71.4%. Spirometric findings are usually normal with mildly reduced diffusing capacity.[15,25,26] In our case, spirometry parameters were within the normal range and DLCO was decreased. The classic roentgenographic appearance of a PAVM is that of a round or oval mass of uniform density, frequently lobulated but sharply defined, more commonly in the lower lobes, and ranging from one to five cm in diameter. The sensitivity of chest radiograph alone is 70% in diagnosing PAVM. In our patient, a chest X-ray showed a homogeneous soft tissue mass suspicious for tumor. CT angiography is considered the 'gold standard test' for the diagnosis of PAVM with sensitivity over 97%. Our case also confirms this observation.
The natural course of PAVM is not benign. These lesions can be associated with a variety of life-threatening complications, such as stroke, brain abscess, hemothorax, and hemoptysis, especially in women.[28,29] Rupture of a PAVM can occur at any age, independently of lesion size.[30–32] Without appropriate treatment mortality exceeds 11%.
All symptomatic PAVMs and asymptomatic PAVMs larger than two cm, or if feeding arteries are larger than two mm, should be treated with surgery or embolotherapy because of the risk of paradoxical embolism.[8,34] The treatment of choice in patients with multiple or bilateral PAVM is transchateter embolotherapy with balloons or stainless steel coils, and vascular plugs (AMPLATZER®).
J Med Case Reports. 2013;7(32) © 2013 BioMed Central, Ltd.