The incidence of PAP is four times higher in males than in females and typically presents between 20 and 50 years of age [7]. Up to now, all the three cases found in Sri Lanka are of female gender, although our case is the only patient who presented in her adolescence. The commonest chest X-ray presentations in patients with PAP are bilateral symmetrical alveolar opacities located centrally in the mid and lower lung zones, often in a “batwing” distribution. The chest X-ray of our patient shows a reticular nodular pattern of bilateral perihilar distribution. The main features of PAP in HRCT were present in our patient, constituting thickened intralobular structures and interlobular septa, with no architectural distortion, often with polygonal shapes, sometimes called “crazy paving” pattern, and areas of ground glass opacification with a “geographic” pattern as the diseased lung is sharply demarcated from the surrounding normal lung tissue [8]. BAL findings are diagnostic in PAP [9]. It is opaque or milky in appearance due to the abundant lipoproteinaceous material, which may settle upon standing. Histology of lung tissue obtained via transbronchial biopsy or open lung biopsy is a useful adjunct in the final diagnosis [10] and our patient’s specimen showed characteristic pathological features. The commonest acquired type of PAP is associated with a high prevalence of anti-granulocyte-macrophage colony-stimulating factor (anti-GM-CSF) antibody. Several lines of evidence suggest that diminished anti-GM-CSF protein or function plays a key role in the pathogenesis of PAP and is responsible for the observed impairment in surfactant processing [11]. An anti-GM-CSF antibody test was not done since it was not available in the local setting.
Secondary PAP can be associated with three main clinical settings. First, infection of the lung, most commonly with Nocardia asteroides, TB (Tuberculosis), Mycobacterium avium-intracellulare, or Pneumocystis carinii. Second, hematologic malignancies and other conditions that alter the patient’s immune status, for example, lymphoma, leukemia, or AIDS (Acquired Immune Deficiency Syndrome). Third, exposure to inhaled chemicals and minerals, for example, fumes, dusts, silica [2], aluminum, insecticides, or titanium [12]. In our patient, infections and malignancies were excluded with investigations. Since she had a history of significant exposure to silica, she is most probably a case of secondary type of PAP caused by inhalation of silica dust. Silicoproteinosis usually manifests within 3 years of the initial exposure as rapidly progressive shortness of breath often associated with constitutional symptoms. The course of the disease is relentlessly progressive. Most of the reported cases have been fatal within months [2, 13]. Although 3 years elapsed following the symptom onset of our case, the disease progression is not as rapid as described in the literature.
WLL was first described by Ramirez and colleagues in 1965 and further modified by Wasserman and coworkers in 1968 [14]. For patients who have moderate to severe symptoms and hypoxemia, WLL under general anesthesia via a double-lumen ET tube is the most widely accepted and effective form of treatment [15]. Specific indications for lung lavage include a definitive histologic diagnosis and one of the following: resting PaO2 <65 mmHg (at sea level), alveolar-arterial O2 gradient ≥40 mmHg, measured shunt fraction >10 to 12 %, or severe dyspnea and hypoxemia at rest or on exercise. Our patient had most of the above indications for undergoing WLL.
The technique of WLL is well described [16]. In general, aliquots of 1 to 1.5 liters of warm saline are required for each lavage, and a total of approximately 10 to 15 lavages are used for clearing of the lavage effluent from each lung [17]. Chest percussion during the lavage procedure significantly increases the recovery of the lipoproteinaceous material [18]. Complications of WLL include malpositioning of the ET tube, saline spillover into the unlavaged ventilated lung, and hydropneumothorax. After WLL, symptoms often improve dramatically; however, long-term follow up is needed since the clinical outcome is variable. While only one lavage may be required for a prolonged remission, up to 55 % cases may need a repeated lavage at 6-month to 12-month intervals [3]. It is often impossible to perform therapeutic total lung lavage in most patients who are newly diagnosed as having PAP due to the above potential complications and because the patients are usually hypoxemic and in poor clinical condition. In such cases, multiple segmental or lobar lavages by fiberoptic bronchoscopy (FOB) have been reported as a possible alternative to WLL [19]. Although our patient underwent therapeutically limited BAL several times under general anesthesia in the operation theatre, she showed minimal improvement in her clinical, radiological, and pulmonary function. So we proceeded to WLL, which is the definitive treatment for PAP. The volume of warm saline needed to be used for the WLL was comparatively low in our patient. This is probably due to the small lung volume in an adolescent patient with a low BMI and chronic interstitial lung disease leading to loss of lung volume. Our patient showed marked improvement in her symptoms, pulmonary function, and X-ray results following sequential WLL of both lungs. However, long-term follow up is essential to assess the need for repeated WLL.
