INTRODUCTION:Pulmonary alveolar microlithiasis is a rare disorder of unclear etiology consists of widespread laminated calcispherites. We present this case of diffuse micronodular pulmonary calcifications in a young female.
CASE PRESENTATION:An 18-year-old female, a recent immigrant from Yemen, presented with a one-year history of chest pain, severe, substernal, radiating to the back; it lasted for an hour and occurred at rest or on exertion. In addition, she complained of dyspnea at rest. There were no other associated symptoms such as cough, hemoptysis, skin rash, night sweats, fever, or chills. She denied exposure to tuberculosis or any tropical illnesses. Physical examination was unremarkable. She had a nonreactive PPD skin test within the last year. Follow-up diagnostic tests revealed abnormal findings on the x-ray and normal ECG and there was no evidence of hypoxemia. A high-resolution CT scan of the thorax showed diffuse scattered small micronodular opacities predominantly in the lung bases, sparing the periphery of the parenchyma and upper lobes. There was no lymphadenopathy noted. Bronchoscopy showed no endo-braonchial lesions; a transbronchial biopsy revealed benign parenchyma with numerous foci of calcifications in a laminated architecture consistent with pulmonary alveolar microlithiasis (PAM). Analysis of bronchoalveolar lavage fluid was negative for malignancy and infection, including negative bacterial, fungal or AFB cultures. Pulmonary function tests and gas exchange were normal. Baseline laboratory values were within normal limits including electrolytes; vitamin D and thyroid function were within normal limits.
DISCUSSIONS:Pulmonary alveolar microlithiasis (PAM) is a rare disorder; first reported in 1918. Five hundred cases with this condition have been reported. Pathogenesis remains unknown. It is often a familial disease with autosomal recessive form, especially in patients from the Mediterranean countries. Other mechanisms include an autoimmune reaction, inborn error of metabolism and acquired abnormality of calcium and phosphorus metabolism. There is a suggestion that apoptosis and the resulting formation of calcified lamellar bodies play an important role in the pathogenesis of this disorder.The differential diagnoses include any condition associated with pulmonary calcification, which consist of three major categories: metastatic pulmonary calcification (benign or malignant), dystrophic disorders (such as amyloidosis or post-varicella pneumonia) or idiopathic. PAM is characterized by intra-alveolar deposition of calcium phosphate microliths, which measure 0.1-3 mm in diameter. The majorities of cases are asymptomatic and have normal or mild restrictive pulmonary physiology. On the other hand, in symptomatic cases, cough and dyspnea are the most common presenting symptoms and usually occur late in the course of the disease. The sand-like micronodularity on chest radiographs can mimic sarcoidosis or miliary TB. The sparing of the lung periphery on high resolution CT-scan (known as a black pleural line) is unique feature. Although the laminated calcium phosphate depositions in the alveolar space are diagnostic, calcispherites in the sputum and bronchoalveolar lavage are not diagnostic. The course of the disease is indolent and most patients die as a result of pulmonary hypertension. There is no known therapy for PAM. Bilateral lung transplantation is an option for advanced cases.
CONCLUSION:Our patient represents another case of pulmonary alveolar microlithiasis, a benign disorder, which should be considered in the differential diagnosis of bilateral, diffuse micronodular calcifications. The association with familial inheritance and other poorly understood pathogenesis makes us believe that further immunologic investigations may lead to better treatment options.
DISCLOSURE:Abdul Ghani Sankri-Tarbichi, No Financial Disclosure Information; No Product/Research Disclosure Information