Pulmonary alveolar microlithiasis: CT and pathologic findings in 10 patients

Stepwise diagnostic algorithm for high-attenuation pulmonary abnormalities on CT

High-attenuation pulmonary abnormalities are commonly seen on CT. These findings are increasingly encountered with the growing number of CT examinations and the wide availability of thin-slice images. The abnormalities include benign lesions, such as infectious granulomatous diseases and metabolic diseases, and malignant tumors, such as lung cancers and metastatic tumors. Due to the wide spectrum of diseases, the proper diagnosis of high-attenuation abnormalities can be challenging. The assessment of these abnormal findings requires scrutiny, and the treatment is imperative. Our proposed stepwise diagnostic algorithm consists of five steps. Step 1: Establish the presence or absence of metallic artifacts. Step 2: Identify associated nodular or mass-like soft tissue components. Step 3: Establish the presence of solitary or multiple lesions if identified in Step 2. Step 4: Ascertain the predominant distribution in the upper or lower lungs if not identified in Step 2. Step 5: Identify the morphological pattern, such as linear, consolidation, nodular, or micronodular if not identified in Step 4. These five steps to diagnosing high-attenuation abnormalities subdivide the lesions into nine categories. This stepwise radiologic diagnostic approach could help to narrow the differential diagnosis for various pulmonary high-attenuation abnormalities and to achieve a precise diagnosis.Critical relevance statement Our proposed stepwise diagnostic algorithm for high-attenuation pulmonary abnormalities may help to recognize a variety of those high-attenuation findings, to determine whether the associated diseases require further investigation, and to guide appropriate patient management. Key points • To provide a stepwise diagnostic approach to high-attenuation pulmonary abnormalities.• To familiarize radiologists with the varying cause of high-attenuation pulmonary abnormalities.• To recognize which high-attenuation abnormalities require scrutiny and prompt treatment.

The world of rare interstitial lung diseases

The world of rare interstitial lung diseases (ILDs) is diverse and complex. Diagnosis and therapy usually pose challenges. This review describes a selection of rare and ultrarare ILDs including pulmonary alveolar proteinosis, pulmonary alveolar microlithiasis and pleuroparenchymal fibroelastosis. In addition, monogenic ILDs or ILDs in congenital syndromes and various multiple cystic lung diseases will be discussed. All these conditions are part of the scope of the European Reference Network on rare respiratory diseases (ERN-LUNG). Epidemiology, pathogenesis, diagnostics and treatment of each disease are presented.

High-Resolution Computed Tomography of Nonfibrotic Interstitial Lung Disease

Nonfibrotic interstitial lung diseases include a heterogeneous group of conditions that can result in various patterns of lung involvement. When approaching the computed tomographic (CT) scan of a patient with a suspected or known interstitial lung disease, the use of the appropriate radiological terms and a systematic, structured approach to the interpretation of the imaging findings are essential to reach a confident diagnosis or to limit the list of differentials to few possibilities. The large number of conditions that cause nonfibrotic interstitial lung diseases prevents a thorough discussion of all these entities. Therefore, this article will focus on the most common chronic lung diseases that can cause these CT findings. A pattern-based approach is used, with a discussion of nodular pattern, consolidation, crazy paving, ground-glass opacities, septal thickening, and calcifications. The different clinical conditions will be described based on their predominant pattern, with particular attention to findings that can help in the differential diagnosis.

Intractable diffuse pulmonary diseases: Manual for diagnosis and treatment

This manual has been compiled by a joint production committee with the Diffuse Lung Disease Assembly of the Japanese Respiratory Society (JRS) to provide a practical manual for the epidemiology, diagnosis, and treatment of intractable diffuse pulmonary diseases. The contents are based upon the results of research into these diseases by the Diffuse Pulmonary Diseases Study Group (principal researcher: Sakae Homma) supported by the FY2014-FY2016 Health and Labor Sciences Research Grant on Intractable Diseases. This manual focuses on: 1) pulmonary alveolar microlithiasis, 2) bronchiolitis obliterans, and 3) Hermansky-Pudlak Syndrome with interstitial pneumonia. As these are rare/intractable diffuse lung diseases (2 and 3 were first recognized as specified intractable diseases in 2015), there have not been sufficient epidemiological studies made, and there has been little progress in formulating diagnostic criteria and severity scales; however, the results of Japan's first surveys and research into such details are presented herein. In addition, the manual provides treatment guidance and actual cases for each disease, aiming to assist in the establishment of future modalities. The manual was produced with the goal of enabling clinicians specialized in respiratory apparatus to handle these diseases in clinical settings and of further advancing future research and treatment.

Pulmonary Alveolar Microlithiasis

Pulmonary alveolar microlithiasis (PAM) is a genetic lung disorder that is characterized by the accumulation of calcium phosphate deposits in the alveolar spaces of the lung. Mutations in the type II sodium phosphate cotransporter, NPT2b, have been reported in patients with PAM. PAM progresses gradually, often producing incremental dyspnea on exertion, desaturation in young adulthood, and respiratory insufficiency by late middle age. Treatment remains supportive, including supplemental oxygen therapy. For patients with end-stage disease, lung transplantation is available as a last resort. The recent development of a laboratory animal model has revealed several promising treatment approaches for future trials.

Pulmonary alveolar microlithiasis: review of the 1022 cases reported worldwide

Pulmonary alveolar microlithiasis (PAM) is a rare disease characterised by the widespread intra-alveolar accumulation of minute calculi called microliths. It is caused by mutation of the SLC34A2 gene encoding the type IIb sodium phosphate cotransporter in alveolar type II cells. The present study explores the epidemiological, familial, genetic, clinical, diagnostic, radiological and therapeutic aspects with the aim of contributing to a better understanding of this uncommon disease.We searched articles on PAM published up to December 2014 and 544 papers were found, accounting for 1022 cases.PAM is present in all continents and in many nations, in particular in Turkey, China, Japan, India, Italy and the USA. Familiality is frequent. The clinical course is not uniform and the causes of this clinical variability seem to be largely nongenetic. The optimal diagnostic procedure is the association of chest high-resolution computed tomography (HRCT) with bronchoalveolar lavage, but a chest radiograph may suffice in families in which a case has already been diagnosed. Moreover, chest radiography and HRCT allow the classification of the evolutionary phase of the disease and its severity. At present lung transplantation is the only effective therapy. However, better knowledge of the gene responsible offers hope for new therapies.

Pulmonary alveolar microlithiasis: an interesting case report with systematic review of Indian literature

Pulmonary alveolar microlithiasis is a rare disease characterized by intra-alveolar presence of microliths. This study reports an interesting case of pulmonary alveolar microlithiasis and provides a systematic review of cases reported from India. A 23-year-old female presented with a history of cough, wheeze, chest pain, and episodic wheeze for five months. Pulmonary function tests demonstrated an obstructive pattern, and chest Xray showed fine micronodular opacities predominantly involving the middle and lower zones of both lungs. Transbronchial lung biopsy revealed the diagnosis. She responded well to inhaled steroid therapy. A systematic review of literature was performed and identified 73 cases of pulmonary alveolar microlithiasis reported from India. The mean (SD) age of the patients was 28.8 (14.9) years, with an almost equal male:female ratio. Many patients were asymptomatic at presentation. Breathlessness and cough were the most common symptoms, and the disease progressed into respiratory failure associated with cor pulmonale. About one-third of the cases were initially misdiagnosed and treated as pulmonary tuberculosis. Extra-pulmonary manifestations and comorbidities were also evident in our series. This systematic review helps to determine epidemiological and clinical characteristics of pulmonary alveolar microlithiasis. Further research is needed to elucidate the etiopathogenesis, diagnosis, and therapeutic options, which are beneficial in developing and identifying cost-effective treatment for pulmonary alveolar microlithiasis.

Sandstorm appearance of pulmonary alveolar microlithiasis incidentally detected in a young, asymptomatic male

Pulmonary alveolar microlithiasis (PAM) is a rare chronic disease with paucity of symptoms in contrast to the imaging findings. We present a case of a 24-year-old Malay man having an incidental abnormal pre-employment chest radiograph of dense micronodular opacities giving the classical "sandstorm" appearance. High-resolution computed tomography of the lungs showed microcalcifications with subpleural cystic changes. Open lung biopsy showed calcospherites within the alveolar spaces. The radiological and histopathological findings were characteristic of PAM.

Pulmonary alveolar microlithiasis

Pulmonary alveolar microlithiasis (PAM) is a rare, chronic lung disease with bilateral intra-alveolar calcium and phosphate deposition throughout the lung parenchyma with predominance to lower and midzone. Although, etiology and pathogenesis of PAM is not fully understood, the mutation in SLC34A2 gene that encodes a sodium-phosphate co-transporter in alveolar type II cells resulting in the accumulation and forming of microliths rich in calcium phosphate (due to impaired clearance) are considered to be the cause of the disease. Chest radiograph and high-resolution CT of thorax are nearly pathognomonic for diagnosing PAM. HRCT demonstrates diffuse micronodules showing slight perilobular predominance resulting in calcification of interlobular septa. Patients with PAM are asymptomatic till development of hypoxemia and cor-pulmonale. No therapy has been proven to be beneficial except lung transplantation.

Pulmonary alveolar microlithiasis: review and management

PURPOSE OF REVIEW

Our knowledge of pulmonary alveolar microlithiasis (PAM) has significantly increased since its detailed description by Sosman in 1957. Here we provide updated information on the long-term clinical course, the specific findings in imaging studies and the genetics of this disease.

RECENT FINDINGS

The responsible gene, the mutation of which is associated with PAM, has been identified as SLC34A2. Characteristic chest computed tomography (CT) findings in patients with PAM have been shown to correlate well with specific pathological findings. Elevated serum levels of surfactant proteins A and D have also been reported in this disease. Long-term follow up information has been updated.

SUMMARY

The gene responsible for PAM, SLC34A2, has been identified. It encodes a type IIb sodium-dependent phosphate transporter, the function of which provides an insight into the pathogenesis of this disease. The demonstration of a mutation in the SLC34A2 gene helps to confirm the diagnosis of PAM. Characteristic chest CT findings that include irregular thickening of perilobular interstitium and calcification along perilobular structures correlate with specific pathological findings. Serum levels of surfactant proteins A and D correlate with the progression of the disease, and may be a useful monitoring tool. Scrutiny of the long-term follow-up data of PAM patients reveals that the prognosis for PAM is poor. The establishment of an effective treatment, which is not yet available, is mandatory.

Microlitíase alveolar pulmonar: achados na tomografia computadorizada de alta resolução do tórax em 10 pacientes

OBJETIVO: Apresentar os achados na tomografia computadorizada de alta resolução (TCAR) do tórax da microlitíase alveolar pulmonar. MÉTODOS: Foram estudadas, retrospectivamente, as tomografias de dez pacientes adultos, sete mulheres e três homens, com idade média de 38,7 anos. Os exames foram analisados por dois radiologistas, de forma independente, e as decisões finais foram obtidas por consenso. RESULTADOS: Os achados mais freqüentes foram as opacidades em vidro fosco e as calcificações subpleurais, ambas presentes em 90% dos pacientes estudados. Os outros achados de maior relevância foram pequenos nódulos parenquimatosos, calcificação ao longo dos septos interlobulares, cissuras nodulares, nódulos subpleurais, cistos subpleurais, consolidações densas e padrão de pavimentação em mosaico. CONCLUSÕES: A microlitíase alveolar pulmonar apresenta aspectos na TCAR que são altamente sugestivos da doença, na maior parte dos casos dispensando a realização de biópsias pulmonares.

Mutations in SLC34A2 cause pulmonary alveolar microlithiasis and are possibly associated with testicular microlithiasis

Pulmonary alveolar microlithiasis (PAM) is a rare disease characterized by the deposition of calcium phosphate microliths throughout the lungs. We first identified a PAM locus by homozygosity mapping to 4p15, then identified, by a candidate-gene approach, the gene responsible for the disease as SLC34A2 (the type IIb sodium-phosphate cotransporter gene), which is involved in phosphate homeostasis in several organs. We identified six homozygous exonic mutations in the seven unrelated patients with PAM we studied. Three of the mutations were frameshifts, one was a chain termination, one was an amino acid substitution, and one was a deletion spanning the minimal promoter and the first exon. Absence of functional protein product of the gene is compatible with calcium phosphate deposition in alveolar airspaces. We show that impaired activity of the phosphate transporter is presumably responsible for the microliths and that PAM is a recessive monogenic disease with full penetrance. Testicular microlithiasis (TM) is a disease that is more common than PAM. It is often associated with cancer and infertility. Since the gene we identified is also expressed in testis, we searched for mutations in subjects with TM. In 2 of the 15 subjects with TM we studied, we identified two rare variants, one synonymous and the other noncoding, that are possibly associated with the condition.