Comment on: Severe pulmonary hypertension in pulmonary alveolar microlithiasis: A comprehensive literature review

This letter commends the study "Severe pulmonary hypertension in pulmonary alveolar microlithiasis: A comprehensive literature review" for its thorough exploration of Pulmonary Alveolar Microlithiasis (PAM) and its association with pulmonary hypertension (PH). The study offers insights into PAM's genetics, clinical manifestations, diagnostic approaches, and treatment modalities. It highlights the importance of early diagnosis and management while discussing limitations such as its retrospective nature and small sample size. Despite these limitations, the study contributes significantly to understanding PAM and PH, emphasizing the need for larger prospective studies to validate findings and explore novel therapeutic avenues.

Severe pulmonary hypertension in pulmonary alveolar microlithiasis: A comprehensive literature review

This review focuses on Pulmonary Alveolar Microlithiasis (PAM), an autosomal recessive genetic disorder characterized by calcium crystal deposits (microliths) resulting from loss of function of the SLC34A2 gene. PAM is a rare disease with approximately 1100 reported cases globally. The historical context of its discovery and the genetic, epidemiological, and pathophysiological aspects are discussed. PAM falls under interstitial lung diseases and is associated with pulmonary hypertension (PH), primarily categorized as Group 3 PH. The clinical manifestations, diagnostic approaches, and challenging aspects of treatment are explored. A clinical case of PAM with severe pulmonary hypertension is presented, emphasizing the importance of comprehensive evaluation and the potential benefits of phosphodiesterase-5 inhibitors (PDE5i) therapy. Despite limited therapeutic options and challenging diagnosis, this review sheds light on recent developments and emerging treatments for PAM and associated pulmonary hypertension.

Losing vigilance in diagnosing pulmonary alveolar microlithiasis: A report on four cases

Pulmonary alveolar microlithiasis (PAM) is a rare chronic lung disease characterized by calcium and phosphate deposition in the alveolar lumen throughout the parenchyma of both lungs, with predominance in the middle and lower lung fields. It is caused by mutations in the recessive gene, SLC34A2, on the autosomal chromosome. In this article, we characterize four cases of PAM and analyze the loss of diagnostic vigilance in two of them. Patients came to medical facilities with clinical manifestations such as cough, shortness of breath, chest pain, and fatigue. The initial diagnosis was unclear in two cases because the X-ray film's quality was not good enough and the medical staff had little experience in clinical and chest X-ray interpretations for PAM. The definitive diagnosis was based on a combination of high-resolution computed tomography (CT) and bronchoalveolar lavage fluid testing. In addition, chest X-ray and high-resolution CT enable the assessment of the stage, progression, and severity of the disease. There is currently no specific treatment for PAM other than lung transplantation.

[Pulmonary alveolar microlithiasis: A report on two familial cases in Morocco]

INTRODUCTION

Pulmonary alveolar microlithiasis (PAM) is a rare autosomal recessive disease. The majority of patients are asymptomatic. The disease is often diagnosed on routine radiological examination.

CASE REPORTS

We report two familial cases of PAM. A 17-year-old girl with a chest X-ray showing an alveolar syndrome, especially on the right side, a bronchointerstitial syndrome, and diffuse calcifications. The thoracic CT scan showed calcified micro- and macronodules with pleural and pericardial calcifications. Respiratory function tests showed restrictive syndrome and normal blood gas values suggestive if PAM, which was confirmed by the presence of microliths in bronchoalveolar lavage (BAL). Family investigation led to chest radiograph of a 14-year-old sister who was asymptomatic but presented with an aspect of "sandstorm" calcifications.

CONCLUSION

PAM is known to be radio-clinically dissociative. In typical cases, radiology can suggest the diagnosis, which is often confirmed by SLC34A2 mutation or microliths in BAL or sputum. The prognosis is compromised in the long-term. The only effective treatment nowadays is lung transplantation.

New insights in the genetic variant spectrum of SLC34A2 in pulmonary alveolar microlithiasis; a systematic review

Pulmonary alveolar microlithiasis (PAM) is a rare autosomal recessive lung disease caused by variants in the SLC34A2 gene encoding the sodium-dependent phosphate transport protein 2B, NaPi-2b. PAM is characterized by deposition of calcium phosphate crystals in the alveoli. Onset and clinical course vary considerably; some patients remain asymptomatic while others develop severe respiratory failure with a significant symptom burden and compromised survival. It is likely that PAM is under-reported due to lack of recognition, misdiagnosis, and mild clinical presentation. Most patients are genetically uncharacterized as the diagnostic confirmation of PAM has traditionally not included a genetic analysis. Genetic testing may in the future be the preferred tool for diagnostics instead of invasive methods. This systematic review aims to provide an overview of the growing knowledge of PAM genetics. Rare variants in SLC34A2 are found in almost all genetically tested patients. So far, 34 allelic variants have been identified in at least 68 patients. A majority of these are present in the homozygous state; however, a few are found in the compound heterozygous form. Most of the allelic variants involve only a single nucleotide. Half of the variants are either nonsense or frameshifts, resulting in premature termination of the protein or decay of the mRNA. There is currently no cure for PAM, and the only effective treatment is lung transplantation. Management is mainly symptomatic, but an improved understanding of the underlying pathophysiology will hopefully result in development of targeted treatment options. More standardized data on PAM patients, including a genetic diagnosis covering larger international populations, would support the design and implementation of clinical studies to the benefit of patients. Further genetic characterization and understanding of how the molecular changes influence disease phenotype will hopefully allow earlier diagnosis and treatment of the disease in the future.

Diffuse pulmonary ossification: A case report unveiling clinical and histopathological challenges

Diffuse pulmonary ossification (DPO) is a rare pulmonary condition characterized by the diffuse formation of mature bone in the lungs. Pulmonary ossification, in general, can be subdivided into diffuse pulmonary ossification (DPO) and nodular pulmonary ossification (NPO). DPO occurs most commonly in the settings of chronic pulmonary conditions; however, idiopathic cases have been reported. We present a case of DPO in a 36-year-old man with progressive exertional dyspnea, productive cough, and occasional hemoptysis. Imaging studies showed innumerable pulmonary nodules scattered throughout both lungs. Initially, the diagnoses of pulmonary alveolar microlithiasis (PAM) or, less likely miliary tuberculosis (TB) were considered. However, Quantiferon TB test was negative and genetic testing was negative for SLC34A2, lowering the probability of PAM. The patient underwent a segmentectomy. Microscopic examination showed ramifying spicules of mature woven bone and fatty marrow consistent with DPO. There were no significant underlying pathologic findings, such as interstitial fibrosis, granulomas, organizing pneumonia, or significant inflammation in the background lung parenchyma. In conclusion, clinicians and radiologists need to be aware of DPO in the differential diagnosis of miliary tuberculosis and pulmonary alveolar microlithiasis. The absence of an underlying chronic pulmonary condition does not exclude the possibility of DPO.

A Rare Case of Pulmonary Alveolar Microlithiasis with Diffuse Lung Uptake on Bone Scintigraphy

Pulmonary alveolar microlithiasis is a rare disease characterized by accumulating intraalveolar small calcium phosphate stones. The disease is slow and does not show any signs in the early stages, but the shortness of breath, cough, and right heart failure may develop as it progresses. Methylene diphosphonate used in bone scintigraphy shows high uptake of calcium deposits in the alveoli and causes diffuse increased radiopharmaceutical uptake in the lungs.

Pulmonary Alveolar Microlithiasis - A Review

Pulmonary Alveolar Microlithiasis (PAM) is a rare genetic disorder causing widespread deposition of calcium-phosphate crystals in the alveolar space. A hallmark of the disease is the discrepancy between perceived symptoms upon diagnosis compared with the extensive, sandstorm-like appearance of the microliths on chest X-ray or HRCT. Caused by a defective sodium-dependent phosphate transport protein due to loss-of-function variants of the SLC34A2 gene, PAM is an autosomal recessive transmitted disorder, and as such has a high correlation to consanguinity. The most common variants of the SLC34A2 gene are single nucleotide biallelic changes, but larger deletions are described. Initial suspicion of PAM on radiological examination should be followed by genetic testing to verify the diagnosis and identify the disease-causing variant. When not available, the diagnosis can be made by means of invasive techniques, such as transbronchial forceps or cryobiopsy, or a surgical lung biopsy. In families with a history of PAM, genetic counseling should be offered, as well as preimplantation/prenatal testing if necessary. As of writing this review, no definitive treatment exists, and PAM may in some cases progress to severe pulmonary disease with respiratory failure and potential death. Patients with PAM should be offered preventative and symptomatic treatments such as vaccinations and oxygen therapy when needed. In some cases, lung transplantation may be required.

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.

Clinicopathological and imaging features of pulmonary alveolar microlithiasis in a dog - a case report

Background

The aetiology of pulmonary alveolar microlithiasis (PAM) in animals is still unknown. In humans, this pulmonary disorder is a rare autosomal recessive disorder triggered by a mutation in the gene SLC34A2, which causes deposition and aggregation of calcium and phosphate in the pulmonary parenchyma with formation of microliths. Although histopathological examination is required for a definite diagnosis, in humans, imaging modalities such as computed tomography can demonstrate typical patterns of the disease. This is the first description of the computed tomographic (CT) features of a histologically confirmed PAM in dogs.

Case presentation

The following report describes a case of a 7-year-old female Boxer dog evaluated for paroxysmal loss of muscle tone and consciousness with excitement. The main differential diagnoses considered were syncope, seizures, and narcolepsy-cataplexy. The results of the complete blood count, serum biochemistry panel, urinalysis, arterial blood pressure, echocardiography, abdominal ultrasound, Holter monitoring, and ECG were all within normal limits. Additional exams included thoracic radiographs, head and thorax CT, bronchoalveolar lavage (BAL), and CT-guided cytology. Thoracic radiographs revealed micronodular calcifications in the lungs, with sandstorm appearance. Computed tomography of the thorax showed the presence of numerous mineralized high-density agglomerates of multiple sizes throughout the pulmonary parenchyma, a reticular pattern with ground glass opacity and intense mineralized fibrosis of the pleural lining. Head CT was unremarkable. BAL and CT-guided cytology were inconclusive, but imaging features strongly suggest the diagnosis of PAM, which was histologically confirmed after necropsy.

Conclusions

This case report contributes to the clinicopathological and imaging characterization of pulmonary alveolar microlithiasis in dogs. In this species, the diagnosis of PAM should be considered when CT features evidence a reticular pattern with ground glass opacity and the presence of an elevated number and size of calcifications.

Tricuspid valve calcification in familial pulmonary alveolar microlithiasis: A case report

Background

Pulmonary Alveolar Microlithiasis (PAM) is an uncommon, gradually progressive and eventually fatal hereditary disease that affects young population. Familial cases account for up to 50% of reported cases. There are few described cases of extrapulmonary manifestations of PAM and rare reports of cardiac involvement.

Case report

A 45-year-old male patient presented to our center with progressive shortness of breath and dry cough. On physical examination, he was tachypneic and chest examination revealed diminished breath sounds with bilateral early inspiratory crackles. Further workup revealed the diagnosis of PAM. Echocardiography revealed calcifications covering the tricuspid valve with elevated right ventricular systolic pressure. He reported having two sisters with similar illnesses and chest radiographic abnormalities, one died at the age of 38 years from respiratory failure and the other is 42-year-old and still alive and was diagnosed with PAM. Another 35 member of his family were diagnosed with PAM. Unfortunately, few days after discharge, he arrested at home.

Conclusions

Recently, type-II sodium/phosphate co-transporter has been identified in a human aortic valve. Studies have suggested penetrance of mutations of SLC34A2 gene might explain such variability of pulmonary and extrapulmonary involvement. Our case reports a familial cluster of PAM, and the first case of concomitant tricuspid calcification. This finding might be a useful in the investigation for a future genetic targeted therapy.

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PAM is a fatal hereditary disease that affects young population.

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There are few described cases of extrapulmonary manifestations of PAM.

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Mutations of SLC34A2 gene might explain variability of extrapulmonary involvement.

Pulmonary alveolar microlithiasis: A report of two unique cases

Pulmonary alveolar microlithiasis (PAM) is an inherited autosomal recessive disease. PAM is classically characterized by calcium phosphate deposition within alveolar airspaces due to SLC34A2 (solute carrier family 34 member 2) gene mutation located on chromosome 4p15.2. Such cellular genetic mutation would lead to a defect in the sodium-phosphate transporter channel located in alveolar epithelial cells type-II. Ultimately, it would result in a malfunction of alveolar epithelial cells and the failure of these cells to clear-up the released phosphorous particles in the cellular surfactant recycling. PAM is usually diagnosed in adulthood, frequently notable in the third and fourth decades of life, occasionally can be associated with more severe clinical presentation and radiological findings.

Nevertheless, the disease could manifest itself in the pediatric age group, which either shows non-specific signs and symptoms or be exclusively asymptomatic. Histopathological examination is the gold standard for the PAM diagnosis. Genetic counseling and testing might benefit the patient's family members. Herein, we present 2 cases of PAM in the pediatric age group, along with their clinical history, presentation, radiological studies, and histopathology findings, as well as a brief literature review.

Single-lung transplantation for pulmonary alveolar microlithiasis: A case report

BACKGROUND

Pulmonary alveolar microlithiasis (PAM) is a rare idiopathic lung disease characterized by the accumulation of innumerable microliths. Currently, effective therapeutics for PAM are not available, and the only treatment for end-stage lung disease is lung transplantation (LuTx). Further, there are few reports that focus on LuTx for the treatment of PAM, and the follow-up reports of postoperative imaging are even rarer.

CASE SUMMARY

A 52-year-old man presented to Shanghai Pulmonary Hospital in 2017 after experiencing shortness of breath and exacerbation. The patient was diagnosed with PAM and referred for single-LuTx (SLuTx) on March 14, 2018. Preoperative imaging results from a chest X-ray demonstrated bilateral, diffuse, symmetrical, sandstorm-like radiopaque micronodules, and pneumothorax and a computed tomography scan revealed minute, calcified military nodules in both lungs. We performed a left SLuTx, and intraoperative pathology was consistent with PAM. One week after surgery, a chest X-ray revealed slight exudation of the left lung, and one month later, the left transplanted lung exhibited good dilation, mild pulmonary perfusion injury with local infection, and left pleural effusion. Fiberoptic bronchoscopy revealed left hyperplastic granulation at the left bronchial anastomosis. Multiple sputum cultures suggested the presence of Klebsiella pneumoniae and Acinetobacter baumannii. The last follow-up was conducted in April 2019; the patient recovered well.

CONCLUSION

This case presents the imaging findings of a patient with PAM before and after LuTx and confirms the effectiveness of LuTx for the treatment of this disease.

Pulmonary alveolar microlithiasis and interstitial pneumonitis: a case report of the west of Iran

Pulmonary alveolar microlithiasis (PAM) is a rare disease with autosomal recessive inheritance. Herein, a 20-year-old lady referred to the hospital with a dry cough for two years. The chest X-ray findings were bilateral reticulonodular opacities in both lungs and honeycomb appearance suspicious for miliary tuberculosis and idiopathic pulmonary fibrosis. A wedge biopsy of lung showed that there were several intraalveolar laminated concretions in the pathology report compatible with pulmonary alveolar microlithiasis and interstitial infiltration of lymphocytes and neutrophils compatible with interstitial pneumonitis. PAM is a rare progressive disease with the production of microliths in pulmonary alveoli. The pathologist, radiologist, and clinician should be familiar with this entity for diagnosis and appropriate management. The family of the patient especially siblings must be evaluated for earlier diagnosis.

An unusual late onset of pulmonary alveolar microlithiasis: A case report and literature review

Pulmonary alveolar microlithiasis (PAM) is an uncommon genetic disorder associated with alveolar cell injury. This injury is caused in most cases by inactivating mutations in SLC34A2 gene, which is responsible for the production of a sodium-dependent phosphate co-transporter. The dysfunction or deficiency of this transporter leads to the aggregation of local phosphate intra-alveolarly and formation of microliths. Most of the patients are asymptomatic at the time of the diagnosis but as the disease progress it leads to fatal respiratory or cardiac failure. We describe a case of a 63-year-old man referred to our department for a surgical lung biopsy. He has been symptomatic for one year with progressive shortness of breath and deteriorating exercise tolerance. The imaging was suggestive of extensive interstitial bilateral lung disease. Histological findings after the lung biopsy by video-assisted thoracic surgery (VATS) established the diagnosis of pulmonary alveolar microlithiasis. His sister suffered from the same disease and passed away at the age of 54. It is remarkably rare for PAM to have such a late onset with a previous normal X-ray and only a few cases have been reported worldwide.

Pulmonary microlithiasis - A case report

Pulmonary alveolar microlithiasis is a rare diffuse lung disease characterized by widespread sand-like intra-alveolar calcifications (calcospherites composed of calcium and phosphorus). Around 800 cases have been reported in the literature to date. We report here a case of a 35 years old female with prolonged h/o of exertional dyspnoea and mild cough. Clinical examination was mostly normal. Her Chest X-Ray revealed bilateral multiple nodular opacities (sand storm appearance). CT Scan chest showed diffuse micronodular calcifications with septal thickening, compatible with alveolar microlithiasis. Pulmonary function tests showed moderately restrictive lung disease. Bronchoscopic alveolar lavage revealed calcospherites in the alveloli and bronchi confirming the diagnosis of pulmonary alveolar microlithiasis.

Pulmonary Alveolar Microlithiasis. Clin Chest Med. 2016;37:441-448. [PMID: 27514591 DOI: 10.1016/j.ccm.2016.04.007]

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.

Can chest high-resolution computed tomography findings diagnose pulmonary alveolar microlithiasis?

Objective

The present study was aimed at retrospectively reviewing high-resolution computed tomography (HRCT) findings in patients with pulmonary alveolar microlithiasis in order to evaluate the frequency of tomographic findings and their distribution in the lung parenchyma.

Materials and Methods

Thirteen patients (9 females and 4 males; age, 9 to 59 years; mean age, 34.5 years) were included in the present study. The HRCT images were independently evaluated by two observers whose decisions were made by consensus. The inclusion criterion was the presence of abnormalities typical of pulmonary alveolar microlithiasis at HRCT, which precludes lung biopsy. However, in 6 cases lung biopsy was performed.

Results

Ground-glass opacities and small parenchymal nodules were the predominant tomographic findings, present in 100% of cases, followed by small subpleural nodules (92.3%), subpleural cysts (84.6%), subpleural linear calcifications (69.2%), crazy-paving pattern (69.2%), fissure nodularity (53.8%), calcification along interlobular septa (46.2%) and dense consolidation (46.2%).

Conclusion

As regards distribution of the lesions, there was preferential involvement of the lower third of the lungs. No predominance of distribution in axial and anteroposterior directions was observed.

The sodium-phosphate co-transporter SLC34A2, and pulmonary alveolar microlithiasis: Presentation of an inbred family and a novel truncating mutation in exon 3

Pulmonary alveolar microlithiasis is a disorder in which many tiny fragments (microliths) of calcium phosphate gradually accumulate in alveoli. Loss of function mutations in the gene SLC34A2 coding for the sodium phosphate co-transporter (NaPi-IIb) are responsible for genetic forms of alveolar microlithiasis. We now report a consanguineous Italian family from Calabria with two affected members segregating alveolar microlithiasis in a recessive fashion. We describe, for the first time, a novel loss of function mutation in the gene coding for NaPi-IIb. A careful description of the clinical phenotype is provided together with technical details for direct sequencing of the gene.

Update on diagnosis and treatment of pulmonary alveolar microlithiasis

Pulmonary alveolar microlithiasis (PAM) (MIM265100) is a rare disease characterized by the diffuse deposit of microlithiasis in alveolar spaces. PAM could occur worldwide with high prevalence in Asia and Europe. Familial occurrence indicates its autosomal recessive trait and the SLC34A2 gene was identified as the responsible gene for the disease. In spite of the versatile mutation sites in patients from other countries, exon 7 and exon 8 might be the most liable gene in Chinese and Japanese patients. Most mutations caused the premature termination of proteins and produced truncated proteins, leading to the blocking of the recycling and degrading of outdated surfactant which is full of phospholipids. The most outstanding clinical feature of PAM is the discrepancy between the paucity of symptoms and the degree of pulmonary involvement. Diagnosis is easy to establish based on typical chest radiograph image and nuclear medicine improves its early diagnosis and active evaluation. Pathology of the unique intra-alveolar lamellar microliths gives strong support for diagnosis. No effective treatment is considered valid currently. However, lung transplantation is effective for advanced-stage patients, and long term treatment of disodium etidronate seems promising.

A silent storm

Pulmonary alveolar microlithiasis is a rare, inherited pulmonary disorder affecting young adults. Diagnosis and monitoring is important as it may progress to pulmonary fibrosis and respiratory failure. No effective treatment has been found to date.

Pulmonary alveolar microlithiasis: a rare case report

Pulmonary alveolar microlithiasis is an uncommon infiltrative pulmonary disease characterized by deposition of microliths in the alveoli. We present the case of a young adult with complaints of shortness of breath on exertion. Chest radiograph showed innumerable small, dense nodules, diffusely involving both the lungs - predominantly in the lower zones. High-resolution CT scan illustrated widespread intra-alveolar microliths, diffuse ground-glass attenuation areas, septal thickening, and black pleural lines - predominantly in the basal regions. Transbronchial biopsy confirmed the diagnosis.

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.

A case of pulmonary alveolar microlithiasis with Cor Pulmonale

Pulmonary alveolar microlithiasis (PAM) is a rare disease characterized by the formation and deposition of microliths within the alveoli and a paucity of symptoms in contrast to the imaging findings. It has familial tendency and is thought to be an autosomal recessive disorder with the mutation in the SLC34A2 gene. We describe a case of PAM with Cor Pulmonale. Ultrasonic cardiogram showed pulmonary hypertension (82 mmHg). Chest radiography revealed diffuse, bilateral sandstorm-like micronodules with greater density in the lower lung fields. HRCT scans demonstrated diffuse ground-grass opacities, thickening and calcification of interlobular septa and confluent calcified nodules. A diagnosis of PAM was suggested and confirmed by transbronchial lung biopsy (TBLB).

Pulmonary alveolar microlithiasis

Pulmonary alveolar microlithiasis is a rare disease of unknown cause. We report a case in a young boy who presented with history of failure to thrive and chest X-ray finding suggestive of miliary mottling. Open lung biopsy revealed pulmonary alveolar microlithiasis.