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.

Pulmonary ossification (PO) is a rare metastatic disease characterized by the formation of diffuse heterotopic bone units in the lung parenchyma. Herein, we describe a 45-year-old Filipino male with dendriform pulmonary ossification in combination with gastroesophageal reflux disease and chronic dust exposure, a notably unique association. Radiographic imaging and pathology findings are examined with discussion of various pulmonary disease entities from current literature. Further recognition of PO will facilitate appropriate treatment and better outcomes for patients diagnosed with this enigmatic condition.

Pulmonary ossification (PO) is a rare finding, characterized by mature bone formation in the lung parenchyma. We report a 20-year-old female patient diagnosed with fibrolamellar hepatocellular carcinoma (FL-HCC) and bilateral diffuse nodular PO. The patient presented with a unifocal left liver mass and multiple bilateral pulmonary lesions, which were treated as metastatic disease. The patient received neoadjuvant chemotherapy, followed by left hepatectomy, and bilateral staged thoracotomies for clearance of the pulmonary disease. The histology of the pulmonary nodules demonstrated nodular type PO. We present the history, the course of treatment, imaging, and histologic findings of this rare disease process that could mimic metastatic pulmonary disease.

We report a case of a 41-year-old male with end-stage renal disease receiving chronic hemodialysis who was referred to this hospital because of dyspnea. He had been on a regular dialysis for 20 years due to chronic glomerulonephritis. His transthoracic echocardiography revealed severe pulmonary hypertension (PH), and cardiac catheterization confirmed this diagnosis. From clinical examination and review of the chest X-ray and computed tomography images, we thought PH was due to multifactorial mechanisms typical of hemodialysis patients. However, microscopic examination of lung tissue from autopsy specimen revealed extensive calcium deposits not only in alveolar septal wall but also in alveolar capillaries and small vessels, which had diffuse intimal thickening causing the narrowing of the lumens. These pathological findings suggest that pulmonary vascular calcification contributed to the PH in this patient. .

We report a case of a persistent right upper lobe opacity following treatment for a Pseudomonas infection in an immunosuppressed patient with a recent renal transplantation. The patient underwent a surgical lung biopsy for definitive diagnosis of the mass. The lesion was composed of extensive calcifications deposited throughout the lung with associated fibrosis. The patient had a history of a remote parathyroidectomy for hyperparathyroidism; however, the parathyroid hormone (PTH) and the calcium levels were still mildly elevated. No other calcified lung lesions had developed in a follow-up after the initial resection. Pulmonary calcification has been classically associated with varicella pneumonia; no viral cytopathic changes were identified for varicella or other viruses in this case. The calcification appears to be secondary to the recent Pseudomonas pneumonia. To our knowledge, this is the first report of a Pseudomonas pneumonia resulting in extensive localized pulmonary calcification. This is an important diagnostic consideration as this benign entity should be considered in patients with persistent opacities following treatment for pneumonia.

Pulmonary alveolar microlithiasis is a rare pulmonary disorder that is caused by abnormal sodium-dependent phosphate co-transporter from the mutation of SLC34A2 gene, leading to accumulation of microliths in the alveoli. We report the extensive pulmonary alveolar microlithiasis in an elderly woman who presented with progressive dyspnea for 2 months. Chest radiograph revealed diffuse pulmonary calcification. Tissue histopathology from open lung biopsy demonstrated widespread intra-alveolar laminated calcium deposits compatible with pulmonary alveolar microlithiasis.