Secondary Pulmonary Alveolar Proteinosis Associated with Aluminum Exposure：a Case Report and Literature Review

The lungs are designed to be a vast, delicate network where oxygen slips from the air into the blood. To keep this exchange smooth, the tiny air sacs called alveoli are lined with a thin, slippery coating known as surfactant. This substance prevents the sacs from sticking together and collapsing, much like oil keeps a pan from sticking. Normally, the body's cleanup crew—specialized immune cells called macrophages—constantly sweeps away old surfactant and debris to make room for fresh material. When this cleaning process fails, the air sacs fill up with a thick, waxy buildup of proteins and fats. This rare condition is called pulmonary alveolar proteinosis. While most cases arise from a glitch in the immune system itself, a smaller group of cases happens because something external, like breathing in toxic dust or fumes, has overwhelmed the lungs' ability to stay clean. Understanding how specific industrial materials trigger this blockage helps doctors protect workers and treat those who fall ill.

In a recent report from Peking Union Medical College Hospital, a team of researchers documented a striking case of this condition linked directly to a specific metal: aluminum. The patient was a forty-five-year-old man who had worked as a steel structure worker for over two decades. His trouble began in early 2026, shortly after he started a new job at a factory making bridge components. His duties involved spraying aluminum and performing electric welding, tasks that fill the air with fine metal particles and fumes. Although he wore a standard disposable dust mask and a face shield, he did not have access to the heavy-duty, powered respirators needed to filter out such fine metallic aerosols. Within months, he developed a worsening shortness of breath, chest tightness, and a dangerous drop in blood oxygen levels that required high-flow oxygen support to survive.

When doctors examined his lungs, they found a pattern that pointed away from common infections or autoimmune diseases. A high-resolution CT scan showed a diffuse, cloudy haze covering both lungs, a sign that the air sacs were filled with something other than air. The most telling clue came from a procedure called bronchoalveolar lavage, where doctors wash the lungs with sterile fluid and pull it back out. The fluid returned from this man's lungs was not clear; it was a thick, milky white liquid, heavy with sediment. Under a microscope, this sediment was confirmed to be the characteristic protein-rich material of pulmonary alveolar proteinosis. Crucially, tests ruled out the most common cause of the disease, which is an autoimmune attack on the cleaning cells. The patient's blood showed no antibodies that would trigger such an attack, and extensive testing found no evidence of cancer, HIV, or fungal infections.

The investigation then turned to the man's work history and the specific materials he had been breathing. The researchers suspected that the aluminum fumes from his welding and spraying were the culprit. To prove this, they needed to find the metal itself inside his body and compare it to the environment where he worked. They analyzed the milky fluid from his lungs and the dust collected from his workplace using highly sensitive chemical scanners. The results were definitive. The fluid from his lungs contained an aluminum concentration of 1473.6 micrograms per liter, a level vastly higher than the 103 micrograms per liter found in healthy controls. Even more compelling, the dust residue from his workplace welding area contained 6011.8 micrograms of aluminum per gram. While other metals like indium and tin were found in tiny traces in his lung tissue, they were absent from the fluid wash and the workplace dust, leaving aluminum as the clear and dominant suspect.

With the diagnosis confirmed as secondary pulmonary alveolar proteinosis caused by aluminum exposure, the medical team moved to treatment. The standard approach for severe cases is whole-lung lavage, a procedure where one lung is washed out at a time with large volumes of saline to physically flush out the clogging material. The patient underwent this procedure on both lungs in sequence. The result was immediate and dramatic. His breathing improved, his oxygen levels stabilized, and follow-up scans showed the cloudy haze in his lungs clearing up significantly. Three months later, he could walk half a kilometer while using portable oxygen, a massive improvement from his initial state of severe respiratory failure.

This case report does more than just describe a successful treatment; it builds a complete chain of evidence linking a specific industrial hazard to a rare disease. Previous reports of aluminum-related lung disease often relied on the patient's job history or a single look at tissue samples. This study went further by measuring the exact amount of aluminum in both the patient's lungs and his work environment, showing a direct match between the two. It suggests that aluminum dust, often overlooked in favor of more famous lung hazards like silica, can be a potent cause of this condition. The findings serve as a reminder that when a patient presents with unexplained lung blockages and a history of metal work, doctors must look closely at the specific materials they handle. In this instance, the combination of a clear occupational history, precise chemical measurements, and a successful physical washout provided a rare and complete picture of how a common industrial metal can stop the lungs from breathing.