Over the course of a year, a man's voice grew progressively more hoarse and his speech became shrill and grating, but he didn't know why.

Upon examining the man, doctors discovered the reason: Fungus was growing in his throat. According to the report of the man's case, published Thursday (4 August) in the journal JAMA Otolaryngology-Head & Neck Surgery, the man appeared otherwise healthy when he went to a clinic in Pennsylvania that treats conditions of the head and neck.

The man, in his 60s, reported that he'd developed "progressively worsening hoarseness" and shortness of breath over the past 12 months. His primary care physician had previously treated him with inhaled corticosteroids – a standard treatment for asthma – but his symptoms hadn't improved.

To examine the man's vocal folds and larynx, the hollow "voice box" that holds the vocal folds, doctors used a high-speed imaging technique called videostroboscopy. This exam revealed "severe" swelling in the tissue lining the patient's throat, and this swelling had caused the airway to narrow.

The doctors also performed a biopsy on tissue from the man's larynx and confirmed that the tissue was swollen, irregular, and "friable" to the touch, meaning it tore easily.

A close-up examination of the sampled tissue revealed patches of dead laryngeal cells surrounded by clusters of immune cells, hinting that the cells had died off due to intense inflammation in the throat. The examination also revealed budding yeast cells, which the immune cells had surrounded and begun to engulf.

A diagnostic test identified the yeast as Blastomyces dermatitidis, a fungus that causes an infection called blastomycosis. 

B. dermatitidis grows in outdoor environments, typically in moist soil and decomposing wood and leaves, according to the Centers for Disease Control and Prevention (CDC).

In the US, the species is especially prevalent in areas surrounding the Ohio and Mississippi River valleys, the Great Lakes, and the St. Lawrence River. People can develop blastomycosis after breathing in B. dermatitidis spores suspended in the air, although most people exposed to the fungus don't become ill. 

Having a weakened immune system raises the risk of infection, and those who become sick typically develop symptoms between three weeks and three months after breathing in the fungal spores. Sometimes, the infection can spread to the lungs, skin, bones, or central nervous system, meaning the brain and spinal cord, according to the CDC.

In the man's case, the fungus grew only in his larynx, which is fairly unusual. "Laryngeal blastomycosis, first reported in 1918, is a rare extrapulmonary manifestation," his doctors noted in the case report.

Due to the significant obstruction of the man's airway, he underwent surgery to have a breathing tube placed in his windpipe and a feeding tube placed in his stomach. He received a long-term prescription for the antifungal drug itraconazole, and at a two-month follow-up appointment, his hoarseness had improved considerably and he had his feeding tube removed. 

At a five-month follow-up, video stroboscopy revealed that the swelling in the man's throat had gone down and that his vocal folds had regained some mobility. At this point, his breathing tube was also removed.