Anxiety is growing in Italy over the rapidly deteriorating health of Silvio Berlusconi on Thursday following the legendary kingmaker’s admission to intensive care at Milan hospital a day earlier. Italian newspapers were reporting that the 86-year-old media tycoon and four-time former premier may have been diagnosed with pneumonia due to a suspected form of leukemia. 

Mr. Berlusconi was admitted to the intensive care section of Milan’s San Rafael Hospital Milan on Wednesday after experiencing difficulties breathing. He had previously been suffering from both lung and cardiovascular problems. He was reportedly in a critical but stable condition and on a ventilator while being treated with antibiotics.

As of Thursday morning his exact diagnosis, as well as his prognosis, were the subject of conflicting reports. But a leading newspaper, Corriere della Sera, was less ambiguous, reporting that there are now “serious fears” for Mr. Berlusconi’s life due to “pneumonia that is the result of leukemia.”

The newspaper also reported that the ex-premier underwent bone marrow testing and PET bone imaging tests, though it was not immediately clear when, and that his current condition may be presenting as “possible complications in an already debilitated individual.”

In another indication of the gravity of the situation, La Stampa reported that Mr. Berlusconi’s partner, the 33-year-old Marta Fascina, visited him in the hospital, as did Mr. Berlusconi’s eldest daughter, Marina and his brother, Paolo. Also present was Licia Ronzulli, an ally in the former premier’s center-right Forza Italia party and known in Italy as the organizer of Mr. Berlusconi’s notorious “bunga bunga” parties. 

Upon leaving the hospital, Paolo Berlusconi told reporters, “Silvio is a rock, he will make it this time too.”

Silvio Berlusconi’s health crisis is causing concern in Italy’s political class. Both allies and opponents sent messages of support to wish him a speedy recovery. Prime Minister Meloni tweeted “Forza Silvio” (“Silvio, be strong”). That is a reference to a soccer chant that inspired Mr. Berlusconi to name his Forza Italia party.

The deputy prime minister, Matteo Salvini of the Northern League party, tweeted a photo of himself alongside Mr. Berlusconi with the message, “Come Silvio, Italy is waiting for you.”

Italy’s deputy prime minister and minister of foreign affairs, Antonio Tajani, told reporters that Mr. Berlusconi is conscious and talking. He confirmed that the reason for his admission is “a poorly treated infection,” but also said that “Silvo is a lion who never gives up.”

A representative of the Forza Italia parliamentary group, Paolo Barelli, confirmed that information, Corriere della Sera reported. 

Mr. Tajani is also leader of Mr. Berlusconi’s Forza Italia, which is the junior member of Italy’s governing coalition of which the Northern League is also a part and is led by Ms. Meloni’s Brothers of Italy party.

Among Mr. Berlusconi’s multiple health problems, the most challenging in recent times, at least up until now, has been Covid-19. After he was discharged from a 10-day hospital stay in 2020 he told reporters that the “insidious” illness was the most dangerous challenge he had ever faced.

The AP reported that Mr. Berlusconi has had a pacemaker for years, underwent heart surgery to replace an aortic valve in 2016, and has overcome prostate cancer. Last January, he was admitted to the hospital for a reported urinary tract infection.

Nicknamed Il Cavaliere (the Knight), Mr. Berlusconi is no stranger to controversies — a friendship with Vladimir Putin among them — but is also known for his capacity for comebacks. The latest was winning a seat in Italy’s senate last September after a conviction for tax fraud had led to a ban from holding public office. 

That election win is what enabled Ms. Meloni to form a new government. 

As of Thursday it was unclear for how long Mr. Berlusconi was expected to be in the hospital.