The glamorous career of the American pianist Byron Janis, the first of Vladimir Horowitz’s few pupils, was blighted by crippling arthritis in both wrists and all 10 fingers. Insisting on playing through the pain, he continued to perform for more than a decade, with everyone bar a handful of people unaware of his condition.

From the time of his Carnegie Hall debut in 1948, Janis, who has died aged 95, had been hailed as a second Horowitz, and his high-octane virtuosity, coupled with a rare potential for poetic expressivity, established him as one of the most formidably accomplished pianists of his age.

His physical challenges began at the age of 11 when the tendon and nerve attached to the little finger of his left hand were severed in an accident. Even after surgical repair the finger was to remain numb, leaving him in full control of only nine fingers.

From 1973 he began to suffer from psoriatic arthritis in his hands and wrists, causing excruciating pain as he persisted with performance. Undergoing endless surgery, Janis was constantly having to change fingering to avoid non-functioning digits. His condition deteriorated so badly that by 1983 he was forced to take a break, going public in 1985 by becoming an ambassador for the arts on behalf of the Arthritis Foundation.

A documentary made by PBS in 2009 shows him pounding away, as though in denial of his condition, in barnstorming performances of heavyweight Russian repertory such as Prokofiev’s Toccata and concertos by Rachmaninov and Tchaikovsky, in which he had always excelled.

Even before arthritis set in, however, he had demonstrated a penchant for explosive, often demonic, accounts of varying repertory, with abrupt juxtapositions and extreme contrasts between sections. His playing, notable for its unpredictability and brooding ferocity, could be uningratiating, but it was invariably stamped with his personality. And he was capable of the most soulfully introspective playing too, with exquisite tonal colouring and control of phrasing.

In the UK he was known best by his recordings, mostly for RCA and Mercury. Philips also put out two compilations in its Great Pianists of the 20th Century series.

In his book Chopin and Beyond: My Extraordinary Life in Music and the Paranormal (2010), co-written with his second wife, Maria, a painter and parapsychology researcher, he revealed his fascination with psychic phenomena such as table-turning, synchronicity and parallel dreams.

He was also frank in the book about his love life. Sexual experience was for a time as important to him as his art: “passion for the one inspiring transcendence in the other”, he said.

Many affairs were brief and with unattached women, but a relationship with Horowitz’s wife, Wanda, a daughter of Toscanini, for a period clouded his close friendship with his former mentor. Maria, whom he married in 1966, was the daughter of the actor Gary Cooper.

Born in McKeesport, Pennsylvania, Byron was the son of Hattie (nee Horelick), a music-loving Russian of Polish ancestry, and Sam Yanks, a Pole who was part-owner of a chain of military surplus stores. The family name had been shortened from Yankilevitch when they emigrated to the US. In his adolescence Byron Yanks’ name was changed first to Byron Jannes and then to Byron Janis.

After tuition from the age of eight by Josef and Rosina Lhévinne, he studied for six years with Adele Marcus. He made his orchestral debut in 1943 with the NBC Symphony Orchestra under Frank Black in Rachmaninov’s Second Piano Concerto and then played the same work the following year with the Pittsburgh Symphony Orchestra under the 13-year-old Lorin Maazel.

At the latter event he was heard by Horowitz, who invited him to study with him in New York. Janis, by his own account, lost the sense of his musical self at this period and did not recover it for some five years after he had stopped working with Horowitz.

His Carnegie Hall debut was received with such acclaim that he was able to embark on an international career as recitalist and concerto soloist. A particularly notable tour was that as the first American to feature in a cultural exchange with the Soviet Union in 1960. The latent hostility of the capacity audience at the first concert, in Moscow, was neutralised by his playing and he received a rapturous ovation.

He was well received too on a return visit in 1962, when he astonished his audience by playing in one concert the Schumann concerto, the first of Rachmaninov’s and the third of Prokofiev’s, followed by the last movement of Tchaikovsky’s first as an encore.

Janis always felt himself to have a special connection with Chopin. In 1967, while visiting the Château de Thoiry, Yvelines, he enquired about the contents of an old trunk labelled “old clothes”, only to discover inside two previously unknown Chopin autographs (of the Waltzes Op 18 and Op 70 No 1), subsequently authenticated. In what Janis described in his book as a notable example of “synchronicity”, two further autographs of the same two waltzes (but in slightly different versions) were revealed when he arbitrarily asked to see the contents of a folder on a high shelf while touring a library at Yale University. A film entitled Frédéric Chopin – A Voyage With Byron Janis relates the first of these discoveries.

In the late 1980s he began to compose popular songs and ballads, as well as music for film and television, including the theme song for a documentary about his film star father-in-law, and a score for a musical based on Victor Hugo’s Hunchback of Notre Dame.

His first marriage, to June Dickson-Wright, ended in divorce. Their son, Stefan, a poet, translator and art critic, died in 2017. He is survived by Maria.

• Byron Janis, pianist, born 24 March 1928; died 14 March 2024