In 2007, a retrodiagnosis of Marx's skin disease was made by dermatologist Sam Shuster of Newcastle University and for Shuster, the most probable explanation was that Marx suffered not from liver problems, but from hidradenitis suppurativa, a recurring infective condition arising from blockage of apocrine ducts opening into hair follicles. This condition, which was not described in the English medical literature until 1933 (hence would not have been known to Marx's physicians), can produce joint pain (which could be misdiagnosed as rheumatic disorder) and painful eye conditions. To arrive at his retrodiagnosis, Shuster considered the primary material: the Marx correspondence published in the 50 volumes of the "Marx/Engels Collected Works". There, "although the skin lesions were called 'furuncles', 'boils' and 'carbuncles' by Marx, his wife, and his physicians, they were too persistent, recurrent, destructive and site-specific for that diagnosis". The sites of the persistent 'carbuncles' were noted repeatedly in the armpits, groins, perianal, genital (penis and scrotum) and suprapubic regions and inner thighs, "favoured sites of hidradenitis suppurativa". Professor Shuster claimed the diagnosis "can now be made definitively".