Part one - The history of psoriasis
Recognition and diagnosis
Psoriasis has probably been around for as long as modern man and has also been reported in non-human primates. Skin diseases were well known to the physicians (known as ašipu) of Ancient Mesopotamia more than 3,000 years ago. There is also a description of a skin condition called khusta in the religious Ayurvedic tradition in India, though this may have been leprosy rather than psoriasis. Astonishingly, it was not until the 19th century that psoriasis - as a disease in its own right – was finally recognised.
Although psoriasis is probably as old as mankind, the roots of the identification of psoriasis lie in Ancient Greece. The Greeks divided skin disease into the categories of psora, lepra and leichen. Psora referred to itch, while lepra was derived from the Greek words lopos (epidermis) and lepo (to scale). Hippocrates (460-377 BC), the Greek “Father of Medicine”, is credited with writing some of the first descriptions of skin disorders. He used the word psora, which meant itch, and lopoi to describe the scaly, dry features of psoriasis and other inflammatory skin conditions, such as leprosy. At that time, skin conditions were lumped together, so that leprosy and psoriasis were frequently confused. This is obviously important, because lepers were generally excluded from normal society, because they were believed (wrongly) to be highly contagious.
Much later, the Roman nobleman Cornelius Celsus (25 BC- AD 50) provided a detailed clinical description of a skin condition which affected the limbs and nails. It was characterised by red skin covered with scales, which he called impetigo, but which was almost certainly psoriasis.
Galen (131-201 AD) of Pergamon was a Greek physician in the Roman Empire and was probably the first to have used the term “psoriasis”. He described an itchy, scaly eruption of the eyelids and genitals, but this was likely to have been seborrheic dermatitis rather than psoriasis.
Overall, it seems that the great physicians of antiquity wrote rather little about skin diseases, which they did not regard as being of any particular importance. Therefore, no coherent or consistent description of psoriasis can be found in this period.
The Middle Ages
Following the demise of the Roman Empire, European history entered what is known as the Middle Ages, roughly the late 5th to the late 15th century.
Most literate men were in monastic orders and spent their days contemplating abstract theological questions, rather than medical or scientific problems. The random grouping together of all inflammatory skin diseases led to stigmatisation of patients with psoriasis. For centuries, patients with psoriasis suffered the same cruel fate as lepers. They were outcasts, who were required to carry a bell or clapper to announce their approach and who could only mix with other “lepers”. In 1313, Phillip the Fair of France ordered that they be burned at the stake. If you were unfortunate enough to have psoriasis during this period, you would have been well-advised to stay out of the way.
The Renaissance, a cultural movement that spanned the 14th to the 17th centuries, began in Florence and later spread to the rest of Europe. During this period, by far the most important work on skin disease - De Morbis Cutaneis (Diseases of the Skin) - was written by Girolamo Mercuriale (1530-1606). In this book, widely regarded as the first scientific treatise on skin conditions, he divided cutaneous diseases into those of the scalp and those of the body, referring to psoriasis under the name of lepra grecorum. Another Italian, Bernardo Ramazzini (1633-1714), is undoubtedly the father of modern occupational medicine. His original work - De Morbis Artificum Diatribe (Diseases of Workers) – includes basic descriptions of some skin conditions, such as eczema, dermatitis and psoriasis.
The 18th century
Although several important figures in the 18th century, such as Daniel Turner, Charles Lorry and Joseph von Plenck, wrote in general terms about skin diseases, none paid specific attention to psoriasis. Indeed, it was not until 1809 that an English doctor named Robert Willan (1757-1812) developed a simple classification of skin diseases, which allowed a more rational approach to diagnosis. Willan was essentially the founder of dermatology as a medical speciality and was the first to offer a clear description of different types of psoriasis, including guttate (small red, dotty patches), scalp and palmar lesions. He also observed that the disease began on the knees and elbows but could also attack the finger and toenails. This was a huge step forward in the recognition of psoriasis as a separate disease entity. Unfortunately, he used term lepra vulgaris rather than psoriasis, which again perpetuated the confusion between psoriasis and leprosy.
The 19th century
One of the great figures in 19th century dermatology was Ferdinand von Hebra (1816-1880), an Austrian physician working at the Vienna General Hospital. He founded the Vienna School of Dermatology and, while still a young man, wrote one of the most influential books on skin diseases of all time - Atlas der Hautkrankeiten (Atlas of Skin Diseases). This was widely regarded throughout Europe, as much for its wonderful illustrations as for its scientific and medical content. Von Hebra is rightly regarded as the father of modern dermatology, in that he was the first to apply modern research methods to the study of skin disorders. He was also a great teacher and students from all over the world came to study with him in Vienna.
Importantly for our story, is the fact that it was Von Hebra who permanently shed the term “lepra” from the description of psoriasis, finally separating the two diseases from one another once and for all.
Another 19th century milestone was the recognition of the association between psoriasis and a particular form of arthritis. Although this was first discovered by the French dermatologist, Jean Louis Alibert, in 1818, it was not until 1860 that Ernest Bazin (another Frenchman) coined the term “psoriasis arthritique” or “arthritic psoriasis”. A detailed characterisation of the condition was provided by Charles Bourdilllion in his doctoral thesis, Psoriasis Arthropathies (1888).
Further refinements in the description of the various forms of psoriasis continued throughout the 19th century. In addition, some authors described signs that might be useful in the diagnosis of the disease. Heinrich Auspitz (1835-1886), one of Hebra’s students, noted that when scale is scraped from psoriatic plaques, tiny bleeding points occur – called the Auspitz sign. It is not, however, specific to psoriasis and is no longer regarded as a reliable diagnostic tool.
Heinrich Köbner (1838-1904) noted that some people with psoriasis developed lesions in areas in which the skin had been traumatised. This could be from a cut, a bruise, or a burn, but lesions may also develop on parts of the body where the skin is irritated by a waistband, or belt buckle. In all these cases, the psoriatic lesions occurred in areas outside those normally affected by psoriasis – called an isomorphic response. Although the Köbner phenomenon is a well-known aspect of psoriasis, it is not completely understood even today.
Finally, in 1898, an Australian dermatologist called William J. Munro described micro-abscess formation in the epidermal layers of the skin of psoriatic patients. Subsequent studies – as recently as 2011 – show that micro-abscess formation is highly specific for the diagnosis of psoriasis vulgaris – the most common form of the disease.
The 20th century
The start of the 20th century ushered in further, detailed descriptions of the various types and sub-types of psoriasis. In 1910, Leo von Zumbusch first described generalised pustular psoriasis. This is a serious - though fortunately rare – condition, characterised by widespread areas of reddening or the skin, which becomes painful and tender. Within hours, tiny pustules appear, many of which will consolidate into larger blisters. There is accompanying fatigue and fever.
Note that von Zumbach’s generalised pustular psoriasis is not the same as the more common form of localised pustular psoriasis, affecting the palms of the hands and soles of the feet, called palmoplantar pustulosis (PPP).
In 1926, Dr D. L. Woronoff, a dermatologist at the clinic for skin diseases of Moscow University, described a pale (hypopigmented) zone of skin which appeared around healing psoriasis lesions. This pale “halo” became known as “Woronoff’s ring”. Until recently, the cause of this phenomenon was a mystery, but it has now been attributed to the effects of various inflammatory molecules, reducing the melanin content of the skin cells surrounding the healing psoriatic lesion.
The recognition of the Auspitz sign, Köbner’s phenomenon, Munro’s abscesses, generalised pustular psoriasis and the Woronoff ring provided important diagnostic tools which allowed physicians to be more confident in diagnosing psoriasis.
Another landmark event came in 1973, with the publication of a paper by John M. Moll and Verna Wright from Leeds, in the UK, on psoriatic arthritis, which proved to be a milestone in the history of psoriasis. Of course, as we have seen earlier, the association between psoriasis and arthritis had already been observed (by Alibert and Bazin), but what Moll and Wright did was show that the arthritis associated with psoriasis is unique to that disease and quite different from rheumatoid arthritis.
Today, psoriasis is no longer regarded simply as a skin condition, but as a chronic autoimmune disease, characterised by systemic inflammation. This inflammatory process affects not just the skin, but also joints and other bodily systems. Over the last decade, developments in molecular science and genetics have provided a deeper scientific understanding of the disease mechanisms involved, leading to exciting new treatments. This will be the subject of Part 2 of this history.
Nevertheless, we are by no means at the end of the journey and there is still a great deal about psoriasis that is completely baffling. As the distinguished American dermatologist, Paul E. Bechet, wrote in 1936: “Psoriasis is an antidote for dermatologists’ ego”.
Author: Dr WD Ashton MD PhD