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The term prurigo, originating from the Latin word pruire (to itch), was first coined by Ferdinand von Hebra in the mid-19th century to characterize intensely itchy papules and nodules that occur mainly on the arms and legs. At that time, prurigo was one of the most frequent forms of skin disease in Europe, being closely associated with the stings of parasites (such as fleas and mites) that commonly afflicted humans. Today, prurigo strophulus - which is generally provoked by stings of fleas, mosquitos, ticks, or dog parasites - has come to designate an acute form of prurigo.
The genuine chronic form of prurigo is prurigo nodularis (PN) of Hyde, after the man who coined the term in 1909 [1]. This review will deal with this and other forms of chronic prurigo secondary to underlying systemic disease or external provoking factors. In addition, it will focus on the preponderance of prurigo in certain ethnic groups.
The diagnosis of prurigo is a clinical one and histopathology confirms what is seen by the naked eye, including hyperkerathosis, acanthosis, and occasionally epidermal necrosis due to picking.
PN of Hyde
PN can occur at any age, although mainly in those aged 20-60 years, with women being more affected than men. The lesions are hemispherical, often irregular nodes with a horny, rhagadiform, or crateriform depressed surface. They may be as large as several centimeters in diameter and are mainly located on extensor surfaces of the extremities, although the trunk, face, and even the palms can be affected [1]. New nodules can develop over time, and existing nodules can remain pruritic indefinitely, although some regress spontaneously and leave scars. The cardinal symptom is itch.
There has been much confusion in the literature concerning PN. "Prurigo nodularis" is often used erroneously for all forms of chronic prurigo. True PN is an endogenous form of chronic pruigo that is often associated with atopy [2]. The lesions are large nodules (up to 3 cm in diameter) compared with smaller nodules of secondary prurigo.
During the 19th century there was much discussion among dermatologists about whether the PN lesion appears first and produces an urge to scratch or whether its appearance is brought about as a consequence of scratching [1]. According to Hebra, the prurigo...