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This image shows typical nodules in their intial form. Raised, discrete, firm and itensely itchy, they can occur on any part of the body, from one or two to many tens of nodules. If not scratched or damaged in any other way they can persist for a very long time. It is quite common for new nodules to arise as other heal and dissapear. Additional problems arise when they are scratched.
It is the primary advice of most doctors that they should not be scratched, but from the experience of our members it is quite clear that although this is sensible advice, it is in most circumstances, almost impossible to avoid doing. The nature of the irritation is such that even knwoing that it is counter-productive to do so, people wil conciously or uncounciously reach a point where to scratch is the only way they can get any relief.
This image shows a typical nodle that has been scratched over a period of time. There is distruction of the top layer of skin. Instead of a firm nodule, its has become cratered and ulcerated. The complication of such scratching is that it gives easy access for skinsurface pathogens, especially bacteria. This leads to further inflammation of the wound with a typical reddening around the nodule. It is our experience that even without this sort of sub-clinical infection, these wounds have delayed healing due to the abnormal cell structure caused by the nodula prurigo. Once infected they have additional problems with healing plus the inflammation makes them even more irritable.
As wounds begin to heal they produce an excess of hard, scaly tissue as shown in this image. This persists for some time before the wound eventaully heals completely. The scaly nature can lead to increased scratching in an attempt to remove it. The hyper-pigmentation (reddening) that often occurs may also remain for some time even after the wound has completely healed often turning dark purple or brown. There is gradual flattening of the nodule until all that remains is a patch of smooth scar tissue.
In terms of diagnosis a skin biopsy is the only way o make a clear diagnosis, so it is important to understand what this may sjow. Searching the Internet with the term "nodular prurigo histology", you can come across statement such as this
“Histopathology reveals psoriasiform hyperplasia or pseudo-epitheliomatous hyperplasia. Marked hyperkeratosis with hypergranulosis and focal parakeratosis. Occasional spongiosis and exocytosis of mononuclear cells. Scale crust formation in association with changes of excoriation (fibrin deposition and cellular debris). Prominent hyperplasia of hair follicles. Mild fibosis of papillary and superficial dermis and telangiectasia. Mild to moderate perivascular mononuclear inflammatory cell infiltrate composed of lymphocytes, histiocytes and plasma cells. Nerve hyperplasia as reported in the past is not usually a feature.”
Although accurate it is difficult for the lay person to fully understand what is going on. So let's try to unpick it.