Pruritus and Neurocutaneous Diseases




Pruritus often produces distinctive skin lesions, characterized by angulated borders. Endogenous diseases (in common parlance, an “inside job”) tend to produce lesions that are rounded in character, whereas exogenous caustic agents, scratching, and other forms of external trauma tend to produce angulated, linear, or geometric shapes (signs of an “outside job”).


Pruritus can also result in the isomorphic (Koebner) phenomenon, where lesions of an endogenous disease localize in areas of trauma. These lesions often demonstrate a hybrid morphology, suggesting both endogenous origin and external trauma.


Lichenification results from chronic scratching or rubbing and is characterized by hyperkeratosis and papillary dermal fibrosis. The resulting clinical morphology includes slight induration and accentuation of skin markings. Excoriation results in eosinophilic necrosis of the granular layer. The corneum can remain intact, but more severe excoriation results in loss of the corneum and viable epidermis. More pronounced trauma can result in ulceration, in which the injury extends to the level of the dermis.


Broad areas of lichenification are characteristic of lichen simplex chronicus. Discrete papules with focal evidence of excoriation are typical of prurigo nodularis and arthropod bites, including those caused by bedbugs. This portion of the atlas will guide you through the clinical manifestations related to pruritic disorders.


Fig. 4.1


Excoriations secondary to pruritus of Hodgkin disease.



Fig. 4.2


Acquired perforating disease in renal failure.



Fig. 4.3


Acquired perforating disease in renal failure.



Fig. 4.4


Acquired perforating disease in renal failure.

Courtesy Steven Binnick, MD.



Fig. 4.5


Prurigo nodularis in a chronic renal failure patient.

Courtesy Steven Binnick, MD.



Fig. 4.6


Jaundice.



Fig. 4.7


Palmar xanthomas in hepatic cholestasis.



Fig. 4.8


Lichen simplex chronicus in Alagille disease.



Fig. 4.9


Hyperpigmentation in primary biliary cirrhosis.



Fig. 4.10


Winter itch.



Fig. 4.11


Lichen simplex chronicus in pruritus ani.



Fig. 4.12


Lichen simplex chronicus of the scrotum.



Fig. 4.13


Lichen simplex chronicus of the vulva.



Fig. 4.14


Prurigo pigmentosa.



Fig. 4.15


Prurigo pigmentosa.

Courtesy Stephen D. Hess, MD, PhD.



Fig. 4.16


Prurigo pigmentosa.

Courtesy of Department of Dermatology, Keio University School of Medicine, Tokyo, Japan.



Sep 3, 2019 | Posted by in Dermatology | Comments Off on Pruritus and Neurocutaneous Diseases
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