Prurigo nodularis (PN) is a skin disease characterised by pruritic (itchy) nodules which usually appear on the
arms or legs. Patients often present with multiple excoriated lesions caused by scratching
Signs and symptoms:
Nodules are discrete, generally symmetric, hyperpigmented or purpuric, and firm. They are greater than 0.5 cm
in both width and depth (as opposed to papules which are less than 0.5 cm). They can appear on any part of the
body, but generally begin on the arms and legs.
Excoriated lesions are often flat, umbilicated, or have a crusted top.
Nodules may appear to begin in the hair follicles.
Nodule pattern may be follicular.
In true prurigo nodularis, a nodule forms before any itching begins. Typically, these nodules are extremely pruritic
and are alleviated only by steroids.
The cause of prurigo nodularis is unknown, although other conditions may induce PN. PN has been linked to an
autoimmune condition, liver disease and T cells. Systemic pruritus has been linked to cholestasis, thyroid
disease, polycythaemia rubra vera, uraemia, Hodgkins disease, HIV and other immunodeficiency diseases.
Internal malignancies, liver failure, renal failure, and psychiatric illnesses may induce PN, although more recent
research has refuted a psychiatric cause for PN