Pruritus and Dysesthesia

Published on 05/03/2015 by admin

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Last modified 05/03/2015

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Pruritus and Dysesthesia

Definitions

• Pruritus: an unpleasant sensation of the skin that elicits a desire to scratch.

• Dysesthesia: an unpleasant, abnormal sensation that can be either spontaneous or evoked; abnormal, unpleasant sensations may include pain, pruritus (‘neuropathic itch’), tingling, burning, ‘pins and needles’.

Pruritus

• The most common skin-related symptom in dermatology; can have a profound negative impact on a patient’s quality of life.

• Results from the activation of the sensory nervous system, involving four sequential levels: the peripheral nervous system → the dorsal root ganglia → the spinal cord → and the brain.

• There are multiple etiologies of pruritus, and it is often a major clinical challenge to diagnose the underlying etiology and to adequately treat.

Etiologies

• May arise secondary to a number of conditions:

– Dermatologic disorders (Table 4.1).

Table 4.1

Common dermatologic diseases with pruritus as a major symptom.

BP, bullous pemphigoid; DH, dermatitis herpetiformis.

– Allergic or hypersensitivity syndromes.

– Systemic diseases (10–25%) and malignancies (Table 4.2; Figs. 4.1 and 4.2).

Fig. 4.1 Extreme xerosis associated with pruritus in an HIV-infected patient. Courtesy, Elke Weisshaar, MD and Jeffrey D. Bernhard, MD.

Fig. 4.2 Xerosis and pruritus in a patient with chronic renal failure on hemodialysis. There are a few papules of acquired perforating dermatosis admixed with the scratch marks. Courtesy, Jean L. Bolognia, MD.

– Toxins associated with kidney or liver dysfunction.

– Medications.

– Neurologic disorders (see text below).

– Psychiatric conditions (see Chapter 5).

• May also be primary or idiopathic – that is, no readily apparent skin disease, underlying etiology, or associated condition.

• Most patients with pruritus due to an underlying dermatologic disorder present with characteristic or diagnostic skin lesions (e.g., dermatitis of the flexures in atopic dermatitis; see Table 4.1).

• In primary pruritus and secondary pruritus NOT due to an underlying dermatologic disorder, the lesions are usually nonspecific (e.g., linear excoriations [Fig. 4.3], prurigo simplex, prurigo nodularis [Fig. 4.4]).

Fig. 4.3 Linear excoriations on the leg. Although this patient had atopic dermatitis, similar lesions can be seen in patients with ‘primary’ or ‘idiopathic’ pruritus. Courtesy, Elke Weisshaar, MD and Jeffrey D. Bernhard, MD.

Fig. 4.4 Prurigo nodularis. Firm papulonodules on the extensor forearm due to repeated scratching and picking. Courtesy, Ronald P. Rapini, MD.

Diagnostic Pearls

• Patients with chronic, idiopathic pruritus need serial examinations because pruritus can antedate clinical manifestations of the underlying disorder (e.g., lymphoma) or with time, more specific lesions may appear (e.g., bullous pemphigoid).

• Sparing of the mid upper back, an area of patient-hand inaccessibility (‘butterfly sign’) (Fig. 4.5), is suggestive of pruritus NOT associated with a dermatologic disorder; note, however, this sign is not seen in those who use back scratchers or similar devices.

Fig. 4.5 Multiple lesions of prurigo nodularis. Note the sparing of the mid upper back (‘butterfly sign’).

• Aquagenic pruritus, provoked by cooling of the skin after emergence from a bath, is often idiopathic but may be a sign of polycythemia vera.

• Of note, some patients may have a combination of specific and nonspecific skin lesions and both may be due to an underlying systemic disorder (e.g., eosinophilic folliculitis associated with HIV infection/AIDS).

Approach to the Patient with Pruritus

• Identifying the underlying etiology of a patient’s pruritus is important in determining the appropriate management.

• A simplified approach to the patient with pruritus is presented in Fig. 4.6.

Fig. 4.6 A simplified approach to the patient presenting with a chief complaint of pruritus.

Management of Pruritus

• General treatment measures for pruritus are outlined in Table 4.3.

Table 4.3

Treatment for pruritus/dysesthesia – general measures.

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