dermatologic disorders
Itching
Evaluation of Itching
History of present illnessshould determine onset of itching, initial location, course, duration, patterns of itching (eg, nocturnal or diurnal, intermittent or persistent, seasonal variation), and whether any rash is present. A careful medication history should be obtained including both prescription and over-the-counter medications with particular attention paid to recently started medications. The patient's use of moisturizers and other topicals (eg,hydrocortisone,diphenhydramine) should be reviewed. History should include any factors that make the itching better or worse. Review of systemsshould seek symptoms of causative disorders, including Irritability, sweating, weight loss, and palpitations ( Hyperthyroidism ) Depression, dry skin, and weight gain ( Hypothyroidism ) Headache, pica, hair thinning, and exercise intolerance ( Iron Deficiency Anemia ) Constitutional symptoms of weight loss, fatigue, and night sweats (cancer) Intermittent weakness, numbness, tingling, and visual disturbances or loss ( Multiple Sclerosis (MS) ) Steatorrhea, Jaundice , and right upper quadrant pain (cholestasis) Urinary frequency, excessive thirst, and weight loss ( Diabetes Mellitus (DM) ) Past medical historyshould identify known causative disorders (eg, renal disease, cholestatic disorder, cancer being treated with chemotherapy) and the patient’s emotional state. Social history should focus on family members with similar itching and skin symptoms (eg, scabies, pediculosis); relationship of itching to occupation or exposures to plants, animals, or chemicals; and history of recent travel. Physical examination begins with a review of clinical appearance for signs of jaundice, weight loss or gain, and fatigue. Close examination of the skin should be done, taking note of presence, morphology, extent, and distribution of lesions. Cutaneous examination also should make note of signs of secondary infection (eg, erythema, swelling, warmth, yellow or honey-colored crusting). The examination should make note of significant adenopathy suggestive of cancer. Abdominal examination should focus on organomegaly, masses, and tenderness (cholestatic disorder or cancer). Neurologic examination should focus on weakness, spasticity, or numbness (multiple sclerosis). The following findings are of particular concern: Constitutional symptoms of weight loss, fatigue, and night sweats Extremity weakness, numbness, or tingling Abdominal pain and jaundice Urinary frequency, excessive thirst, and weight loss Generalized itching that begins shortly after use of a medication or exposure to a substance (eg, IV contrast) is likely caused by that agent. Localized itching (often with rash) that occurs in the area of contact with a substance is likely caused by that substance. However, many systemic allergies can be difficult to identify because patients typically have consumed multiple different foods and have been in contact with many substances before developing itching. Similarly, identifying a drug cause in a patient taking several medications may be difficult. Sometimes the patient has been taking the offending medication for months or even years before developing a reaction. If an etiology is not immediately obvious, the appearance and location of skin lesions can suggest a diagnosis (see table). ). Rarely, itching is the first manifestation of significant systemic disorders (eg, Polycythemia Vera , certain cancers, Many dermatologic disorders are diagnosed clinically. However, when itching is accompanied by discrete skin lesions of uncertain etiology, Skin Biopsy can be appropriate. When an allergic reaction is suspected but the substance is unknown, skin testing (either prick or Diagnosis depending on suspected etiology) is often done. When a systemic disorder is suspected, testing is directed by the suspected cause and usually involves complete blood count; liver, renal, and thyroid function measurements; and appropriate evaluation for underlying cancer. 