++
A 59-year-old man presents with a 3-month history of an itchy rash on his face (Figures 157-1 and 157-2). He states that he has had this rash intermittently for many years, but that it had recently worsened. He denies any major risk factors for HIV and does not have Parkinson disease. He has been under more stress lately and has noticed that this exacerbates his rash. There was scale visible on the forehead, under the eyebrows, and in the beard. There is also some mild erythema on the cheeks and around the nasolabial folds. The diagnosis of seborrheic dermatitis was made and treatment began with appropriate topical agents to treat the inflammation and the Malassezia. On the following visit, the patient had complete clearance of his seborrheic dermatitis.
++++
++
Seborrheic dermatitis is a common, chronic, relapsing dermatitis affecting sebum-rich areas of the body. Presentation may vary from mild erythema to greasy scale to, rarely, erythroderma. Treatment goals include reducing inflammation and irritation.
++
Seborrhea, seborrheic eczema, dandruff, and cradle cap.
++
Seborrheic dermatitis is most commonly seen in male patients between the ages of 20 to 50 years, though it can affect women, infants, and the elderly as well.
The prevalence is approximately 3% to 5% in healthy young adults who are HIV-negative.1 The statistics may be underrepresented, as many do not seek medical attention for mild cases.
The prevalence is higher in immunocompromised persons (e.g., HIV-positive/AIDS); however, the vast majority of affected persons have a normal immune system.
More common in persons with underlying neurologic disease including Parkinson disease and tardive dyskinesia.2
+++
ETIOLOGY AND PATHOPHYSIOLOGY
++
The actual cause of seborrheic dermatitis is not well understood. It appears to be related to the interplay between host factors including hormonal expression, environmental factors, and local immune response to antigens.2-5
Patients with seborrheic dermatitis may be colonized with certain species of lipophilic yeast of the genus Malassezia (also called Pityrosporum). However, Malassezia is considered normal skin flora, as it is also found in unaffected persons.
Some evidence suggests that Malassezia may produce different irritants or metabolites on affected skin.5
Genomic analyses of the Malassezia genus has revealed genetic sequences for lipases and ...