Approach
Characteristic history and physical examination findings are usually sufficient to diagnose the condition. Skin biopsy is reserved for atypical cases.
History
Disease history typically reveals onset of scalp itching and scaling during and after puberty. Months or years later, erythema may involve the nasolabial folds or spread to the beard region in men. Typically a fluctuating course of flares and remission is described. Exploration of aggravating factors may reveal a link to environmental, emotional, or infectious factors. In older adults, there are well-recognised associations with Parkinson's disease, phenothiazine drugs, syringomyelia (development of a cyst in the spinal cord), and motor loss after a stroke.[12]
Physical examination
In adolescents and adults erythematous, circumscribed and scaly patches are commonly found on the scalp. Erythema accompanied by greasy scales in the nasolabial folds, postauricular area, forehead, and anterior chest are often present. In infants, the characteristic distribution is extensive coverage of the scalp, hence the term 'cradle cap'.
Generalised infantile SD tends to occur in healthy children, and erythematous scaly lesions are widespread. When the distribution is extensive or onset severe, other features of impaired immune function should also be sought.
Investigations
Skin biopsy may be performed to confirm SD. However, this is only necessary when there is significant doubt about the diagnosis.[14]
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