Pityriasis capitis, also known as pityriasis sicca, seborrhea sicca, or pityriasis capitis simplex, commonly known as dandruff, is the most common disease of the scalp, with furfuraceous scales all over the scalp. Sometimes, the condition is also known as pityriasis steatoides as the scales are sticky and greasy.
Malassezia furfur is often considered to be the pathogen of pityriasis capitis, but this lipophilic polymorphic fungus is ubiquitous in nature, and also inhabits the scalp or other skin of large amounts of normal humans without causing symptoms. Under certain condition, the fungus can cause the disease. Sex hormones have a greater impact on Malassezia furfur. Most patients are adult males, and dandruffs often decrease in amount and even are absent in pregnant women.
Hairdressing tools are the main vector for the transmission of Malassezia furfur, and dandruffs of adults can also infect infants or children by falling on their heads. However, the saprophytic fungus is ubiquitous, and the source and route of infection cannot be determined. In addition, staphylococcus epidermidis albus and acne bacillus are also common in the dandruffs, and are thought to be associated with dandruff.
It is also believed that this disease has nothing to do with any microorganisms, and is not affected by the secretion of sebaceous glands. The massive exfoliation of epidermal keratinocytes is only a physiological phenomenon under the domination of genes, and the amount of sebum secreted by the scalp is not more than that of normal humans. Dandruffs provide nutrients and places for Malassezia furfur to propagate and survive, so there are more microorganisms such as Malassezia furfur when there are numerous dandruffs.
Signs and Symptoms
Small, silver gray, lamellar or furfuraceous scales deposit on one or more sites on the scalp, usually symmetrical, sometimes involving the entire scalp. If premature alopecia is present, there is not pityriasis in the affected areas. The scales are mostly sticky, and fall off from the hair shafts only after being brushed or combed. Scalp pityriasis patients are more susceptible to seborrheic dermatitis. Mild seborrheic dermatitis sometimes is known as pityriasis steatoides, and its scales are larger, thicker, and stickier. If the scales are forcibly removed, the exposed scalp is madid and reddened.
Figure 1 pityriasis capitis
There are hyperkeratosis, parakeratosis, and mild hypertrophy of prickle cell layer in the epidermis. The sebaceous and sweat glands are normal. The scales are composed of keratinocytes, contain Malassezia furfur, and often have clustered staphylococcus epidermidis albus. Sometimes, there is coagulated serum in the scales, so the sticky scales result in pityriasis steatoides.
On the typical clinical manifestations, the disease can be diagnosed.
Shampoos containing antifungals such as ketoconazole, climbazole, and selenium disulfide can be applied.