MALASSEIZIA 365 



forehead and grow backward, until, when baldness is complete, only a narrow 

 fringe is left at the back and sides of the head. At first the number of hairs 

 is not diminished, but they become finer in texture and, as the follicles are 

 destroyed, the space between the hairs increases, until all the follicles are 

 destroyed and the scalp is thin, shiny, and bald. During and after middle 

 age, extensions to the body are more common than in adolescence, when it 

 extends to the forehead as corona seborrhoeica, rarely to the whole face. The 

 skin becomes dry and harsh, thickened and indurated and from irritation of 

 the corium, the melanoblasts and basal layers are stimulated with deepening 

 of pigmentation. When the nape of the neck becomes involved, with the added 

 irritation of collar and other clothing, the skin is thickened, indurated, with 

 deep furrows where the normal lines of skin were (lichenification). More 

 rarely pustules form and the scars become keloid (dermatitis papillaris capil- 

 litii. In elderly people Malassezia may also attack the skin at the flexures of 

 the elbows and knees, producing lichenification or even acute exfoliative der- 

 matitis. 



Among the poorer classes of England, circinate lesions with a slightly in- 

 flamed base and greasy scales appear on the body, a condition known as flan- 

 nel rash. During middle age the acneiform type of lesions tend to disappear. 

 In acne rosacea, there is a reflex erythema on the nose or the face produced 

 by some irritation in the upper portion of the alimentary canal, causing the skin 

 to become red and thickened and the sebaceous glands to become hypertro- 

 phied. The latter are then invaded by Malassezia, with the production of 

 papular lesions. 



As a result of the irritation of the mouths of the sebaceous glands these are 

 blocked and the sebum cannot find an outlet; as age advances the glands be- 

 come enlarged from the accumulation of sebum, and retention cysts (wens) are 

 formed. More rarely in adult life the moist skin of the axilla and scrotum is 

 attacked, being covered with a layer of greasy scales, where retention of the 

 secretion of the sebaceous glands and staphylococcal infection occur. Sometimes 

 the glands of the scrotum become blocked, producing a condition similar to 

 Fordyce's disease of the lips, with thickening, induration, and intense irritation, 

 an eczematous condition whose diagnosis is to be carefully distinguished from 

 tinea cruris. 



In the tissues, Malassezia appears as a yeastiike budding form (the flask- 

 shaped bacillus of Unna or the Morococcus of Sabouraud) . During its growth 

 it interferes with the flattening and the proper keratinization of the super- 

 ficial cells of the scalp, and they are shed as the delicate scales of dandruff. 

 When the disease is spreading rapidly, the scales separate rapidly, and only 

 the yeast cells are seen. At middle age, the mouth of the hair follicle is in- 

 vaded, the homy layer fails to keratinize, and the mouth of the follicle is filled 

 with large swollen cells. The yeast cells divide rapidly at the bottom of the 

 follicle and invade the sebaceous gland, while the leucocytes show an inflam- 

 matory reaction about the neck of the gland. The hair becomes distorted and 



