Ectopic sebaceous glands are commonly seen in the mouth, where they occur as multiple, symmetrical, barely elevated, discrete yellow papules, referred to as Fordyce disease . They are asymptomatic and occur in about 45 per cent of the population over  the age  of 35 years.  Puberty exerts only a marginal accelerating influence upon their development, the effect being more marked in boys. Only  rarely do comedones develop (0.1 per cent).  Lipid analysis  confirms that the  glands are similar to sebaceous glands at other sites.

  Similar ectopic glands may be seen as papules on the skin overlying the shaft of the penis. They are asymptomatic and are rarely recognized by the patient. They are more numerous ventrally and there may be as many as 100 of them, each being a fraction of a millimetre in size.  Squeezing of the lesion will express a cheesy material and histology demonstrates sebaceous glands in the upper dermis usually unassociated with follicular structures. Occasionally, such ectopic sebaceous glands may be seen on the prepuce, but never on the corona. Uncommonly,  an inflammatory papule or a superficial pustule develops at the site of these ectopic sebaceous glands. No doubt, as in the mouth, the absence of the complex anatomical duct allows free passage of the sebum, and so functional blockage at this site does not occur and inflammation therefore only happens infrequently.

  In the differential diagnosis,  the so-called Tyson's glands must be considered. These lesions are a variation of normal and are found in 25 per cent of adult males. They present as an incomplete circle of skin-coloured or whitish-pink  papillomatous  excrescences;  they  are usually hemispherical and of uniform size, less than 3 mm in diameter and arranged in 1-5 rows. Microscopically  they consist of varying proportions of fibrous and vascular  proliferations and sebaceous glands are absent. Tyson's glands are mentioned here because of their  confusion  by  some  physicians  with  ectopic sebaceous glands.  They produce no symptoms apart from unnecessary anxiety. The differential diagnosis is almost exclusively that of penile warts.