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Author: Dr Amanda Oakley Dermatologist, Hamilton New Zealand. Updated February 2014.
Steatocystoma multiplex is a rare inherited disorder in which numerous cysts develop at puberty. The lesions have been described as hamartomatous malformations of the pilosebaceous duct junction (hair follicle unit).
If a single cyst of this type is found, it is called steatocystoma simplex.
In steatocystoma multiplex, the tendency to develop cysts is inherited in an autosomal dominant fashion, so one parent can be expected to also have steatocystoma multiplex. It may also occur sporadically. Both males and females may be affected.
The onset at puberty is presumably due to hormonal stimulus of the pilosebaceous unit. They most often arise on the chest and may also occur on the abdomen, upper arms, armpits and face. In some cases cysts may develop all over the body.
The cysts are mostly small (2-20 mm) but they may be several centimetres in diameter. They tend to be soft to firm semi-translucent bumps, and contain an oily, yellow liquid. Sometimes a small central punctum can be identified and they may contain one or more hairs (eruptive vellus hair cysts). They may become inflamed and heal with scarring, like acne nodules (see nodulocystic acne and hidradenitis suppurativa).
Steatocystomas are thought to come from an abnormal lining of the passageway to the oil glands (sebaceous duct).
Localised, generalised, facial, acral, and suppurative types of steatocystoma multiplex have been described. Isolated steatocystoma of the vulva can develop late in life as a sporadic condition not inherited (see Vulval cysts).
Familial steatocystoma multiplex is associated with mutations in the keratin 17 gene (K17). This gene is responsible for a keratin protein found in the nail bed, hair follicles and sebaceous glands. Mutations in K17 may also result in one form of pachyonychia congenita, in which cysts, plantar keratoderma and natal teeth are common.
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