First described by Jamieson in 1873, and coined by Pringle in 1899, steatocystoma multiplex (SM) is an uncommon disorder of the pilosebaceous unit characterized by the development of numerous sebum-containing dermal cysts. Although steatocystoma multiplex has historically been described as an autosomal dominant inherited disorder, most presenting cases are sporadic.
Steatocystoma simplex is the sporadic solitary tumor counterpart to steatocystoma multiplex.
Steatocystoma multiplex occurs as either a sporadic or autosomal dominant inherited condition characterized by benign sebaceous gland tumors. Lesions consist of a nevoid formation of abortive hair follicles at the site where sebaceous glands attach. Electron microscopy studies demonstrate cyst wall cells undergoing trichilemmal keratinization similar to that of the isthmus portion of the outer hair sheath. The relationship of steatocystoma multiplex to the development of sebaceous glands and common presentation at puberty suggest a hormonal trigger for lesion growth.
In the familial form of steatocystoma multiplex, mutations are localized to the keratin 17 (K17) gene in areas identical to mutations found in patients with pachyonychia congenita type 2 (PC-2). Pachyonychia congenita type 2, an autosomal dominant inherited disorder, is characterized by hypertrophic nail dystrophy, focal keratoderma, multiple pilosebaceous cysts, and a variety of conditions associated with ectodermal dysplasia. Keratin 17 is expressed in several epithelial structures, most notably in sebaceous glands, the outer root sheath of hair follicles, and the nail bed; its expression correlates well to the clinical phenotypic expression of both steatocystoma multiplex and pachyonychia congenita type 2. To date, 14 mutations have been described in patients with either steatocystoma multiplex or pachyonychia congenita type 2, all of which are localized to the helix initiation domain (1A domain) of the K17 gene.
Some authors propose that steatocystoma multiplex is simply a variant of pachyonychia congenita type 2 because they both share the same underlying etiology. Sporadic forms of steatocystoma multiplex have not been shown to be associated with K17 mutations. In previous reports, specific mutations were attributed to early-onset cyst formation in pachyonychia congenita type 2 and steatocystoma multiplex; however, more recent reports suggest that the age of onset is multifactorial.
Steatocystoma multiplex is associated with eruptive vellus hair cysts (EVHCs). Both diseases share overlapping clinical features, including age of onset, location, appearance of lesions, and mode of inheritance. Reports of hybrid lesions showing histological features of both steatocystoma multiplex and eruptive vellus hair cysts exist.[4, 5] Given these similarities, some postulate that steatocystoma multiplex and eruptive vellus hair cysts are, in fact, variants of the same disease. However, major differences in keratin expression patterns between steatocystoma multiplex and eruptive vellus hair cysts have been elucidated, leading others to believe that they are 2 distinct disease entities. In steatocystoma multiplex associated with eruptive vellus hair cyst, no K17 mutation has been found.
Steatocystoma multiplex is considered rare; the true incidence is unknown.
Steatocystoma multiplex is a benign disorder. In some patients, it may have psychosocial implications resulting from the disfigurement due to widespread lesions or from scarring seen in the inflammatory variant, steatocystoma suppurativa.
No racial predilection has been found.
Both sexes are equally affected.
In the classic presentation, cysts manifest during adolescence and early adulthood, with average age of onset of 26 years. Cases of steatocystoma multiplex presenting at birth have been reported, and sporadic forms of steatocystoma multiplex with presentation as late as 78 years have been described. Once present, steatocystoma multiplex is a lifelong condition.
Affected individuals often present with an increasing number of smooth flesh-to-yellow–colored cysts. The cysts are usually nontender and asymptomatic. On occasion, individual lesions may rupture into the dermis, become inflamed, and form sinus tracts with scarring. Secondary bacterial colonization can lead to malodorous discharge.
Lesions present as numerous flesh-to-yellow–colored dermal cysts ranging in size from 3 mm to 3 cm. Individual cysts range from elastic to firm and are often freely movable. The lesions lack a central punctum. Cyst contents appear as an odorless creamy or oily fluid. Individual lesions of steatocystoma multiplex may become suppurative, increase in size, and become prone to rupture (termed steatocystoma multiplex suppurativum). In these cases, secondary bacterial colonization often leads to malodorous discharge. Significant scarring with sinus tract formation may occur.
In typical cases of steatocystoma multiplex, cysts are distributed in areas where high numbers of sebaceous glands are found, most commonly the chest, arms, axillae, and neck. Several reports of localized steatocystoma multiplex limited to the scalp, face, retroauricular region, groin, and nasal region have been reported.[9, 10] Acral steatocystoma multiplex, in which involvement of the extremities is more prominent than the trunk, is uncommon and was described by Rollins et al in 2000.
Steatocystoma multiplex on the chest of an adolescent female.
Steatocystoma multiplex with typical-appearing, smooth, yellow and white dermal cysts.
While some authors refer to localized steatocystoma multiplex as a specific condition, it shares pathological and clinical features of typical cases and is thought to represent a variant of the steatocystoma multiplex rather than a separate disease entity. Linear variants have been reported, and, although rare, generalized eruptions may occur.
Steatocystoma multiplex is a disorder of the pilosebaceous unit that occurs in either a sporadic or an autosomal dominant fashion. Androgenic stimulation of the sebaceous gland, along with environmental factors and the site and type of the keratin mutation, influence the onset of the sebaceous cysts.
Cysts are located in the mid dermis. The cyst lining is a crenulated or wavy, homogeneous, eosinophilic horny layer collapsed around thin cystic spaces. The spaces hold varying amounts of keratin, vellus hairs, and sebum esters, the latter of which often are removed by tissue processing. Walls are formed from several layers of epithelial cells, with embedded flattened lobules of sebaceous glands among the epithelial cells. Invaginations resembling hair follicles can also be found emptying into the cyst. Cyst units may be attached to the overlying normal epidermis by a thin strand of undifferentiated epithelial cells. All reported cases of steatocystoma multiplex exhibit an eosinophilic cuticle and lack of a granular layer. In contrast, eruptive vellus hair cysts are lined by mature squamous cells with a granular layer and are not associated with sebaceous glands.
Note the crenulated eosinophilic lining of the cyst wall (10X magnification).
Note the sebaceous glands within the cyst wall (2X scanning view).
Medical treatments have been used with variable results to lessen inflammation, minimize scarring, and reduce the need for surgery.
Cysts can be widespread and difficult to treat. A variety of surgical treatment options have been used in the treatment of steatocystoma multiplex.
The goals of pharmacotherapy are to reduce morbidity and to prevent complications.
Clinical Context: Treats gram-positive and gram-negative organisms and mycoplasmal, chlamydial, and rickettsial infections. Inhibits bacterial protein synthesis by binding with 30S and possibly 50S ribosomal subunit(s). Also useful for its anti-inflammatory effects.
Tetracycline derivatives with their anti-inflammatory side effects have been helpful in treating steatocystoma suppurativa.
Clinical Context: Synthetic 13-cis isomer of naturally occurring tretinoin (trans -retinoic acid). Both agents are related structurally to beta-carotene. Decreases sebaceous gland size and sebum production. May inhibit sebaceous gland differentiation and abnormal keratinization.
Only those physicians experienced or trained in use should prescribe. A US Food and Drug Administration–mandated registry is now in place for all individuals prescribing, dispensing, or taking isotretinoin. For more information on this registry, see iPLEDGE. This registry aims to further decrease the risk of pregnancy and other unwanted and potentially dangerous adverse effects during a course of isotretinoin therapy.
Decrease size of sebaceous glands and decrease their sebum production. Retinoids also have anti-inflammatory effects by decreasing production of certain leukotrienes.
The prognosis for patients with steatocystoma multiplex is excellent. No reports describe malignant transformation within these benign adnexal tumors.