ANSWERS TO QUIZ

Innumerable Yellow Papules Predominantly Involving the Forehead: A Commentary

Diagnosis: Steatocystoma multiplex

The diagnosis is steatocystoma multiplex. Histo- pathological examination revealed 2 dermal cysts in the biopsy specimen, both lined by a thin stratified squamous epithelium without a granular layer. The cyst walls showed an eosinophilic, corrugated cuticle, and sebaceous lobules composed of clear cells were attached to or closely associated with the cyst walls (Fig. 1C, D). These findings were consistent with steatocystoma multiplex (1).

Steatocystoma multiplex is a benign disorder of the pilosebaceous unit characterized by multiple sebum-containing dermal cysts. It usually develops in adolescence or early adulthood, and the classic distribution involves the trunk, axillae, groin, and proximal extremities (2). Although facial involvement can occur, predominant facial localization is uncommon compared with the classic truncal distribution. Clinically, lesions are typically smooth, skin-colored to yellowish papules or small nodules, and may therefore be difficult to recognize when they arise at unusual sites.

In the present case, lesions were confined to the face and were strikingly concentrated on the forehead, with only minimal involvement of the nose. Moreover, they presented as innumerable small yellow papules rather than as scattered cystic papules or nodules. This pattern created a clinical impression different from the classic form of steatocystoma multiplex and broadened the differential diagnosis substantially. The patient’s age further increased the diagnostic difficulty. Steatocystoma multiplex is generally thought of as a disease of younger patients, whereas our patient first noticed the eruption in her early 60s (3). In an older adult with multiple yellow papules on the forehead, clinicians are more likely to first suspect acquired entities such as sebaceous hyperplasia, milia, syringoma or xanthomatous disorders.

Although steatocystoma multiplex is often sporadic, familial cases with autosomal dominant inheritance have been reported and are associated with mutations in KRT17. KRT17 is expressed in the nail bed, hair follicles and sebaceous glands, which may explain the overlap between steatocystoma multiplex and pachyonychia congenita (4). In the present case, there was no relevant family history and no abnormalities of the nails or teeth, making a syndromic inherited form less likely, although genetic testing was not performed.

Dermoscopy provided a limited but useful clue. Our patient showed homogeneous yellow structureless areas without central umbilication or crown vessels. This pattern favoured a cystic lesion over sebaceous hyperplasia, in which a central dell and surrounding crown vessels are more typical (1, 5). However, dermoscopic findings alone are not diagnostic, and histopathological examination remained essential for definitive diagnosis.

The differential diagnosis includes sebaceous hyperplasia, eruptive vellus hair cysts, syringoma, milia and xanthogranulomatous disorders (5, 6, 7). Sebaceous hyperplasia is a particularly important clinical mimic in elderly patients because it commonly presents as yellow papules on the forehead; histologically, however, it shows enlarged sebaceous lobules around a dilated duct rather than a true cyst lined by squamous epithelium with attached sebaceous lobules. Eruptive vellus hair cysts can also present as multiple small papules, but they characteristically contain laminated keratin and numerous vellus hairs in the cyst cavity. Syringoma shows eccrine ductal proliferation in a fibrous stroma, and milia are superficial keratin-filled cysts without sebaceous differentiation. Xanthogranulomatous lesions show dermal histiocytic infiltration, often with Touton giant cells, rather than a sebum-containing cyst.

Previously reported facial or forehead-predominant cases are summarized in Table I. These reports indicate that a facial variant of steatocystoma multiplex is not unprecedented. Nishimura et al. described a facial papular variant involving the forehead, temple and periauricular region (8). Requena et al. reported a face-confined case, and Ahn et al. later described steatocystoma multiplex localized only in the face (9, 10). Additional reports have included multiple papules on the scalp and forehead, facial disease associated with pilar cyst and bilateral preauricular sinus, late-onset facial disease in an elderly woman, a face-and-scalp-limited case and a recent frontal localized case (Table I). Taken together, the literature supports a recognizable facial/forehead-predominant variant but also suggests heterogeneity in age, associated sites and lesion burden.

Table I. Previously reported cases of facial or forehead-predominant steatocystoma multiplex.

What appears most notable in our patient is not merely the site, but the extraordinary lesional burden. While facial cases have been reported, our patient showed an exceptional number of small yellow papules densely aggregated on the forehead, with only slight nasal involvement and no lesions on the trunk, axillae, groin or extremities. This density produced a striking clinical picture and strongly invited alternative diagnoses. In that sense, the present case is educational less because it establishes a new anatomical variant than because it demonstrates how an established but uncommon variant may masquerade as more familiar yellow papular facial disorders.

This case also has practical implications for management. When lesions are few, surgical excision or other localized procedures may be feasible. In contrast, when innumerable papules involve a cosmetically sensitive facial area, destructive or surgical approaches become more difficult, and correct diagnosis becomes especially important before treatment planning. Even when therapy is conservative, diagnostic confirmation can help avoid repeated unnecessary biopsies or concern for xanthomatous, sebaceous or histiocytic disorders. Treatment reviews describe a range of options, including minimally invasive procedures, laser-based approaches and isotretinoin in selected contexts, but cosmetic burden and lesion number substantially influence feasibility.

In summary, we present a forehead-predominant facial variant of steatocystoma multiplex in a 66-year-old woman with innumerable yellow papules confined to the face. Although facial and frontal localized variants have been reported, the present case is notable for its unusually high lesion burden and the resulting broad clinical differential diagnosis. Awareness that steatocystoma multiplex may present in this manner is important, particularly when evaluating multiple yellow papules on the forehead of an older patient.

REFERENCES

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