Smooth Papules on the Left Hand

The Diagnosis: Adult Colloid Milium

A 4-mm punch biopsy was performed and histopathologic evaluation revealed collections of amorphic eosinophilic material and fissures in the papillary dermis with sparing of the dermoepidermal junction, indicating adult colloid milium (Figure 1).

Figure 1. Histopathology revealed collections of amorphic eosinophilic material and fissures in the papillary dermis with sparing of the dermoepidermal junction (H&E, original magnification ×40).

Adult colloid milium is an uncommon condition with grouped translucent to whitish papules that present on sun-exposed skin on the hands, face, neck, or ears in middle-aged adults.¹ It has been associated with petrochemical exposure, tanning bed use, and excessive sun exposure. Our patient had a history of sun exposure, specifically to the left hand while driving. This condition is widely thought to be a result of photoinduced damage to elastic fibers and may potentially be a popular variant of severe solar elastosis.² Due to vascular fragility, trauma to these locations often will result in hemorrhage into individual lesions, as observed in our patient (Figure 2).

Figure 2. Few hemorrhagic papules from mechanical trauma within a large collection of flesh-colored to translucent, dome-shaped papules on the left hand.

Adult colloid milium is diagnosed clinically and may mimic lichen or systemic amyloidosis, syringomas, lipoid proteinosis, molluscum contagiosum, steatocystoma multiplex, and sarcoidosis.²

Biopsy often is helpful in determining the diagnosis. Histopathology reveals amorphous eosinophilic deposits with fissures in the papillary dermis. These deposits are thought to be remnants of degenerated elastic fibers. Stains often are helpful, as the deposits are weakly apple-green birefringent on Congo red stain and are periodic acid-Schiff and thioflavin T positive. Laminin and type IV collagen stains are negative with adult colloid milium but are positive with amyloidosis and lipoid proteinosis.³ Electron microscopy also may help distinguish between amyloidosis and adult colloid milium, as these conditions may have a similar histologic appearance.

Treatment has not proven to be consistently helpful, as cryotherapy and dermabrasion have been the mainstay of treatment, often with disappointing results.⁴ Laser treatment has been shown to be of some benefit in treating these lesions.²