Figure 13-7 Chalazion. Granulomatous inflammation (epithelioid histiocytes and multinucleated giant cells) surrounds clear spaces formerly occupied by lipid (lipogranuloma).

Degenerations

Xanthelasma

Xanthelasmas are single or multiple soft yellow plaques occurring in the medial canthal region of the eyelids. Associated hyperlipoproteinemic states, particularly hyperlipoproteinemia types II and III, are present in 30%–40% of patients with xanthelasma. These eyelid xanthomas consist of collections of histiocytes with foamy lipid-laden cytoplasm distributed diffusely, often around blood vessels, within the dermis (Fig 13-8). Associated inflammation is minimal to nonexistent.

Amyloid

The term amyloid refers to a heterogeneous group of extracellular proteins that exhibit birefringence and dichroism under polarized light when stained with Congo red (see Chapter 5 and Fig 5-13). These features result from the 3-dimensional configuration of the proteins into a β-pleated sheet. Examples of proteins that may form amyloid deposits include

immunoglobulin light chain fragments (AL amyloid) in plasma cell dyscrasias

transthyretin mutations in familial amyloid polyneuropathy (FAP) types I and II (see Chapter 10) gelsolin mutations in FAP type IV (Meretoja syndrome [lattice corneal dystrophy type II])

Figure 13-8 A, Patient with prominent xanthelasma. Note the yellow papules on the medial aspect of the upper and lower eyelids. B, Note the foam cells (filled with lipid) surrounding a venule (asterisk). (Part A from External Disease and

Cornea: A Multimedia Collection. San Francisco: American Academy of Ophthalmology; 1994:slide 10.)

Amyloid within the skin of the eyelid is highly indicative of a systemic disease process, either primary or secondary, whereas deposits elsewhere in the ocular adnexa but not in the eyelid are more likely a localized disease process.

Amyloid deposits in the skin are usually multiple, bilateral, symmetric, waxy yellow-white nodules. The deposition of amyloid within blood vessel walls in the skin causes increased vascular fragility and often results in intradermal hemorrhages, accounting for the purpura seen clinically (Fig 13-9). On routine histologic sections, amyloid appears as an amorphous, eosinophilic extracellular deposit, usually within vessel walls but also in soft tissue and around peripheral nerves and sweat glands. Stains useful in demonstrating amyloid deposits include Congo red, crystal violet, and thioflavin T. Electron microscopy reveals the deposits to be composed of randomly oriented extracellular fibrils measuring 7–10 nm in diameter (Fig 10-11).

Other systemic diseases with eyelid manifestations are listed in Table 13-2.