Hyaline

Hyaline (from Greek hyalos = glass) is the term used to describe extracellular deposits of homogeneous, strongly eosinophilic protein substances through which light shines during microscopy.

Hyaline may resemble amyloid; however, in contrast to amyloid, it is a heterogeneous protein substance (e.g. hyaline degeneration of collagen fibres, "hyaline corpuscles or so-called cytoid bodies" in lupus erythematosus or in lichen planus).

There are different types of hyaline:

• Connective tissue hyaline e.g. degenerated collagen
• Epithelial hyaline e.g. hyaline corpuscles in lichen planus (see also Russel corpuscles)
• Hyaline plaques: e.g. in the peritoneum, the pleura or the spleen capsule ("sugar icing spleen")
• Hyaline membranes: e.g. in the alveoli of the lungs
• Haematogenic hyaline e.g. plasma proteins, old macrothrombi, hyaline
• Vascular hyaline e.g. plasma proteins, which are deposited on the walls and in the lumens of small vessels (arterioles and capillaries) or in the kidney (arteriolosclerosis).

In dermatology, the disease group of "hyalinoses" is so named because it is characterized by hyaline deposits in skin and mucous membranes (hyalinosis cutis et mucosae).