[5][6] Fibromodulin is a 42kDa protein of a family of small interstitial leucine-rich repeat proteoglycans (SLRPs).

It can have up to four N-linked keratan sulfate chains attached to the core protein within the leucine-rich region.

[6] There is an age-dependent decline in the synthesis of keratan sulfate chains, so non-glycated forms of fibromodulin can accumulate in tissues such as cartilage.

Mice with the gene for fibromodulin knocked out (Fmod-/-) have very fragile skin[12] and abnormal tail and Achilles tendons.

The levels of lumican, a SLRP with one of the same collagen binding sites as fibromodulin, is increased 4 fold in the tail tendons of Fmod-knockout mice.