Mastocytosis is a rare disorder characterized by the excessive accumulation of mast cells within various body tissues. These immune cells normally handle allergic responses and inflammation but proliferate abnormally and release chemical mediators. While the skin and internal organs are most commonly affected, the eyes can also be involved, leading to a range of symptoms and potential complications. Ocular involvement occurs across different forms of the disease, including both cutaneous and systemic mastocytosis.
Specific Ocular Manifestations
The clinical presentation of mastocytosis in the eye often mimics chronic allergic conjunctivitis, manifesting as persistent irritation and discomfort. Patients frequently report intense ocular itching, excessive tearing, and redness. This constant irritation often leads to a diagnosis of dry eye disease, which is a common finding in individuals with mastocytosis.
The disease can affect multiple structures on the eye’s surface, including the conjunctiva, cornea, and eyelids. Inflammation of the eyelids, known as blepharitis, is a frequent occurrence, and chronic inflammation can lead to corneal involvement. A less common but distinct sign is the presence of mast cell tumors, or mastocytomas, which appear as visible lesions on the eyelids or conjunctiva.
More severe, though rare, presentations involve deeper eye structures like the orbit, uvea, and choroid. Infiltration of the orbit can cause symptoms like bilateral eyelid edema, exophthalmos (protrusion of the eyeball), and diplopia (double vision). Choroidal infiltration can cause acute or subacute vision changes and may require specific treatment to prevent vision loss. Blurry vision may result from surface damage, such as keratitis, or from deeper involvement within the eye.
The Underlying Mechanism of Ocular Involvement
The symptoms experienced in the eye result from mast cell infiltration and subsequent mediator release. Mast cells, normally resident in connective tissues, accumulate in abnormally high numbers within ocular tissues, particularly the conjunctiva. This accumulation is a hallmark of mastocytosis.
Once accumulated, these abnormal mast cells are prone to activation and degranulation, releasing their stored chemical arsenal. These mediators include inflammatory substances such as histamine, tryptase, prostaglandin D2 (PGD2), and leukotrienes. Histamine, a primary mediator, interacts with receptors on surrounding cells, directly causing the intense itching, redness, and swelling seen in the conjunctiva.
The continuous release of these chemicals sustains a chronic inflammatory state on the ocular surface. Tryptase, a protease released during degranulation, can contribute to tissue breakdown, potentially playing a role in the degeneration of structures like the retinal pigment epithelium.
Diagnosis and Treatment Strategies
Diagnosis of ocular mastocytosis begins with a thorough clinical examination, but confirmation requires specialized testing to identify mast cells or their products. A systemic workup is performed to determine if the ocular symptoms are isolated or part of broader systemic mastocytosis. This workup frequently includes measuring serum tryptase levels, which are often elevated in systemic disease.
If a localized lesion is present on the conjunctiva or eyelid, a biopsy may be performed. The tissue sample is stained with specialized techniques, such as Giemsa or toluidine blue, to identify the presence of mast cells. For deeper involvement, such as in the orbit or choroid, diagnosis relies on advanced imaging and ruling out other conditions, as a biopsy of these areas carries a high risk.
Treatment focuses on managing symptoms and controlling mast cell activity to prevent progressive tissue damage. The first line of management involves topical ophthalmic medications. These include topical mast cell stabilizers, such as cromolyn sodium, which inhibit the mast cell’s degranulation process.
Topical antihistamines are also used to block the effect of released histamine, providing relief from itching and redness. Many current treatments utilize dual-action drops, such as olopatadine, which combine both a mast cell stabilizer and an antihistamine. For severe inflammation that does not respond to these topical agents, a short course of topical corticosteroids may be prescribed, though their use must be managed carefully due to potential side effects. In cases of aggressive systemic mastocytosis with severe ocular infiltration, systemic therapies like midostaurin or cladribine are used to reduce the overall mast cell burden, leading to the resolution of ocular manifestations.