Mastocytosis Eyes: Insights into Allergic Eye Disease

Mastocytosis is a rare condition marked by excessive mast cell accumulation, which drives allergic and inflammatory responses. While often linked to systemic symptoms or skin involvement, it can also affect the eyes, causing discomfort and vision issues.

Ocular Manifestations

Mastocytosis triggers various eye symptoms due to mast cell buildup in conjunctival and periorbital tissues. Patients frequently report persistent itching, redness, and grittiness, often mistaken for allergic conjunctivitis. Unlike seasonal allergies, these symptoms persist year-round and vary in severity with mast cell activation. Chronic irritation can cause conjunctival hyperemia, where engorged blood vessels create a perpetually inflamed appearance.

Beyond surface discomfort, mastocytosis can impact deeper ocular structures. The cornea may suffer recurrent epithelial erosions from proteolytic enzymes released by mast cells, causing pain and temporary visual disturbances. Chronic inflammation can lead to keratoconjunctivitis, marked by persistent dryness and corneal irregularities, increasing the risk of secondary infections that threaten vision.

Periorbital tissues are also affected. Some individuals experience eyelid edema due to increased vascular permeability, leading to puffiness that mimics angioedema. Severe cases may cause recurrent swelling and mechanical ptosis, where the upper eyelid droops and obstructs vision. Histamine release can also trigger ocular vasodilation, potentially increasing intraocular pressure and posing a long-term glaucoma risk.

Mast Cell Activity In Eye Tissues

Mast cells are concentrated in the conjunctiva, eyelid dermis, and periorbital connective tissues, playing a central role in inflammation. In mastocytosis, these cells release excessive histamine, tryptase, and prostaglandins, disrupting ocular homeostasis and increasing sensitivity to environmental triggers. The conjunctival epithelium suffers from frequent mast cell degranulation, leading to persistent vasodilation and inflammation. Over time, this weakens the conjunctival barrier, making the eye more vulnerable to irritants and allergens.

Despite its immune-privileged status, the cornea is also affected. Proteolytic enzymes such as chymase and tryptase degrade the extracellular matrix, weakening corneal epithelium stability. This can cause recurrent epithelial erosions, compromising the cornea’s smooth refractive surface. Inflammatory cytokines like interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) perpetuate stromal inflammation, potentially leading to corneal thinning and irregular astigmatism. These changes impair vision and heighten infection risk in individuals with frequent epithelial disruptions.

Mast cell hyperactivity can also impact deeper ocular structures, including the uveal tract. Elevated histamine and leukotrienes in the aqueous humor suggest mast cell activity extends beyond surface layers. This biochemical shift may affect intraocular pressure regulation, increasing the risk of ocular hypertension. While the link between mastocytosis and glaucoma remains under study, chronic mast cell degranulation is associated with trabecular meshwork dysfunction, potentially impairing fluid outflow and contributing to optic nerve damage.

Diagnostic Procedures

Diagnosing ocular mastocytosis requires clinical examination, patient history, and specialized testing to distinguish it from other inflammatory or allergic eye conditions. Symptoms often overlap with allergic conjunctivitis or dry eye disease, necessitating thorough assessment. Slit-lamp biomicroscopy helps detect conjunctival hyperemia, corneal irregularities, and periorbital edema indicative of mast cell overactivity. Fluorescein staining can reveal microerosions on the cornea, signaling recurrent epithelial damage linked to mast cell activity.

Conjunctival cytology provides a targeted approach for detecting mast cell proliferation. Impression cytology, a non-invasive technique, collects superficial conjunctival cells for microscopic analysis, where toluidine blue or Giemsa staining highlights mast cell density. Increased mast cell counts, particularly without seasonal allergen exposure, suggest mastocytosis-related ocular involvement. In some cases, a conjunctival biopsy may be necessary to assess deeper tissue layers when chronic inflammation raises concerns about long-term complications.

Laboratory tests refine the diagnosis by measuring systemic markers of mast cell activation. Elevated serum tryptase levels indicate systemic mastocytosis and help confirm ocular involvement. Urinary histamine metabolites, such as N-methylhistamine, may also be assessed to monitor mast cell degranulation. These biomarkers differentiate mastocytosis from other allergic or inflammatory eye diseases. Skin or bone marrow biopsies may be considered in patients with systemic symptoms, providing a broader diagnostic context for ocular management.

Relation To Systemic Categories

Mastocytosis manifests in different systemic forms, each impacting ocular health uniquely. The two main classifications—cutaneous and systemic mastocytosis—vary in mast cell involvement, with systemic types often causing more severe eye complications. Indolent systemic mastocytosis (ISM), the most common form, involves mast cell infiltration in organs such as the gastrointestinal tract, bone marrow, and skin. Ocular symptoms in ISM are typically milder but can worsen with stress, temperature changes, or allergens. More aggressive forms, such as systemic mastocytosis with an associated hematologic neoplasm (SM-AHN), may lead to persistent ocular inflammation due to widespread mast cell proliferation.

The KIT D816V mutation, present in most systemic cases, drives uncontrolled mast cell expansion and chronic ocular inflammation through sustained histamine and cytokine release. Patients with highly elevated tryptase levels often experience more severe systemic involvement, correlating with refractory ocular symptoms unresponsive to standard antihistamines or mast cell stabilizers. Additionally, individuals with mast cell activation syndrome (MCAS), a condition distinct from mastocytosis but characterized by episodic mast cell degranulation, may exhibit similar eye symptoms without detectable mast cell accumulation.