What is the most likely diagnosis for non-itchy, dry, flaky skin on the lower lash line of one eye?

Most Likely Diagnosis: Seborrheic Blepharitis

The most likely diagnosis for non-itchy, dry, flaky skin on the lower lash line of one eye is unilateral seborrheic blepharitis, though the unilateral presentation warrants careful evaluation to exclude malignancy, particularly sebaceous cell carcinoma. 1

Primary Diagnostic Considerations

Seborrheic Blepharitis

• Presents with scaling, flaking, and dry skin along the eyelid margin, which matches the described presentation 1
• Characterized by collarettes (cylindrical debris) at the base of eyelashes and abnormal deposits on the eyelid margin 1
• Frequently associated with seborrheic dermatitis, with 95% of patients with seborrheic blepharitis also having seborrheic dermatitis elsewhere 1
• Can present asymmetrically or unilaterally, though bilateral involvement is more common 1

Critical Red Flag: Unilateral Presentation

• Chronic blepharitis unresponsive to therapy with unilateral involvement should raise suspicion for carcinoma, particularly sebaceous cell carcinoma 1, 2
• Additional concerning features include focal lash loss (ciliary madarosis), loss of normal eyelid margin anatomy, and unifocal recurrent chalazia 1, 3
• Eyelid biopsy is indicated for marked asymmetry, resistance to therapy, or persistent unilateral disease 1, 2

Alternative Diagnoses to Consider

Demodex Blepharitis

• Presents with cylindrical dandruff or sleeves at the eyelash base, which is pathognomonic for Demodex infestation 1, 4
• Found in 30-68% of patients with chronic blepharitis, particularly in older patients 1
• The collarettes (waste product of Demodex mites) are a key diagnostic feature 4

Atopic Dermatitis

• Highly associated with blepharitis in both children and adults 1
• Typically presents with itching, which is absent in this case, making it less likely 5

Psoriasis

• Can be associated with blepharitis and presents with scaling 1
• Usually involves other body areas with characteristic silvery scales

Diagnostic Approach

Initial Examination

• Evaluate the eyelid margin for vascularization, hyperemia, abnormal deposits at the base of eyelashes, and scaling 1, 2
• Assess for meibomian gland dysfunction by applying pressure to the lower eyelid to express secretions 1, 2
• Look specifically for collarettes at the lash base, which indicate Demodex infestation 1, 4
• Examine for focal lash loss, which may suggest malignancy 1, 3

When to Pursue Further Testing

• Microscopic evaluation of epilated eyelashes for Demodex mites if cylindrical dandruff is present 1, 2
• Eyelid biopsy is mandatory if there is marked asymmetry, resistance to standard therapy, or unifocal recurrent chalazia 1, 2
• Before biopsy for suspected sebaceous carcinoma, consult with pathology regarding frozen sections and mapping for pagetoid spread 1

Management Strategy

First-Line Treatment

• Warm compresses and eyelid hygiene form the mainstay of treatment, applied to the affected lower eyelid margin 2, 6
• Gentle eyelid cleansing with diluted baby shampoo or commercial eyelid cleansers 6, 7
• This regimen must be continued long-term as blepharitis is a chronic condition with exacerbations and remissions 2, 6

Adjunctive Therapies

• Topical antibiotics to reduce bacterial load if bacterial involvement is suspected 2, 6
• Topical corticosteroids for marked inflammation, though use cautiously and short-term 2, 6
• Preservative-free artificial tears if concurrent dry eye is present 8

When to Escalate Care

• Refer to ophthalmology if symptoms persist beyond 2-3 weeks despite conservative management 3
• Immediate ophthalmology referral for unilateral disease unresponsive to initial therapy due to malignancy risk 1, 3, 2
• Consider Demodex-specific therapy (lotilaner ophthalmic solution 0.25%) if collarettes are present and standard treatment fails 4

Common Pitfalls

• Dismissing unilateral presentation without proper evaluation for malignancy is the most critical error 1, 3, 2
• Failing to recognize that blepharitis is chronic and requires long-term management, not a cure 2
• Not evaluating for underlying dermatologic conditions like seborrheic dermatitis or rosacea 1, 8
• Overlooking medication history, particularly isotretinoin or dupilumab, which can induce blepharitis 1, 2