Can congenital or acquired nevi, such as port-wine stains or spider nevi, be considered in the differential diagnosis of a patient presenting with reddish-brown, telangiectatic macules and patches, associated with flushing, itching, and burning?

Differential Diagnosis: Nevi in Telangiectatic Skin Lesions

Telangiectasia macularis eruptiva perstans (TMEP), a rare form of cutaneous mastocytosis, should be added to your differential diagnosis, as it presents with reddish-brown telangiectatic macules and is associated with flushing, itching, and burning. 1

Primary Consideration: Telangiectasia Macularis Eruptiva Perstans (TMEP)

TMEP is the most relevant nevoid condition to consider in your differential diagnosis given the specific presentation of telangiectatic macules with associated symptoms. 1, 2

Clinical Features of TMEP

• Lesion characteristics: Red telangiectatic macules with a tan or brown background 1
• Associated symptoms: Episodic flushing, pruritus, and burning sensation 1, 2, 3
• Age presentation: Rarely presents in childhood; more common in adults 1, 3
• Darier's sign: Typically positive (urtication and flare upon rubbing lesions) 1

Distinguishing TMEP from Other Conditions

• Unlike congenital melanocytic nevi (CMN): TMEP lesions are telangiectatic rather than pigmented melanocytic proliferations 1, 2
• Unlike urticaria pigmentosa: TMEP specifically features prominent telangiectasia as the defining characteristic 1, 2
• Can coexist with urticaria pigmentosa: Some patients may have both presentations simultaneously 1

Congenital Melanocytic Nevi: Less Likely but Consider

While CMN should be in your differential, they are less likely to match your described presentation:

Why CMN is Less Compatible

• Color presentation: CMN typically present as shades of brown and black, though rare "amelanotic" red-pink papules can occur 1
• Telangiectasia: Not a primary feature of CMN 1
• Timing: CMN are present at birth or develop within the first year of life in 78-94% of cases 1
• Associated symptoms: Pruritus is common in larger CMN, but flushing and burning are not typical features 1

CMN Subtypes to Consider (if relevant)

• "Classic" CMN: Brown-black macules, papules, patches, or plaques 1
• Blue nevus: Gray-blue patches or plaques due to dermal melanocytes 1
• Nevus spilus: Brown patch with overlying darker macules 1

Port-Wine Stains: Unlikely in This Context

Acquired port-wine stains are extremely rare and do not typically present with the symptom complex you describe. 4

Why Port-Wine Stains Don't Fit

• Symptomatology: Port-wine stains (capillary malformations) are typically asymptomatic without flushing, itching, or burning 4
• Telangiectasia pattern: While vascular, they present as persistent red-purple patches rather than discrete telangiectatic macules 4
• Acquired forms: Rare and often associated with trauma, not spontaneous flushing episodes 4

Spider Nevi: Not Appropriate for This Differential

Spider nevi are not relevant to this differential diagnosis as they present as central arterioles with radiating vessels, not diffuse telangiectatic macules with patches. 5

Diagnostic Workup for TMEP

If TMEP is suspected based on clinical presentation:

Essential Investigations

• Skin biopsy: Shows increased mast cells in papillary dermis, aggregating around blood vessels 1
• Immunostaining: Tryptase and KIT staining to confirm mast cell proliferation 1
• Serum tryptase level: May be elevated, correlating with disease extent and symptom severity 1
• Darier's sign testing: Rub lesion to elicit urtication and flare 1

Additional Considerations

• Complete blood count: To evaluate for systemic involvement 1
• Bone marrow evaluation: Consider if tryptase significantly elevated or severe systemic symptoms present 1
• c-kit mutation analysis: Recommended in skin mast cells 1

Critical Clinical Pitfall

Do not confuse TMEP with generalized essential telangiectasia, which presents with progressive telangiectases but lacks the mast cell-mediated symptoms of flushing, pruritus, and positive Darier's sign. 6 Generalized essential telangiectasia is a diagnosis of exclusion and does not involve mast cell proliferation. 6