```html

Hexagonal Rash

What is Hexagonal Rash?

A hexagonal rash is a skin eruption made up of distinct, six‑sided (hexagon‑shaped) lesions. The pattern can appear as a single large hexagon, a cluster of smaller hexagons, or a “honeycomb” arrangement that spreads across the trunk, limbs, or face. Although the shape itself is unusual, the rash is not a disease—rather, it is a visual clue that points to an underlying condition.

Hexagonal lesions are often sharply demarcated, slightly raised, and may be red, pink, violaceous, or dusky depending on the cause. Because the skin’s natural tension lines (Langer’s lines) sometimes follow a polygonal geometry, certain inflammatory or infectious processes can naturally produce a hexagonal outline.

In clinical practice the term is most commonly associated with erythema chronicum migrans (the “bull’s‑eye” rash of early Lyme disease) when it takes on a polygonal configuration, and with certain drug eruptions or contact dermatitis that form geometric patterns.

Sources: Mayo Clinic <sup>1</sup>, CDC <sup>2</sup>, NIH Dermatology Handbook <sup>3</sup>

Common Causes

• Lyme disease (early disseminated stage) – the spirochete Borrelia burgdorferi can produce a hexagonal or annular erythema.
• Granuloma annulare – a benign, self‑limited skin condition that may form ring‑shaped or polygonal plaques.
• Psoriasis (guttate or plaque type) – lesions can coalesce into hexagonal patterns, especially on the trunk.
• Contact dermatitis – exposure to a patterned irritant (e.g., woven fabric, repeated pressure) can create geometric patches.
• Drug eruption (fixed drug reaction) – certain medications trigger sharply demarcated, often polygonal erythema.
• Cutaneous sarcoidosis – granulomatous lesions may assume a honeycomb configuration.
• Vasculitic disorders (e.g., leukocytoclastic vasculitis) – palpable purpura can merge into polygonal patches.
• Fungal infections (tinea corporis) – the peripheral edge may appear angular when the fungal growth follows skin creases.
• Angioedema‑related urticarial plaques – chronic urticaria sometimes settles into polyhedral shapes after repeated scratching.
• Neurocutaneous syndromes (e.g., tuberous sclerosis) – although rare, some patients develop hypopigmented hexagonal macules.

Sources: Cleveland Clinic <sup>4</sup>, WHO Skin NTD Guidelines <sup>5</sup>

Associated Symptoms

The presence of a hexagonal rash often coincides with additional systemic or local signs that help narrow the diagnosis:

• Fever, chills, or flu‑like malaise (common in Lyme disease and vasculitis).
• Joint pain or swelling – especially of the knees and ankles (Lyme arthritis, psoriatic arthritis).
• Muscle aches (myalgias) or generalized fatigue.
• Itching or burning sensation at the rash site (contact dermatitis, drug reaction).
• Headache, neck stiffness, or neurological deficits (early disseminated Lyme disease).
• Painful nodules or subcutaneous lumps (granuloma annulare, sarcoidosis).
• Swollen lymph nodes proximal to the rash.
• Scale or fine crusting on the edge of the lesions (tinea corporis, psoriasis).

When to See a Doctor

A hexagonal rash itself is often benign, but the following warning signs should prompt prompt medical evaluation:

• Rapid expansion of the rash within hours or days.
• Fever ≥ 101 °F (38.3 °C) or persistent malaise.
• Severe itching, pain, or burning that interferes with sleep.
• Joint swelling, especially if asymmetrical.
• Neurologic symptoms – facial droop, confusion, numbness, or vision changes.
• History of recent tick bite or outdoor exposure in endemic areas.
• New medication started within the past 2 weeks (possible drug reaction).
• Signs of infection – pus, increasing redness, or warmth.

If any of these are present, seek care within 24 hours or sooner for acute neurological or systemic signs.

Diagnosis

Diagnosing the root cause of a hexagonal rash involves a stepwise approach that combines history, physical examination, and targeted tests.

1. Detailed History

• Onset and progression of the rash.
• Recent travel, outdoor activities, or tick exposure.
• Medication list (including over‑the‑counter and herbal).
• Contact with potential irritants (new soaps, detergents, clothing).
• Associated systemic symptoms.

2. Physical Examination

• Measure size, shape, border, color, and texture of lesions.
• Check for scaling, pustules, ulceration, or central clearing.
• Examine lymph nodes, joints, and neurologic status.

3. Laboratory & Imaging Studies

• Serology for Lyme disease – ELISA followed by Western blot if positive.
• Complete blood count (CBC) & ESR/CRP – assess inflammation.
• Skin scraping or biopsy – for fungal culture, histopathology (psoriasis, sarcoidosis, vasculitis).
• Patch testing – if contact dermatitis is suspected.
• Autoimmune panel – ANA, ANCA when vasculitis is considered.
• Imaging (X‑ray, MRI) – if joint involvement or neurologic complications are present.

4. Differential Diagnosis Checklist

Condition	Key Clues
Lyme disease	Tick bite, expanding erythema, flu‑like symptoms, positive serology.
Granuloma annulare	Asymptomatic, smooth, firm plaques, often on hands/feet.
Psoriasis	Silvery scale, nail changes, family history.
Contact dermatitis	Exposure to irritant, itching, improvement with avoidance.
Drug eruption	Temporal relation to new drug, fixed location, possible systemic symptoms.

Treatment Options

Treatment is tailored to the underlying cause. Below are evidence‑based options for the most common etiologies.

Lyme Disease

• Doxycycline 100 mg PO twice daily for 10–21 days (adults). For children <8 years or pregnant women, use amoxicillin or cefuroxime.
• Adjunctive NSAIDs for joint pain.
• Early treatment prevents progression to neuro‑ or carditis.

Granuloma Annulare

• Observation – many lesions resolve spontaneously within 2 years.
• Topical or intralesional corticosteroids for symptomatic lesions.
• For extensive disease, phototherapy (PUVA) or systemic agents (hydroxychloroquine) may be considered.

Psoriasis

• High‑potency topical steroids or vitamin D analogs (calcipotriene).
• Phototherapy (narrow‑band UVB) for widespread plaques.
• Biologic agents (e.g., secukinumab) for moderate‑to‑severe disease.

Contact Dermatitis

• Avoid the offending allergen or irritant.
• Cool compresses and emollients to restore barrier function.
• Topical corticosteroids (medium‑strength) for inflammatory flares.

Drug Eruption

• Immediate discontinuation of the suspected medication.
• Antihistamines for itching.
• Short course of systemic corticosteroids (prednisone 0.5 mg/kg) if lesions are extensive or bullous.

Fungal Infection (Tinea corporis)

• Topical azoles (clotrimazole, terbinafine) BID for 2–4 weeks.
• Oral therapy (terbinafine 250 mg daily) for extensive disease.

Vasculitis

• Identify and treat the trigger (infection, drug).
• Systemic steroids (prednisone 0.5–1 mg/kg) for moderate disease.
• Immunosuppressants (azathioprine, cyclophosphamide) for severe or organ‑threatening cases.

General Home Care Measures

• Keep the area clean with mild soap and lukewarm water.
• Use fragrance‑free moisturizers to prevent dryness.
• Avoid scratching – apply cool compresses or calamine lotion.
• Wear loose, breathable clothing to reduce friction.

Prevention Tips

• Tick prevention – wear long sleeves, use EPA‑registered repellents (e.g., DEET or picaridin), and perform daily tick checks in endemic areas.
• Skin barrier care – moisturize daily, especially after bathing.
• Avoid known irritants – switch to hypoallergenic detergents and fabrics.
• Medication review – discuss any new drug with your provider, particularly antibiotics, anticonvulsants, or NSAIDs, which are common culprits for drug eruptions.
• Prompt treatment of fungal infections – keep feet dry, change socks regularly, and treat athlete’s foot early.
• Vaccinations & health maintenance – maintaining overall immune health reduces the risk of opportunistic skin infections.

Emergency Warning Signs

References:
1. Mayo Clinic. “Lyme disease.” https://www.mayoclinic.org/diseases-conditions/lyme-disease/symptoms-causes/syc-20374671 (accessed July 2026).
2. Centers for Disease Control and Prevention. “Tickborne Diseases of the United States.” https://www.cdc.gov/tickborne/index.html (accessed July 2026).
3. National Institutes of Health. “Dermatology: Clinical Overview.” https://www.ncbi.nlm.nih.gov/books/NBK279394/ (accessed July 2026).
4. Cleveland Clinic. “Granuloma Annulare.” https://my.clevelandclinic.org/health/diseases/21912-granuloma-annulare (accessed July 2026).
5. World Health Organization. “Guidelines for the Diagnosis and Management of Skin NTDs.” https://www.who.int/publications/i/item/9789241549665 (accessed July 2026).

```