Hypomelanotic macule (ash-leaf macule)
Ash-leaf macule; ash-leaf spot; hypopigmented macule of tuberous sclerosis; congenital hypomelanosis
Hypomelanotic macules are congenital or early-childhood hypopigmented patches that are present in approximately 90% of patients with tuberous sclerosis complex (TSC) and are usually the earliest detectable cutaneous sign. Classical lance-ovate ("ash-leaf") shape with a tapered end accounts for ~ 50% of TSC macules. ≥ 3 macules of ≥ 5 mm diameter is a major diagnostic criterion of TSC (2012 consensus, updated 2021). They are usually present at birth or appear in infancy; Wood's lamp examination accentuates the pale patches and is invaluable in pale-skinned infants where lesions may be subtle. Hypomelanotic macules are functionally and cosmetically benign but their identification is critical for TSC diagnosis and surveillance.
Clinical features
- Hypopigmented (not depigmented) macule with poorly-demarcated borders — Wood's lamp emphasises the patch.
- Common shapes:
- Lance-ovate or "ash-leaf" — tapered at one or both ends (50%).
- Polygonal / "thumbprint" (40%).
- "Confetti" macules — multiple tiny hypopigmented dots, < 5 mm, on shins / forearms (~ 30% of TSC adults).
- Sites — any but typically trunk, buttocks, lower limbs.
- Present at birth or appear in infancy; persist lifelong.
- White lock of hair (poliosis) — a hypomelanotic feature of the scalp.
Tuberous sclerosis complex
- Hypomelanotic macules are one of the major diagnostic criteria of TSC (2021 International Consensus Conference):
- Hypomelanotic macules — ≥ 3, at least 5 mm diameter — is a major criterion.
- Confetti skin lesions are a minor criterion.
- Other major skin features — facial angiofibromas (≥ 3), shagreen patch, ungual fibromas (≥ 2).
- Definite TSC diagnosis — two major OR one major + two minor criteria OR pathogenic TSC1 / TSC2 germline variant.
- Refer for TSC evaluation if ≥ 3 hypomelanotic macules of ≥ 5 mm are identified:
- Family history, seizures, developmental delay, autism.
- Skin examination — facial angiofibromas, shagreen patch, ungual fibromas.
- Eye examination — retinal hamartomas.
- Brain MRI — tubers, subependymal nodules, SEGA.
- Cardiac echo — rhabdomyomas (infant); resolve over time.
- Renal ultrasound — angiomyolipomas.
- Lung CT in women — lymphangioleiomyomatosis (LAM).
- Genetic testing — TSC1 / TSC2.
- See tuberous sclerosis for management.
Differential — congenital hypopigmentation
- Naevus depigmentosus — congenital, stable; segmental or focal; no syndromic association.
- Piebaldism — bilateral, symmetric, anterior; white forelock; KIT mutation.
- Vitiligo — acquired complete depigmentation; sharp border; autoimmune.
- Hypomelanosis of Ito (incontinentia pigmenti achromians) — segmental hypopigmentation along Blaschko lines; neurological / musculoskeletal anomalies.
- Post-inflammatory hypopigmentation — preceding eczema / trauma.
- Pityriasis alba — atopic; ill-defined.
References
- Northrup H et al. Updated international tuberous sclerosis complex diagnostic criteria and surveillance and management recommendations. Pediatr Neurol; 2021.
- Krueger DA et al. Tuberous sclerosis complex — surveillance and management. Pediatr Neurol; 2013.
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