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D8 Dermatology
Common Skin Lesions
Toronto Notes 2019
DDx of Hyperpigmented Macules
• Purpura (e.g. solar, ASA, anti-coagulants, steroids, hemosiderin stain)
• Post-inflammatory
• Melasma
• Melanoma
• Fixed drug eruption
Pigmented Lesions
CONGENITAL NEVOMELANOCYTIC NEVI (CNMN)
Clinical Presentation
• sharplydemarcatedpigmentedpapuleorplaquewithregularborders±coarsehairs
• classifiedbysize:small(<1.5cm),medium(M1:1.5-10cm,M2:>10-20cm),large(L1:>20-30cm,L2
>30-40 cm), giant (G1: >40-60 cm, G2: >60 cm)
• maybesurroundedbysmallersatellitenevi
Pathophysiology
• nevomelanocytesinepidermis(clusters)anddermis(strands)
Epidemiology
• presentatbirthordevelopsinearlyinfancytochildhood
• malignanttransformationisrare(1-5%)andmorecorrelatedwithsizeofthelesion • neurocutaneousmelanosiscanoccuringiantCNMN(melanocytesintheCNS)
Management
• takeabaselinephotoandobservelesionforchangeinshape,colour,orsizeoutofproportionofgrowth • surgicalexcisionifsuspicious,duetoincreasedriskofmelanoma
• MRIifsuspiciousforneurologicalinvolvement
OTHER CONGENITAL PIGMENTED LESIONS
Table 4. Comparison of Other Congenital Pigmented Lesions
Other Nevi
• Halo nevus: often a typical appearing nevus
surrounded by a ring of depigmentation; not rare in children; uncommonly associated with vitiligo; no treatment required unless irregular colour or borders
• Blue nevus: round to oval macule/papule with homogenous blue to blue-black colour; often appears in childhood and late adolescence; no treatment required unless atypical features are noted
Café-au-lait Macule
Speckled Lentiginous Nevus (nevus spilus)
Dermal Melanocytosis (historically known as Mongolian Spot)
Clinical Presentation
Flat light brown lesions with smooth or jagged borders
Brown pigmented macular background (café- au-lait macule-like) with dark macular or papular speckles
Congenital grey- blue solitary or grouped macules commonly on lumbosacral area
Pathophysiology
Areas of increased melanogenesis
Increased melanocyte concentration
Ectopic melanocytes in dermis
Epidemiology
6 or more is suggestive of neurofibromatosis type I
Also associated with McCune- Albright syndrome
Risk of melanoma similar to that of a CNMN of the same size
99% occurs
in Asian and Indigenous infants
Differential Diagnosis
Flat congenital melanocytic nevus, speckled lentiginous nevus
Café-au-lait macule, agminated lentigines, Becker’s nevus
Ecchymosis
Clinical Course and Management
Enlarge in proportion to the child
No effective treatment
Usually the light macular background is present at birth
and speckles develop over time Management is similar to that of CNMNs
Usually fades in early childhood but may persist into adulthood
ACQUIRED NEVOMELANOCYTIC NEVI
Clinical Presentation
• commonmole:wellcircumscribed,round,uniformlypigmentedmacules/papules<1.5cm • averagenumberofmolesperperson:18-40
• 3stagesofevolution:junctionalNMN,compoundNMN,anddermalNMN
Table 5. Evolution of Acquired Nevomelanocytic Nevi
Type
Junctional Compound
Dermal
Age of Onset
Childhood
Majority progress to compound nevus
Any age
Adults
Clinical Presentation
Flat, regularly bordered, uniformly tan-dark brown, sharply demarcated macule
Domed, regularly bordered, smooth, round, tan-dark brown papule
Face, trunk, extremities, scalp
NOT found on palms or soles
Soft, dome-shaped, skin-coloured to tan/brown papules or nodules
Sites: face, neck
Histology
Melanocytes at dermal-epidermal junction above basement membrane
Melanocytes at dermal-epidermal junction; migration into dermis
Melanocytes exclusively in dermis