hypopigmentation

There are multiple potential sites for dysfunction in the formation of melanin pigment in basal melanocytes. Attempts have been made to categorize the various diseases with hypopigmentation on the basis of their presumed pathogenesis. The following categories may be considered.

 1. Abnormal migration/differentiation of melanoblasts

• piebaldism
• Waardenburg syndrome
• Woolf syndrome

 2. Destruction of melanocytes

• vitiligo
• Vogt–Koyanagi–Harada syndrome
• chemical leukoderma

 3. Reduced tyrosinase activity

• oculocutaneous albinism type 1A
• phenylketonuria(?)

 4. Abnormal structure of melanosomes

• ‘ash leaf spots’ of tuberous sclerosis
• Chediak–Higashi disease
• progressive macular hypomelanosis

 5. Reduced melanization and/or numbers of melanosomes

• albinism (other tyrosinase-positive variants)
• Griscelli disease
• Elejalde disease
• idiopathic guttate hypomelanosis
• hypomelanosis of Ito
• ‘ash leaf spots’
• pityriasis versicolor (tinea versicolor)
• nevus depigmentosus

 6. Reduced transfer to keratinocytes (Increased degradation of melanosomes within melanocytes may also apply in some conditions listed in this section.)

• nevus depigmentosus
• pityriasis alba
• postinflammatory leukoderma
• pityriasis versicolor (tinea versicolor)
• Chediak–Higashi disease

 7. Abnormal vasculature: nevus anemicus

Types

 acquired hypopigmentation
 genetic hypopigmentation

References

 A review of genetic disorders of hypopigmentation: lessons learned from the biology of melanocytes. Dessinioti C, Stratigos AJ, Rigopoulos D, Katsambas AD. Exp Dermatol. 2009 Sep;18(9):741-9. PMID: 19555431