Albinism and Congenital Disorders of Pigmentation at a Glance
- Worldwide occurrence
- Albinism is usually inherited as a recessive trait, but other congenital disorders of pigmentation are usually inherited as dominant traits. There can be marked differences in penetrance.
- Clinical features of albinism may include lightly pigmented or nonpigmented skin and silvery-white or light hair color.
- Ocular nystagmus and reduced visual acuity are important features of albinism that distinguish albinism from other congenital disorders of pigmentation.
- Clinical features of congenital disorders of pigmentation include patches of white hair (poliosis), variations in iris color, and depigmented patches of white skin.
- The presence of ocular nystagmus is useful for distinguishing albinism from congenital disorders of pigmentation.
- Albino skin contains melanocytes with reduced or absent DOPA-positivity. Depigmented patches in congenital disorders of pigmentation lack melanocytes.
Oculocutaneous albinism (OCA) is the most common inherited disorder of generalized hypopigmentation, with an estimated frequency of 1 in 20,000 in most populations. Four different types of OCA have been described. OCA1 and OCA2 are the most frequent types and account for approximately 40% and 50%, respectively, of OCA worldwide. OCA2 occurs in approximately 1 in 30,000 to 1 in 36,000 Caucasians and 1 in 10,000 to 1 in 17,000 blacks in the United States,1–3 but is reported at higher frequencies ranging from 1 in 1,400 to 1 in 7,000 in Sub-Saharan Africa4,5 and even as high as 1 in 170 individuals in the Kuna population of the Panama coast.6 OCA3 and OCA4 are far less frequent, although the rufous OCA phenotype, described later, associated with OCA3 in South African blacks has been reported at an incidence of approximately 1/8,500,7 while OCA4 accounts for 27% of all cases of OCA in Japan.8
Hermansky–Pudlak syndrome (HPS) is rare except in the Caribbean island of Puerto Rico, particularly in the northwestern region where the majority of patients are found, with an incidence of 1 in 1,800.9 Chediak–Higashi syndrome is also quite rare.
Epidemiology of Congenital Disorders of Pigmentation
Waardenburg syndrome (WS) is probably less frequent than OCA. The highest reported incidence is 1/20,000 in Kenya, although most estimates of its incidence in the Netherlands where it was originally reported are in the range of 1/40,000. The incidence of WS with deafness is lower, ranging between 1/50,000 and 1/212,000. WS has been described occurring in a range of frequencies in the congenitally deaf, ranging from 0.9%–2.8% to 2%–5% in different reports. The incidence of piebaldism is estimated to be less than 1/20,000.10,11
Awareness of the biologic basis of the distinction between congenital disorders of pigmentation, which are disorders of melanocyte development, and the varieties of albinism, which are disorders of melanocyte differentiation, is important for fully understanding their clinical manifestations. Albinism results from the dysfunction of a normal complement of ...