Chediak-Higashi syndrome (CHS) is characterized by partial oculocutaneous albinism (OCA), immunodeficiency, a mild bleeding tendency, and late adolescent- to adult-onset neurologic manifestations (e.g., learning difficulties, peripheral neuropathy, ataxia, and parkinsonism). While present in nearly all individuals with CHS, these clinical findings vary in severity. Of note, all individuals with CHS are at risk of developing neurologic manifestations and hemophagocytic lymphohistiocytosis (HLH). Individuals with severe childhood-onset presentations are considered to have "classic" CHS, whereas individuals with milder adolescent- to adult-onset presentations are considered to have "atypical" CHS. Because of the considerable overlap between classic CHS and atypical CHS, the disorder is best understood as a continuum of severe to milder phenotypes, with the universal feature being the pathognomonic giant granules within leukocytes observed on peripheral blood smear.

Anterior segment dysgeneses (ASGD or ASMD) are a heterogeneous group of developmental disorders affecting the anterior segment of the eye, including the cornea, iris, lens, trabecular meshwork, and Schlemm canal. The clinical features of ASGD include iris hypoplasia, an enlarged or reduced corneal diameter, corneal vascularization and opacity, posterior embryotoxon, corectopia, polycoria, an abnormal iridocorneal angle, ectopia lentis, and anterior synechiae between the iris and posterior corneal surface (summary by Cheong et al., 2016). Anterior segment dysgenesis is sometimes divided into subtypes including aniridia (see 106210), Axenfeld and Rieger anomalies, iridogoniodysgenesis, Peters anomaly, and posterior embryotoxon (Gould and John, 2002). Patients with ASGD4 have been reported with iridogoniodysgenesis or Peters anomaly subtypes. Iridogoniodysgenesis, which is characterized by iris hypoplasia, goniodysgenesis, and juvenile glaucoma, is the result of aberrant migration or terminal induction of the neural crest cells involved in the formation of the anterior segment of the eye (summary by Mears et al., 1996). Peters anomaly consists of a central corneal leukoma, absence of the posterior corneal stroma and Descemet membrane, and a variable degree of iris and lenticular attachments to the central aspect of the posterior cornea (Peters, 1906).

Koolen-de Vries syndrome (KdVS) is characterized by congenital malformations, developmental delay / intellectual disability, neonatal/childhood hypotonia, epilepsy, dysmorphisms, and behavioral features. Psychomotor developmental delay is noted in all individuals from an early age. The majority of individuals with KdVS function in the mild-to-moderate range of intellectual disability. Other findings include speech and language delay (100%), epilepsy (~33%), congenital heart defects (25%-50%), renal and urologic anomalies (25%-50%), and cryptorchidism. Behavior in most is described as friendly, amiable, and cooperative.

Waardenburg syndrome type 2 (WS2) is an auditory-pigmentary syndrome characterized by pigmentary abnormalities of the hair, skin, and eyes; congenital sensorineural hearing loss; and the absence of 'dystopia canthorum,' the lateral displacement of the inner canthus of each eye, which is seen in some other forms of WS (review by Read and Newton, 1997). Individuals with WS type 2E (WS2E) may have neurologic abnormalities, including mental impairment, myelination defects, and ataxia. Waardenburg syndrome type 2 is genetically heterogeneous (see WS2A, 193510). For a description of other clinical variants of Waardenburg syndrome, see WS1 (193500), WS3 (148820), and WS4 (277580).