Watson syndrome (WTSN) is an autosomal dominant disorder characterized by pulmonic stenosis, cafe-au-lait spots, decreased intellectual ability (Watson, 1967), and short stature (Partington et al., 1985). Most affected individuals have relative macrocephaly and Lisch nodules and about one-third of those affected have neurofibroma (Allanson et al., 1991).

Campomelic dysplasia (CD) is a skeletal dysplasia characterized by distinctive facies, Pierre Robin sequence with cleft palate, shortening and bowing of long bones, and clubfeet. Other findings include laryngotracheomalacia with respiratory compromise and ambiguous genitalia or normal female external genitalia in most individuals with a 46,XY karyotype. Many affected infants die in the neonatal period; additional findings identified in long-term survivors include short stature, cervical spine instability with cord compression, progressive scoliosis, and hearing impairment.

A rare genetic developmental defect during embryogenesis disorder with characteristics of craniofacial dysmorphism (including brachycephaly, prominent forehead, sparse lateral eyebrows, severe hypertelorism, upslanting palpebral fissures, epicanthal folds, protruding ears, broad nasal bridge, pointed nasal tip, flat philtrum, anteverted nostrils, large mouth, thin upper vermilion border, highly arched palate and mild micrognathia) associated with osteopenia leading to repeated long bone fractures, severe myopia, mild to moderate sensorineural or mixed hearing loss, enamel hypoplasia, sloping shoulders and mild intellectual disability. There is evidence the disease can be caused by homozygous mutation in the IRX5 gene on chromosome 16q11.2.

6q25 microdeletion syndrome is a recently described syndrome characterized by developmental delay, facial dysmorphism and hearing loss.

Neurodevelopmental disorder with dysmorphic facies, impaired speech, and hypotonia (NEDDISH) is an autosomal recessive disorder characterized by global developmental delay and mildly to severely impaired intellectual development with poor speech and language acquisition. Some patients may have early normal development with onset of the disorder in the first years of life. More variable neurologic abnormalities include hypotonia, seizures, apnea, mild signs of autonomic or peripheral neuropathy, and autism. Aside from dysmorphic facial features and occasional findings such as scoliosis or undescended testes, other organ systems are not involved (summary by Schneeberger et al., 2020).

Immunodeficiency-75 with lymphoproliferation (IMD75) is an autosomal recessive immunologic disorder characterized by immunodeficiency, immune dysregulation, and the development of lymphoproliferative disorders, including lymphoma. Affected individuals usually present in infancy with severe and recurrent infections, mainly viral and affecting the respiratory tract. Some patients may have autoimmune cytopenias, anemia, or thrombocytopenia. Patients also develop hepatosplenomegaly, lymphadenopathy, lymphoproliferative disorders, and various types of T- or B-cell lymphomas. Immunologic work-up shows decreased class-switched B cells, impaired B-cell terminal differentiation, and hypo- or hypergammaglobulinemia. There is skewed differentiation and dysregulation of T cells, as well as possibly disrupted hematopoiesis. Additional features include failure to thrive and global developmental delay. The phenotype may be reminiscent of ALPS (601859), including laboratory evidence of impaired Fas-dependent T-cell apoptosis. Although hematopoietic stem cell transplantation may be effective treatment, many patients die in childhood (summary by Stremenova Spegarova et al., 2020).

Deafness, cataract, impaired intellectual development, and polyneuropathy (DCIDP) is characterized by early-onset of deafness, cataract, severe developmental delay, and severely impaired intellectual development. Patients later develop polyneuropathy of the lower extremities, associated with depigmentation of the hair in that area (Kroll-Hermi et al., 2020).