The main clinical manifestations of chromosome 18p deletion syndrome are mental retardation, growth retardation, craniofacial dysmorphism including round face, dysplastic ears, wide mouth and dental anomalies, and abnormalities of the limbs, genitalia, brain, eyes, and heart. The round face characteristic in the neonatal period and childhood may change to a long face with linear growth of the height of the face (summary by Tsukahara et al., 2001).

Hypergonadotropic ovarian failure is a heterogeneous disorder that, in the most severe forms, is a result of ovarian dysgenesis. Ovarian dysgenesis accounts for about half the cases of primary amenorrhea (Timmreck and Reindollar, 2003). Genetic Heterogeneity of Ovarian Dysgenesis Even in its isolated form, 46,XX ovarian dysgenesis is etiologically heterogeneous. See ODG2 (300510), caused by mutation in the BMP15 gene (300247); ODG3 (614324), caused by mutation in the PSMC3IP gene (608665); ODG4 (616185), caused by mutation in the MCMDC1 gene (610098); ODG5 (617690), caused by mutation in the SOHLH1 gene (610224); ODG6 (618078), caused by mutation in the NUP107 gene (607617); ODG7 (618117), caused by mutation in the MRPS22 gene (605810); ODG8 (618187), caused by mutation in the ESR2 gene (601663); ODG9 (619665), caused by mutation in the SPIDR gene (615384); and ODG10 (619834), caused by mutation in the ZSWIM7 gene (614535). See also ovarian dysgenesis with sensorineural deafness, or Perrault syndrome (233400).

WT1 disorder is characterized by congenital/infantile or childhood onset of steroid-resistant nephrotic syndrome (SRNS), a progressive glomerulopathy that does not respond to standard steroid therapy. Additional common findings can include disorders of testicular development (with or without abnormalities of the external genitalia and/or müllerian structures) and Wilms tumor. Less common findings are congenital anomalies of the kidney and urinary tract (CAKUT) and gonadoblastoma. While various combinations of renal and other findings associated with a WT1 pathogenic variant were designated as certain syndromes in the past, those designations are now recognized to be part of a phenotypic continuum and are no longer clinically helpful.

WT1 disorder is characterized by congenital/infantile or childhood onset of steroid-resistant nephrotic syndrome (SRNS), a progressive glomerulopathy that does not respond to standard steroid therapy. Additional common findings can include disorders of testicular development (with or without abnormalities of the external genitalia and/or müllerian structures) and Wilms tumor. Less common findings are congenital anomalies of the kidney and urinary tract (CAKUT) and gonadoblastoma. While various combinations of renal and other findings associated with a WT1 pathogenic variant were designated as certain syndromes in the past, those designations are now recognized to be part of a phenotypic continuum and are no longer clinically helpful.

Sex reversal in an individual with 46,XY karyotype caused by point mutations or deletions in the SRY gene, encoding sex-determining region Y protein.

Any primary ovarian failure in which the cause of the disease is a mutation in the NR5A1 gene.

Sex reversal in an individual associated with a 9p24.3 deletion.

Lung fibrosis-immunodeficiency-46,XX gonadal dysgenesis syndrome is characterised by immune deficiency, gonadal dysgenesis and fatal lung fibrosis. So far, it has been described in two sisters born to consanguineous parents. Both karyotypes were normal female (46,XX). No genetic anomalies could be identified by comparative genome hybridization analysis of their genomes or by analysis of genes known to be associated with these types of anomalies.

Congenital muscular dystrophy-dystroglycanopathy with brain and eye anomalies (type A) is an autosomal recessive disorder with characteristic brain and eye malformations, profound mental retardation, congenital muscular dystrophy, and death usually in the first years of life. The brain shows cobblestone lissencephaly, a cortical malformation. The phenotype includes the alternative clinical designations Walker-Warburg syndrome (WWS) and muscle-eye-brain disease (MEB). The disorder represents the most severe end of a phenotypic spectrum of similar disorders resulting from defective glycosylation of alpha-dystroglycan (DAG1; 128239), collectively known as 'dystroglycanopathies' (summary by Vuillaumier-Barrot et al., 2012). For a general phenotypic description and a discussion of genetic heterogeneity of muscular dystrophy-dystroglycanopathy type A, see MDDGA1 (236670).

Perrault syndrome is characterized by sensorineural hearing loss (SNHL) in males and females and ovarian dysfunction in females. SNHL is bilateral and ranges from profound with prelingual (congenital) onset to moderate with early-childhood onset. When onset is in early childhood, hearing loss can be progressive. Ovarian dysfunction ranges from gonadal dysgenesis (absent or streak gonads) manifesting as primary amenorrhea to primary ovarian insufficiency (POI) defined as cessation of menses before age 40 years. Fertility in affected males is reported as normal (although the number of reported males is limited). Neurologic features described in some individuals with Perrault syndrome include learning difficulties and developmental delay, cerebellar ataxia, and motor and sensory peripheral neuropathy.

46,XY females with gonadal dysgenesis have streak gonads but look like normal females at birth. They do not develop secondary sexual characteristics at puberty and do not menstruate. They are chromatin-negative and are usually of normal stature, without the somatic stigmata of Turner syndrome (see 163950) (summary by Mann et al., 1983). For a discussion of genetic heterogeneity of 46,XY sex reversal, see SRXY1 (400044).

Nonsyndromic 46,XX testicular disorders/differences of sex development (DSD) are characterized by: the presence of a 46,XX karyotype; external genitalia ranging from typical male to ambiguous; two testicles; azoospermia; absence of müllerian structures; and absence of other syndromic features, such as congenital anomalies outside of the genitourinary system, learning disorders / cognitive impairment, or behavioral issues. Approximately 85% of individuals with nonsyndromic 46,XX testicular DSD present after puberty with normal pubic hair and normal penile size but small testes, gynecomastia, and sterility resulting from azoospermia. Approximately 15% of individuals with nonsyndromic 46,XX testicular DSD present at birth with ambiguous genitalia. Gender role and gender identity are reported as male. If untreated, males with 46,XX testicular DSD experience the consequences of testosterone deficiency.

Perrault syndrome is characterized by sensorineural hearing loss (SNHL) in males and females and ovarian dysfunction in females. SNHL is bilateral and ranges from profound with prelingual (congenital) onset to moderate with early-childhood onset. When onset is in early childhood, hearing loss can be progressive. Ovarian dysfunction ranges from gonadal dysgenesis (absent or streak gonads) manifesting as primary amenorrhea to primary ovarian insufficiency (POI) defined as cessation of menses before age 40 years. Fertility in affected males is reported as normal (although the number of reported males is limited). Neurologic features described in some individuals with Perrault syndrome include learning difficulties and developmental delay, cerebellar ataxia, and motor and sensory peripheral neuropathy.

Myoectodermal gonadal dysgenesis syndrome (MEGD) is characterized by 46,XY complete or partial gonadal dysgenesis, or 46,XX gonadal dysgenesis, in association with extragonadal anomalies, including low birth weight, typical facies, rod and cone dystrophy, sensorineural hearing loss, omphalocele, anal atresia, renal agenesis, skeletal abnormalities, dry and scaly skin, severe myopathy, and neuromotor delay. Dysmorphic facial features along with muscular habitus are the hallmarks of the syndrome. Abnormal hair patterning with frontal upsweep and additional whorls, eyebrow abnormalities comprising broad, arched, and sparse or thick eyebrows, underdeveloped alae nasi, smooth philtrum, and low-set ears with overfolded helices facilitate a gestalt diagnosis. (Guran et al., 2019; Altunoglu et al., 2022).

Individuals with PPP1R12A-related urogenital and/or brain malformation syndrome (UBMS) usually present with multiple congenital anomalies, commonly including brain and/or urogenital malformations. The brain abnormalities are variable, with the most severe belonging to the holoprosencephaly spectrum and associated with moderate-to-profound intellectual disability, seizures, and feeding difficulties. In individuals without brain involvement, variable degrees of developmental delay and/or intellectual disability may be present, although normal intelligence has been seen in a minority of affected individuals. Eye abnormalities and skeletal issues (kyphoscoliosis, joint contractures) can also be present in individuals of either sex. Regardless of the presence of a brain malformation, affected individuals with a 46,XY chromosome complement may have a disorder of sex development (DSD) with gonadal abnormalities (dysgenetic gonads or streak gonads). Individuals with a 46,XX chromosome complement may have varying degrees of virilization (clitoral hypertrophy, posterior labial fusion, urogenital sinus).

46,XY gonadal dysgenesis-motor and sensory neuropathy syndrome is a rare, genetic, developmental defect during embryogenesis disorder characterized by partial (unilateral testis, persistence of Müllerian duct structures) or complete (streak gonads only) gonadal dysgenesis, usually manifesting with primary amenorrhea in individuals with female phenotype but 46,XY karyotype, and sensorimotor dysmyelinating minifascicular polyneuropathy, which presents with numbness, weakness, exercise-induced muscle cramps, sensory disturbances and reduced/absent deep tendon reflexes. Germ cell tumors (seminoma, dysgerminoma, gonadoblastoma) may develop from the gonadal tissue.