Wiedemann-Steiner Syndrome

A number sign (#) is used with this entry because of evidence that Wiedemann-Steiner syndrome (WDSTS) is caused by heterozygous mutation in the MLL gene (KMT2A; 159555) on chromosome 11q23. The KMT2A gene is involved in histone modification.

Description

Wiedemann-Steiner syndrome is a congenital malformation syndrome characterized by hypertrichosis cubiti associated with short stature; consistent facial features, including long eyelashes, thick or arched eyebrows with a lateral flare, wide nasal bridge, and downslanting and vertically narrow palpebral fissures; mild to moderate intellectual disability; behavioral difficulties; and hypertrichosis on the back (summary by Jones et al., 2012 and Miyake et al., 2016).

Clinical Features

Wiedemann et al. (1989) reported a Caucasian boy with pre- and postnatal growth deficiency, psychomotor delay, and a round and flat face, short nose, hypertelorism, long philtrum, short palpebral fissures, low-set ears, and high-arched palate. Other findings included an alternating convergent squint, dilatation of the renal calyces, and short and thick limbs.

MacDermot et al. (1989) reported a mother and daughter with hairy elbows who also had short stature, rhizomelic shortening of the limbs, round face, and heavy jaw. MacDermot et al. (1989) also reported a sporadic case in a 7-year-old boy with short stature and facial dysmorphism that included downslanting palpebral fissures, mild hypertelorism, and short nose with thick alae.

Flannery et al. (1989) described a 4.8-year-old girl with hairy elbows and short stature who also had facial asymmetry, developmental delay, and delayed speech. She had hypertrichosis of the distal-lateral arms and proximal-lateral forearms, where the hair was longer, darker, and somewhat coarser than the normal hair on her arms. Facial features included hypotonia and left-sided hypoplasia, left ptosis, epicanthal folds, and highly arched palate; she also had generalized hypotonia.

Edwards et al. (1994) described a 3.25-year-old girl with hairy elbows, facial asymmetry, and delayed speech. She had right-sided hypoplasia of the face and right ptosis. There was patchy hypertrichosis involving the right side of the lip and the right zygomatic area, the lateral half of each arm between the deltoid insertion and the elbow, the right side of the trunk posteriorly, and the right posterior thigh. Height was between the 75th and 97th centile, and there was no evidence of growth asymmetry other than the face. Edwards et al. (1994) noted similarities between this patient and the girl described by Flannery et al. (1989), and suggested that they might have a distinct hypertrichosis syndrome associated with asymmetric facial growth and delayed development.

Steiner and Marques (2000) reported an 8-year-old girl with manifestations similar to those of the patient described by Wiedemann et al. (1989). She was born after an uncomplicated pregnancy and had a delivery birth weight of 2,740 grams, with a birth length of 45 cm and an occipitofrontal head circumference (OCF) of 33 cm. The parents were unrelated. At the age of 4 months, hypotonia was noted. The patient had mild to moderate mental retardation and growth deficiency. Physical features included dolichocephaly, telecanthus, mild synophrys, narrow and downslanting palpebral fissures, low nasal bridge, long and broad philtrum, thin upper lip, high-arched palate, sacral dimple, and mild fifth finger clinodactyly. She initially had mild hypertrichosis, which became more accentuated with age and was most evident over the limbs, especially at the elbows, and the back. Evaluations for inborn errors of metabolism, TORCH infection, chromosomal abnormalities, and endocrinologic abnormalities were all normal. Radiologic evaluation showed normal skeletal bones and bone age. CT of the brain, EEG, echocardiogram, and ultrasound of the abdomen and pelvis were normal.

Visser et al. (2002) reported 2 Dutch girls with hairy elbows, short stature, slightly dysmorphic facies, and psychomotor developmental delay. One of the girls had ptosis of the left eye and mild generalized hypotonia; the hypotonia disappeared spontaneously at age 2 years. In a review of the literature, Visser et al. (2002) found reports of 26 cases of hypertrichosis cubiti since the first report of Beighton (1970). In approximately three-quarters of the cases, hypertrichosis cubiti was isolated or associated with short stature only (see 139600), whereas the remaining cases involved short stature as well as other features such as facial dysmorphism, limb anomalies, and psychomotor retardation or speech delay.

Polizzi et al. (2005) reported 2 unrelated girls with hairy elbows, short stature, facial dysmorphism, and mental retardation. One was an 11-year-old girl, originally described by Sorge et al. (2002), whose features included marked dolichocephaly and a high, prominent forehead, downslanting eyes, low-set ears, large eyebrows that were sparse medially, small nose with triangularly shaped nostrils, short philtrum with small mouth, high-arched palate, bilateral fifth-finger clinodactyly, deep palm and plantar creases, and mild mental retardation with hyperactivity. The other patient was a 7-year-old girl who had brachycephaly, small forehead, large ears, thin nose, thin lips, irregular margins of the teeth, asymmetric chest with pectus excavatum, delayed bone age, and mild to moderate mental retardation. Reviewing the 28 previously reported cases of hairy elbows, Polizzi et al. (2005) stated that individuals with hairy elbows could be grossly divided into 2 groups: those with and those without associated systemic findings. They noted that laboratory studies, including full endocrinologic and metabolic evaluations, were unrevealing in the previously reported cases as well as in the current 2 patients, indicating that extensive testing in these patients could be unrewarding. Histologic studies on hair from the affected areas had revealed normal findings, although a high percentage (greater than 90%) of hair follicles in the anagen phase was noted, which might explain the longer length of the excess hair.

Koc et al. (2007) reported an 8-year-old Turkish girl, born of consanguineous parents, referred for short stature and developmental delay. She had hyperextensible elbows with localized hypertrichosis. The hair on the elbows was unusually longer, darker, and coarser than elsewhere. She was thin with height at the 3rd centile and had microcephaly, triangular and asymmetric face, high forehead with thick eyebrows, long eyelashes, downslanting palpebral fissures, bilateral ptosis, high and wide nasal bridge, thin upper lip, big anteverted ears, and a long, thin, webbed neck. She also had delayed bone age and borderline mental retardation. A 22-year-old brother, who was not examined, had mental retardation and a speech disorder, but according to the family did not have hypertrichosis. Koc et al. (2007) noted phenotypic similarities to the Floating-Harbor syndrome (136140).

Jones et al. (2012) studied 6 patients with hypertrichosis cubiti who also had distinct, consistent facial characteristics including long eyelashes, thick or arched eyebrows with a lateral flare, and downslanting and vertically narrow palpebral fissures. The patients also had mild to moderate intellectual disability and behavioral difficulties. In addition to hairy elbows, the patients all had excessive hair on the back with a whorl-like distribution. All 6 were below the 10th centile for height, and a sacral dimple was observed in 4 of the 6 patients.

Koenig et al. (2010) reported 3 unrelated patients with features similar to those reported by Wiedemann et al. (1989) and Steiner and Marques (2000). The 2 girls and 1 boy had mental retardation and a distinctive facial gestalt that became more apparent in adolescence. The features included hypertelorism, narrow and downslanting palpebral fissures, broad nose, thick eyebrows with synophrys, long philtrum, small mouth with high-arched palate, and short fingers and/or toes with short middle phalanges and clinodactyly V. Early in life, these patients had hypotonia and failure to thrive. The 2 girls had hypertrichosis, and 1 girl developed seizures. One girl had a pericentric inversion of chromosome 9, and the other girl had an interstitial duplication of chromosome 12q14.1 inherited from her unaffected mother. The boy had normal karyotyping and array CGH results. Koenig et al. (2010) concluded that this represents a distinct and recognizable sporadic syndrome.

Miyake et al. (2016) reported 6 unrelated children, ranging from 3 to 9 years of age, with WDSTS. One was of Australian origin and 5 were Japanese. Five patients were available for detailed clinical evaluation. Common features included thick eyebrows, long eyelashes, downslanting palpebral fissures, generalized hirsutism, hypertrichosis of the elbows and back, short stature, postnatal growth retardation, developmental delay, and intellectual disability. More variable features included wide nasal bridge with depressed nasal tip, thin upper vermilion borders, clinodactyly, fleshy hands, and hypotonia in infancy. Examination of bone age in 3 patients showed normal results. Miyake et al. (2016) noted that several of the patients were initially diagnosed with Kabuki syndrome (see, e.g., 147920), which shows phenotypic overlap with WDSTS and is due to mutation in other genes involved in histone modification, suggesting disruption of common functional molecular pathways.

Inheritance

Jones et al. (2012) demonstrated that Wiedemann-Steiner syndrome is an autosomal dominant disorder.

Molecular Genetics

Jones et al. (2012) performed whole-exome sequencing in 4 patients with Wiedemann-Steiner syndrome and identified heterozygous de novo truncating mutations in the MLL gene (159555.0001-159555.0003) in 3 of the 4 patients. Analysis of MLL in 2 additional patients with a similar phenotype revealed 2 more truncating mutations (159555.0004 and 159555.0005). The variants were confirmed by Sanger sequencing, and none were found in the dbSNP or 1000 Genomes Project database, in 600 unrelated control exome profiles, or in DNA from the unaffected parents. Jones et al. (2012) concluded that haploinsufficiency of MLL causes Wiedemann-Steiner syndrome. They noted that the 1 patient in whom a mutation was not identified had subtle phenotypic differences: the hair on his arms was at the upper limit of normal and more diffuse than the hypertrichosis cubiti of the other 5 patients, and the hair growth on his back was considerably longer, extending up to 12 cm. In addition, his facial features differed, with absence of downslanting palpebral fissures. Jones et al. (2012) suggested that this individual had a phenotype within the spectrum of WDSTS with a distinct molecular genetic basis.

In 6 unrelated children with WSS, Miyake et al. (2016) identified 6 different heterozygous mutations in the KMT2A gene (see, e.g., 159555.0006-159555.0008). The mutations, which were found by whole-exome sequencing and confirmed by Sanger sequencing, were demonstrated to have occurred de novo in 4 of the patients; complete parental DNA was not available for 2 patients. Four of the mutations resulted in nonsense or frameshift mutations, whereas 2 were missense mutations affecting highly conserved residues. Functional studies of the variants and studies of patient cells were not performed.