2.1. Clinical Description
Patient 1 (GM13-3816) is the third female child of healthy non-consanguineous parents (Table 1
, and Figure 1
A). At birth the mother was 34 years old, the father 36. A family history disclosed learning difficulties in an older brother, depression in the paternal grandmother, a psychotic disorder in a maternal uncle, and epilepsy in a maternal niece. The baby was born by vaginal delivery at term of an uneventful pregnancy. The birth weight was 3260 g (50th centile), length 50 cm (50–75th centile), and head circumference 34 cm (50th centile). Apgar scores were 9 and 10 at 1 and 5 min. We first evaluated the patient at the age of 6.1 years for learning difficulties and facial dysmorphisms. The weight was 26 kg (97th centile), height 119 cm (75–90th centile), and head circumference 49.5 cm (10th centile). Facial anomalies included sparse lateral eyebrows, long palpebral fissures with thick eyelids, mild palpebral ptosis, flat philtrum, thick everted lips, and large prominent ears with abnormal helix and a large pinna. The proximal fourth fingers’ phalanges were hypoplastic, with clinodactylous fifth fingers. She does not have fetal fingertip pads. Tapering fingers were present. Pigmentary anomalies were also present, including partial hypochromia of eyelashes, white cutaneous spots in the trunk midline and on the dorsum, a single café-au-lait spot on the abdomen. Body asymmetry was evident, the left side of the face being larger and the left lower limb 1 cm longer in comparison to the right one. Ophthalmogic examination, audiological brainstem audiometry, electroencephalography, 2-Dimensional color-Doppler echocardiography and renal ultrasonography were unremarkable.
The neurobehavioral profile was evaluated through standardized instruments at the age of eight years and seven months. The cognitive profile was assessed using WISC IV [7
]. In the verbal comprehension index (VCI) and perceptual reasoning index (PRI), the patient achieved average scores (VCI 108; PRI 87). The working memory index (WMI) and processing speed index (PSI) disclosed scores one standard deviation (SD) below the mean (WMI 82; PSI: 76). The general intellectual ability was in the average range (Total Intelligence Quozient (TIQ) 87). Adaptive behaviour was evaluated using the ABAS-II (Adaptive Behavior Assessment System—Second Edition) questionnaire parent form [8
]. In the conceptual (CON) and practical domain (PR), the patient’s scores were below two SD from the mean (respectively CON: 65 and PR: 68), while in the social domain (SO) the score was one SD below the mean (SO: 81). The general adaptive composite (GAC) score was 65, two SD below the mean. The patient presented learning disabilities, with a score below one SD from the mean in the MT-2 reading task [9
] in the speed and accuracy indexes, and a score two SD below the mean in the writing accuracy index of the BVSCO-2 task (Batteria per la Valutazione della Scrittura e della Competenza Ortografica—2) [10
]. The psychopathological profile was investigated by psychiatric evaluation and psychodiagnostic evaluation through K-SADS-PL [11
]. The patient met the criteria for generalized anxiety disorder and multiple phobias (bugs, fireworks, loud noises). She also had bizarre behaviour (talking to herself, soliloquy) and emotional dysregulation (Table 2
Patient 2 (KB450) is the female, first child of healthy non-consanguineous parents, with the mother 33 years old and the father 37 years old (Table 1
). The family history was uneventful for disabilities. The baby was born by caesarean section due to breech presentation, at term of an uncomplicated pregnancy. Birth weight was 3345 g (75th centile), length 51 cm (90th centile), and head circumference 35 cm (75th centile). Apgar scores were 9 and 10 at 1 and 5 min. A grade 3/6 L ejection systolic murmur was noted on clinical evaluation. A cardiac ultrasonography, on the first day of the patient’s life, showed a non-restrictive intraventricular subaortic defect. Kabuki syndrome’s evocative facial dysmorphisms were evident in the perinatal period, including elongated palpebral fissures extending laterally, hypertelorism, axial hypotonia and joint hypermobility, fetal finger pads, micrognathia, long and flat philtrum, low set and cup-shaped ears. Hip’s ultrasonography disclosed a right hip dysplasia. Tapering fingers were not present. Renal and brain ultrasonography, ophtalmologic examination, and audiological brainstem audiometry were all unremarkable. An X-ray at birth showed a paracardiac opacity in the right lung, 2.6 cm in diameter, interpreted by chest tomography as a small diaphragmatic hernia. The infant underwent a closure procedure of ventricular septal defects and correction of diaphragmatic hernia at one month of life with an uneventful postoperative course. Discharged at two months of life with a suspicion of KS, the patient underwent a cardiological and neuropsychiatric follow-up.
The neurobehavioral profile was assessed between six and eight years of life. The cognitive profile was evaluated using WISC IV [7
]. In the WMI and PSI, the patient achieved average scores (respectively 91 and 87). In PSI and VCI, the disclosed scores were one SD below the mean (respectively 74 and 76). The general intellectual ability was one SD below the mean (Total IQ) TIQ of 84. Adaptive behaviour was evaluated using ABAS-II. In the conceptual and social domains, the patient’s scores were average (CON: 112, SO: 108), while in the practical domain the score was one SD above the mean (PR: 120). The patient presented learning disabilities with a score below one SD in the MT-2 in the reading/comprehension task [9
] and below two SD in the writing accuracy index of the BVSCO-2 task [10
]. Computation abilities were evaluated with the AC-MT 6–11 tests [13
], reaching a total score between the fifth and tenth centile. The psychopathological profile was investigated through psychiatric evaluation, which showed mild emotional dysregulation.
Patient 3 (KB 369) is the first female child of non-consanguineous parents (Table 1
and Figure 1
B). At birth, the HCV-positive mother was 36 years old and the father 27. A younger brother has a mild intellectual disability. The baby was born by vaginal delivery at term of an uneventful pregnancy. The birth weight was 3230 g (50th centile), length 50 cm (50–75th centile). Apgar scores was 9 at 1 min. At three and a half years she was diagnosed having premature puberty and was treated with Enantone up to 12 years of age. We first evaluated the patient at five years of age, because of her tendency to isolation and poor social participation. The neurobehavioral profile was assessed at 11 years (Table 2
). The cognitive profile was evaluated using WISC III [7
], showing an IQ below two SD of the mean (TIQ 46, verbal IQ 58, performance IQ 46). Adaptive behaviour was assessed using ABAS-II. In the practical domain, the patient’s scores were two SD below the mean (PR: 58), while in conceptual domain the score was one SD below the mean (CON: 72). In the social domain, the score was average (SO: 88). The psychopathological profile was investigated through both psychiatric and psychodiagnostic evaluation through K-SADS-PL [11
]. The patient met the criteria for generalized anxiety disorder and multiple phobias (stuffed animals, dolls and some real animals). She also had bizarre behaviour (soliloquy). At age of 12, ADOS (Autism Diagnostic Observation Schedule) Module 3 disclosed autistic-like behaviour. The weak academic competence level (reading, writing, comprehension skills) achieved by the patient did not permit a structured assessment.
At the age of 13, the family pediatrician required new medical advice for the presence of dysmorphisms. Her weight was 51 kg (>50th centile), height 153 cm (<25 centile), and head circumference 53.5 cm (<50th centile). Facial anomalies included long palpebral fissures with thick eyelids, flat philtrum, and thick everted lips (Figure 1
B). Limb/skeletal anomalies were also present, including persistent fetal pads, clinodactylous of 5th fingers, and tapering fingers. Early breast development was present. Neurologic brain MRI, ophthalmologic, brainstem audiometry, electroencephalography, colour Doppler echocardiography, and renal ultrasonography evaluations were all unremarkable.
2.2. Mutational Analysis
Patient GM13-3816 disclosed a c.15061C=/>T, p.R5021X heterozygous variant in KTM2D
], in a small fraction of alleles from the blood cells. Pyrosequencing analysis estimated a 16% of mosaic in peripheral blood, corresponding to a ~32% mosaic in leukocytes (Figure 2
A). By testing other tissue, we found 15% mutated alleles in urine cells, 2% in buccal swab, and no mosaic in hairs (data not shown).
In patient KB450 and KB369 we identified the nonsense c.13450C=/>T (p.R4484X) mutation [15
], and the novel frameshift c.3596_3597=/del (p.L1199HfsX7) mutation, respectively, both in mosaic.
Pyrosequencing was used to confirm and quantify the mosaicism in different tissues. KMT2D
c.13450C=/>T (p.R4484X) mutation was found in ~34% of peripheral blood alleles (in ~68% of leucocytes) and in ~46% of saliva cells (~92% in epithelial cells) (Figure 2
B). The c.3596_3597=/del (p.L1199HfsX7) mutation was found in 20% of peripheral blood alleles (~40% in leucocytes), and in ~27% of saliva cells (~54% in epithelial cells) (Figure 2
Due to the unavailability of DNA we were not able to sequence any relatives from patients GM13-3816 and KB450, while both KB369 parents were negative for c.3596_3597=/del (p.L1199HfsX7).