Mandibulofacial dysostosis with microcephaly: an expansion of the phenotype via parental survey

Abstract

Mandibulofacial dysostosis with microcephaly (MFDM) is due to haploinsufficiency of spliceosomal GTPase EFTUD2. Features include microcephaly, craniofacial dysmorphology, developmental disability, and other anomalies. We surveyed parents of individuals with MFDM to expand knowledge about health, development, and parental concerns. Participants included attendees of the inaugural MFDM family conference in June 2019 and members of the MFDM online group. To explore MFDM variable expressivity, we offered targeted Sanger sequencing for untested parents.

Forty-seven parents participated in the survey. 59% of individuals with MFDM were male, with mean age 6.4 years (range 8 months to 49 years). Similar to the literature (n=123), common features include microcephaly, cleft palate, choanal stenosis, tracheoesophageal fistula, heart problems, and seizures. New information includes airway intervention details, age-based developmental outcomes, rate of vision refractive errors, and lower incidences of prematurity and IUGR. Family concerns focused on development, communication, and increased support.

Targeted Sanger sequencing for families of seven individuals demonstrated de novo variants, for a total of 91.9% de novo EFTUD2 variants (n=34/37). This study reports the largest single cohort of individuals with MFDM, expands phenotypic spectrum and inheritance patterns, improves understanding of developmental outcomes and care needs, and identifies development as the biggest concern for parents.

Introduction:

Mandibulofacial dysostosis syndromes arise from abnormal development of the first and second brachial arches, which leads to malar and mandibular hypoplasia, cleft palate, inner and outer ear malformations, and conductive, sensorineural, or mixed hearing loss (Gordon et al., 2012; Lehalle et al., 2014). Acrofacial dysostosis syndromes further include limb anomalies (Yu et al., 2018), with Nager syndrome and Miller syndrome as notable examples (Trainor & Andrews, 2013). Mandibulofacial dysostosis with microcephaly (MFDM, OMIM # 610536), also called mandibulofacial dysostosis Guion-Almeida type, or acrofacial dysostosis Guion-Almeida type, is due to haploinsufficiency of EFTUD2, which encodes U5–116KD, a splicesosomal GTPase important in mRNA intron splicing (Lines et al., 2012; Luquetti et al., 2013). Missense, non-sense, frameshift, splice-site, and microdeletion variants in EFTUD2 have all been reported to cause MFDM (Huang et al., 2016; Yu et al., 2018). Most variants arise de novo, but variable expressivity with transmission from mildly affected parents, as well as germline mosaicism have been reported (Huang et al., 2016; Lacour et al., 2019).

Common phenotypic features of MFDM include micrognathia, malar hypoplasia, microcephaly, cleft palate, abnormal internal and external ears with hearing loss, tracheoesophageal fistula/esophageal atresia (TEF/EA), developmental delay, as well as radial ray defects and other congenital anomalies (Gordon et al., 2012; Huang et al., 2016; Lines et al., 2012; Yu et al., 2018). As with other facial dysostosis syndromes, phenotypic features associated with MFDM show a substantial inter- and intrafamilial variability. Mildly affected parents may not be detected until a diagnosis of MFDM is made in their child (Huang et al., 2016; Trainor & Andrews, 2013).

To date, there have been 123 individuals with molecularly confirmed MFDM reported in the literature. To expand clinical knowledge about health, development, inheritance patterns, and parental concerns for those with MFDM, a survey was created for parents of individuals with MFDM and targeted Sanger sequencing testing was offered for families in which the inheritance for their child’s MFDM was unknown. We combined our survey results with a literature review to increase knowledge about MFDM, and to refine anticipatory guidance and management recommendations for patients with MFDM.

Patients and Methods:

Survey:

We designed a survey for biological or adoptive parents of individuals with molecularly confirmed MFDM (per parent report). Participants for the survey were recruited from attendees of the 2019 MFDM Conference held in Cincinnati, OH in June 2019. To allow participation from those who could not attend the conference, members of the online MFDM family group were invited to participate afterward in an online survey. This study was approved by the internal institutional review board (conference survey distribution approval in protocol # 2019–1049, and online survey distribution approval in protocol # 2019–1100). Online surveys were anonymous, but month and year of birth, as well as location (country and/or state) were used to ensure surveys were not duplicated between the conference attendees and online respondents. Formal genetic testing reports for molecular confirmation of diagnosis were unable to be verified, except for those participants enrolled in parental variant testing, as described below.

The 130 question survey was divided into 15 sections: parent demographics, child demographics, MFDM diagnostic work-up, prenatal findings, facial features, general health problems, airway problems, feeding interventions, care outside the hospital, hospitalizations and surgeries, overall developmental assessment, and individual assessment of gross motor, fine motor, communication skills, and parental experiences. The survey utilized open and close ended questions, as well as skip-logic to exclude non-applicable questions. Two clinical geneticists and a parent familiar with MFDM reviewed the survey prior to distribution. The survey responses were collected and managed using REDCap (Research Electronic Data Capture) electronic data capture tools hosted at Cincinnati Children’s Hospital and analyzed in Excel. Answers to open-ended questions regarding parent concerns were coded into categories independently by two reviewers, and discrepancies were discussed and resolved. The survey is available as supplemental material (Supplementary Information 1).

Family variant analysis:

Targeted familial variant testing via Sanger sequencing was offered to attendees of the 2019 MFDM Conference held in Cincinnati, OH in June 2019. Testing was approved by the internal institutional review board (protocol # 2019–1049). Testing was offered to biological parents of children with MFDM who did not have parental testing performed previously and who could provide a copy of the clinical test report for their child’s EFTUD2 variant. DNA was obtained via Oragene Discover OGR-575 (DNA Genotek) saliva kits from the child and available parents (trio samples n = 6, duo samples n = 1). Forward and reverse primers were created for each proband’s EFTUD2 variant. PCR products were obtained using a T100 Thermal Cycler (Bio-Rad) and concentrated using DNA Clean & Concentrator 5 (Zymo Research). Variants were confirmed via Sanger sequencing by an Applied Biosystems 3730xl DNA Analyzer (Thermo Fisher Scientific). Sequencing was manually reviewed.

Literature review:

We identified 123 molecularly confirmed cases of MFDM in the literature (Bernier et al., 2012; Bick et al., 2017; Deml, Reis, Muheisen, Bick, & Semina, 2015; Gandomi, Parra, Reeves, Yap, & Gau, 2015; Huang et al., 2016; Lacour et al., 2019; Lehalle et al., 2014; Lines et al., 2012; Mouthon et al., 2019; Need et al.; Paderova et al., 2018; Rengasamy Venugopalan, Farrow, & Lypka, 2017; Sarkar et al., 2015; Silva, Soares, Leão, & Santos, 2019; Smigiel et al., 2015; Vincent et al., 2016; Voigt et al., 2013; Williams, Quinonez, & Uhlmann, 2017; Yu et al., 2018; Zarate, Bell, & Schaefer, 2015). The clinical phenotypes and variants were summarized and compared to those of the surveyed MFDM individuals.

Results:

Study Population and MFDM Diagnosis:

A total of fifty surveys (n=50) were received and reviewed, 24 from the family conference, and 26 completed online. Two surveys were excluded due to reported lack of molecularly confirmed diagnosis (n=2), and one individual with MFDM who completed the survey about themselves (n=1). No parents reported more than one child with MFDM. Demographic data for the 47 surveys are shown in Table 1. Most surveys were completed by biological mothers. Participants represented 10 countries, with most from the United States. The individuals with MFDM included 28 (59.6%) males, 18 (38.3%) females, and 1 (2.1%) without gender disclosed. Average age was 6.41 years (range 0.67 to 49 years). The majority of children and parents reported a white, non-Hispanic background.

Table 1:

Demographics for children with MFDM and their parents.

Child / Parent	Characteristic	Total
Child gender	Male	28, (59.6%)
	Female	18, (38.3%)
	No response	1, (2.1%)
Child age	Average	6.3 yr
	Range	8 mo – 49 yr
Child race	White	45, (95.7%)
	Asian	3, (6.4%)
Child ethnicity	Non-Hispanic	41, (87.2%)
	Hispanic	3, (6.4%)
	Unknown	1, (2.1%)
	No response	2, (4.3%)
Parent relationship	Biological parent	43, (91.5%)
	Adoptive parent	4, (8.5%)
Parent gender	Male	5, (10.6%)
	Female	41, (87.2%)
	No answer	1, (2.1%)
Parent age	Average	35 yr
	Range	24 – 80 yr
Parent race	White	47, (100%)
	Asian	1, (2.1%)
Parent ethnicity	Non-Hispanic	43, (91.5%)
	Hispanic	1, (2.1%)
	Unknown	1, (2.1%)
	No response	2, (4.3%)
Parent country of origin	United States	30, (63.8%)
	United Kingdom	4, (8.5%)
	Australia	3, (6.4%)
	Canada	3, (6.4%)
	Netherlands	2, (4.3%)
	Belgium	1, (2.1%)
	France	1, (2.1%)
	Germany	1, (2.1%)
	Poland	1, (2.1%)
	South Africa	1, (2.1%)

MFDM = mandibulofacial dysostosis with microcephaly, mo = month, yr = year

Parental testing was previously performed in 30 respondents (n=30/47, 63.8%). There were three reports of inheritance from an affected parent (n=3/47, 6.4%), however no further information was available about the phenotypes or genotypes of these parents. A diagnosis of MFDM was made at an average age of 4.13 years (range 0 years to 48 years, median 2 years). None reported prenatal diagnosis. Prior to a diagnosis of MFDM, 21 individuals (46.7%) reported an alternative clinical diagnosis, including CHARGE syndrome, Treacher Collins, Goldenhar syndrome, and Klippel-Feil syndrome.

Based on age at publication, year of publication, gender, and genotype of the previously reported cases, all effort was made to review for overlap with individuals with MFDM in this cohort, as to not double report on rare and unique features. Previous publication was not directly queried on the survey. One individual reported here is known to have been previously published in Lacour et al. as Case 1 (2019).

Medical Information:

Craniofacial:

Phenotypic data is shown in Table 2, with comparison to the 123 reported MFDM cases in the literature. We found similar rates of microcephaly, cleft palate, and hearing loss. Of those with hearing loss, the majority required hearing aids (n=29/39, 74.4%). The average age of diagnosis of hearing loss was 1.2 years, with many diagnosed in the newborn period (n=17/39, 43.6% between ages 0 to 1 month), and most prior to age 1 year (n=24/39, 61.5%). Photographs of the participants highlight common phenotypic features of MFDM, including microcephaly, micrognathia, malar hypoplasia, and external ear abnormalities, among others (Figure 1).

Table 2:

General phenotypic characteristics for MFDM individuals, both from this survey (n=47) and reported in the literature (n=123).

Category	Feature	This survey, (%)†,‡ n = 47	Reported, (%)† n = 123
Craniofacial	Microcephaly	44/47, (93.6%)	100/114, (87.7%)
	Hearing loss	39/47, (83.0%)	88/105, (83.8%)
	Conductive	NR	37/52, (71.2%)
	Sensorineural	NR	6/43, (14.0%)
	Cleft palate	19/47, (40.3%)	48/107, (44.9%)
	Micrognathia	NR	107/110, (97.3%)
	External ear anomaly	NR	103/109, (94.5%)
	Ear canal anomaly	NR	59/88, (67.1%)
	Ossicular ear anomaly	NR	13/29, (44.8%)
	Semicircular canal anomaly	NR	20/39, (51.3%)
	Malar hypoplasia	NR	87/94, (92.6%)
	Facial asymmetry	NR	35/58, (60.3%)
	Zygomatic cleft	NR	7/10
Airway	Choanal stenosis	15/47, (31.9%)	30/96, (31.3%)
	Tracheosphageal fistula / Esophageal atresia	10/47, (21.28%)	32/88, (36.4%)
	Tracheo / laryngomalacia	9/47, (19.2%)	2/3
	Obstructive sleep apnea	12/47, (25.5%)	1/2
	Laryngeal cleft	2	1
	Laryngeal cyst	1	NR
Interventions	Tracheostomy	3/47, (6.4%)	13/59, (22.0%)
	Mandibular distraction osteogenesis	8/47, (17.0%)	1/2
	T&A	12/47, (25.53%)	NR
	G-tube placement	12	5/15
	Ear tube placement	27	NR
Other anomalies	Congenital heart defect	5	37/108, (34.3%)
	ASD	2	10/23 (43.5%)
	PDA	2	5/13
	Truncus arteriosus	1	NR
	VSD	NR	11/28 (39.3%)
	PFO	NR	3/4
	Aortic arch anomaly	NR	2/11
	Peripheral pulmonic stenosis	NR	1/7
	Tetrology of Fallot	NR	1/1
	Any vision problem	14/47, (29.8%)	3/17, (17.7%)
	Astigmatism	10/14	1/3
	Myopia	6/14	3/15
	Hyperopia	2/14	NR
	Strabismus	1/14	1/3
	Short stature	27/45, (60.0%)	16/19
	Seizures	17/47, (36.2%)	24/89, (27.0%)
	Kidney problems	5/47, (10.64%)	6/19
	Limb anomaly	3	30/99, (30.3%)
	Proximally placed thumb	NR	12/29, (41.4%)
	Hypoplastic thumb	NR	2/6
	Duplicated thumb	NR	2/20 (10%)
	Cryptorchidism	2	4/44, (9.1%)
	Abnormal brain MRI	NR	14/29, (48.3%)

^†Percentages (%) are shown when the total n for a characteristic equals 20 or more reported occurrences

^‡When a feature was self-reported and not surveyed directly, a total denominator is not provided.

ASD = atrial septal defect, NR = not recorded, PDA = patent ductus arteriosus, PFO = patent foramen ovale, T&A = tonsillectomy and adenoidectomy, VSD = ventricular septal defect

Figure 1:

Phenotypic spectrum of individuals with MFDM

Airway:

Incidence of choanal stenosis in the study cohort was similar to previously reports, but there was a lower incidence of TEF/EA. This cohort additionally includes rates of tracheo- / laryngomalacia (n=9/47, 19.2%), and obstructive sleep apnea (n=12/47, 25.53%). Two individuals reported laryngeal clefts, a known rare feature in MFDM. An additional individual reported a laryngeal cyst, not previously reported. At the time of this survey, most individuals did not need airway support (n=39/44, 88.64%). Of those that currently needed support (n=5), two individuals required CPAP or BiPAP, and three did not specify.

Interventions:

Here, three patients reported tracheostomy (n=3/47, 6.4%), which is lower than reported rates in the literature. Of these, one had a laryngeal cleft, one had tracheo-/laryngomalacia, and one had a TEF/EA and choanal stenosis. At the time of this survey, all three individuals were six years old, and no longer required tracheostomy. Rates of tonsillectomy and/or adenoidectomy and mandibular distraction osteogenesis were 25.5% (n=12/47) and 17.0% (n=8/47) respectively. Twelve patients reported gastrostomy tube placement, and 27 myriongotomy tube placement.

Other features:

Congenital heart defects reported include ASD (n=2), PDA (n=2), and truncus arteriosus (n=1). These five defects all required a surgery, and one additional individual reported “open heart surgery” without specifying a heart defect. Vision problems were reported in 29.79% of individuals (n=14/47), ten with astigmatism, six with myopia, two with hyperopia, and one with strabismus. The majority reported short stature (n=27/45, 60.0%). There was a higher reported rate of seizures than in the literature, and lower rate of kidney problems. Limb anomalies were not directly queried on our survey, but were reported in three patients. Additionally, two patients reported cryptorchidism.

The majority of individuals reported a history of feeding difficulties (n=43/47, 91.49%), but most were at least partially fed by mouth (n=42/45 93.3%). Just over half required tube feeding at some point (n=26/47, 55.32%), with around a quarter (n=12/47, 25.53%) requiring tube feeding at the time of the survey. Individuals who no longer required tube feeding (n=14) were older than those who still require tube feeding (mean age 6.67 years vs 3.6 years respectively). The three individuals who did not take food by mouth were 3, 4, and 8 years old. All three had a history of cleft palate, with one also requiring mandibular distraction osteogenesis, one requiring choanal stenosis repair, and one requiring both. Airway anomalies were more common in those with a history of requiring tube feeding (n=23/26, 88.5% vs 3/26, 11.5%). Specifically, feeding tubes were required at some point in 57.9% of individuals with cleft lip or palate (n=11/19), 90% of individuals with TEF/EA (n=9/10), and 80% of those with choanal stenosis (n=12/15). Twelve reported requiring G-tube placement for long-term management.

Prenatal:

Pregnancy complications were reported in 46.7% of individuals (n=21/46), and are displayed in Table 3. Polyhydramnios was most common, with a similar incidence to published cases. Our cohort had a lower proportion of individuals with intrauterine growth restriction and delivery earlier than 35 weeks gestation than previously published cases. Prenatal anomalies identified include cleft palate, heart defects, placental defects, micrognathia, and increased nuchal fold. Prenatal genetic screening or testing procedures were performed in 19.1% of individuals (n=9/47), with NIPT in seven, and amniocentesis in three.

Table 3:

Prenatal complications for mothers carrying MFDM individuals in this survey and with reported cases in the literature

Category	Feature	This survey, (%)	Reported, (%)
Complications	Polyhydramnios	10/46, (21.7%)	11/42, (26.2%)
	IUGR	6/46, (13.0%)	10/39, (25.6%)
	Prematurity < 35wk EGA	5/46, (10.9%)	12/62, (19.4%)
	Hypertension	5/46, (10.9%)	NR
	Diabetes	1/46, (2.2%)	1
	Pre-eclampsia	1	2/31, (6.5%)
	Twin gestation	1	2
	Oligohydramnios	NR	1/30, (3.3%)
	PROM	NR	1/5, (20%)
	IVF	NR	1
Anomalies	Cleft palate	4/46, (8.7%)	2
	Heart defect	2	1/30, (3.3%)
	Placenta defect	2	NR
	Micrognathia	1	4/32, (12.5%)
	Increased nuchal fold	1	2/5
	Cerebellar hypoplasia	NR	1/2

EGA = estimated gestational age, IUGR = intrauterine growth retardation, IVF = in vitro fertilization, NR = not recorded, PROM = premature rupture of membranes, wk = week

Hospitalizations/Surgeries:

Most individuals required prolonged hospitalization at birth (n=29/46, 63.04%), with a reported average stay of 66 days (range 1 to 180 days). Additional hospitalizations were experienced in most (n=42/47, 89.36%), with an average of eight additional hospitalizations. Most required at least one surgery (n=44/47, 93.62%), with an average of six surgeries per individual (range 1 to 22). Types of surgeries reported included any type of airway surgery (n=42), myringotomy tube placement (n=27), G-tube placement (n=12), palatoplasty (n=11), heart surgery (n=6), limb anomaly repair (n=3), orchidopexy (n=2), tethered cord release (n=1), and metopic craniectomy (n=1).

Therapy services/clinic appointments:

Individuals with MFDM were cared for by multiple health care providers (Supplemental Figure 1), and attended an average of 2 specialist visits per month. The majority (n=45/47, 95.74%) attended some form of therapy, with speech therapy being the most common (n=43/45, 95.56%), followed by occupational therapy (n=33/45, 73.33%), then physical therapy (n=29/45, 64.44%). State supported in-home services (n=16/45, 35.56%), feeding therapy (n=12/45, 26.67%), and developmental therapy (n=12/45, 26.67%) were also commonly attended. Figure 2 demonstrates the average number of appointments per month, therapies per week, and medications per day by age group. On average, individuals attended four therapy sessions a week. Overall, there were decreasing number of visits, therapies, and medications required with increasing age.

Figure 2:

Average number of specialist provider appointments per month, therapies per week, and medications per day by age range.

Development:

Developmental milestones are outlined in Table 4. All of the 47 respondents (100%) reported developmental delays in their child, with the average age of concern beginning at five months. The most commonly reported delay was communication (n=45/47, 95.74%), followed by gross motor delay (n=36/47, 76.6%), and fine motor delay (n=33/47, 70.21%). Most achieved single words (n=34/44, 77.27%) at an average age of 34 months. Of the ten individuals who had not achieved single words, three were 12 months age or younger. Three of the remaining individuals were able to use signs and point to communicate, with one also using a communication device. Three others could only babble for communication (ages 23 months, 23 months, and 42 months). The remaining individual had no babbling or other reported communication at 4 years old. The majority of individuals over age 12 months were able to walk (n=37/42, 88.1%) and this milestone was achieved at an average age of 21.4 months.

Table 4:

Developmental milestones overall, and both MFDM patients aged 2 years and older, and 5 years and older

	Skill	Overall n=47		Ages 2yo + n=42	Ages 5yo + n=24
		Achieved, (%)	Average age	Achieved, (%)	Achieved, (%)
Gross motor	Sitting with support	43/44, (97.7%)	7 mo	38/39, (97.4%)	21/22, (95.5%)
	Crawling	39/42, (92.9%)	14.1 mo	37/38, (97.4%)	22/22, (100%)
	Walking	37/45, (82.2%)	21.4 mo	37/40, (92.5%)	22/22, (100%)
	Stairs	33/44, (75.0%)	3.3 yr	33/39, (84.6%)	21/22, (95.5%)
Fine motor	Reaches for objects	44/44 (100%)	8.3 mo	39/39, (100%)	22/22, (100%)
	Scribbles	38/44 (86.4%)	29.5 mo	38/39, (97.4%)	21/22, (95.5%)
	Uses utensils	33/43 (76.7%)	3.2 yr	33/38, (86.8%)	21/21, (100%)
	Dresses self	16/45 (35.6%)	6 yr	16/40, (40%)	14/23, (60.9%)
Communication	Single words	34/44 (77.3%)	34 mo	34/39, (87.2%)	21/22, (95.5%)
	Signs	28/43 (65.1%)	27.9 mo	28/38, (73.7%)	15/21, (71.4%)
	Communication device	9/42 (21.4%)	3.7 yr	9/37, (24.3%)	4/20, (25.0%)
	Points	33/43 (76.7%)	21.3 mo	33/38, (86.8%)	18/21, (85.7%)

MFDM = mandibulofacial dysostosis with microcephaly, mo = months, yr = years

Of those who were age 2 years and older, most walked (n=37/40, 92.5%), used single words (n=34/39, 87.18%), and used utensils (n=33/38, 86.84%). Of those who were age 5 years and older, all walked (n=22/22, 100%), almost all used single words (n=21/22, 95.45%), and all used utensils (n=21/21, 100%).

Parental concerns:

Parents were asked open-ended, free-text questions about concerns, challenges, and areas of improvement relating to caring for their child with MFDM, and responses are categorized in Table 5. In regards to overall concerns for their child, most referenced development (n=35/45, 77.8%), with communication (n=23/35, 65.7%) the most frequently mentioned developmental component. Concerns for overall health were expressed by 40% (n=17/45), with feeding being the most frequent specific health concern (n=7/17, 35.3%), followed by neurologic problems (n=5/17, 29.4%). 26.7% of parents expressed concern for the future (n=12/45), and included comments focusing on independence, need for upcoming interventions, and uncertain expectations for their child. Many parents expressed that overall care for their child was a challenge (n=13/43, 30.2%), specifically in regards to financial support, number of appointments and therapies, and finding providers with expertise in MFDM. Three-quarters of parents (n=21/28, 75.0%) felt support regarding care of their child could be improved, specifically the need for improved expertise with MFDM, and communication between care providers. The need for improved support for developmental interventions overall and from schools was expressed by many parents (n=13/28, 46.4%). However, most (n=25/39, 64.1%) had positive comments about their experiences with their child’s school. Overall, speech therapy was felt to be the most helpful developmental intervention for individuals with MFDM (n=35/41, 85.37%).

Table 5:

Categories of parental comments regarding concerns, challenges, and areas of improvement of care for children with MFDM.

Development	Overall	35/45 (77.8%)
	Communication	23/35 (65.7%)
	Developmental delays	13/35 (36.1%)
Health	Overall	17/45 (40.0%)
	Feeding difficulties	7/17 (35.3%)
	Neurologic problems	5/17 (29.4%)
	Hearing problems	4/17 (23.5%)
Uncertain future	Overall	12/45 (26.7%)
Challenges in caring for their child	Overall	13/43 (30.2%)
Improved support in caring for their child	Overall	21/28 (75%)
	Improved provider expertise	8/21 (38.1%)
	Improved provider communication	4/21 (19.1%)
	Improved health care for their child	6/21 (28.6%)
Improved support for development	Overall	13/28 (46.4%)

MFDM = mandibulofacial dysostosis with microcephaly

Family variant analysis:

EFTUD2 family variant testing via Sanger sequencing was performed on seven families’ DNA samples, 6 trios and 1 duo. The probands’ variants consisted of two nonsense variants, three frameshift variants, one intronic variant, and one microdeletion. Three have not been previously reported in available online variant databases (ClinVar, HGMD Professional Version 2017). All parents tested negative for their child’s EFTUD2 variant (Supplementary Table 1). Thirty parents reported prior parental testing, with three reporting parental inheritance for their child with MFDM. Thus the overall de novo rate of EFTUD2 variants in this cohort was 91.8% (n=34/37).

Discussion:

The prevalence of MFDM has been reported at less than 1 in 1,000,000 (Silva et al., 2019). We suspect that the syndrome was previously under-recognized or diagnosed as an alternative mandibulofacial dysostosis syndrome, and that the prevalence of MFDM will increase with more testing of individuals with overlapping features. We utilized parental survey to gather health information about this unique syndrome, as well as to capture parent specific attitudes and perspectives towards care of an individual with MFDM. This paper serves not only to compare a new cohort of individuals with MFDM to the literature to provide phenotypic expansion, but also to summarize specific recommendations for management of complications in MFDM.

The individuals with MFDM reported here show both similarities and differences when compared to the literature. Key craniofacial features are overall similar to previously reported cases (Table 2). Microcephaly was reported in almost all of our patients, however this study does not distinguish the onset of microcephaly, which can be present at birth or acquired (Huang et al., 2016). “Catch-up” growth has also been demonstrated in some individuals with MFDM, who achieve normal adult head measurement parameters (Huang et al., 2016). Thus, we recommend that with or without microcephaly, MFDM must remain on the differential diagnosis in the context of the key craniofacial features, especially if there is also developmental delay.

Individuals with MFDM have the potential for multilevel airway obstruction, including choanal stenosis, glossoptosis and obstruction, and tracheal anomalies. Airway surgery was reported in most (n=42) individuals, including choanal stenosis, TEF/EA repair, tonsillectomy and adenoidectomy, mandibular distraction osteogenesis, tracheostomy, and others. Therefore, we recommend that all individuals with MFDM receive a formal airway evaluation, with polysomnography as indicated, to assess for interventional needs.

Many individuals with MFDM meet criteria for Pierre Robin sequence, defined as micrognathia, glossoptosis, and airway obstruction after birth. Pierre Robin sequence should be suspected with prenatal detection of micrognathia, cleft palate, and polyhydramnios (Di Pasquo et al., 2017; Insalaco & Scott, 2018). Mouthon et al. reported on prenatal diagnosis of micrognathia in 41 pregnancies, with two eventually diagnosed with MFDM (2019). We recommend that MFDM should be considered in the differential diagnosis for prenatal syndromic Pierre Robin sequence, especially in conjunction with prenatal microcephaly or intrauterine growth restriction.

Feeding difficulties were prevalent in our cohort, and are a frequent comorbidity in individuals with airway anomalies, including Pierre Robin sequence and TEF/EA (Mahoney & Rosen, 2017; Rathé et al., 2015). While just over half ever required a feeding tube, this had decreased to a quarter at the time of this survey, demonstrating improvement in oral skills with age and treatment of airway abnormalities. We recommend a detailed feeding evaluation and continued therapy interventions on all individuals with MFDM, especially those with additional airway complications.

Six individuals reported a need for cardiac surgery (n=6/46, 13.04%), and five described a structural heart defect (ASD n=2; PDA n=2, truncus arteriosus n=1). This combined with other structural heart defects in the literature (VSD, PFO, peripheral pulmonic stenosis, and aortic arch anomalies), highlights the need for cardiology assessment in individuals with MFDM, with echocardiogram as indicated.

Here, we investigated the types of refractive errors in those with MFDM, and demonstrated a higher proportion that in the literature (n=14/47, 29.8% vs n=3/17, 17.7%), with astigmatism the most commonly seen (n=10/14). Due to this prevalence of vision changes, we recommended an ophthalmology exam be performed to assess refractive errors. Some unique, rarely reported features are represented in our study cohort, including two individuals with laryngeal clefts. Another patient reported a laryngeal cyst, which has not been reported previously.

Developmentally, individuals with MFDM have global delays, with communication being the most frequently reported. Families consistently reported that speech therapy was the most beneficial support therapy for their child. Many children utilized forms of non-verbal communication, including signing (n=28/43, 65.1%) and communication devices (n=9/42, 21.4%), highlighting the need for evaluation of alternative forms of communication. While hearing loss is certainly prevalent in this population and can impact communication, in this study even those without hearing loss (n=5) reported speech delays. It should also be noted that while most children had a diagnosis of hearing loss prior to age one year (n=24/39, 61.5%), hearing loss was identified in early childhood as well. We thus recommend early and sustained speech therapy and detailed hearing assessment at birth and annually during childhood for individuals with MFDM.

Additionally, the detailed developmental milestones documented demonstrate that individuals with MFDM are able to make progress in milestone achievement (Table 4). For example, while 82.2% (n=37/45) of individuals walked overall, when broken down by age, 92.5% of those two years and older walked (n=37/40), and 100% of those 5 years and older (n=22/22) walked. Notably, even communication, the most frequently reported and more severe developmental concern in MFDM, improved with age, with most having some single words (n=21/22, 95.5%) by age five years. We therefore recommended formal developmental assessments for all individuals with MFDM and early referrals to and continued use of appropriate supportive therapies.

When asked for free responses, most parents were concerned about development in their child with MFDM, specifically communication (Table 5). Health related concerns from parents included feeding, hearing loss, and neurologic concerns, which we recommend as areas where providers can engage with families to address concerns about their child when appropriate. The number of provider and therapy visits, as well as medications, generally decreased with age (Figure 2). However, this trend may be influenced by older individuals receiving services through schools, and thus underestimate the burden of care in older individuals. This is valuable information to share with families regarding long-term expectations in care of their child with MFDM.

The majority (75%) of patients reported with MFDM have had de novo EFTUD2 variants with inherited variants reported in 19% (Huang et al., 2016). We confirmed an additional seven individuals with de novo inheritance (6 trios, 1 duo), with genotypes as shown in Supplemental Table 1. Three individuals in this cohort reported inheritance from an affected parent. Germline mosaicism has been reported in 6% of MFDM individuals (two sibling pairs), but none in this survey (Huang et al.). Given the variable expressivity of MFDM, we recommend offering testing to all parents of individuals with MFDM.

There are several limitations to our study. First, the data reported here rely on self-reported survey responses which may be subject to recall or reporting biases and may be confounded by parental understanding of medical terminology. Further, we were unable to verify health details with medical record review. Additionally, these study participants were recruited from the MDFM family conference or the online support group, and may not accurately reflect the collective MFDM patient population. Future directions for study of long-term outcomes for MFDM include formal developmental assessments in children, as well as evaluation of additional adults.

MFDM is associated with a spectrum of congenital anomalies and developmental delays, and this study provides additional information on the prevalence of features in MFDM. Additionally, it highlights additional phenotypic information such as new or rarely reported airway anomalies, the need for airway interventions, and prenatal findings. This study also enhances the understanding of the associated developmental profile. Our findings will help provide expectations for providers and caregivers in the management of individuals with MFDM. Further, identification of key parental concerns, including developmental progress, specific health concerns, and increased support, will help guide conversations on how to optimize care for individuals with MFDM.

Supplementary Material

Supplemental Figure 1

Supplemental Figure 1: Types of specialist appointments and evaluations utilized by individuals with MFDM (n=47)