Pontine hypoplasia in Carey-Fineman-Ziter (CFZ) syndrome

Identification of STAC3 variants in non-Native American families with overlapping features of Carey-Fineman-Ziter syndrome and Moebius syndrome

Horstick et al. (2013) previously reported a homozygous p.Trp284Ser variant in STAC3 as the cause of Native American myopathy (NAM) in 5 Lumbee Native American families with congenital hypotonia and weakness, cleft palate, short stature, ptosis, kyphoscoliosis, talipes deformities, and susceptibility to malignant hyperthermia (MH). Here we present two non-Native American families, who were found to have STAC3 pathogenic variants. The first proband and her affected older sister are from a consanguineous Qatari family with a suspected clinical diagnosis of Carey-Fineman-Ziter syndrome (CFZS) based on features of hypotonia, myopathic facies with generalized weakness, ptosis, normal extraocular movements, cleft palate, growth delay, and kyphoscoliosis. We identified the homozygous c.851G>C;p.Trp284Ser variant in STAC3 in both sisters. The second proband and his affected sister are from a non-consanguineous, Puerto Rican family who was evaluated for a possible diagnosis of Moebius syndrome (MBS). His features included facial and generalized weakness, minimal limitation of horizontal gaze, cleft palate, and hypotonia, and he has a history of MH. The siblings were identified to be compound heterozygous for STAC3 variants c.851G>C;p.Trp284Ser and c.763_766delCTCT;p.Leu255IlefsX58. Given the phenotypic overlap of individuals with CFZS, MBS, and NAM, we screened STAC3 in 12 individuals diagnosed with CFZS and in 50 individuals diagnosed with MBS or a congenital facial weakness disorder. We did not identify any rare coding variants in STAC3. NAM should be considered in patients presenting with facial and generalized weakness, normal or mildly abnormal extraocular movement, hypotonia, cleft palate, and scoliosis, particularly if there is a history of MH.

A defect in myoblast fusion underlies Carey-Fineman-Ziter syndrome

Multinucleate cellular syncytial formation is a hallmark of skeletal muscle differentiation. Myomaker, encoded by Mymk (Tmem8c), is a well-conserved plasma membrane protein required for myoblast fusion to form multinucleated myotubes in mouse, chick, and zebrafish. Here, we report that autosomal recessive mutations in MYMK (OMIM 615345) cause Carey-Fineman-Ziter syndrome in humans (CFZS; OMIM 254940) by reducing but not eliminating MYMK function. We characterize MYMK-CFZS as a congenital myopathy with marked facial weakness and additional clinical and pathologic features that distinguish it from other congenital neuromuscular syndromes. We show that a heterologous cell fusion assay in vitro and allelic complementation experiments in mymk knockdown and mymk^insT/insT zebrafish in vivo can differentiate between MYMK wild type, hypomorphic and null alleles. Collectively, these data establish that MYMK activity is necessary for normal muscle development and maintenance in humans, and expand the spectrum of congenital myopathies to include cell-cell fusion deficits.

Temporomandibular joint ankylosis as part of the clinical spectrum of Carey-Fineman-Ziter syndrome?

The Carey-Finema-Ziter syndrome (CFZS, MIM 254940) is an apparently autosomal recessively inherited disorder consisting of the combination of non-progressive congenital myopathy with Moebius and Pierre Robin sequence, facial anomalies and growth delay. Mental development has been described as normal or delayed. Temporomandibular joint (TMJ) ankylosis is the immobility of the joint caused by ankylotic fusion of the mandible to the cranial base or zygoma. It is a serious and disabling condition that may cause problems in mastication, digestion, speech, appearance, and oral hygiene. Most often is a true ankylosis of the TMJ but other pathological mechanisms are described (i.e., the fusion of the coronoid process to temporal bone or with the zygoma, or a variety of soft tissues disorders like Fibrodysplasia Ossificans Progressiva). Here we report a 2-year-old girl fitting with a clinical diagnosis of CFZS associated with a limited mouth opening in which temporomandibular joint ankylosis was suspected. Because it has been postulated that many clinical features in CFZS may only be secondary effects of brainstem anomalies and muscle weakness during development, the limited opening of the mouth observed in our patient could represent a rare clinical feature of CFZS itself. © 2016 Wiley Periodicals, Inc.

Carey-Fineman-Ziter syndrome: a spectrum of presentations

Carey-Fineman-Ziter syndrome is characterized by facial diplegia with an ophthalmoplegia comprising the Moebius sequence, Pierre Robin sequence with micrognathia, short stature, postnatal-onset microcephaly, hypotonia and muscular hypoplasia, extensive brainstem involvement, and pontine hypoplasia. We report a 38-week-gestation infant with features consistent with Carey-Fineman-Ziter syndrome but with phenotypical features that have not previously been described. The infant had severe hypoplasia of the pons and cerebellum, seizures, hypotonia, ophthalmoplegia, downslanting palpebral fissures, tongue hypoplasia, micrognathia, and facial diplegia. The karyotype was normal. Of note, there was a focal contour abnormality in the anterior two-thirds of the tongue, which necessitated tracheostomy on the third day of life to maintain the airway, and a well-circumscribed mass on both sides of the chest. These features have not been previously found to be associated with this syndrome, and the clinical significance is unknown. Case reports of rare disorders give significant information on the diagnosis, description, and evolving phenotype of rare syndromes.