Prenatal diagnosis of fibular aplasia-tibial campomelia-oligosyndactyly syndrome: Two case reports and review of the literature

Fibular aplasia-tibial campomelia-oligosyndactyly also known as FATCO syndrome is a rare condition characterized by fibular aplasia, shortening and anterior bowing of the lower limb at the tibia with overlying soft tissue dimpling and oligosyndactyly. Its etiology is currently unknown, but there is a male predominance. There are less than 30 cases reported in the literature but only three with prenatal diagnosis. We report two cases of FATCO syndrome with prenatal lower limb malformation diagnosis. Identification of the ultrasound findings of this condition in the prenatal stages allows an adequate parental counselling regarding the clinical features, prognosis, and potential treatments.

A novel association of campomelic dysplasia and hydrocephalus with an unbalanced chromosomal translocation upstream of SOX9

Campomelic dysplasia is a rare skeletal dysplasia characterized by Pierre Robin sequence, craniofacial dysmorphism, shortening and angulation of long bones, tracheobronchomalacia, and occasionally sex reversal. The disease is due to mutations in SOX9 or chromosomal rearrangements involving the long arm of Chromosome 17 harboring the SOX9 locus. SOX9, a transcription factor, is indispensible in establishing and maintaining neural stem cells in the central nervous system. We present a patient with angulation of long bones and external female genitalia on prenatal ultrasound who was subsequently found to harbor the chromosomal abnormality 46, XY, t(6;17) (p21.1;q24.3) on prenatal genetic testing. Comparative genomic hybridization revealed deletions at 6p21.1 and 17q24.3, the latter being 2.3 Mb upstream of SOX9 Whole-exome sequencing did not identify pathogenic variants in SOX9, suggesting that the 17q24.3 deletion represents a translocation breakpoint farther upstream of SOX9 than previously identified. At 2 mo of age the patient developed progressive communicating ventriculomegaly and thinning of the cortical mantle without clinical signs of increased intracranial pressure. This case suggests ventriculomegaly in some cases represents not a primary impairment of cerebrospinal fluid dynamics, but an epiphenomenon driven by a genetic dysregulation of neural progenitor cell fate.

FATCO Syndrome (Fibular Aplasia, Tibial Campomelia, Oligosyndactyly with Talar Aplasia). A Case Study

FATCO syndrome consists of fibular hemimelia, tibial campomelia and oligosyndactyly. FATCO syndrome can also be associated with other congenital anomalies; therefore, every case needs thorough evaluation so as to make the management of the patient easier. A few cases of this syndrome have been described in literature but only two cases have been reported in India so far. We present a 3-year-old male child born of a non-con-sanguinous marriage with FATCO syndrome and ipilateral talar aplasia without any other congenital anomalies.

Molecular diagnosis of hypophosphatasia and differential diagnosis by targeted Next Generation Sequencing

Hypophosphatasia (HPP) is a rare inherited skeletal dysplasia due to loss of function mutations in the ALPL gene. The disease is subject to an extremely high clinical heterogeneity ranging from a perinatal lethal form to odontohypophosphatasia affecting only teeth. Up to now genetic diagnosis of HPP is performed by sequencing the ALPL gene by Sanger methodology. Osteogenesis imperfecta (OI) and campomelic dysplasia (CD) are the main differential diagnoses of severe HPP, so that in case of negative result for ALPL mutations, OI and CD genes had often to be analyzed, lengthening the time before diagnosis. We report here our 18-month experience in testing 46 patients for HPP and differential diagnosis by targeted NGS and show that this strategy is efficient and useful. We used an array including ALPL gene, genes of differential diagnosis COL1A1 and COL1A2 that represent 90% of OI cases, SOX9, responsible for CD, and 8 potentially modifier genes of HPP. Seventeen patients were found to carry a mutation in one of these genes. Among them, only 10 out of 15 cases referred for HPP carried a mutation in ALPL and 5 carried a mutation in COL1A1 or COL1A2. Interestingly, three of these patients were adults with fractures and/or low BMD. Our results indicate that HPP and OI may be easily misdiagnosed in the prenatal stage but also in adults with mild symptoms for these diseases.

A case of campomelic dysplasia without sex reversal

Campomelic dysplasia (CD; OMIM #114290), a rare form of congenital short-limbed dwarfism, is due to mutations in SOX9, a member of the SOX (SRY-related HMG box) gene family. Multiparous mother at 38 weeks' gestation delivered a 3,272 g baby boy with characteristic phenotypes including bowing of the lower limbs, a narrow thoracic cage, 11 pairs of ribs, hypoplastic scapulae, macrocephaly, flattened supraorbital ridges and nasal bridge, cleft palate, and micrognathia. He underwent a tracheostomy at the age of three months for severe laryngomalacia after a number of repeated hospitalizations due to respiratory problems and died at the age of four months from progressive respiratory failure. He was diagnosed as having CD based on a novel frameshift mutation (p.Gln458ArgfsX12) in the SOX9 gene, the mutation which has not yet been reported in Korea.

A novel SOX9 nonsense mutation, q401x, in a case of campomelic dysplasia with XY sex reversal

Campomelic dysplasia (CD, MIM 114290) is a rare, often lethal, dominantly inherited, congenital skeletal dysplasia, associated with male-to-female autosomal sex reversal and due to de novo mutations of the SOX9 gene, a tissue-specific transcription factor gene involved both in skeletogenesis and male sexual differentiation. Here we report on a 4 months-old 46,XY sex reversed infant with typical clinical features for CD due to a novel mutation of the SOX9 gene, Q401X, leading to synthesis of a truncated SOX9 protein that completely lacks the C-terminal transactivation domain.

Camptomelia in a rhesus macaque (Macaca mulatta)

An 8.5-mo-old female rhesus macaque was examined for an apparent lump on the right arm, below the elbow. The macaque showed no signs of pain or discomfort. Examination revealed that the lump was actually a bend in the forearm. Radiography demonstrated that some of the long bones of the animal were bowed. Differential diagnoses included rickets, hyperparathyroidism, pseudohyperparathyroidism, and a growth dysplasia. No other similar abnormalities in animals from that cage or any other enclosure in our large colony were observed. Blood chemistries and a complete hemogram were within normal limits for a macaque of this age. Serum was submitted for a vitamin D profile that included assays for parathyroid hormone, 25-hydroxyvitamin D, and ionized calcium. Serum samples from sex- and age-matched normal controls were sent for comparison and to establish a baseline profile. The affected animal had vitamin D levels comparable to unaffected controls. Bone biopsies appeared normal for a macaque of this age. Fluorine levels in the drinking water supply were within acceptable limits. Consistent with the information available, a diagnosis of idiopathic camptomelia, or bowing of the long bones, was made. In humans, developmental camptomelia is associated with several bone dysplasias in infants and children. These conditions are thought to be caused by genetic mutations in enzymes or transcription factors that control development of the epiphyses and are almost always associated with other lethal and nonlethal developmental abnormalities.