Intestinal malrotation in a female newborn affected by Osteopathia Striata with Cranial Sclerosis due to a de novo heterozygous nonsense mutation of the AMER1 gene

Background: Osteopathia Striata with Cranial Sclerosis (OS-CS), also known as Horan-Beighton Syndrome, is a rare genetic disease; about 90 cases have been reported to date. It is associated with mutations (heterozygous for female subjects and hemizygous for males) of the AMER1 gene, located at Xq11.2, and shows an X-linked pattern of transmission. Typical clinical manifestations include macrocephaly, characteristic facial features (frontal bossing, epicanthal folds, hypertelorism, depressed nasal bridge, orofacial cleft, prominent jaw), hearing loss and developmental delay. Males usually present a more severe phenotype than females and rarely survive. Diagnostic suspicion is based on clinical signs, radiographic findings of cranial and long bones sclerosis and metaphyseal striations, subsequent genetic testing may confirm it.

Case presentation: Hereby, we report on a female newborn with frontal and parietal bossing, narrow bitemporal diameter, dysplastic, low-set and posteriorly rotated ears, microretrognathia, cleft palate, and rhizomelic shortening of lower limbs. Postnatally, she manifested feeding intolerance with biliary vomiting and abdominal distension. Therefore, in the suspicion of bowel obstruction, she underwent surgery, which evidenced and corrected an intestinal malrotation. Limbs X-ray and skull computed tomography investigations did not show cranial sclerosis and/or metaphyseal striations. Array-CGH analysis revealed normal findings. Then, a target next generation sequencing (NGS) analysis, including the genes involved in skeletal dysplasias, was performed and revealed a de novo heterozygous nonsense mutation of the AMER1 gene. The patient was discharged at 2 months of age and included in a multidisciplinary follow-up. Aged 9 months, she now shows developmental and growth (except for relative macrocephaly) delay. The surgical correction of cleft palate has been planned.

Conclusions: Our report shows the uncommon association of intestinal malrotation in a female newborn with OS-CS. It highlights that neonatologists have to consider such a diagnosis, even in absence of cranial sclerosis and long bones striations, as these usually appear over time. Other syndromes with cranial malformations and skeletal dysplasia must be included in the differential diagnosis. The phenotypic spectrum is wide and variable in both genders. Due to variable X-inactivation, females may also show a severe and early-onset clinical picture. Multidisciplinary management and careful, early and long-term follow-up should be offered to these patients, in order to promptly identify any associated morbidities and prevent possible complications or adverse outcomes.