Johanson-Blizzard syndrome: hepatic and hematological features with novel genotype

Johanson-Blizzard Syndrome: A Case Report From Bahrain With a Literature Review

Johanson-Blizzard syndrome (JBS) is a rare hereditary autosomal recessive disorder caused by a mutation in the ubiquitin protein ligase E3 component n-recognin 1 (UBR1) gene. This syndrome is characterized by the following typical clinical features: hypoplasia or aplasia of the alae nasi, congenital scalp defects, sensorineural hearing loss, hypothyroidism, growth retardation, psychomotor retardation, imperforate anus, genitourinary anomalies, and atypical hair patterns. Here, we describe a case of a 12-year-old girl with JBS of consanguineous parents. During the last trimester of pregnancy, a congenital abnormality affecting the nose was detected. Immediately after birth, the clinical examination revealed dysmorphic features in the form of hypoplastic alae nasi, microcephaly, mild hypotelorism, and cutis aplasia on the scalp. The genetic testing of the patient showed a novel sequence change mutation of the UBR1 gene (1bp duplication causing a frameshift), while both parents were carriers for this mutation. Moreover, a diagnosis of pancreatic insufficiency and subclinical hypothyroidism was made based on clinical presentation and laboratory results. The patient was started on pancreatic enzyme replacement therapy and fat-soluble vitamins, minerals, and antioxidant syrup. Further assessment revealed hypotonia, growth impairment, delay in reaching developmental milestones, and bilateral profound sensorineural hearing loss, which was managed with bilateral cochlear implantation. In addition, the patient underwent multiple craniofacial reconstructive surgeries. This case report highlights the importance of early diagnosis and multidisciplinary care of patients with JBS.

Clinical Characteristics and Genetic Causes of Infantile Exocrine Pancreatic Insufficiency in Chinese Patients: Study From a Tertiary Care Center

OBJECTIVE

Infantile exocrine pancreatic insufficiency is a rare disease. We examined phenotypes and performed genetic sequencing in children with this disorder.

METHODS

We enrolled 4 infants with exocrine pancreatic insufficiency. Patients were characterized by phenotypes and radiologic findings. Genetic sequencing was performed.

RESULTS

Average age of disease onset was 2 months. Average (standard deviation [SD]) age at diagnosis was 11.9 (7.0) months. Patients presented with chronic steatorrhea and failure to thrive. Two had mild zinc deficiency. Imaging showed pancreatic lipomatosis and metaphyseal dysplasia among all patients. For these patients with similar phenotypes, genetic sequencing revealed that 2 patients had novel UBR1 mutations (c.[3043_3046delAAAG; c.3848 + 6T > C] and c.[1850-2A > T;c.4290T > G], reference sequence NM_174916), and another 2 patients had homozygous SBDS c.258 + 2T > C mutation and SBDS c.[258 + 2T > C;c.428C > T] mutations (reference sequence NM_016038.2). All patients received pancreatic enzyme replacement therapy.

CONCLUSIONS

Here we described 4 patients with infantile exocrine pancreatic insufficiency confirmed by laboratory tests and imaging. Whole-exome sequencing and Sanger sequencing showed that 2 patients had Johanson-Blizzard syndrome and 2 patients had Shwachman-Diamond syndrome. Genetic sequencing should be applied for definite diagnosis among these patients.

Mutations in the human UBR1 gene and the associated phenotypic spectrum

Johanson-Blizzard syndrome (JBS) is a rare, autosomal recessive disorder characterized by exocrine pancreatic insufficiency, typical facial features, dental anomalies, hypothyroidism, sensorineural hearing loss, scalp defects, urogenital and anorectal anomalies, short stature, and cognitive impairment of variable degree. This syndrome is caused by a defect of the E3 ubiquitin ligase UBR1, which is part of the proteolytic N-end rule pathway. Herein, we review previously reported (n = 29) and a total of 31 novel UBR1 mutations in relation to the associated phenotype in patients from 50 unrelated families. Mutation types include nonsense, frameshift, splice site, missense, and small in-frame deletions consistent with the hypothesis that loss of UBR1 protein function is the molecular basis of JBS. There is an association of missense mutations and small in-frame deletions with milder physical abnormalities and a normal intellectual capacity, thus suggesting that at least some of these may represent hypomorphic UBR1 alleles. The review of clinical data of a large number of molecularly confirmed JBS cases allows us to define minimal clinical criteria for the diagnosis of JBS. For all previously reported and novel UBR1 mutations together with their clinical data, a mutation database has been established at LOVD.