Recognition of Zellweger syndrome in infancy

Inborn Errors of Metabolism and the Gastrointestinal Tract

Inborn errors of metabolism (IEMs) are usually recognized by characteristic neurologic and metabolic manifestations and sometimes by dysmorphism. However, IEMs can present with a wide variety of gastrointestinal manifestations, whether as the primary or a minor clinical symptom. Regardless, gastrointestinal and hepatic manifestations of IEMs are important clinical features that can help identify an underlying defect; these disorders should be taken into consideration as part of a patient's clinical assessment. It is prudent to include metabolic disorders in the differential diagnosis because in some cases, gastrointestinal symptoms may be the only presenting feature in a patient with an underlying IEM.

A clinical case of Zellweger syndrome in a patient with a previous history of ocular medulloepithelioma

Peroxisomal biogenesis disorders (PBDs) are autosomal recessive diseases caused by mutations in one of the 14 PEX genes described in the scientific literature.

All of these syndromes may be associated with different mutations in the PEX genes, the most frequent being PEX1 for patients with Zellweger syndrome (ZS).

In this paper, we present the case of a patient with a peculiar clinical history: evisceration of the left eye (LE) at 4 years of age because of a benign ocular teratoid medulloepithelioma and a progressive loss of visual acuity (VA) in the right eye (RE) beginning at 9 years of age, leading to the diagnosis of ZS. In addition, the patient presented a mutation in the PEX14 gene that has not been previously described in the literature.

This case broadens the spectrum of clinical expression in ZS patients because of not only the presence of a benign ocular teratoid medulloepithelioma at 4 years of age but also the late clinical expression of ZS (at 9 years of age).

Biochemical and clinical profiles of 52 Tunisian patients affected by Zellweger syndrome

BACKGROUND

Zellweger syndrome (ZS) is a peroxisome biogenesis disorder attributed to a mutation of the PEX genes family. The incidence of this disease in Africa and the Arab world remains unknown. This contribution is aimed at describing the clinical phenotype and biochemical features in Tunisian patients with ZS in order to improve the detection and management of this severe disorder.

METHODS

A total of 52 patients diagnosed with ZS and 60 age- and sex-matched healthy controls were included in this study. Patients were recruited during the past 21 years, and the diagnosis of ZS was based on clinical and biochemical characteristics. Plasma very long chain fatty acids (VLCFA) were analyzed using capillary gas chromatography. The estimated incidence of ZS was calculated using the Hardy-Weinberg formula.

RESULTS

The estimated incidence of ZS is 1/15,898 in Tunisia. Age at diagnosis varied between 3 days and 18 months. Severe neurological syndrome, polymalformative features, and hepatodigestive signs were observed in 100%, 67.9%, and 32% of patients, respectively. Values for plasma C26:0 and C26:0/C22:0 and C24:0/C22:0 ratios were noticeably higher in ZS patients than in controls. Distributions of values were completely different for C26:0 (0.10-0.37 vs. 0.001-0.009), C26:0/C22:0 ratio (0.11-1.29 vs. 0.003-0.090), and C24:0/C22:0 ratio (1.03-3.18 vs. 0.4-0.90) in ZS patients versus controls, respectively.

CONCLUSIONS

This study highlights the high incidence of ZS in Tunisia and the possibility of simple and reliable biochemical diagnosis, thus permitting early genetic counseling for families at risk.

Novel compound heterozygous mutations in the PEX1 gene in two Chinese newborns with Zellweger syndrome based on whole exome sequencing

Peroxisome biogenesis disorders (PBDs) represent a spectrum of human genetic disorders that are characterized by damaged peroxisome assembly. In the newborn period, the characteristics of affected patients include dysmorphic facial features, neonatal hypotonia, seizures, ocular abnormalities, poor feeding, liver cysts with hepatic dysfunction and skeletal defects. These can be caused by a defect in at least 14 different PEX genes. In this study, whole-exome sequencing (WES) was performed on samples from two Chinese newborns with clinical features of Zellweger syndrome. WES identified two novel mutations (c.2416+1G>T and c.2489delT) in patient 1 and another two novel mutations (c.1483+1G>A and c.1727dupG) in patient 2 in the PEX1 gene. All four mutations have a serious influence on the protein function, which also highlights the power of WES, particularly in clinically challenging cases.

Fetal echogenic bowel in association with Zellweger syndrome

Increased echogenicity of fetal bowel in the second trimester obstetrical ultrasound has been described in association with several pathologic conditions, such as growth restriction, aneuploidy, cystic fibrosis, congenital infections, and gastrointestinal malformations. Zellweger syndrome (ZS) is the prototype of peroxisomal disorders characterized by craniofacial dysmorphism and severe neurologic abnormalities. We report two cases with fetal echogenic bowel (FEB) but no associated anomalies and normal fetal growth. After birth, clinical and laboratory findings led to diagnosis of ZS. Association of FEB with neurometabolic disorders is limited to a few case reports in the medical literature. To the best of our knowledge, this is the first report of ZS associated with FEB.

Child neurology: Zellweger syndrome

Zellweger syndrome (ZS) is a severe manifestation of disease within the spectrum of peroxisome biogenesis disorders that includes neonatal adrenoleukodystrophy, infantile Refsum disease, and rhizomelic chondroplasia punctata. Patients with ZS present in the neonatal period with a characteristic phenotype of distinctive facial stigmata, pronounced hypotonia, poor feeding, hepatic dysfunction, and often seizures and boney abnormalities. In patients with ZS, a mutation in one of the PEX genes coding for a peroxin (a peroxisome assembly protein) creates functionally incompetent organelles causing an accumulation of very long chain fatty acids (VLCFA), among other complications. Despite an absence of treatment options, prompt diagnosis of ZS is important for providing appropriate symptomatic care, definitive genetic testing, and counseling regarding family planning.

Infantile hypertrophic pyloric stenosis--genetics and syndromes

Infantile hypertrophic pyloric stenosis (IHPS) is a common condition in neonates that is characterized by an acquired narrowing of the pylorus. The aetiology of isolated IHPS is still largely unknown. Classic genetic studies have demonstrated an increased risk in families of affected infants. Several genetic studies in groups of individuals with isolated IHPS have identified chromosomal regions linked to the condition; however, these associations could usually not be confirmed in subsequent cohorts, suggesting considerable genetic heterogeneity. IHPS is associated with many clinical syndromes that have known causative mutations. Patients with syndromes associated with IHPS can be considered as having an extreme phenotype of IHPS and studying these patients will be instrumental in finding causes of isolated IHPS. Possible pathways in syndromic IHPS include: (neuro)muscular disorders; connective tissue disorders; metabolic disorders; intracellular signalling pathway disturbances; intercellular communication disturbances; ciliopathies; DNA-repair disturbances; transcription regulation disorders; MAPK-pathway disturbances; lymphatic abnormalities; and environmental factors. Future research should focus on linkage analysis and next-generation molecular techniques in well-defined families with multiple affected members. Studies will have an increased chance of success if detailed phenotyping is applied and if knowledge about the various possible causative pathways is used in evaluating results.

MR imaging workup of inborn errors of metabolism of early postnatal onset

Immediate or early postnatal onset forms of neurometabolic disorders represent a clinically important subgroup because these often present as a life-threatening episode of metabolic decompensation shortly after birth. This article focuses on this group of diseases, often referred to as "devastating neurometabolic diseases" of the newborn. Awareness of the most common entities and their clinical, biochemical, and diagnostic imaging manifestations is important because if undiagnosed and untreated, the diseases may have catastrophic consequences. Although formal diagnosis relies on laboratory tests, diagnostic imaging is often pivotal in both reaching the correct diagnosis and/or orienting further targeted investigative efforts.

Peroxisomal disorder-unusual presentation as failure to thrive in early infancy

Failure to thrive is not uncommon in paediatric practice and often leads to multiple investigations to find the underlying cause. We report an infant who presented mainly with mild dysmorphism, failure to thrive and elevated alanine transferase (ALT) in early infancy. She was diagnosed to have a peroxisomal biogenesis disorder on further investigation. Peroxisomal disorders represent a spectrum of conditions with absent or abnormal function of intra-cytoplasmic organelles called peroxisomes. Clinical presentation is quite varied, depending on both the type and severity. We describe the clinical presentation of this case, followed by a brief discussion on peroxisomal disorders.