A clinical case of a familial form of hereditary metabolic disease from the group of peroxisomal diseases (D-bifunctional protein deficiency) in the neonatal period

The purpose of this report is to highlight the clinical manifestations, as well as variants of the course and diagnosis complexity of peroxisomal disorders to a wide range of practitioners (specializing in perinatology, pediatrics, neurology, genetics, and endocrinology).

Clinical and pathogenetic mechanisms of peroxisomal disorders

Peroxisome biogenesis disorders are a group of hereditary human diseases, based on a deficiency in the functional activity of peroxisomes due to their complete absence or insufficient amount in the body cells. Peroxisomes were discovered in 1954 and they were the last cell organelles that had remained unexplored. The peroxisome matrix has a granular structure and contains a large number of proteins, but at the same time, DNA and ribosomes are absent in it. Mammalian cells (with the exception of erythrocytes) contain hundreds of peroxisomes; the liver, brain, and kidneys contain most of them [1]. The most important function of eukaryotic cells is the β-oxidation of fatty acids, which may occur both in mitochondria and in peroxisomes in four steps, which are dehydration, hydration, dehydrogenation again, and thiolytic cleavage. There are great differences between the mitochondrial and peroxisomal β-oxidation systems in terms of both their enzymatic organization and their role in the cellular oxidation of fatty acids. Mitochondria are involved in the β-oxidation of most of the fatty acids obtained from the human daily diet, whereas peroxisomes play an indispensable role in the oxidation of very long-chain fatty acids, branched-chain fatty acids such as pristanic acid, and bile acids of intermediate compounds such as dihydroxycholestane (DHSA) and trihydroxycholestane (THCA) acids. Though peroxisomes were initially supposed to play only a minor role in mammalian metabolism, it has become obvious that they catalyze the main reactions in a number of different metabolic pathways and thus play an indispensable role in intermediate metabolism [2]. Like mitochondria, the peroxisome is considered to be one of the main oxygen utilization centers in the cell, but as a result of peroxisomal oxidation, hydrogen peroxide (not macroergic compounds) is formed. Two main models of peroxisome biogenesis have been established; they provide for the participation of special proteins, called peroxins, in their biogenesis. They are indicated by the abbreviation Pexp and the number corresponding to the order of their detection. Recently, 32 peroxins have been discovered, and 14 of them have been described in humans. Peroxins take part in the assembly of a mature, functional peroxisome by participating in the import of proteins into peroxisomes, biogenesis of peroxisome membranes, and division of these organelles.

Various mutations in the genes of these 14 peroxins may lead to hereditary disorders of peroxisome biogenesis. Mutations in different genes may also lead to the same clinical phenotype. At the same time, mutations of the same gene may cause different clinical forms. The disorders of the Pexp 1 gene are the most common ones.

The importance of peroxisomes for humans is obvious due to the existence of a group of hereditary diseases, peroxisomal disorders caused by a violation of one or more peroxisomal functions. The prototype of this group of diseases is considered to be the cerebro-hepato-renal (Zellweger) syndrome. Patients suffering from this disease do not have any morphologically distinguishable peroxisomes, which leads to the loss of almost all the peroxisome functions. Clinically, patients with Zellweger syndrome have a wide variety of severe abnormalities, which often result in early death [3][4]. The mode of inheritance is autosomal-recessive. In the United States, the total incidence of diseases from the group of peroxisomal diseases is 1:50,000 alive newborns. The epidemiological data for Russia are not provided. Thus, it is the defects of peroxins that determine the violation of biogenesis by peroxisomes, which were first described in Zellweger syndrome by Goldfisher et al. [5].

Classically, the group of peroxisomal diseases of the spectrum of Zellweger syndrome includes neonatal adrenoleukodystrophy and infantile Refsum disease. These disorders are three manifestations of the ongoing disease, from the most to the least severe one. The disease-causing genetic defect occurs in 1 of at least 11 genes involved in peroxisome formation or protein import (PEX family of genes). The manifestations also include facial dysmorphic disorder, malformations of the central nervous system, demyelination, neonatal seizures, hypotension, hepatomegaly, kidney cysts, short limbs with rough epiphysis (spot chondrodysplasia), cataracts, retinopathy, hearing deficiency, delayed psychomotor development, and peripheral neuropathy. The biochemical diagnosis is established by detecting elevated blood levels of very long-chain fatty acids having 20–26 carbon atoms, phytanic acid, intermediate bile acids, and pipecolic acid.

The experimental studies have shown that several enzymes are involved at each stage of the peroxisomal β-oxidation pathway. Two acetyl-CoA oxidases with different substrate specificity have been identified in humans.

At the turn of the 21^st century, a new enzyme of peroxisomal β-oxidation was described, which was called D-bifunctional protein (DBP) with the activity of enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase, primarily reacting with α-methyl fatty acids, such as pristanic acid, di- and trihydroxycholestanic acid. The subsequent results have shown that the identified DBP plays an essential role in the peroxisomal β-oxidation pathway and it cannot be compensated for by the previously known L-specific bifunctional protein (L-BP) [6]. These data helped to identify the defect in some patients suffering from peroxisomal β-oxidation disorder (as it had been supposed, a disorder of an unknown origin) [7]. The term “D-bifunctional protein” arose due to the fact that this single enzyme contains several active domains responsible for successive stages of peroxisomal β-oxidation.

The HSD17B4 gene mapped on the 5^th chromosome at the 5q23.1 locus encodes a DBP, which is a multifunctional enzyme catalyzing the second and the third stages of peroxisomal β-oxidation of fatty acids and their derivatives [8][9][10].

Therefore, DBP is a homodimeric enzyme with 79 kDa subunits containing three functional domains: 3-hydroxyacyl-CoA dehydrogenase, 2-enoyl-CoA hydratase, and a domain similar to sterol carrier protein 2. Three functional units of DBP are necessary for the decomposition of very long-chain fatty acids, α-methyl branched-chain fatty acids, and bile acid intermediates such as DHCA and THCA [11].

The deficiency of D-functional protein is divided into three subtypes depending on the insufficient activity of the enzyme. Type I DAD deficiency is a deficiency of both 2-eniol-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase activity; type II DAD is a deficiency of only hydratase activity, and type III DAD is a deficiency of only dehydrogenase activity [3][12]. All three types have a similar clinical picture, but they differ in severity. Thus, patients suffering from type I deficiency showed the most severe symptoms with an average life expectancy of 6.9 months, while patients with types II and III had a life expectancy of 10.7 and 17.6 months, respectively [11].

A recent clinical and biochemical review of more than 100 patients with DAD deficiency documented a similar clinical phenotype among patients with all three biochemical subtypes [13][14]. The majority of infants (>80%) with DAD deficiency die before the age of 2 years [13]. Biochemical testing usually reveals elevated plasma levels of C26:0, DHCA, THCA, as well as pristanic acid and its precursor, phytanic acid [15]. Only a small part (<2%) of patients with DAD deficiency demonstrate normal biochemical parameters [13][16][17].

The classical phenotype of hereditary peroxisome disease (HPD) – Zellweger syndrome – was first described in 1964 [18]. It received the specified name in 1969. A distinctive feature of the disease, as it has been mentioned above, is a congenital complex of craniofacial dysmorphia [19]. Already in the first hours of life, newborns suffering from this pathology are in extremely serious condition. In the following days, disorders of the nervous and digestive systems begin to dominate the clinical picture.

Disorders of the nervous system are characterized by severe generalized muscular hypotension, sluggish sucking (feeding through a probe), lack of reaction to the environment, convulsions, hyporeflexia (areflexia), severe delay in psychomotor development, and EEG changes. As for the digestive system, hepatomegaly, jaundice, nonspecific digestive disorders, hypotrophy, and growth retardation may be detected. Liver failure and seizures also often develop against the background of malabsorption syndrome, along with hypolipoproteinemia and hypocholesterolemia. Ultrasound and biopsy in the liver may reveal cholestasis, periportal inflammation, cystic changes, siderosis, and fibrosis, turning into cirrhosis. Polycystic kidney disease, detected by ultrasound, may be observed. In the organs of vision, nystagmus, epicanthus, corneal opacity, glaucoma, and cataract may occur, in the organs of hearing – sensorineural deafness. Computed tomography and magnetic resonance imaging (MRI) of the brain may determine multiple small periventricular cysts and diffuse demyelination along the sylvian sulcus and the frontoparietal region, a violation of the gyrus pattern in the form of a combination of pachygyria and polymicrogyria. The described changes may be detected by ultrasound of the fetus already in the third trimester of pregnancy. Death in the case of Zellweger syndrome usually occurs in the first year of life against the background of severe hypotrophy and progressive liver failure. Due to the rarity, peculiarities, and variability of the Zellweger syndrome clinical course, the authors of this study present their own medical observation.

Clinical case description

The patient was the boy V., born on September 1, 2021 from the 3^rd pregnancy (the 1^st pregnancy – a healthy boy, born in 2010; the 2^nd pregnancy – a boy, born in 2019, died at the age of 11 months, diagnosis – “Peroxisomal disease”), the woman was 34 years old. The mother suffered from grade I obesity, cardiomyopathy with metabolic disorders, which occurred against the background of Dufaston taking in the 8^th–10^th weeks of pregnancy; the genetic screening proved a low risk of chromosomal abnormality. She did not pass the glucose tolerance test in the 2^nd trimester; the 3^rd trimester was also without features. The boy V. was born from the 3^rd surgical delivery (2 scars on the uterus) in the 39^th week of gestation, with a birth weight of 3700 g, 52 cm long, with an Apgar score of 7–8 points in a satisfactory condition, with deterioration to a moderate-severe condition in the first day of life due to the appearance of neurological symptoms in the form of oppression syndrome and weak sucking.

Taking into account the severity of the child's condition, the increase in neurological symptoms, and the burdened hereditary mother’s history, a transfer to the neonatal pathology unit was offered, but the mother refused.

However, on the 8^th day (September 9, 2021), the child was taken by the emergency team to the neonatal pathology unit of the Research Institute of Obstetrics and Pediatrics with complaints of seizures persisting throughout the day and increasing in frequency and intensity, sluggish sucking, choking, and refusal to eat.

The body weight at admission was 3487.0 grams, the body length was 54 cm, the head circumference was 38 cm, and the chest circumference was 32 cm.

The general condition at admission was regarded as a severe one, due to generalized clonic-tonic convulsions in the form of tonic tension in the lower extremities with a “strephopodia” and tonic convulsions in the upper extremities with their reduction to the body, floating movements of the eyeballs, a symptom of the “sunset eyes” followed by painful crying by the end of the attack. The pupil was narrowed evenly on both sides; there was not any reaction to the light. The duration of the attack was about 1 minute. After the end of the attack, the reaction to the examination was sharply reduced, with pain irritation, and a weak grimace. Physiological reflexes of oral-spinal automatism were suppressed, sucking and swallowing reflexes were suppressed as well. The reaction to the introduction of an orogastric probe was weak negative, “foamy” discharge from the mouth. As for the motor system – the “frog” pose, the symptom complex of a “sluggish” child. The volume of active movements was sharply reduced. Pronounced diffuse hypotension was detected as well. Tendon reflexes from the upper and lower extremities were not aroused. Abdominal reflexes were not aroused. When hanging vertically, the child sagged. The “elongated” neck was fixed by the cervical collar. Varus stop installation was used as well.

The skin was dry to the touch, pale, and with a subicteric tint (the level of total bilirubin transcutaneously was 150 mmol/L), perioral and acrocyanosis. The scleras were subicteric. There was not any swelling or pastosity. The turgor of soft tissues was reduced, the subcutaneous fat layer was thinned, and the skin gathered into folds. The muscular system was poorly developed. The lymph nodes were not enlarged. There was “souring” and serous discharge from the left eye. The shape of the skull was hydrocephalic, the large fontanel (1.5 × 1.5 cm) was not tense, it did not pulsate, the sagittal suture was open, the occipital fontanel was 0.5 × 0.5 cm, there also was an additional fontanel 0.5 × 0.5 cm between the large and occipital fontanels. There was a moderate expansion of the venous network on the head. The chest was funnel-shaped; the limbs were not deformed. Breathing was without the participation of auxiliary muscles, dysrhythmic, superficial, and auscultation-weakened in both lungs, carried out in all the departments, without any wheezing. The boundaries of the heart corresponded to the age norm, the heart tones were rhythmic, muted, gentle systolic noise at the top. The abdomen was soft, painless on palpation, and moderately swollen; there was hypotension of the muscles of the anterior abdominal wall. The liver protruded 1.5 cm from under the edge of the costal arch; the edge was elastic. The spleen was not palpable. The genitourinary system was formed according to the male type, the testicles in the scrotum rose into the inguinal canal.

Upon admission, the child was diagnosed with “Cerebral ischemia of the 2^nd degree, acute period, suppression syndrome, severe course. An intraventricular hemorrhage (IVF) of the 2^nd stage from 2 sides, peri-intraventricular hemorrhage (PIH) of the 1^st stage, neonatal seizures and unspecified hereditary genetic disease”.

During the medical examination, clinical, laboratory, and instrumental studies were conducted as well; they revealed the following data:

Against the background of multicomponent therapy in acute renal failure dated September 9, 2021, the child's condition was stabilized, seizures were stopped. However, at the age of 1 month, his condition deteriorated again, which required a transfer to the anesthesiology and intensive care unit (ICU). The child's condition at the time of admission to the ICU was extremely severe, due to respiratory insufficiency and neurological symptoms. Objectively, the reaction to the examination was sharply reduced, there was not any motor activity. Atony and areflexia were detected. There were not any convulsions at the time of examination. The reaction of the pupils to light was alive. The large fontanel was not tense. The skin was pale grey, perioral and acrocyanosis, decreasing during oxygen therapy. Tissue turgor was reduced, and there was an expanded venous network on the skin of the anterior abdominal wall. The heart tones were deaf, rhythmic. The pulse was of satisfactory tension and filling. The ventilator was maladapted. There was auscultation-weakened breathing in both lungs, especially in the posterior-lower parts, with crepitating wheezing over the entire surface of the lungs. The abdomen was soft, moderately swollen, the peristalsis was heard. The liver was palpated by 3.0 cm, the spleen was 1.0 cm from the edge of the costal arch. Urination was free, urine was straw-yellow. There was not any bowel movement during the medical examination. Multicomponent intensive and respiratory therapy was carried out in the department (infusion therapy, antibacterial therapy, immunotherapy, antifungal, heparin therapy, anticonvulsant therapy, symptomatic therapy, hepatoprotective therapy, respiratory therapy: moistened oxygen through a facial mask, nasal cannulas, ventilator, HF ventilator with nitric oxide, probiotics, correction of anemia with erythrocyte suspension (0 (1) Rh positive October 5, 2022, October 6, 2022, October 11, 2022), enteral feeding through a probe with a mixture of NAN, PreNAN. Despite the whole complex of measures, the child died at the age of 1.5 months, on October 12, 2021.

Thus, it was possible to detect the rapid deterioration of the condition after birth, phenotypic features (facial dysmorphic disorder), clinical picture of the disease (generalized muscular hypotension, sluggish sucking (feeding through a probe), lack of reaction to the environment, convulsions, areflexia, biliousness), hereditary history (both parents were carriers of the pathogenic variant C.46G>A (p.G16S) in the HSD17B4 gene (OMIM 601860); there was a child in the family whose cause of death was hereditary metabolic peroxisomal disease with an autosomal recessive type of inheritance (deficiency of DBP or deficiency of 17-beta-hydroxysteroid dehydrogenase IV), and the confirmation of the genetic defect in this case allowed concluding on the main diagnosis – “Familial form of hereditary metabolic disease from the group of peroxisomal diseases, deficiency of D-bifunctional protein (OMIM261515) (pathogenic missense mutation in the 17-beta-hydroxysteroid dehydrogenase IV (HSD17B4) gene with the development of muscular hypotension syndrome, early neonatal seizures, macrocrania, delayed psycho-motor development, sensorineural hearing loss”.

The postmortem diagnosis was presented by two main competing clinical diagnoses:

1. E88.8 Familial form of hereditary metabolic disease from the group of peroxisomal diseases-deficiency of D-bifunctional protein (OMIM261515) (pathogenic missense mutation in the 17-beta-hydroxysteroid dehydrogenase IV (HSD17B4) gene with the development of muscular hypotension syndrome, early neonatal seizures, macrocrania, delayed psychomotor development, sensorineural hearing loss.
2. A41.9 Unspecified bacterial sepsis with the development of rhinitis, bilateral bronchopneumonia, respiratory insufficiency 0–III, hepatitis, anemia against the background of an immunodeficiency condition.

Complications of the main diagnosis: Multiple organ failure syndrome: respiratory insufficiency of stage III, cardiovascular insufficiency of stage III, coma of stage III, pulmonary edema, cerebral edema; persistent pulmonary hypertension.

Polymorphism and age-related features of the phenotypic spectrum of the DAD deficiency

It should be noted that the phenotypic spectrum of DAD deficiency is not completely clear. It follows from the presented case that the most frequent manifestation of the hereditary metabolic peroxisomal disease is the neonatal or infantile onset of severe incurable rapidly progressing multisystem disorder [20], although there have been reports of late-onset and slowly progressing disease when patients had a normal metabolic profile and complex heterozygous mutations that led, for example, to hearing loss, symptoms and signs of impaired development of the nervous system [7][16][21][22].

Also, there is information [13][14] on the expansion of the clinical, biochemical, and molecular phenotypic spectrum, which allowed establishing a genotype-phenotype correlation to a certain extent. It is shown that almost all the children with neonatal hypotension and seizures died during the first 2 years of life without reaching any milestones of development. However, few patients survived after 2 years. At the same time, five of them had longer survival (>7.5 years). In general, patients with a less severe lesion had predominantly more missense mutations compared to patients with a more severe lesion, in whom mutations predominated, leading to a premature process of protein termination due to structural abnormalities affecting the DBP protein as a whole [20]. Along with the traditionally detected disorders, the available academic literature presents clinical and laboratory observations of atypical fetal manifestations characterized, for example, by a deficiency of DBP protein in a fetus with ascites, polyhydramnios and contractures of the arms and legs [23]. Similar fetal abnormalities, including chylous ascites, polyhydramnios, clawed hands, and hammer-like fingers, were detected in an infant with a missense mutation R106P and a deletion of 52 bps in the gene of the peroxisomal enzyme β-oxidation, D-3-hydroxyacyl-CoA-dehydratase and D-3-hydroxyacyl-CoA-dehydrogenase D-bifunctional protein. A patient with severe psychomotor retardation and craniofacial dysmorphic disorder died at the age of 7 months.

In the available academic literature, there is an increasing number of cases indicating that HSD17B4 mutations can persist for a longer time without pronounced clinical manifestations and can be identified, for example, in a relatively slowly progressing juvenile disease, including cerebellar ataxia, hearing loss, peripheral neuropathy, and premature ovarian insufficiency.

The authors of this study find interesting the case of two boys from the same family (brothers) who did not suffer from any neonatal symptoms, moreover, they continued to demonstrate satisfactory cognitive functions. The slow clinical course of DAD deficiency in these patients for the first time allowed conducting serial electrodiagnostic testing in the late period. This was done because clinical examinations and nerve conduction studies for several years documented a gradual decrease in coordination, reflecting the increasing dysfunction of the cerebellum and sensory nerves. Progressive sensorimotor polyneuropathy demonstrated a uniform deceleration of conduction velocity, reminiscent of what is observed in many hereditary demyelinating polyneuropathies (for example, Charcot-Marie-Tooth, type 1). The older brother has demonstrated not only progressive demyelination (increased latency and slowing down the speed of conduction) but also signs of progressive, length-dependent axon loss. This study confirms that the expansion of the use of sequencing in non-traditional variants of DAD deficiency will improve the understanding of the phenotypic spectrum and the natural course of such diseases. The authors suggest that the DBP phenotype observed in this family represents a separate and new subtype of DBP deficiency, which was named type IV based on the presence of a missense mutation in each of the DBP domains, reduced but detectable hydratase and dehydrogenase activity, and relatively mild clinical and biochemical features. Without exon sequencing, the diagnosis of DAD deficiency might not have been made in these patients, given their normal biochemical analyses in plasma and urine, which underlines the importance of exome sequencing as a diagnostic tool, especially in phenotypically and genotypically heterogeneous diseases or in cases with atypical clinical manifestations [7].

In recent years, the number of reports of milder cases with normal or atypical biochemical profiles has increased [24]. Individuals with DBP deficiency are at risk of developing adrenal dysfunction due to pronounced clinical overlap with peroxisome biogenesis disorders, DBP homology with a steroid-converting enzyme, and previously reported changes in the adrenal cortex in patients with DBP deficiency [25][26][27][28][29]. However, in more than 130 cases of DAD deficiency described in the literature to date, there is a limited number of reports of the manifestation of adrenal dysfunction [30]. The analysis of clinical cases conducted in this direction allowed drawing attention to the fact that many patients with DAP deficiency have a severe neonatal form associated with early death at the age of about 2 years [14], therefore, primary adrenal insufficiency could not manifest at the time of death or remain unnoticed. In 2006, Ferdinandusse et al. found the postmortem atrophy of the adrenal cortex in 5 out of 12 patients with DAD deficiency [13], which is consistent with the description of the small adrenal glands with the loss of all three cortical zones in a patient with DAD deficiency [29]. This discovery may indicate that these patients had adrenal insufficiency and, according to the authors' conclusions, there could have been laboratory signs of adrenal dysfunction before death.

Moreover, complete exome sequencing made it possible to diagnose the deficiency of peroxisomal DBP not only in older age groups of children but also in adults. They are represented by a 38-year-old brother and two 39- and 35-year-old sisters of non-blood Italian origin, with a slowly progressive juvenile phenotype, including cerebellar atrophy and ataxia, decreased intelligence, hearing loss, hypogonadism, hyperreflexia, demyelinating sensorimotor neuropathy (in 2 out of 3 probands). The MRI of the skull of a 39-year-old sister revealed pronounced diffuse cerebellar atrophy without cerebral atrophy (D–F). The MRI of the brother with a more severe clinical course of the disease showed an even greater degree of cerebellar atrophy with additional cystic lesions of the white matter, thinning of the corpus callosum, and diffuse loss of brain volume. This was accompanied by progressive peripheral neuropathy with a decrease in deep tendon reflexes, a decrease in vibration sensitivity and demyelinating motor polyneuropathy during nerve conduction testing. In all the cases, the symptoms gradually progressed, but the course of the disease in the brother was further complicated by episodes of left-sided weakness with abnormal eye movements and the appearance of multiple lesions of the white matter. Being re-visualized, individual areas showed interval evolution and contraction, followed by a general progression of supratentorial lesions in the direction of fusion. From the functional point of view, the patient became confined to the wheelchair at the age of 32, and at the age of 38, he became dependent on all the aspects of his care. For comparison, both of his sisters are still able to work as volunteers in the society. The older sister (39 years old) has recently developed nonspecific changes in the T2 signal in the deep white matter of the brain.

The patients underwent many diagnostic and laboratory tests, none of which allowed establishing a specific diagnosis. They included very long chain fatty acids and phytanic acid in plasma with the full verification of mitochondrial disease and genetic testing for each of the following: spinocerebellar ataxia types 1, 2, 3, 6, 7, 8, and 17, Friedreich's ataxia, autosomal recessive hereditary spastic paraplegia (CYP7B1, SPG11, SPG7, SPG15, PNPLA6, SPG20, SPG21, CCT5, and SPG44), and autosomal recessive spastic Charlevoix-Saguenay ataxia. In order to identify the causal gene in this family, the entire exome was sequenced, revealing the presence of 2 rare non-synonymous coding variants in HSD17B4 in all the 3 affected people.

In the presented study, the difficulty of the clinical recognition of the true condition is associated with its extreme rarity, poor similarity with the classical neonatal form, and the presence of many key signs of other, relatively common conditions. Given the low pre-test probability of each of these disorders, exomic or panel molecular testing may indeed be the most practical initial test in patients with complex and ambiguous clinical manifestations. At the same time, it should be noted that the white matter lesions characteristic of such patients are a known consequence of classical DAD insufficiency, with periventricular cerebral demyelination and thinning of the corpus callosum, which are reported to occur in 17% and 55% of cases, respectively [22].

Conclusion

Various clinical observations carried out in recent decades by means of using modern methods of medical examination, including biochemical and molecular genetic studies, have significantly expanded the understanding of the pathogenetic features and variants of the course of hereditary metabolic disease from the group of peroxisomal diseases. All the further introduction of exome sequencing led to an expansion of the range of patients with milder, non-traditional variants of DAD deficiency, and improved understanding of the phenotypic spectrum and the natural course of such diseases. Nowadays, the detectability of this pathology has far surpassed neonatal age and infancy. Despite the opinion about the most severe and unfavorable course of hereditary peroxisome disease detected in the early neonatal (in the perinatal) period (multiple small periventricular cysts and a violation of the gyrus pattern in the form of a combination of pachygyria and polymicrogyria can be detected by ultrasound of the fetus already in the third trimester of pregnancy), it is possible to talk not only about the expansion of age boundaries but also about a wide range of phenotypic variants in the absence of an absolutely clear correlation between the disease genotype and phenotype.

The analysis of the prolonged clinical course of hereditary peroxisome disease, detected in childhood, adolescence, and adulthood, despite a milder course, in some cases sufficiently preserved motor and cognitive abilities and life expectancy, indicates the severity of the pathology, progressively worsening the quality of life with the development of disability and programming an unfavorable prognosis for the patient's life. Thus, the severity of the disease and an unfavorable prognosis in the absence of current therapy indicate the need to expand the clinical, biochemical, and molecular phenotypic spectrum, which will allow establishing a reliable genotype-phenotype correlation, increase knowledge about phenotypic traits and diagnostic capabilities for this disease to a wide range of specialists, without removing the urgent issue of expanding neonatal screening and the development of methods of specific gene therapy.