Spectrum of Organic Aciduria Diseases in Tunisia: A 35-year Retrospective Study.

Background: Organic aciduria diseases (OADs) occur worldwide, with differences in prevalence and patterns between populations. Objectives: To describe the spectrum of OADs identified in Tunisia over a 35-years period. Materials and Methods: This retrospective study included patients who were diagnosed with OADs between 1987 and 2022 in the Laboratory of Biochemistry, Rabta Hospital, Tunisia. Organic acids were analyzed using gas chromatography-mass spectrometry. Results: A total of 30,670 urine samples were analyzed for OADs, of which 471 were positive for OADs. The estimated incidence of OADs in Tunisia was 6.78 per 100,000 live births. Methylmalonic (n = 146) and propionic (n = 90) acidurias were the most common OADs (estimated incidence: 2.10 and 1.30 per 100,000 live births, respectively). There were 54 cases of L-2-hydroxyglutatric acidurias and 30 cases of pyroglutamic acidurias, which makes it one of the highest in the world. The main clinical features were hypotonia (65%) and feeding difficulties (41%). Age at diagnosis was highly variable, ranging from 1 day to 49 years. Only 27% of the patients were diagnosed within the first month of life. The prevalence of OADs was highest in the Center-East and Southeast regions. Conclusions: In Tunisia, OADs are relatively frequent, but there are shortcomings regarding the diagnosis of these disorders. The frequency and health/social impact of these disorders warrant the need for implementing newborn screening programs and suitable patient management.

Analysis of Branched Amino Acids by UPLC as an Alternative Method for the Management of Patients with MUSD.

BACKGROUND: Maple syrup urine disease (MSUD) is a severe life-threatening metabolic disorder. Patients' poor outcomes could be prevented by early diagnosis and regular monitoring, which mainly depend on the analysis of branched amino acids (BCAAs) in plasma. The study aimed to test whether the analysis of BCAAs by ultra-performance liquid chromatography (UPLC) is an alternative to an analysis by ion-exchange chromatography (IEC) for the diagnosis and monitoring of MSUD. METHODS: The two methods analyzed fifty plasma samples obtained from treated and untreated patients with MSUD. Data were analyzed using Passing-Bablok and Bland-Altman methods. RESULTS: The slope of the regression lines was equal or close to one for the three BCAAs, indicating no significant proportional differences between the two methods. A slight positive or negative bias was found for leucine and alloisoleucine, respectively. However, for each amino acid, one or two measurement pairs were out of statistical interval of agreement. Despite small analytical differences, the two methods could be considered in clinical agreement since the differences have no impact on the diagnosis and management of patients. CONCLUSIONS: UPLC and IEC methods are in clinical agreement for plasma BCAAs analysis. The UPLC method could be used simultaneously or interchangeably with the IEC method for diagnosing and monitoring MSUD patients. However, for reasons of practicability, the alternative method should only be used when the usual method cannot be carried out.

Incidence of the Mucopolysaccharidoses in Tunisia, 1999 - 2021.

BACKGROUND: This cross-sectional study aimed to describe and discuss the epidemiology of mucopolysaccharidoses (MPS) in Tunisia. METHODS: Patients diagnosed with a MPS disorder in two referral laboratories in Tunisia between 1999 and 2021 were included. Diagnosis was based on clinical and radiological features and analysis of urinary glycosaminoglycans, and enzyme assay in some of the patients. RESULTS: Over the twenty-two years, 199 patients were diagnosed with MPS in Tunisia. The disorder was classified as MPS I, MPS II, MPS III, MPS IV, and MPS VI in 15.07%, 1.5%, 38.69%, 17.08% and 7.03% patients, respectively. Due to the lack of enzyme analysis, the disorder was classified as MPS I or II in 20.6% of patients, and no cases of MPS VII and IX were documented. Gender-ratio was 1.5 and age at diagnosis varied from 3 months to 18 years with a median of 46 months. Patients originated from across Tunisia, and no hotspot site was identified. During the survey period, 3,822,983 births occurred, which provides an estimated global incidence of MPS of 1:20,123 live births (4.97 per 100,000). MPS III was the most frequent type with an estimated incidence of 1.91 cases per 100,000 newborns. CONCLUSIONS: MPS disorders, especially MPS III are relatively frequent in Tunisia, likely due to a high rate of consanguineous marriages. Implementation of enzyme and genetic tests in Tunisia will allow diagnosis confirmation and subtype recognition, as well as accurate genetic counseling and prenatal diagnosis for MPS.

Semen Creatine and Creatine Kinase Activity as an Indicator of Sperm Quality.

BACKGROUND: The role of creatine (Cr) and creatine kinase (CK) in sperm function remains unclear. The study aimed to assess Cr and CK in seminal plasma and test their association with sperm characteristics. METHODS: The study included 62 males with couple's infertility and 26 males who have already fathered children. Semen Cr and CK were assessed by GC-MS and spectrophotometry, respectively. Seminogram parameters were analyzed using conventional methods. RESULTS: Cytomorphologic analysis of sperm showed normozoospermia in 53 men (NS) and an asthenozoospermia (AS) in 35 men. Semen Cr was high with no significant difference between the two groups (791 ± 342 and 744 ± 422 µmol/L, respectively). However, semen CK activity was higher in AS group (1,360 ± 1,050 vs. 830 ± 580 U/L, p = 0.013). Semen Cr was positively related to progressive motility (r = 0.284; p = 0.010). Semen CK was negatively correlated with sperm concentration (r = -0.29; p = 0.01), progressive motility (r = -0.26; p = 0.03), and the percentage of abnormal spermatozoa (r = -0.28; p = 0.02). CONCLUSIONS: Semen contains high amounts of Cr and increased CK activity. Low semen Cr is associated with reduced sperm motility while high CK activity is associated with poor sperm quality. The findings suggest that Cr is of importance for sperm metabolism and that Cr supplementation could be useful in males with poor quality sperm.

Nonketotic Hyperglycinemia in Tunisia. Report upon a Series of 69 Patients.

AIM: The aim of the study is to report on epidemiological, clinical, and biochemical characteristics of nonketotic hyperglycinemia (NKH) in Tunisia. METHODS: Patients diagnosed with NKH in Laboratory of Biochemistry at Rabta hospital (Tunis, Tunisia) between 1999 and 2018 were included. Plasma and cerebrospinal fluid (CSF) free amino acids were assessed by ion exchange chromatography. Diagnosis was based on family history, patient's clinical presentation and course, and increased CSF to plasma glycine ratio. RESULTS: During 20 years, 69 patients were diagnosed with NKH, with 25 patients originating from Kairouan region. Estimated incidences were 1:55,641 in Tunisia and 1:9,684 in Kairouan. Consanguinity was found for 73.9% of the patients and 42% of the families have history of infantile death due to a disease of similar clinical course than the propositus. Clinical symptoms initiated within the first week of life in 75% of the patients and within the first 3 months in 95.7% ones. The phenotype was severe in 76.8% of the patients. Main symptoms were hypotonia, feeding difficulties, coma, apnea, and seizures. Most patients died within few days to months following diagnosis. CSF to plasma glycine ratio was increased in all patients. CSF and plasma glycine levels were negatively correlated with age of disease onset and severity. CONCLUSION: NKH is quite frequent in Tunisia. Kairouan region has the highest NKH incidence rate, worldwide. However, due to lack of confirmatory enzymatic and genetic tests, NKH diagnosis was based on first-line biochemical tests. Characterization of causal mutations is needed for accurate diagnosis and prenatal diagnosis of this devastating life-threatening disease.

Altered Semen Quality is Associated with Decreased Semen Docosahexaenoic Acid and Increased Oleic Acid Levels.

BACKGROUND: Fatty acids composition of the spermatozoa may be an important determinant of sperm quality and fertility. This study aimed to evaluate the fatty acids profile of seminal plasma and membrane spermatozoa and to study the association between fatty acids and sperm properties. METHODS: Semen samples were collected by masturbation from 45 middle-aged men consulting for infertile couples. Semen cytomorphological analysis was performed after liquefaction. Semen was classified as normal or abnormal according to World Health Organization criteria 2010. Plasma seminal and spermatozoa membrane fatty acids composition were analyzed by capillary gas chromatography. RESULTS: Docosahexaenoic acid level was decreased while oleic acid level and n-6:n-3 ratio were increased in spermatozoa membrane in men with abnormal sperm. However, no variation in seminal plasma fatty acid composition was found between men with normal and abnormal sperms. Spermatozoa docosahexaenoic acid was positively correlated with sperm concentration and progressive motility and inversely related to atypical spermatozoa number, while oleic acid showed the inverse correlations. CONCLUSIONS: Altered fatty acids composition in the spermatozoa membrane, especially a decreased docosahexaenoic acid content, is associated with poor sperm quality. Although a causal association could not be established, intervention that recovers normal spermatozoa fatty acid composition could contribute to improved sperm quality.

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.

X-linked Adrenoleukodystrophy, The Tunisian Experience.

BACKGROUND: X-linked adrenoleukodystrophy is a genetic disease affecting the degradation of very long chain fatty acids. This study aims to describe the clinical phenotype and biochemical feature of Tunisian patients; it also seeks to describe recognition of pattern analysis on the level of very long chain fatty acids in plasma for the visual discrimination of X-linked patients from a healthy group. METHODS: During the last 21 years, 19 patients were diagnosed with X-linked adrenoleukodystrophy based on the clinical features combined with the area percentage of hexacosanoic acid (C26:0) as well as the ratio of C26:0 and lignoceric acid (C24:0) relative to behenic acid (C22:0) by gas chromatography. For the biochemical diagnosis of X-ALD with better accuracy, it has been desired to transform the numerical values of these biochemical markers into visually discriminating patterns. RESULTS: The clinical features of 19 patients aged between 4 to 47 years were classified into cerebral form (57.8%), adrenomyeloneuropathic (26.3%), and a few patients were asymptomatic. The ratio C24:0/C22:0 ranged from 1.12 to 2.41 (normal value: 0.46 - 0.9) and C26:0/C22:0 ratio ranged from 0.03 to 0.36 (normal value: 0.003 - 0.009). The concentration of fatty acids with 22 or more carbons in body fluid did not change with age in control subjects and patients. For the visual diagnostic of patients, the Scatter plot was a reliable method for the diagnostic patterns of very long chain fatty acids of patients with X-linked adrenoleukodystrophy disorders. CONCLUSIONS: The incidence of X-linked adrenoleukodystrophy disorders is under diagnosed in Tunisia. The diagnosis was confirmed by enzymatic activity study and molecular analysis but the analysis of very long chain fatty acids by gas chromatography remains a reliable tool for the diagnosis and early initiation of the treatment.

Clinical and Biochemical Profile of Tyrosinemia Type 1 in Tunisia.

BACKGROUND: Hereditary tyrosinemia type 1 (HT1) is an autosomal recessive disease caused by a defect of fumarylacetoacetate hydrolase. This study aimed to estimate the prevalence of HT1 in Tunisia and report its clinical, biochemical and genetic features. METHODS: During the last 25 years, 69 patients were diagnosed with HT1 based on clinical features and increased succinylacetone (SA) in blood and urine. SA was detected by GC-MS after oximation and quantified by a spectrophotometric method. Nine prenatal diagnoses for HT1 have been done and nine unrelated patients were screened for the hotspot IVS6-1(G-T) mutation using PCR. RESULTS: Using the Hardy-Weinberg formula, the incidence of HT1 was estimated at 1/14804 births in Tunisia. According to clinical form, 21 patients (30%) had the acute form and 48 patients (70%) had the chronic form. Mean plasma and urine SA were higher in the acute form (24 and 193 µmol/L vs. 9 and 90 µmol/L, respectively). Diagnosis of HT1 was done for 4 fetuses. The hotspot IVS6-1(G-T) mutation was found in six of nine explored patients. CONCLUSIONS: The incidence of HT1 is relatively high in Tunisia with a predominance of the chronic form. It is important to diagnose the disease as early as possible to prevent unfavorable issues. Prenatal diagnosis should be recommended to minimize the recurrence of the disease.

Guanidinoacetate methyltransferase (GAMT) deficiency in two Tunisian siblings: clinical and biochemical features.

BACKGROUND: Guanidinoacetate methyltransferase (GAMT) deficiency is a recently described disorder and few cases have been reported to date. As it is a treatable pathology, we seek to contribute to its better understanding, particularly to further elucidate its biochemical diagnosis for early treatment. METHODS: The patients, two brothers aged 13 years (P1) and 11 years (P2), have been explored for signs and symptoms suggestive of inborn errors of metabolism. The quantification of creatine (Cr), guanidinoacetate (GAA), and GAMT activity was performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS: The two brothers presented a similar clinical picture: developmental delay, epilepsy, axial hypotonia, spastic tetraparesis, severe mental and language delay, and autistic behaviour. GAA concentrations were markedly increased in plasma and in urine [2796 and 3342 micromol/mmol creatinine (control range: 4 - 220 micromol/mmol creatinine)/14 and 29 micromol/L (control range: 0.35 - 1.8 micromol/L), respectively] while plasma and urine creatine concentrations were at the lower normal range limit. Activity of GAMT in lymphoblasts was extremely reduced (< 0.01 nmol/mg protein/hour) compared to healthy subjects. GAMT activity was found to be intermediary in patients' parents. CONCLUSIONS: It appears that the clinical picture is heterogeneous but should be considered as potential signs of creatine metabolism disorders, however, the biochemical diagnosis is reliable as the enzyme activity is zero in most cases. To date, it is still too early to establish correlations between symptoms and biochemical profile. However, the identification of additional cases of GAMT deficiency should help elucidate such relationships and the progress of patients treated with creatine in conjunction with ornithine supplementation.

GC/MS determination of guanidinoacetate and creatine in urine: A routine method for creatine deficiency syndrome diagnosis.

OBJECTIVES: To further facilitate the diagnosis of creatine deficiency syndromes (CDS) a modified method was developed for the quantification of urinary creatine and guanidinoacetoacetate using gas chromatography/mass spectrometry (GC/MS) and having the additional advantage of using the same derivatizing agents, column and equipment usually used for the diagnosis of the organic acidurias in the clinical biochemistry laboratories. MATERIAL AND METHODS: Guanidinoacetic acid, creatine standard solutions and pooled urines and pathological samples were used to validate a new and simple GC/MS technique modified from reported methods; its accuracy was assessed by comparing with liquid chromatography-electrospray tandem mass spectrometry (HPLC-MS/MS) method. RESULTS: The method is precise: intra assay and inter assay variability for low and high concentrations were 3%, 6.4%/1.4%, 6.9% for creatine and 1.4%, 6.4%/0.9%, 6.9% for guanidinoacetoacetate. Agreement with HPLC/MS-MS method is good. CONCLUSION: The GC/MS modified method is fast, reliable and practical for the diagnosis of CDS using the same means as those for organic acidurias diagnosis.

Creatine and creatine deficiency syndromes: biochemical and clinical aspects.

Creatine deficiency syndromes, which have only recently been described, represent a group of inborn errors of creatine synthesis (L-arginine-glycine amidinotransferase deficiency and guanidinoacetate methyltransferase deficiency) and transport (creatine transporter deficiency). Patients with creatine deficiency syndromes present with mental retardation expressive speech and language delay, and epilepsy. Patients with guanidinoacetate methyltransferase deficiency or creatine transporter deficiency may exhibit autistic behavior. The common denominator of these disorders is the depletion of the brain creatine pool, as demonstrated by in vivo proton magnetic resonance spectroscopy. For diagnosis, laboratory investigations start with analysis of guanidinoacetate, creatine, and creatinine in plasma and urine. Based on these findings, enzyme assays or DNA mutation analysis may be performed. The creatine deficiency syndromes are underdiagnosed, so the possibility should be considered in all children affected by unexplained mental retardation, seizures, and speech delay. Guanidinoacetate methyltransferase deficiency and arginine-glycine amidinotransferase deficiency are treatable by oral creatine supplementation, but patients with creatine transporter deficiency do not respond to this type of treatment.