A Rare Cause of Hypergonadotropic Hypogonadism: Transaldolase Deficiency in Two Siblings

Transaldolase deficiency is a rare inborn autosomal recessive disorder caused by biallelic mutations in the TALDO1 gene. It is characterized by intrauterine growth restriction, dysmorphism, abnormal skin, cytopenia, hepatosplenomegaly, liver cirrhosis, endocrine problems, renal and cardiac abnormalities. We present two siblings of Turkish origin with early-onset form of transaldolase deficiency and hypergonadotropic hypogonadism in both sexes. The girl (index) was followed-up with cryptogenic cirrhosis, leukopenia and thrombocytopenia, skin abnormalities, congenital heart defects, hypercalciuria, nephrolithiasis, proteinuria, chronic kidney disease throughout childhood. She developed hypergonadotropic hypogonadism in adolescence period. Whole exome sequencing due to the multisystemic involvement revealed a previously described homozygous inframe deletion in TALDO1 gene. Her brother was born as a small for gestational age baby and was also followed-up with cryptogenic cirrhosis since his infancy, together with cytopenia, congenital heart defects, bilateral cryptorchidism, short stature, hypercalciuria, proteinuria and chronic kidney disease in childhood. He presented with testicular microlithiasis and hypergonadotropic hypogonadism in adolescence. Sanger sequencing of TALDO1 gene confirmed the presence of the same homozygous deletion with his sister. The mother was found to be a heterozygous carrier for this deletion. We describe two patients with multisystemic involvement since neonatal period who presented with an additional hypergonadotropic hypogonadism in adolescence. The diagnosis of transaldolase deficiency should be kept in mind for these patients, and they must be evaluated for gonadal functions especially during puberty.

Hypergonadotrophic hypogonadism in a patient with transaldolase deficiency: novel mutation in the pentose phosphate pathway

BACKGROUND

Transaldolase (TALDO) deficiency (OMIM #606003) is a rare autosomal recessive multi-systemic disorder of carbohydrate metabolism. It has a vast phenotypic spectrum ranging from neonatal liver failure to slowly progressive liver cirrhosis and is characterized by intrauterine growth restriction, hepatosplenomegaly, bicytopenia, nephrolithiasis, and congenital heart disease.

METHODS AND RESULTS

We report a patient with a late-onset form of TALDO deficiency characterized by hypergonadotropic hypogonadism and slightly elevated levels of alpha-fetoprotein (AFP). A novel TALDO1 mutation was detected through the application of reverse genetics with the use of clinical exome sequencing (CES).

CONCLUSION

This report provides further evidence that reverse genetics is a useful approach in patients who do not manifest the hallmark features of known and recognizable syndromes. TALDO deficiency should be considered in the differential diagnosis of unexplained elevated AFP levels and hypergonadotropic hypogonadism with microlithiasis.

Untargeted metabolomics as an unbiased approach to the diagnosis of inborn errors of metabolism of the non-oxidative branch of the pentose phosphate pathway

Inborn errors of metabolism (IEM) involving the non-oxidative pentose phosphate pathway (PPP) include the two relatively rare conditions, transketolase deficiency and transaldolase deficiency, both of which can be difficult to diagnosis given their non-specific clinical presentations. Current biochemical testing approaches require an index of suspicion to consider targeted urine polyol testing. To determine whether a broad-spectrum biochemical test could accurately identify a specific metabolic pattern defining IEMs of the non-oxidative PPP, we employed the use of clinical metabolomic profiling as an unbiased novel approach to diagnosis. Subjects with molecularly confirmed IEMs of the PPP were included in this study. Targeted quantitative analysis of polyols in urine and plasma samples was accomplished with chromatography and mass spectrometry. Semi-quantitative unbiased metabolomic analysis of urine and plasma samples was achieved by assessing small molecules via liquid chromatography and high-resolution mass spectrometry. Results from untargeted and targeted analyses were then compared and analyzed for diagnostic acuity. Two siblings with transketolase (TKT) deficiency and three unrelated individuals with transaldolase (TALDO) deficiency were identified for inclusion in the study. For both IEMs, targeted polyol testing and untargeted metabolomic testing on urine and/or plasma samples identified typical perturbations of the respective disorder. Additionally, untargeted metabolomic testing revealed elevations in other PPP metabolites not typically measured with targeted polyol testing, including ribonate, ribose, and erythronate for TKT deficiency and ribonate, erythronate, and sedoheptulose 7-phosphate in TALDO deficiency. Non-PPP alternations were also noted involving tryptophan, purine, and pyrimidine metabolism for both TKT and TALDO deficient patients. Targeted polyol testing and untargeted metabolomic testing methods were both able to identify specific biochemical patterns indicative of TKT and TALDO deficiency in both plasma and urine samples. In addition, untargeted metabolomics was able to identify novel biomarkers, thereby expanding the current knowledge of both conditions and providing further insight into potential underlying pathophysiological mechanisms. Furthermore, untargeted metabolomic testing offers the advantage of having a single effective biochemical screening test for identification of rare IEMs, like TKT and TALDO deficiencies, that may otherwise go undiagnosed due to their generally non-specific clinical presentations.

Systemic lupus erythematosus in a girl with PTEN variant and transaldolase deficiency: a novel phenotype

Genetic defect of phosphatase and tensin homolog (PTEN) gene might play a role in B cell hyperactivity and result in the development of systemic lupus erythematosus (SLE), while transaldolase deficiency has a spectrum of clinical features including autoimmune endocrinopathy. Herein, we identified a novel phenotype in a girl presenting with clinical and laboratory findings consistent with SLE. Exome sequencing identified pathogenic heterozygous variant in PTEN gene (NM_000314: exon 6: c.518G > C: p. R173P) and homozygous variant in TALDO1 gene (NM_006755: exon 6: c.793C del: p. Q265f). Our report highlights the association of PTEN mutation and autoimmunity and the possibility that transaldolase deficiency may be indirectly involved in the development of SLE.

Apparent Acetaminophen Toxicity in a Patient with Transaldolase Deficiency

Transaldolase deficiency (MIM#: 606003) is a rare autosomal recessive defect in the pentose phosphate pathway. Affected individuals are at risk for progressive liver failure and hepatocarcinoma. In the transaldolase-deficient mouse model (Taldo1 ^-/-), these hepatic complications are accentuated by oxidative stress related to acetaminophen administration. We report a 13-month-old transaldolase-deficient male who developed mild liver failure after receiving standard doses of acetaminophen during a febrile respiratory syncytial virus infection. He was admitted for respiratory distress with neutropenia and thrombocytopenia, but developed an enlarged nodular liver with accompanying splenomegaly and rising alpha-fetoprotein which peaked 2 weeks after acetaminophen exposure. Whole exome sequencing revealed compound heterozygous variants c.512_514delCCT (p.Ser171del) and c.931G > T (p.Gly311Trp) in TALDO1 (HGNC:11559), which encodes transaldolase (EC 2.2.1.2), a key enzyme in ribose metabolism. Urine polyols and plasma metabolomics confirmed the diagnosis of transaldolase deficiency. Studies on the Taldo1 ^-/- mouse model demonstrate acetaminophen-induced liver failure can be prevented by administration of the antioxidant N-acetylcysteine. Moreover, a published report showed treatment of a transaldolase-deficient patient with N-acetylcysteine was associated with a decrease in alpha-fetoprotein levels. After discontinuation of acetaminophen and prior to initiation of N-acetylcysteine treatment, our patient demonstrated resolving alpha-fetoprotein levels suggesting acetaminophen incited the liver failure. Conclusion: Our observations support the conclusion from mouse model studies that transaldolase-deficient patients are uniquely sensitive to acetaminophen and should avoid this antipyretic. Recognition of this individualized toxicity and avoidance of acetaminophen are essential for management of these patients.

N-Acetylcysteine Therapy in an Infant with Transaldolase Deficiency Is Well Tolerated and Associated with Normalization of Alpha Fetoprotein Levels

Transaldolase deficiency is a rare autosomal recessive disorder of the pentose phosphate pathway that presents clinically with infantile-onset hepatopathy progressing to cirrhosis, nephropathy, connective tissue abnormalities resembling cutis laxa, coagulopathy, cytopenias, and increased risk of hepatocellular carcinoma. In many cases, death occurs in infancy or early childhood. There is no established treatment for transaldolase deficiency in humans. Recent work in a knockout mouse model of transaldolase deficiency has demonstrated a benefit to supplementation with the glutathione precursor N-acetylcysteine (NAC). We describe an infant with genetically confirmed transaldolase deficiency with multisystem involvement, including liver enlargement and markedly elevated alpha fetoprotein. Acetaminophen was strictly avoided. Treatment with oral NAC over a 6-month period was well tolerated and was associated with a sustained normalization of alpha fetoprotein levels and stable clinical course. The clinical significance of normalized serum alpha fetoprotein in this patient is not certain, although it may reflect decreased hepatocyte injury and reduced hepatocarcinogenesis as has been suggested in the mouse disease model. NAC supplementation may provide benefit in humans with transaldolase deficiency. Longer follow-up and data on the response of additional patients with transaldolase deficiency to NAC supplementation will be required to further evaluate efficacy and optimize dosing.