Clinical analysis of late-onset methylmalonic acidaemia and homocystinuria, cblC type with a neuropsychiatric presentation

Late-onset methylmalonic acidemia and homocysteinemia (cblC disease): systematic review

INTRODUCTION

Combined methylmalonic acidemia and homocystinuria, cblC type is an inborn error of intracellular cobalamin metabolism and the most common one. The age of onset ranges from prenatal to adult. The disease is characterised by an elevation of methylmalonic acid (MMA) and homocysteine and a decreased production of methionine. The aim is to review existing scientific literature of all late onset cblC patients in terms of clinical symptoms, diagnosis, and outcome.

METHODS

A bibliographic database search was undertaken in PubMed (MEDLINE) complemented by a reference list search. We combined search terms regarding cblC disease and late onset. Two review authors performed the study selection, data extraction and quality assessment.

RESULTS

Of the sixty-five articles included in this systematic review, we collected a total of 199 patients. The most frequent clinical symptoms were neuropathy/myelopathy, encephalopathy, psychiatric symptoms, thrombotic microangiopathy, seizures, kidney disease, mild to severe pulmonary hypertension with heart failure and thrombotic phenomena. There were different forms of supplementation used in the different studies collected and, within these studies, some patients received several treatments sequentially and/or concomitantly. The general outcome was: 64 patients recovered, 78 patients improved, 4 patients did not improve, or the disease progressed, and 12 patients died.

CONCLUSIONS

Most scientific literature regarding the late onset cblC disease comes from case reports and case series. In most cases treatment initiation led to an improvement and even recovery of some patients. The lack of complete recovery underlines the necessity for increased vigilance in unclear clinical symptoms for cblC disease.

Case Report: A Case of Adult Methylmalonic Acidemia With Bilateral Cerebellar Lesions Caused by a New Mutation in MMACHC Gene

Methylmalonic acidemia is a severe heterogeneous disorder of methylmalonate and cobalamin (Cbl; vitamin B12) metabolism with poor prognosis. Around 90% of reported patients with methylmalonic acidemia (MMA) are severe infantile early onset, while cases with late-onset MMA have been rarely reported. Few reported late-onset MMA patients presented with atypical clinical symptoms, therefore, often misdiagnosed if without family history. Herein, we report a 29-year-old female who was admitted to our hospital due to symptoms manifested as encephalitis. The brain MRI showed symmetrical bilateral cerebellar lesions with Gd enhancement. Laboratory tests showed significantly elevated levels of homocysteine and methylmalonic acid. A genetic analysis identified a novel homozygous mutation (c.484G>A; p.Gly162 Arg) in the MMACHC gene. The patient was diagnosed with MMA, and her symptoms improved dramatically with intramuscular adenosine cobalamin treatment. In conclusion, for patients with symmetrical lesions in the brain, the possibility of metabolic diseases should be considered, detailed medical and family history should be collected, and metabolic screening tests as well as gene tests are necessary for correct diagnosis. The mutation diversity in MMACHC gene is an important factor leading to the heterogeneity of clinical manifestations of patients with MMA.

Clinical, phenotypic and genetic landscape of case reports with genetically proven inherited disorders of vitamin B12 metabolism: A meta-analysis

Inherited disorders of B₁₂ metabolism produce a broad spectrum of manifestations, with limited knowledge of the influence of age and the function of related genes. We report a meta-analysis on 824 patients with a genetically proven diagnosis of an inherited disorder of vitamin B₁₂ metabolism. Gene clusters and age categories are associated with patients' manifestations. The "cytoplasmic transport" cluster is associated with neurological and ophthalmological manifestations, the "mitochondrion" cluster with hypotonia, acute metabolic decompensation, and death, and the "B₁₂ availability" and "remethylation" clusters with anemia and cytopenia. Hypotonia, EEG abnormalities, nystagmus, and strabismus are predominant in the younger patients, while neurological manifestations, such as walking difficulties, peripheral neuropathy, pyramidal syndrome, cerebral atrophy, psychiatric disorders, and thromboembolic manifestations, are predominant in the older patients. These results should prompt systematic checking of markers of vitamin B₁₂ status, including homocysteine and methylmalonic acid, when usual causes of these manifestations are discarded in adult patients.

Peripheral Nervous System Involvement in Late-Onset Cobalamin C Disease?

Background: Cobalamin C (cblC) has a fundamental role in both central and peripheral nervous system function at any age. Neurologic manifestations may be the earliest and often the only manifestation of hereditary or acquired cblC defect. Peripheral neuropathy remains a classical but underdiagnosed complication of cblC defect, especially in late-onset cblC disease caused by mutations in the methylmalonic aciduria type C and homocysteinemia (MMACHC) gene. So the clinical, electrophysiological, and pathological characteristics of late-onset cblC disease are not well-known.

Methods: A retrospective study of patients with late-onset cblC disease was conducted at our hospital on a 3-year period. The neuropathy was confirmed by the nerve conduction study. Sural biopsies were performed in 2 patients.

Results: Eight patients were identified, with a mean onset age of 16.25 ± 6.07 years. All patients had methylmalonic aciduria, homocysteinemia, compound heterozygous MMACHC gene mutations were detected in all patients, and 7/8 patients with c.482G>A mutation. One patient concomitant with homozygote c.665C>T mutation in 5,10-methylenetetrahydrofolate reductase (MTHFR) gene. All patients showed limb weakness and cognitive impairment. Five patients had possible sensorimotor axonal polyneuropathy predominantly in the distal lower limbs. Sural biopsies showed loss of myelinated and unmyelinated fibers. Electro microscopy revealed crystalline-like inclusions bodies in Schwann cells and axonal degeneration.

Conclusion: Late-onset cblC disease had possible heterogeneous group of distal axonal neuropathy. c.482G>A mutation is a hot spot mutation in late-onset cblC disease.

Clinical feature and outcome of late-onset cobalamin C disease patients with neuropsychiatric presentations: a Chinese case series

OBJECTIVE

The Cobalamin C (cblC) disease is an inborn error of cobalamin metabolism. Late-onset cblC disease was diagnosed in patients having overt symptoms after 4 years of age. The late-onset cblC disease patients were rare and easily misdiagnosed. This study analyzed the clinical presentations, gene mutations, and treatments of Chinese patients with late-onset cblC disease.

METHODS

The clinical data of 26 Han Chinese patients diagnosed with late-onset cblC disease were retrospectively analyzed. All patients underwent serum homocysteine level exam, urine concentrations of organic acids measurement, neuroimaging scans, gene analysis, and treatments evaluations.

RESULTS

The mean age at disease onset and diagnosis was 17.8±7.0 years. The most frequent neuropsychiatric disturbances were lower limb weakness (50%), psychiatric disturbances (46.2%), and gait instability (42.3%). The mean methylmalonic acid level in urine was 107.4±56.6 μmol/L, and mean serum total homocysteine was 105.4±41.0 μmol/L. The most common abnormal radioimaging changes were observed in the spinal cord (88%) and brain (32%). Scoliosis was detected in 85.7% of patients. The methylmalonic aciduria and homocystinuria type C protein gene analysis showed that c.482G>A (57.7%) and c.609G>A (34.6%) mutations were the most frequent genotypes. After treatments with hydroxycobalamin, betaine, folic acid, L-carnitine, and compound vitamin B, the clinical features and biochemical parameters of patients with late-onset cblC disease were found to be alleviated.

CONCLUSION

In our late-onset cblC disease cases, lower limb weakness, psychiatric disturbances, and gait instability were the most frequent manifestations. Patients responded well to the drug treatments with hydrocobalamin and betaine. When juvenile or adult patients with hyperhomocysteinemia present with neurological symptoms, cblC disease needs to be considered.

Late-onset cobalamin C deficiency Chinese sibling patients with neuropsychiatric presentations

The Cobalamin C deficiency (cblC), characterized with elevated methylmalonic acidemia and homocystinuria in plasma, is an inborn error of cobalamin metabolism. The late-onset cblC siblings patients were rarely reported. In this study, we analyzed the clinical presentations and treatment outcomes of late-onset cblC in Chinese sibling patients with neuropsychiatric presentations. The clinical data of four pairs of Chinese patients were retrospectively analyzed. Serum homocysteine, urine organic acids measurements, neuroimaging exams and gene analysis were carried out in all patents. Patients were reevaluated after treatments with cobalamin, folate, betaine, L-carnitine and compound vitamin B. The mean age at disease onset was 13.7 (range 2-19) years. The neuropsychiatric disturbances including cognitive decline (3/8), psychiatric disturbances (4/8), gait instability (2/8), lower extremity weakness and numbness (3/8) and thromboembolic events (1/8). Two patients suffered nephropathy. The mean serum homocysteine when patients were diagnosed was 109.4 (range 69.5-138) μM/L. The abnormal radioimaging included scoliosis by X-ray (5/6), cerebral atrophy (4/6) and spinal cord atrophy (3/6) by MRI scan. Three pairs of siblings showed heterozygous mutations of MMACHC gene including c.482G > A (4/6), c.354G > C (2/6), c.570insT (2/6), c.445_446del (2/6) and c.656_4658del (2/6). The other two siblings showed homozygous mutation with c.452A > G in MMACHC gene. After treatments, the psychiatric symptoms were obviously relieved in all the patients. In Chinese siblings with late-onset cblC, the main clinic manifestation and abnormal radioimaging were cognitive decline and cerebral atrophy respectively. The most common gene mutation was c.482G > A of MMACHC gene. The patients responded well to the treatments.

Eight novel mutations of CBS gene in nine Chinese patients with classical homocystinuria

BACKGROUND

Classical homocystinuria (homocysteinemia type 1, MIM# 236200) is a rare inherited disorder in Mainland China. This study aimed to identify mutations in the cystathionine β-synthase (CBS) gene which are associated with classical homocystinuria in nine Chinese patients.

METHODS

Nine Chinese patients were diagnosed at the age of 5 years 4 months to 18 years by plasma total homocysteine and blood methionine determination. CBS gene analysis was performed for the patients and their families.

RESULTS

All nine patients had significantly increased plasma total homocysteine (142-500 μmol/L vs. the normal range of 0-15 μmol/L) and blood methionine (144.3-500 μmol/L vs. the normal range of 0-50 μmol/L). None of the patients was pyridoxine responsive. Eleven mutations in CBS gene were identified in the nine patients. Eight mutations (IVS3+1G>A, p.Thr493fsX46, p.Thr236Asn, p.Leu230Gln, p.Lys72Ile, p.Ser201ProfsX36, p.Met337IlefsX115, and IVS14-1G>C) were novel. Three mutations (p.Arg125Gln, p.Thr257Met and p.Gly116Arg) had been previously reported.

CONCLUSIONS

In this study, eight novel mutations in CBS were identified in nine Chinese patients with classical homocystinuria. None of the hotspot mutations reported in other regions previously was found. These data indicated that Chinese maybe had different CBS mutation spectrum from other population. The identification of mutations not only confirms the diagnosis but also enables accurate genetic counselling and prenatal diagnosis for the fetuses of the families.