Temporary myoclonus with treatment of congenital transcobalamin 2 deficiency

Abnormal Movement Following Transcobalamin II Deficiency Treatment Responding to Clonazepam: A Case Report

Transcobalamin II (TCII) is a transporter protein that facilitates cobalamin release from the bloodstream to the cell. Deficiency in TCII is an autosomal recessive disorder caused by a mutation in the TCN2 gene. Treatment with intramuscular injection of hydroxocobalamin is greatly effective in improving the symptoms of this disorder. However, abnormal involuntary movements can occur and have been reported in patients with cobalamin deficiency caused by nutritional deficiency. Though, it is rarely associated with the treatment of hereditary TCII deficiency. Here, we report such a case, aiming to alert practitioners treating hereditary TCII deficiency. A 2-year-old boy born to a consanguineous parents presented with failure to thrive, recurrent infection, and pancytopenia. His condition deteriorated rapidly, and his investigation was remarkable for pancytopenia, elevated methylmalonic acid, and myelodysplastic changes in the bone marrow. A flash whole-exome sequence confirmed the diagnosis of TCII deficiency. The patient began treatment with IM hydroxocobalamin, and on the second day, he developed an abnormal involuntary movement that was abated by clonazepam. Abnormal nonepileptic movements following IM hydroxocobalamin in a patient with TCII deficiency shows a remarkable response to clonazepam.

Development of infantile tremor syndrome after initiation of hydroxycobalamin treatment in an infant with a late diagnosis of cobalamin C disorder

Combined methylmalonic aciduria and homocystinuria (cobalamin C deficiency, cblC) is a well-described disorder of vitamin B12 metabolism caused by mutations in the MMACHC gene with multisystemic manifestations. While there is no cure, combined treatment with intramuscular hydroxycobalamin and oral betaine may reduce the severity of symptoms and improve clinical outcome. We report a female patient diagnosed with late-onset cobalamin C deficiency at the age of 8 months who presented with developmental regression and severe dermatitis. She developed a movement disorder after initiation of hydroxycobalamin treatment. Similar movement disorders have been described in patients with nutritional vitamin B12 deficiencies following cobalamin supplementation but have not previously been reported in patients with cobalamin C disorder. The movement disorder in our patient gradually resolved with clonazepam treatment, despite no seizure activity detected on EEG. She was eventually weaned off the clonazepam and the abnormal movements have not recurred. The patient remains developmentally delayed but is showing no other symptoms related to cobalamin C deficiency. The patient has a younger affected sibling who was treated from birth and who is physically and developmentally entirely normal; she did not have abnormal movements after treatment with hydroxycobalamin was initiated. There is no clear consensus on the cause of movement disorders that develop following initiation of intramuscular vitamin B12 treatment.

A variety of abnormal movements in 13 cases with nutritional cobalamin deficiency in infants

HYPOTHESIS

Abnormal movements such as tremor, myoclonus, and choreoathetosis due to infantile nutritional vitamin B12 (Cbl, cobalamin) deficiency or after Cbl injection have been recognized for many years. However, nutritional Cbl deficiency may be more common than recognized and a variety of the abnormal movements may be beyond our estimates.

OBJECTIVE

To define the relationship between a large variety of abnormal movements in infants and vitamin B12 deficiency even if serum vitamin B12 levels and/or examination are normal.

MATERIALS AND METHODS

This study analyzed a variety of abnormal movements such as involuntary eye movements, limb and body contractions, and gasping as well as clinical, metabolic, radiologic, and treatment results in 13 infants with nutritional Cbl deficiency. This is a retrospective study based on observation and experience.

RESULTS

This study included 13 infants (11 boys and 2 girls) with a large spectrum of abnormal movements, the mean age at admission was 8.3 months with a range of 3-22 months. All patients were breastfeeding. In seven cases and their mothers serum vitamin B12 levels were below 200 pg/ml. About one-third of cases serum vitamin B12 levels were over 200 pg/ml. Clinically, mild hypotonia was present in 5 cases, inadequate social interactions in 2 cases, and sensorineural hearing loss in one case. Brain MRI showed frontotemporal enlarged subarachnoid spaces and thinning of the corpus callosum in two cases. EEG examinations were normal in all cases at admission. All cases recovered rapidly within one month with treatment.

CONCLUSION

Nutritional Cbl deficiency is a treatable disease that should be considered in the etiology of a variety of movement abnormalities in infants even if serum vitamin B12 values and neurological development are normal.

Update on transcobalamin deficiency: clinical presentation, treatment and outcome

Transcobalamin (TC) transports cobalamin from blood into cells. TC deficiency is a rare autosomal recessive disorder usually presenting in early infancy with failure to thrive, weakness, diarrhoea, pallor, anemia, and pancytopenia or agammaglobulinemia. It can sometimes resemble neonatal leukemia or severe combined immunodeficiency disease. Diagnosis of TC deficiency is suspected based on megaloblastic anemia, elevation of total plasma homocysteine, and blood or urine methylmalonic acid. It is confirmed by studying the synthesis of TC in cultured fibroblasts, or by molecular analysis of the TCN2 gene. TC deficiency is treatable with supplemental cobalamin, but the optimal type, route and frequency of cobalamin administration and long term patient outcomes are unknown. Here we present a series of 30 patients with TC deficiency, including an update on multiple previously published patients, in order to evaluate the different treatment strategies and provide information about long term outcome. Based on the data presented, current practice appears to favour treatment of individuals with TC deficiency by intramuscular injections of hydroxy- or cyanocobalamin. In most cases presented, at least weekly injections (1 mg IM) were necessary to ensure optimal treatment. Most centres adjusted the treatment regimen based on monitoring CBC, total plasma homocysteine, plasma and urine methylmalonic acid, as well as, clinical status. Finally, continuing IM treatment into adulthood appears to be beneficial.

Involuntary movements associated with vitamin B12 deficiency

Involuntary movements are not a known feature of vitamin B12 (vB12) deficiency in adults, though they are a characteristic feature of vB12 deficiency in infants. This case report presents an adult patient with vB12 deficiency in whom, myoclonus-like muscular contractions appeared soon after the initiation of vB12 and disappeared after the first week of this therapy. To our knowledge, this is the first report of involuntary movements in an adult patient with vB12 deficiency. Although the mechanism remains unknown, involuntary movements similar to myoclonus should be considered as one of the extraordinary neurological manifestations of vB12 deficiency in adults.

Myoclonus in childhood

The term "myoclonus" sounds esoteric, yet it is part of our normal physiology, occurring as a muscle jerk on drowsiness or falling asleep, during rapid eye movement (REM) sleep, and as hiccoughs. Myoclonus is also a developmental feature of the human nervous system, comprising some of the earliest fetal movements. In pathologic settings, myoclonus may be the only neurologic abnormality, as in essential myoclonus, but more often it is one symptom of a larger neurologic problem. The vast etiologic spectrum of symptomatic myoclonus can be bewildering, but defining the underlying problem may provide the opportunity to develop specific therapies. Otherwise, treatment is merely symptomatic. The approach to the patient should be to verify the nature of the movement disorder and establish a specific etiologic diagnosis. A battery of neurophysiologic, neuroradiologic, and other laboratory studies is needed to localize the origin of the myoclonus and identify causative lesions. Drug treatment is largely empiric but must be systematic and aimed at restoring activities of everyday living. Unlike in epilepsies, in myoclonus multiple drugs usually must be combined to attain functional improvement.