Severe neurological complications in an infant during vitamin B12 deficiency treatment: a case report

Abstract

Disorders of metabolism of vitamin B₁₂ known as cobalamin can be manifested in children by numerous symptoms. They result from dysfunction of many systems, including the central nervous system. The most common cause of cobalamin deficiency in infants is inadequate supplementation of the vitamin with food. This mainly affects children who are exclusively breastfed by mothers who follow a diet with insufficient supplementation of vitamin B₁₂, including an imbalanced vegetarian or vegan diet. Adequate vitamin B₁₂ supplementation is essential for proper growth and development of a child. However, attempts to compensate for severe vitamin B₁₂ deficiency can paradoxically lead to severe adverse reactions to cobalamin treatment. We present a case of a 10-month-old boy with global developmental delay, muscle hypotonia and profound cobalamin deficiency with megaloblastic anemia. The boy developed pathological neurological signs after intramuscular injections of vitamin B₁₂. The symptoms included muscle tremors of the upper extremities, head, tongue and lips. A broad differential diagnosis including inborn errors of metabolism and other genetic disorders is discussed. We describe treatment that led to complete resolution of symptoms related to side effects of B₁₂ therapy. The patient's psychomotor development during over one year of clinical follow-up is also analyzed.