Cobalamin J Disorder in a Teenage Boy with Recurrent Abdominal Pain Attacks: A Case Report and Literature Review

Cobalamin J disease (CblJ) is an ultrarare autosomal recessive disorder of intracellular cobalamin metabolism associated with combined methylmalonic academia and homocystinuria (MAHCJ; 614857).

A new patient with MAHCJ, representing the eighth documented instance, is reported here. A novel homozygous missense variant c.1591C>T (p.Arg531Trp) in exon 17 of ABCD4 (NM_005050.4) was identified. The patient, a 15-year-old male of Azerbaijani descent, presented with severe abdominal pain beginning at the age of 1 year. These episodic pain attacks were accompanied by hypotonia, pallor, nausea, and vomiting. Initial evaluations were inconclusive. At the age of 8 years, the patient developed megaloblastic anemia due to vitamin B12 deficiency, leading to the initiation of replacement therapy. The pain attacks ceased during treatment but recurred whenever vitamin B12 levels dropped after discontinuation. The patient exhibited no dysmorphology, skin hyperpigmentation, somatic abnormalities, seizures, or neurodevelopmental delays and remains in remission with ongoing vitamin B12 treatment.

This patient is the oldest diagnosed with MAHCJ and has the longest documented clinical course. This report expands the known clinical and molecular spectrum of this rare disease. We recommend remembering cobalamin defects in the differential diagnosis of unresolved abdominal pain attacks.