Vitamin B12 deficiency secondary to cobalamin F deficiency simulating dyskeratosis congenita

Cobalamin F deficiency in a girl with severe skin hyperpigmentation and a homozygous LMBRD1 variant

“…3,4,6 To our knowledge, our patient is only the second case reported with skin hyperpigmentation due to LMBRD1 variants. 4 Most of the previously reported patients with Cbl deficiency and unusual pigmentation had a diagnosis of CblJ, an even rarer Cbl disorder due to pathogenic variants within ABCD4 gene. 2 The respective proteins, LMBRD1 (CblF) and ABCD4 (CblJ), colocalize to the lysosome membrane, forming a complex critical to the export of lysosomal Cbl to the cytoplasm.…”

“…Our patient’s disorder, CblF, is a rare IEM with a heterogeneous presentation, ranging from patients with early‐onset severe manifestations to asymptomatic patients who are ascertained only incidentally by newborn screening 3,4,6 . To our knowledge, our patient is only the second case reported with skin hyperpigmentation due to LMBRD1 variants 4 . Most of the previously reported patients with Cbl deficiency and unusual pigmentation had a diagnosis of CblJ, an even rarer Cbl disorder due to pathogenic variants within ABCD4 gene 2 .…”

“…Our patient’s disorder, CblF, is a rare IEM with a heterogeneous presentation, ranging from patients with early‐onset severe manifestations to asymptomatic patients who are ascertained only incidentally by newborn screening 3,4,6 . To our knowledge, our patient is only the second case reported with skin hyperpigmentation due to LMBRD1 variants 4 .…”

“…Depending on their localization within the pathway, the deficiencies can cause hyperhomocysteinaemia, methylmalonic aciduria or both 2 . These inborn errors of metabolism (IEM) can share symptoms with nutritional Cbl deficiency, such as skin hyperpigmentation, megaloblastic anaemia and glossitis 3–5 …”

“…2 These inborn errors of metabolism (IEM) can share symptoms with nutritional Cbl deficiency, such as skin hyperpigmentation, megaloblastic anaemia and glossitis. [3][4][5] We report a patient with disseminated skin hyperpigmentation caused by a homozygous LMBRD1 variant. The patient presented at the age of 13 years to the Dermatology and Genetics clinics for evaluation of skin hyperpigmentation and short stature.…”