Mutations in Hcfc1 and Ronin result in an inborn error of cobalamin metabolism and ribosomopathy

Combined methylmalonic acidemia and homocystinuria (cblC) is the most common inborn error of intracellular cobalamin metabolism and due to mutations in Methylmalonic Aciduria type C and Homocystinuria (MMACHC). Recently, mutations in the transcriptional regulators HCFC1 and RONIN (THAP11) were shown to result in cellular phenocopies of cblC. Since HCFC1/RONIN jointly regulate MMACHC, patients with mutations in these factors suffer from reduced MMACHC expression and exhibit a cblC-like disease. However, additional de-regulated genes and the resulting pathophysiology is unknown. Therefore, we have generated mouse models of this disease. In addition to exhibiting loss of Mmachc, metabolic perturbations, and developmental defects previously observed in cblC, we uncovered reduced expression of target genes that encode ribosome protein subunits. We also identified specific phenotypes that we ascribe to deregulation of ribosome biogenesis impacting normal translation during development. These findings identify HCFC1/RONIN as transcriptional regulators of ribosome biogenesis during development and their mutation results in complex syndromes exhibiting aspects of both cblC and ribosomopathies.

L’omocistinuria classica in età pediatrica

Classical homocystinuria is an inborn error of methionin metabolism. It is characterized by an accumulation of homocysteine, due to a deficiency of the enzyme involved in its metabolism, namely cystathionine beta synthase. If not treated, the increase in homocysteine leads to a multisystem syndrome that involves connective tissue, nervous and vascular systems with a predisposition to thromboembolism and developmental delay in childhood. An early diagnosis allows the specific therapy to be promptly started and prevents the classical manifestations of the disease. Since 2016 in Italy homocystinuria detection has been included in the expanded newborn screening. However, it is important not to forget this disease, because of its severe consequences of an untreated condition on the quality and expectancy of life.

An Atypical Case of Congenital Erythropoietic Porphyria

Congenital erythropoietic porphyria (CEP, OMIM #606938) is a severe autosomal recessive inborn error of heme biosynthesis. This rare panethnic disease is due to a deficiency of uroporphyrinogen III synthase (or cosynthase). Subsequently, its substrate, the hydroxymethylbilane is subsequently converted into uroporphyrinogen I in a non-enzymatic manner. Of note, uroporphyrinogen I cannot be metabolized into heme and its accumulation in red blood cells results in intramedullary and intravascular hemolysis. The related clinical symptoms occur most frequently during antenatal or neonatal periods but may also appear in late adulthood. The main antenatal clinical presentation is a non-immune hydrops fetalis. We report here two cases of antenatal CEP deficiency and a review of the reported cases in the literature.

Case Report: Acquired Disseminated BCG in the Context of a Delayed Immune Reconstitution After Hematological Malignancy

ContextDisseminated infections due to Mycobacterium bovis Bacillus Calmette-Guérin (BCG) are unusual and occur mostly in patients with inborn error of immunity (IEI) or acquired immunodeficiency. However, cases of secondary BCGosis due to intravesical BCG instillation have been described. Herein, we present a case of severe BCGosis occurring in an unusual situation.Case DescriptionWe report one case of severe disseminated BCG disease occurring after hematological malignancy in a 48-year-old man without BCG instillation and previously vaccinated in infancy with no complication. Laboratory investigations demonstrated that he was not affected by any known or candidate gene of IEI or intrinsic cellular defect involving IFNγ pathway. Whole genome sequencing of the BCG strain showed that it was most closely related to the M. bovis BCG Tice strain, suggesting an unexpected relationship between the secondary immunodeficiency of the patient and the acquired BCG infection.ConclusionThis case highlights the fact that, in addition to the IEI, physicians, as well as microbiologists and pharmacists should be aware of possible acquired disseminated BCG disease in secondary immunocompromised patients treated in centers that administrate BCG for bladder cancers.