FAM20C is a gene coding for a protein kinase that targets S-X-E/pS motifs on different phosphoproteins belonging to diverse tissues. Pathogenic variants of FAM20C are responsible for Raine syndrome (RS), initially described as a lethal and congenital osteosclerotic dysplasia characterized by generalized atherosclerosis with periosteal bone formation, characteristic facial dysmorphisms and intracerebral calcifications. The aim of this review is to give an overview of targets and variants of FAM20C as well as RS aspects. We performed a wide phenotypic review focusing on clinical aspects and differences between all lethal (LRS) and non-lethal (NLRS) reported cases, besides the FAM20C pathogenic variant description for each. As new targets of FAM20C kinase have been identified, we reviewed FAM20C targets and their functions in bone and other tissues, with emphasis on novel targets not previously considered. We found the classic lethal and milder non-lethal phenotypes. The milder phenotype is defined by a large spectrum ranging from osteonecrosis to osteosclerosis with additional congenital defects or intellectual disability in some cases. We discuss our current understanding of FAM20C deficiency, its mechanism in RS through classic FAM20C targets in bone tissue and its potential biological relevance through novel targets in non-bone tissues.

Two siblings from a Mexican family who carried lethal Raine syndrome are presented. A newborn term male (case 1) and his 21 gestational week brother (case 2), with a similar osteosclerotic pattern: generalized osteosclerosis, which is more evident in facial bones and cranial base. Prenatal findings at 21 weeks and histopathological features for case 2 are described. A novel combination of biallelic FAM20C pathogenic variants were detected, a maternal cytosine duplication at position 456 and a paternal deletion of a cytosine in position 474 in exon 1, which change the reading frame with a premature termination at codon 207 and 185 respectively. These changes are in concordance with a negative detection of the protein in liver and kidney as shown in case 2. Necropsy showed absence of pancreatic Langerhans Islets, which are reported here for the first time. Corpus callosum absence is added to the few reported cases of brain defects in Raine syndrome. This report shows two new FAM20C variants not described previously, and negative protein detection in the liver and the kidney. We highlight that lethal Raine syndrome is well defined as early as 21 weeks, including mineralization defects and craniofacial features. Pancreas and brain defects found here in FAM20C deficiency extend the functional spectrum of this protein to previously unknown organs.

Tuberculosis (TB) is a global public health issue requiring early and accurate diagnosis. The loop-mediated isothermal amplification (LAMP) assay is a promising alternative recommended by the WHO for the initial diagnosis of pulmonary TB, particularly in resource-limited settings. This study evaluated the sensitivity and specificity of a commercial LAMP assay for TB detection using 198 samples from different countries including Mexico. The LAMP assay results were compared to the results of standard tests: AFB smear microscopy, cell culture, and Xpert PCR. Across all samples, LAMP showed a sensitivity of 96.20% and a specificity of 84.61%. When compared specifically to “true positives” and “true negatives” (defined by the consistency across the standard tests), LAMP demonstrated 100% sensitivity and 92.30% specificity. For context, the sensitivity of AFB smear microscopy against the culture and Xpert tests was 79.04%. A significant finding was that the LAMP test detected a high percentage (92.5%) of samples found positive by the culture and Xpert tests but negative by the AFB smear, highlighting its ability to identify cases missed by traditional microscopy. This study concluded that the LAMP assay is a sensitive and specific tool for TB diagnosis with potential for rapid and accurate diagnosis, especially in resource-limited areas.

FAM20C (family with sequence similarity 20, member C) is a serine/threonine-specific protein kinase that is ubiquitously expressed and mainly associated with biomineralization and phosphatemia regulation. It is mostly known due to pathogenic variants causing its deficiency, which results in Raine syndrome (RNS), a sclerosing bone dysplasia with hypophosphatemia. The phenotype is recognized by the skeletal features, which are related to hypophosphorylation of different FAM20C bone-target proteins. However, FAM20C has many targets, including brain proteins and the cerebrospinal fluid phosphoproteome. Individuals with RNS can have developmental delay, intellectual disability, seizures, and structural brain defects, but little is known about FAM20C brain-target-protein dysregulation or about a potential pathogenesis associated with neurologic features. In order to identify the potential FAM20C actions on the brain, an in silico analysis was conducted. Structural and functional defects reported in RNS were described; FAM20C targets and interactors were identified, including their brain expression. Gene ontology of molecular processes, function, and components was completed for these targets, as well as for potential involved signaling pathways and diseases. The BioGRID and Human Protein Atlas databases, the Gorilla tool, and the PANTHER and DisGeNET databases were used. Results show that genes with high expression in the brain are involved in cholesterol and lipoprotein processes, plus axo-dendritic transport and the neuron part. These results could highlight some proteins involved in the neurologic pathogenesis of RNS.

Liver cirrhosis causes include alcoholism, viral infections (hepatitis B virus (HBV) and hepatitis C virus (HCV)), alcohol-associated liver disease (ALD), and metabolic dysfunction associated with steatotic liver disease (MASLD), among others. Cirrhosis frequency has increased in recent years, with a prevalence of 1395 cases per 100,000 and a mortality rate of 18 per 100,000, which corresponded to 1,472,000 deaths during 2017. In Mexico, liver disease is a public health problem since it was associated to 41,890 deaths in 2022, including liver cirrhosis (>25,000) and ALD (14,927). This represents 114 daily deaths due to these causes, and corresponds to the 4th or 5th place of all causes. The global prevalence of MASLD is estimated to affect 25% of the world's population, while in the pediatric population it could be higher. In Mexican population it is more prevalent since estimations were around 41.3% in 2023. Alcohol consumption, a global health issue due to its high prevalence and associated morbidities, is associated to ALD in 32.9%, with a mortality rate of 23.9%, primarily due to liver-related causes. In Mexico, ALD is present in 23% of all cirrhosis cases, already surpassed by hepatitis B cases in 2009. HCV and HBV frequencies changed due to programs implementing screening detection, vaccines and direct-acting antivirals during the last years. A switch of causes has occurred, increasing MASLD and diminishing viral causes. Efficient performed liver transplantation has grown as a response to increasing cirrhosis cases, including recent authorized centers. These efforts are necessary, whereas preventive strategies should be implemented according to leading causes.