ObjectivesIn achondroplastic patients with slight complaints of medullary compression the cervical spinal cord regularly exhibits an intramedullary (CHII) lesion just below the craniocervical junction with no signs of focal compression on the cord. Currently, the prevalence of the lesion in the general achondroplastic population is studied and its origin is explored.MethodsEighteen achondroplastic volunteers with merely no clinical signs of medullary compression were subjected to dynamic magnetic resonance imaging (MRI). The presence of a CHII lesion and craniocervical medullary compression in flexed and retroflexed craniocervical positions was explored. Several morphological characteristics of the craniocervical junction, possibly related to compression on the cord, were assessed.ResultsA CHII lesion was observed in 39% of the subjects and in only one of these was compression at the craniocervical junction present. Consequently, no correlation between the CHII lesion and compression could be established. None of the morphological characteristics demonstrated a correlation with the CHII lesion, except thinning of the cord at the site of the CHII lesion.ConclusionsCHII lesions are a frequent finding in achondroplasia, and are generally unaccompanied by clinical symptoms or compression on the cord. Further research focusing on the origin of CHII lesions and their clinical implications is warranted.Key Points• MRI now reveals exquisite detail of the cervical spinal cord.• Cervical cord lesions are observed in one third of the achondroplastic population.• These lesions yield high signal intensity on T2 weighted MRI.• They are generally unaccompanied by clinical symptoms or cord compression.• Their aetiology is unclear and seems to be unrelated to mechanical causes.

Key Points• An N411K mutation in the external gate of the proton-coupled folate transporter within the aqueous channel results in impaired function.• The N411K mutation produces a substratespecific defect in transport, resulting in hereditary folate malabsorption.Hereditary folate malabsorption (HFM) is an autosomal recessive disorder characterized by impaired intestinal folate absorption and impaired folate transport across the choroid plexus due to loss of function of the proton-coupled folate transporter (PCFT-SLC46A1). We report a novel mutation, causing HFM, affecting a residue located in the 11th transmembrane helix within the external gate. The mutant N411K-PCFT was stable, trafficked to the cell membrane, and had sufficient residual activity to characterize the transport defect and the structural requirements at this site for gate function. The influx V max of the N411K mutant was markedly decreased, as was the affinity for most, but not all, folate/antifolate substrates.The greatest loss of activity was for 5-methyltetrahydrofolate. Substitutions with positive charged residues resulted in a loss of activity (arginine . lysine . histidine). Function was retained for the negative charged aspartate, but not the larger glutamate substitutions, whereas the bulky hydrophobic (leucine), or polar (glutamine) substitutions, were tolerated.Homology models of PCFT, in the inward and outward open conformations, based upon the mammalian Glut5 fructose transporter structures, localize Asn411 protruding into the aqueous pathway. This is most prominent when the carrier is in the inward open conformation when the external gate is closed. Mutations at this site likely result in highly specific steric and electrostatic interactions between the Asn411-substituted, and other, residues in the gate region that impede carrier function. The substrate specificity of the N411K mutant may be due to alterations of substrate flows through the external gate, downstream allosteric alterations in the folate-binding pocket, or both.

Safety issues and complications associated with dietary management are prevalently reported by (caregivers of) 249 GSD patients. A discrepancy has been observed between the patient's perspective on safety of dietary management and occurrence of complications as a result of dietary management.

There is a paucity in literature on eating and psychosocial problems in patients with hepatic glycogen storage disease (GSD) and idiopathic ketotic hypoglycemia (IKH), problems that can greatly affect quality of life. This is a monocentre, retrospective, observational mixed method study of patients with hepatic GSD or IKH treated at the Beatrix Children's Hospital Groningen, who had been referred to SeysCentra, a specialist centre for the treatment of eating problems. Additionally, a systematic literature review has been performed to identify instruments to quantify patient‐reported outcome measures of psychosocial problems in hepatic GSD patients. Sixteen patients from 12 families were included with ages ranging between 3 and 24 years. Five out of sixteen patients were diagnosed with Avoidant/Restrictive Food Intake Disorder and six patients showed characteristics of this disorder. Fourteen patients experienced sleeping problems, and 11 out of 12 parent couples experienced stress about the illness of their child. We subsequently identified 26 instruments to quantify patient‐reported outcome measures for GSD patients. This study demonstrates that GSD patients can develop Avoidant/Restrictive Food Intake Disorder influencing quality of life at multiple domains. The identification of instruments to assess psychosocial wellbeing is an important step towards a standard set of patient‐reported outcome measures.