Uncommon sublingual ulceration in an infant

Sir, An eight-month-old girl was referred to our department with an extensive lingual ulceration. The parents noted that she had habitually bitten her tongue since the release of her first teeth at the age of six months. She was a poor feeder and did not sleep well because of the painful lingual ulceration. There was no family history of developmental disorders or congenital syndromes. Intraoral examination revealed a deep, circular, and extensive ulceration of the whole ventral surface of the tongue with intermittent bleeding in the tongue (Figs. 1a – c). An examination of the rest of the intraoral mucosa revealed that the lower central incisors had recently erupted. However, there were two other ulcerations of the palmar surface of the second and third fingers caused by nocturnal finger biting. Neurological examination noted a lack of pain sensitivity related to peripheral neuropathy diagnosed as congenital insensitivity to pain. Based on the clinical features and the particular site on the ventral surface of the tongue against the lower central incisors and ulcerative lesions of the fingers due to self-biting, the lesion was diagnosed as Riga–Fede disease. Because of the size of the ulceration, significant pain during feeding led to inadequate nutrient intake associated with permanent sleep disturbances. Radical treatment was chosen and the lower central incisors were extracted. Topical corticosteroids were prescribed to help with healing. The term Riga–Fede disease has been used to describe a traumatic ulceration that has occurred on the ventral surface of the tongue in newborn babies and infants. It is most commonly related to neonatal or natal teeth but may also occur in infants after the eruption of the primary lower incisors [1]. This benign ulceration occurs as a result of repetitive mechanical trauma caused to the oral mucosal surfaces by the teeth and is most commonly located on the ventral surface of the tongue against the teeth [1,2]. Riga–Fede disease may reveal an underlying developmental or neurologic disorder, including congenital insensitivities to pain [3]. The case of our patient was associated with congenital insensitivity to pain. Failure to diagnose may lead to dehydration and inadequate nutrient intake in the infant because of the significant pain during feeding. No biopsy is needed. The diagnosis of Riga–Fede disease is based on clinical characteristics [1,2]. Treatment should focus on eliminating the source of trauma. Conservative treatment is attempted at first by grinding the sharp edges of the teeth and placing composite resin in a dome shape or by placing a protective ring. If conservative treatment fails to heal the wounds, radical treatment may be necessary, such as extraction of the teeth [2,3]. We believe that Riga–Fede disease must be recognized by clinicians to avoid misdiagnosis and delayed treatment.

Involvement of Rare Mutations of SCN9A, DPP4, ABCA13, and SYT14 in Schizophrenia and Bipolar Disorder

Rare mutations associated with schizophrenia (SZ) and bipolar disorder (BD) usually have high clinical penetrance; however, they are highly heterogeneous and personalized. Identifying rare mutations is instrumental in making the molecular diagnosis, understanding the pathogenesis, and providing genetic counseling for the affected individuals and families. We conducted whole-genome sequencing analysis in two multiplex families with the dominant inheritance of SZ and BD. We detected a G327E mutation of SCN9A and an A654V mutation of DPP4 cosegregating with SZ and BD in one three-generation multiplex family. We also identified three mutations cosegregating with SZ and BD in another two-generation multiplex family, including L711S of SCN9A, M4554I of ABCA13, and P159L of SYT14. These five missense mutations were rare and deleterious. Mutations of SCN9A have initially been reported to cause congenital insensitivity to pain and neuropathic pain syndromes. Further studies showed that rare mutations of SCN9A were associated with seizure and autism spectrum disorders. Our findings suggest that SZ and BD might also be part of the clinical phenotype spectra of SCN9A mutations. Our study also indicates the oligogenic involvement in SZ and BD and supports the multiple-hit model of SZ and BD.

Investigation of a Novel NTRK1 Variation Causing Congenital Insensitivity to Pain With Anhidrosis

Background: Congenital insensitivity to pain with anhidrosis (CIPA), a rare autosomal recessive sensory neuropathy, was caused mainly by biallelic mutations in the NTRK1 gene. The pathogenesis of CIPA still needs further elucidation.Methods: Here, we recruited a CIPA case and introduced whole-exome sequencing (WES) to identify the causative variation. Subsequently, an in silico molecular dynamic (MD) analysis was performed to explore the intramolecular impact of the novel missense variant. Meanwhile, in vitro functional study on the novel variant from a metabolomic perspective was conducted via the liquid chromatography–mass spectrometry (LC-MS) approach, of which the result was verified by quantitative real-time PCR (qRT-PCR).Results: A novel compound heterozygous variation in NTRK1 gene was detected, consisting of the c.851–33T > A and c.2242C > T (p.Arg748Trp) variants. MD result suggested that p.Arg748Trp could affect the intramolecular structure stability. The results of the LC-MS and metabolic pathway clustering indicated that the NTRK1Arg748Trp variant would significantly affect the purine metabolism in vitro. Further analysis showed that it induced the elevation of NT5C2 mRNA level.Conclusion: The findings in this study extended the variation spectrum of NTRK1, provided evidence for counseling to the affected family, and offered potential clues and biomarkers to the pathogenesis of CIPA.

Non-invasive Imaging of Sense of Smell by Tracking the Voltage-Gated Sodium Channel NaV1.7

Background: Anosmia/hyposmia affects 13.3 million people in the U.S. alone according to the recent U.S. National Health and Nutrition Examination Survey (NHANES). Hundreds of thousands more people with persistent olfactory dysfunction will be added to this number due to the COVID-19 pandemic. Patients with loss-of-function mutations in SCN9A, the gene encoding NaV1.7, experience anosmia in addition to congenital insensitivity to pain. Tsp1a is a recently discovered peptide that inhibits NaV1.7 with high potency and selectivity. In this study, we examined whether a fluorescently tagged version of Tsp1a could be used to visualize normal and damaged mouse olfactory nerves. Methods: Athymic nude mice were intravenously injected with Tsp1a-IR800. As a control, mice were injected with PBS only, and as a blocking control were injected with combination of Tsp1a and Tsp1a-IR800. All mice were imaged in-vivo and epifluorescence images were acquired using an IVIS Spectrum animal imaging system. Semiquantitative analysis of the Tsp1a-IR800 signal was conducted by measuring the average radiant efficiency in the region of the olfactory epithelium/bulb (ROEB). Methimazole was used to chemically ablate the olfactory epithelium. We performed a food buried test to correlate the level of anosmia with the level of radiance efficiency. Results: The area of olfactory epithelium/bulb was clearly visible in epifluorescence in-vivo images of mice receiving the imaging agent. The radiant efficiency was significantly less in both mice injected with PBS and in mice injected with the blocking formulation. The mice after olfactory ablation had a significantly reduced radiant efficiency compared with normal mice. Moreover, there was a statistically significant and inverse correlation between the time required for the mouse to find buried food and the radiant efficiency. We also performed immunohistochemistry using NaV1.7 antibody. Mice after olfactory ablation as well as COVID-19-infected mice had significantly lower expression of NaV1.7 on the level of olfactory epithelium/bulb. Conclusion: We show that the fluorescent imaging of mouse olfactory epithelium/bulb is possible, suggesting that labeled Tsp1a tracers may serve as the first objective diagnostic tool of smell disorders, including those caused by COVID-19.

PRDM12 Is Transcriptionally Active and Required for Nociceptor Function Throughout Life

PR domain-containing member 12 (PRDM12) is a key developmental transcription factor in sensory neuronal specification and survival. Patients with rare deleterious variants in PRDM12 are born with congenital insensitivity to pain (CIP) due to the complete absence of a subtype of peripheral neurons that detect pain. In this paper, we report two additional CIP cases with a novel homozygous PRDM12 variant. To elucidate the function of PRDM12 during mammalian development and adulthood, we generated temporal and spatial conditional mouse models. We find that PRDM12 is expressed throughout the adult nervous system. We observed that loss of PRDM12 during mid-sensory neurogenesis but not in the adult leads to reduced survival. Comparing cellular biophysical nociceptive properties in developmental and adult-onset PRDM12 deletion mouse models, we find that PRDM12 is necessary for proper nociceptive responses throughout life. However, we find that PRDM12 regulates distinct age-dependent transcriptional programs. Together, our results implicate PRDM12 as a viable therapeutic target for specific pain therapies even in adults.