A novel FAM83G variant from palmoplantar keratoderma patient disrupts WNT signalling via loss of FAM83G-CK1α interaction.

Palmoplantar keratoderma (PPK) is a multi-faceted skin disorder characterized by the thickening of the epidermis and abrasions on the palms and soles of the feet. Among the genetic causes, biallelic pathogenic variants in the FAM83G gene have been associated with PPK in dogs and humans. Here, a novel homozygous variant (c.794G>C, p.Arg265Pro) in the FAM83G gene, identified by whole exome sequencing in a 60-year-old female patient with PPK, is reported. The patient exhibited alterations in the skin of both hands and feet, dystrophic nails, thin, curly and sparse hair, long upper eyelid eyelashes, and poor dental enamel. FAM83G activates WNT signalling through association with ser/thr protein kinase CK1α. When expressed in FAM83G-/- DLD1 colorectal cancer cells, the FAM83GR265P variant displayed poor stability, a loss of interaction with CK1α and attenuated WNT signalling response. These defects persisted in skin fibroblast cells derived from the patient. Our findings imply that the loss of FAM83G-CK1α interaction and subsequent attenuation of WNT signalling underlie the pathogenesis of PPK caused by the FAM83GR265P variant.

Predictive factors for anti-MDA5 antibody in patients with dermatomyositis: a retrospective multicenter study.

BACKGROUND AND OBJECTIVES: Melanoma differentiation-associated gene 5 antibody (anti-MDA5) in dermatomyositis (DM) is associated with rapidly progressive interstitial lung disease and poor prognosis. Early diagnosis is key to improving the prognosis of these patients. The aim was to confirm cutaneous characteristics in patients with anti-MDA5 dermatomyositis and to explore new diagnostic markers for the presence of anti-MDA5 (anti-MDA5+ ). PATIENTS AND METHODS: A multicenter cross-sectional retrospective cohort study of 124 patients diagnosed with DM, of which 37 were anti-MDA5+ . Demographic data, laboratory data, and clinical manifestations were collected. RESULTS: Anti-MDA5+ DM is characterized by a distinct mucocutaneous phenotype that includes oral lesions, alopecia, mechanic's hands, palmar and dorsal papules, palmar erythema, vasculopathy, and skin ulceration. We found vasculopathy and digit tip involvement very frequently in anti-MDA5+ patients (p <0.001), being a diagnostic marker of anti-MDA5+ (OR, 12.355; 95% CI 2.850-79.263; p  =  0.012 and OR, 7.447; 95% CI 2.103-46.718; p  =  0.004, respectively). The presence of ulcers deserves special mention, especially in anti-MDA5+ patients, because in our cohort, up to 97% of the anti-MDA5+ patients had ulcers. CONCLUSIONS: In patients with suspected DM with digit tip involvement or vasculopathy, the presence of anti-MDA5 antibodies must be ruled out, as it may be a clinical predictor.