PA05 Two babies with self-improving collodion ichthyosis with <i>ALOX12B</i> mutations demonstrating novel diagnostic clinical signs

Abstract Baby C was born at 36 + 4 weeks by spontaneous vaginal delivery and was transferred to Oxford on day two of life. On examination she had a yellow parchment-like collodion with hyperkeratotic plaques over the torso with desquamation and fissures of the flexors. Her parents are Romanian in origin and were not related, and there was no family history of congenital skin or autoimmune disorders. The antenatal investigations and maternal infection screen were unremarkable. Baby A was born via elective caesarean section at 37 + 5 weeks and there had been no antenatal concerns regarding development. She was noted to have a collodion membrane with desquamation and skin that was generally dry and erythematous with fine scale present. The parents are Pakistani in origin and were not related, and all antenatal and maternal investigations were unremarkable. Both babies were managed with close nursing care, with topical paraffin-based emollients applied in a temperature- and humidity-controlled incubator in the neonatal intensive care unit. Baby C was reported heterozygous for two pathogenic variants in the ALOX12B gene consistent with autosomal recessive congenital ichthyosis. Baby A was reported homozygous for a pathogenic ALOX12B frameshift variant. ALOX12B mutations account for 9% of the genotypic spectrum of recessive ichthyosis in England, as reported by Simpson et al., who studied 146 babies in England (Simpson JK, Martinez-Queipo M, Onoufriadis A et al. Genotype–phenotype correlation in a large English cohort of patients with autosomal recessive ichthyosis. Br J Dermatol 2020; 182: 729–37). The same study suggested novel diagnostic clues for the underlying genotype of recessive ichthyosis. Babies with ALOX12B mutation have associations with being born with a collodion membrane, being erythematous with fine, white spicules of nonadherent scale and showing signs of self-improvement with age. These features are summarized in the Table. Distinctive features included anteriorly overfolded ear from birth and pseudoclubbing of the nails, which are exclusive to the ALOXB12 genotype. Baby C and baby A both demonstrated all of these distinctive signs and are showing evidence of self-improvement at 4 months. The clinical assessment of a collodion baby is not straightforward, with great uncertainty surrounding the underlying aetiology and genotype. Empathetic support and giving time to the families were a crucial aspect in managing both of our cases. The families very much appreciated the patience with which the dermatology team explained the situation and were transparent with the prognostic outcomes. We have demonstrated two novel clinical signs that have exclusively been associated with ALOX12B mutation, which could help with diagnosis of a potentially self-improving genotype of ichthyosis and help manage the expectations of families.TableALOXB12 genotype–phenotype associationsFeatureAssociationCollodion membrane71%Anteriorly overfolded ears43% – exclusive to ALOXB12Self-improving collodion43%Fine nonadherent scale45%Pseudoclubbing of fingersExclusive to ALOXB12