PA32 Terra firma-forme dermatosis in siblings

Abstract A 3-year-old boy was referred to our dermatology service due to multiple capillary malformations affecting the palmar aspect of the left hand, bilateral soles of the feet and bilateral knees. He was found to have a pathogenic variant in RASA1, confirming a diagnosis of capillary malformation–arteriovenous malformation (CM-AVM) syndrome. Separately, he was noted to have raised, dirty-appearing areas of skin on his feet and lower legs. On closer inspection, there were thickened, brown papules and plaques on the medial malleolus, shins and dorsal feet. Wiping affected areas with a pad soaked in 70% isopropyl alcohol completely removed the lesions. His parents brought our attention to his 5-year-old sister, who had an identical pattern of brown marks in the same distribution, which were also removed easily with an alcohol wipe. Based on the clinical appearance and removal with 70% isopropyl alcohol wipe, a diagnosis of terra firma-forme dermatitis (TFFD) was made in the siblings. A 30% urea cream was prescribed to both siblings, and further investigations were planned given the diagnosis of CM-AVM syndrome. To our knowledge, this is the first case of TFFD reported in siblings. TFFD represents a benign acquired condition that presents with ‘dirt’-coloured pigmented plaques. TFFD has been reported in all age groups; however, it is most common in children. While the pathogenesis of TFFD is unknown, it has been hypothesized that it represents a forme fruste of confluent and reticulated papillomatosis of Gougerot and Carteaud. The co-occurrence of the condition in siblings suggests that TTFD may be caused by an autosomal dominant mutation, potentially in a keratin gene.