DEAR EDITOR, Heterozygous mutations in the DSG1 gene (encoding desmoglein 1) are known to cause autosomal dominant striate palmoplantar keratoderma (PPK)(MIM 148700). 1, 2 A new phenotype due to biallelic mutations in DSG1, which is characterized by severe dermatitis, multiple allergies and metabolic wasting, has been recently described as SAM syndrome (MIM 615508). 3, 4

In one Norwegian family with two affected half-brothers (III-2 and III-4) we observed a phenotype that includes variable combinations of skin symptoms such as severe PPK, circumscribed skin erosions and psoriasiform erythroderma. The clinical features showed overlap with Olmsted syndrome, SAM syndrome and psoriasis, but with a different progression, and none of these diagnoses was fully compatible with the patients’ symptoms (Fig. 1, Table 1). More details of SAM and other desmosomal genodermatoses are given in Appendix S1 and Table S1 (see Supporting Information). The proband (III-2, age 27 years) was born at term after an uneventful pregnancy. Although no signs of skin disease were present at birth, he soon developed a mild PPK, and several months later patchy eczematous lesions with fine scaling appeared on the trunk and extremities and around the orifices. During childhood the PPK gradually grew thicker and extended over the Achilles tendon and over the back of the hands and feet (Fig. 1b–d). Total IgE was elevated with symptoms of allergy to fish and hazelnuts. His psychomotor development has been normal and he has had no systemic illnesses, metabolic wasting or susceptibility to infectious diseases. His hair and teeth are normal. His nails have some transverse lines but are otherwise normal. The skin signs have been constant since childhood. On dermatological examination at age 24 years, patchy keratoderma of the palms and soles with marginal extensions was noted, as well as psoriasiform dermatitis on the back of the neck (Fig. 1e) and patchy eczematous lesions on the extremities. Patient III-4, at the time an 11-year-old boy (same mother as III-2 but a different father), had no obvious signs of skin disease at birth. In the first few months of life, PPK developed and soon thereafter patchy eczematous lesions appeared all over the body and around the orifices (Fig. 1f, g), including the perianal area. His hair, nails, teeth, sweating ability