SLURP1, also known as MDM, ARS, ANUP (anti-neoplastic urinary protein), LY6LS or ArsB (ARS component B), is a 103 amino acid secreted protein that exists as a homodimer possessing antitumor activity. Found in esophagus, stomach, exocervix, gums, urine, sweat, saliva, plasma and tears, SLURP1 is most highly expressed in the acrosyringium of the granular layer of skin, where it helps maintain the structure of the keratinocyte layers of the skin. Also considered a marker for late skin differentiation, SLURP1 contains one UPAR/Ly6 domain and is the cause of an autosomal recessive disorder of the skin known as Mal de Meleda (MDM). MDM Is characterized by nail abnormalities, keratotic skin lesions, transgressive palmoplantar keratoderma (PPK), perioral erythema and may sometimes include hyperhidrosis.