Severe thiopurine-induced leukocytopenia and hair loss in Japanese patients with defective NUDT15 variant: Retrospective case-control study.

Azathioprine (AZA)-metabolizing enzyme gene polymorphism is strongly related to thiopurine-induced leukocytopenia, which has not been well recognized in dermatological practice. We tried to see whether NUDT15 gene polymorphism can be the most susceptible genetic factor for AZA toxicity and the gene screening is beneficial to avoid the adverse events of AZA for the treatment of skin diseases. A retrospective study was carried out on 15 adult Japanese patients who were treated with AZA. Gene polymorphism of thiopurine-metabolizing enzymes NUDT15 R139C, ITPA 94C>A, TPMT*2, TPMT*3B and TPMT*3C was analyzed. The single nucleotide polymorphisms were prospectively investigated in eight patients who were considered to have received AZA treatments. Two NUDT15 R139C homozygous patients developed agranulocytosis, severe thrombocytopenia and massive hair loss. The gene screening prior to AZA treatment identified one heterozygote of NUDT15 R139C and ITPA 94C>A, and three heterozygotes of ITPA 94C>A or TMPT*3C. Although this study was a retrospective single-center case-control observational study that enrolled a small number of patients, NUDT15 R139C homozygosity is a genetic risk of thiopurine-induced potentially fetal hematological abnormalities. To avoid serious adverse events, gene screening of thiopurine-metabolizing enzymes, at least NUDT15 R139C, should be considered prior to administration in genetically predisposed populations, such as Japanese. We highlight that massive hair loss in the early period of the initiation of AZA would be a sign of impending severe myelotoxicity.

LEKTI is localized in lamellar granules, separated from KLK5 and KLK7, and is secreted in the extracellular spaces of the superficial stratum granulosum.

Lympho-epithelial Kazal-type-related inhibitor (LEKTI) is a putative serine protease inhibitor encoded by serine protease inhibitor Kazal-type 5 (SPINK5). It is strongly expressed in differentiated keratinocytes in normal skin but expression is markedly reduced or absent in Netherton syndrome (NS), a severe ichthyosis caused by SPINK5 mutations. At present, however, both the precise intracellular localization and biological roles of LEKTI are not known. To understand the functional role of LEKTI, we examined the localization of LEKTI together with kallikrein (KLK)7 and KLK5, possible targets of LEKTI, in the human epidermis, by confocal laser scanning microscopy and immunoelectron microscopy. In normal skin, LEKTI, KLK7, and KLK5 were all found in the lamellar granule (LG) system, but were separately localized. LEKTI was expressed earlier than KLK7 and KLK5. In NS skin, LEKTI was absent and an abnormal split in the superficial stratum granulosum was seen in three of four cases. Collectively, these results suggest that in normal skin the LG system transports and secretes LEKTI earlier than KLK7 and KLK5 preventing premature loss of stratum corneum integrity/cohesion. Our data provide new insights into the biological functions of LG and the pathogenesis of NS.