Mutations in lipid transporter ABCA12 in harlequin ichthyosis and functional recovery by corrective gene transfer.

Harlequin ichthyosis (HI) is a devastating skin disorder with an unknown underlying cause. Abnormal keratinocyte lamellar granules (LGs) are a hallmark of HI skin. ABCA12 is a member of the ATP-binding cassette transporter family, and members of the ABCA subfamily are known to have closely related functions as lipid transporters. ABCA3 is involved in lipid secretion via LGs from alveolar type II cells, and missense mutations in ABCA12 have been reported to cause lamellar ichthyosis type 2, a milder form of ichthyosis. Therefore, we hypothesized that HI might be caused by mutations that lead to serious ABCA12 defects. We identify 5 distinct ABCA12 mutations, either in a compound heterozygous or homozygous state, in patients from 4 HI families. All the mutations resulted in truncation or deletion of highly conserved regions of ABCA12. Immunoelectron microscopy revealed that ABCA12 localized to LGs in normal epidermal keratinocytes. We confirmed that ABCA12 defects cause congested lipid secretion in cultured HI keratinocytes and succeeded in obtaining the recovery of LG lipid secretion after corrective gene transfer of ABCA12. We concluded that ABCA12 works as an epidermal keratinocyte lipid transporter and that defective ABCA12 results in a loss of the skin lipid barrier, leading to HI. Our findings not only allow DNA-based early prenatal diagnosis but also suggest the possibility of gene therapy for HI.

Nail dystrophy and blisters as sole manifestations in myeloma-associated amyloidosis.

We report the case of a 61-year-old Japanese man with IgG lambda-type multiple myeloma, who presented with nail dystrophy as the initial manifestation of systemic amyloidosis. Subsequently he developed bullous amyloidosis. This report documents these two rare signs of systemic amyloidosis and demonstrates the precise location of cutaneous blister formation and amyloid deposition by fluorescence antigen mapping and electron microscopy.

Correlation of clinical severity and ELISA indices for the NC16A domain of BP180 measured using BP180 ELISA kit in bullous pemphigoid.

BACKGROUND: Titres of circulating autoantibodies detected by indirect immunofluorescence (IIF) have been used for the diagnosis and evaluation of disease activity in bullous pemphigoid (BP). In BP, the major pathogenic epitope is known to be the non-collagenous extracellular domain (NC16A) of the 180-kDa transmembrane hemidesmosomal protein (BPAG2). Recently, an enzyme-linked immunosorbent assay (ELISA) kit using the NC16A domain recombinant protein (BP180 ELISA kit) has become commercially available to measure the quantities of pathogenic autoantibodies circulating in BP patients. OBJECTIVE: To investigate the correlation of clinical severity and ELISA indices in BP. METHODS: Fourteen patients with a typical form of BP and one refractory BP patient who died despite extensive treatment were included in this study. Antibody titres in sera from these patients were measured using BP180 ELISA kit and an analysis of ELISA indices with disease activity was performed. RESULTS: ELISA indices were significantly reduced after successful therapy, although IIF titres did not always show apparent correlations. In the patient with refractory BP, ELISA indices also showed a good correlation with disease course. ELISA indices measured using the BP180 ELISA kit were well correlated with the disease activity. CONCLUSION: This commercially available kit more closely followed disease activities than the IIF titres. The BP ELISA system may be a useful tool to evaluate the disease activity and to assess the effectiveness of the treatment of BP.

DNA-based prenatal exclusion of bullous congenital ichthyosiform erythroderma at the early stage, 10 to 11 weeks' of pregnancy, in two consequent siblings.

The proband was a Japanese woman with bullous congenital ichthyosiform erythroderma harboring a keratin 10 gene mutation M150T. DNA-based prenatal exclusion of bullous congenital ichthyosiform erythroderma was successfully performed in her two consequent pregnancies using chorionic villus samples at 10 to 11 weeks' gestation, several weeks earlier than the previously reported cases.