Yasushi Tomita

Recurrent dermatofibrosarcoma protuberans with myxoid and fibrosarcomatous changes paralleled by loss of CD34 expression.

A 38‐year‐old woman complained of recurrent nodules on her anterior chest wall. She noticed the first nodule at the age of 12 and has since undergone surgical removal a total of 31 times. Finally, wide resection of parts of the rib cartilage and sternum and chest wall reconstruction were required. Histopathological examination of a series of surgical specimens were reevaluated. Immunohistochemical staining of the tumors by anti‐CD34 antibody provided a definite diagnosis of dermatofibrosarcoma protuberans (DFSP). A noteworthy result was that her DFSP did not always express CD34; the recurrent tumors with myxoid and fibrosarcomatous changes lost their CD34 expression.

Comparison of the melanogenesis in human black and light brown melanocytes

We examined how and to what extent the constitution of melanin and the expression, as well as the activity, of melanosomal proteins influence the production of melanin pigment by human black and light brown melanocytes, Mel (b) cells and Mel (l) cells, respectively. Melanin pigment in Mel (b) and Mel (l) cells consisted of a mixture of eumelanin and pheomelanin, and Mel (b) cells contained a larger amount. The signal intensity ratio of eumelanin to pheomelanin was similar in both cell types, though the two cell types differed in appearance. Tyrosinase activity and the amount of tyrosinase-related protein (TRP-1) of Mel (b) cells were higher than those of Mel (l) cells. Dopachrome tautomerase (DCT) activity and the amount of 6H5MICA were reduced in Mel (b) cells in comparison with Mel (l) cells. No significant difference in DHICA-converting activity or catechol-O-methyltransferase activity was found between Mel (b) and Mel (l) cells. There was no correlation between DHICA-converting activity and amount of TRP-1. These results suggest that the difference in the pigmentation of the two human melanocyte cell lines, Mel (b) and Mel (l), is derived from differences in the activity and expression of tyrosinase, TRP-1 and DCT, which affect the content and constitution of melanin polymers.

A Splicing Mutation of the Tyrosinase Gene Causes Yellow Oculocutaneous Albinism in a Japanese Patient with a Pigmented Phenotype

Background: Yellow oculocutaneous albinism (OCA) that is caused by tyrosinase gene mutations shows two characteristics: extreme hypopigmentation at birth and the eventual development of yellow or blond hair. Objective: We studied a Japanese girl who had brown hair, a lighter skin color than her unaffected family and brown eyes at 9 months of age. Methods: We performed direct sequencing analyses of the tyrosinase gene in her genomic DNA. Results: The patient was a compound heterozygote for the +ΔC310 mutation (known to result in absent melanogenic activity) and a second t→a transition at the 3′ end of intron 2. Conclusion: The t→a transition has previously been reported as a splicing mutation in other Caucasian patients with a typical yellow OCA phenotype. However, this patient showed much more pigmentation than that reported in Caucasians. Therefore, we estimate that the mild phenotype results from her genetic pigment background.

Sequence-Based Diagnosis of Tyrosinase-Related Oculocutaneous Albinism: Successful Sequence Analysis of the Tyrosinase Gene from Blood Spots Dried on Filter Paper

Background: A large number of mutations of the tyrosinase gene result in oculocutaneous albinism (OCA). Therefore, at present, sequence analysis of the tyrosinase gene has become necessary to diagnose OCA patients and their relatives. Objective: The aim of this study was to facilitate the sequence-based diagnosis of tyrosinase-related OCA by using small amounts of the patient’s blood. Methods: Blood spots dried on filter papers were used as sources of genomic DNA. The exons and flanking regions of the tyrosinase gene were amplified by polymerase chain reaction (PCR) and were directly sequenced in both directions. Results: We successfully amplified all exons of the tyrosinase gene by PCR and were able to characterize compound heterozygous mutations of R278X and +ΔC310 in the patient’s gene. Conclusion: Recent advances of PCR-related technology allowed us to use fairly limited samples of blood for sequence analysis of the tyrosinase gene.

Specific distribution patterns of hCDC47 expression in cutaneous diseases

hCDC47 is a human member of the MCM family, which has been implicated to be concerned with the regulatory machinery causing DNA to replicate once per cell cycle. In a previous paper, we described hCDC47 expression as being localized in the proliferative component of normal tissues, and showed greater expression in squamous cell skin carcinomas than in seborrheic keratosis. In the present study, we compared its expression in another type of skin tumor and variotis non‐neoplastic cutaneous proliferative diseases. Two patterns of distribution of hCDC47‐positive cells were observed. Keratoacanthomas showed a peripheral pattern in which only the cells located the basal cell layers were positive. Psoriasis vulgaris also showed this peripheral type of location, with the cells in the suprabasal layers also occasionally expressing hCDC47. Verruca vulgaris demonstrated a diffuse pattern, with positive epithelial cells distributed throughout the layers. Basal cell carcinomas also showed a similar pattern. The keratoacanthomas showed the highest hCDC47 positive cell rate (43.1%), followed by verruca vulgaris (42.5%). psoriasis vulgaris (23.4%), and basal cell carcinoma (17.3%). Our results suggest participation of hCDC47 in these proliferative disorders involving keratinocytes.

Phospholipases Induce Melanogenesis in Organ‐Cultured Skin

Guinea pig skin becomes more pigmented following exposure to UV rays. This melanization was accompanied by enhanced intensity of tyrosinase‐staining and increased number of tyrosinase‐positive melanocytes (MELty+), with resultant enhancement of melanin synthesis. To clarify the regulatory mechanism for melanization following UV irradiation, organ‐cultured guinea pig skins have been used to examine their melanogenic responses to exogenous stimulation. This organ culture system responded well to UV irradiation, by increasing melanogenic activity. Also, in this system, phospholipases (PL), arachidonic acid, interleukin‐1α and melanocytestimulating hormone, but not endothelin‐1 or phosphatidylinositol‐specific PLC (PI‐PLC), stimulated melanogenesis to various extents as indicated by the number of MELty+ and morphological changes. Among them, the PLA2 and PLD were found to have a potent stimulatory property for melanocytes. They might affect melanocytes directly or indirectly through an effect on keratinocytes. These results suggest that PLA2 and PLD play a key role in epidermal hyperpigmentation after UV irradiation or inflammation.

Giant Xanthomatous Dermatofibroma – A Case Distinguished Histologically and Immunohistochemically from Invasive Fibrohistiocytic Tumors

A 50-year-old woman presented with a skin tumor on her right calf. The tumor had been noticed 20 years previously and grew to more than 60 mm in diameter. The histological findings were characterized by numerous bland xanthomatous histiocytes and a few atypical giant cells with pyknotic nuclei, although mitotic figures were few. These findings led to the diagnosis of dermatofibroma with unusual xanthomatous expression. Immunohistochemical studies using several markers for histiocytes (lysozyme, alpha 1-antitrypsin, alpha 1-antichymotrypsin and anti-CD68 antibody), anti-factor-XIIIa antibody and anti-CD34 antibody supported the diagnosis.

Detection of point mutations in human tyrosinase gene by improved allele‐specific amplification

Abstract Allele‐specific amplification (ASA) is a simple and non‐radioactive technique for detecting known point mutations that produce genetic diseases. Although this technique is based on the specific amplification of the target allele by a polymerase chain reaction (PCR) with allele‐specific primers, the specificity of the amplification may depend on various PCR conditions. To avoid non‐specific amplification which leads to false‐positive results in ASA, we modified both the normal and mutant allele‐specific primers so that they would have one constant base mismatch, located at the penultimate 3′ position. We confirmed that our modification could inhibit such unfavorable amplification by using as templates genomic DNAs of patients affected with tyrosinase‐negative oculocutaneous albinism (OCA). We then analyzed new patients affected with tyrosinase‐negative OCA, and based the diagnosis on both the results of a clinical examination and those of a hair bulb test using ASA with the modified allele‐specific primers. The results indicated that more than 3 alleles of the tyrosinase gene with a pathological mutation existed in Japanese patients.

R278TER AND P431L MUTATIONS OF THE TYROSINASE GENE EXIST IN JAPANESE PATIENTS WITH TYROSINASE-NEGATIVE OCULOCUTANEOUS ALBINISM

We examined the tyrosinase gene of two Japanese patients with tyrosinase-negative oculocutaneous albinism by allele-specific amplification analysis on two known point mutations in Japanese, and the results indicated that they were compound heterozygouts, namely, one allele of the tyrosinase gene harbored one of two known mutations and another allele probably had a mutation unknown in Japanese patients. Therefore, we have cloned and sequenced the tyrosinase gene of the two patients and identified two different point mutations. One is a nonsense mutation, codon 278CGA (Arg) to TGA (TER), and the other is a substitution mutation, codon 431CCA (Pro) to CTA (Leu). However, these same mutations have already been observed in a Guyanan and a Moroccan Jewish patient, and in an Indo-Pakistani patient, respectively.

Fixed Drug Eruption Due to Afloqualone : The First Reported Case

To the Editor: We present a case of fixed drug eruption due to afloqualone with a positive provocation test. It is well known that afloqualone can cause drug-induced photosensitivity (1-4). To the best of our knowledge, no such case has been previously reported. Case Report: A 42-year-old Japanese female visited us with pinkish to brownish discoloration on her neck of 1 month duration. She often suffered from muscle contraction headaches and had taken afloqualone (20 mg) and bromazepam (1 mg) for the previous two years. A few days before the consultation, she took both drugs because of a headache in the occipital region. She noted a burning sensation and flush which had often occurred in the same location on her neck. However, she did not recognize any relationship between the drug and the skin eruption on her neck. On physical examination, a solitary, well-defined, slightly violaceous, erythematous patch measuring approximately 2 em in diameter with hyperpigmentation appeared on the left side of her neck. No mucosal involvement was seen. We suspected a fixed drug eruption caused by afloqualone or bromazepam based on her history and clinical manifestations. A provocation test was performed with her consent. Oral administration of bromazepam (1 tablet/1 mg) gave a negative result. Readministration of afloqualone (1 tablet/20 mg) induced a flare-up of the skin lesion with a burning sensation on her neck five hours after the oral challenge. No adverse reaction was found. She discontinued afloqualone, and the eruption subside. Comment: Afloqualone is a centrally acting muscle relaxant that was developed in Japan. It has been widely used in the treatment of myotonic disorders since 1983 in Japan (5). Drug eruptions due to afloqualone are generally classified as photosensitive, lichenoid, and maculopapular in Japan (6). To the best of our knowledge, no fixed drug eruption caused by afloqualone has been reported. Afloqualone should be recognized as a possible cause of fixed drug eruption.