Zygomatic Region Research Articles

Cone beam computed tomographic comparison of infrazygomatic crest bone thickness in patients with different facial types

ABSTRACT Purpose To evaluate cortical bone thickness in the infra zygomatic crest region for subjects with low, normal and high angle facial patterns by bone mapping using cone beam computed tomography. Material and methods The study was conducted using CBCT images of 33 subjects, who were assigned to low-, normal- or high-angle groups. Cortical bone thickness was measured from the cementoenamel junction towards the maxillary sinus floor at heights of 8, 10, 12 and 14 mm along the mesial aspect of upper first molar, middle of the crown through the furcation area of the maxillary first molar, inter radicular bone/interdental region between the maxillary first and second molars, middle of the crown through the furcation area of the maxillary second molar and distal of the maxillary second molar. Results Low angle patients had significantly higher values of bone thickness compared to normal and high-angle patients between the first and second molars at a height of 12 mm and distal to second molars at a height of 14 mm. Conclusion The ideal site for insertion of temporary anchorage devices in the infrazygomatic crest region lies between the maxillary first and second molars at a height of 12 mm in all facial types. To avoid the risk of trauma or mini-implant failure, clinicians should be aware of the probability of thinner cortical bone in high angle patients as compared to normal and low angle patients.

CENTRAL OSSIFICANT FIBROMA IN THE MAXILLA: DISCUSSION OF A CLINICAL CASE

Ossifying fibroma is a benign neoplasm of fibro-osseous origin, rare, and mainly affecting the mandible. It is characterized by the replacement of bone tissue by connective tissue rich in fibroblasts and collagen fibers that present morphologies and varying amounts of calcified tissue. Our objective is to report the case of a male, 18 years old, who attended the odontologic clinic with complaint of edema in the face of evolution of 5 months without symptomatology. In the extra-oral examination, there was an increase of volume in the zygomatic region and right malar. An incisional biopsy was performed for histopathologic analysis, and panoramic radiography and multislice computed tomography were requested. The diagnosis was made with a combination of clinical, radiographic, and histopathologic examination, which confirmed a fibro-osseous lesion compatible with ossifying fibroma. Surgical enucleation with tumor curettage under general anesthesia was performed. The patient was followed up clinically and radiographically postoperatively, without complaints. Ossifying fibroma is a benign neoplasm of fibro-osseous origin, rare, and mainly affecting the mandible. It is characterized by the replacement of bone tissue by connective tissue rich in fibroblasts and collagen fibers that present morphologies and varying amounts of calcified tissue. Our objective is to report the case of a male, 18 years old, who attended the odontologic clinic with complaint of edema in the face of evolution of 5 months without symptomatology. In the extra-oral examination, there was an increase of volume in the zygomatic region and right malar. An incisional biopsy was performed for histopathologic analysis, and panoramic radiography and multislice computed tomography were requested. The diagnosis was made with a combination of clinical, radiographic, and histopathologic examination, which confirmed a fibro-osseous lesion compatible with ossifying fibroma. Surgical enucleation with tumor curettage under general anesthesia was performed. The patient was followed up clinically and radiographically postoperatively, without complaints.

SOLITARY PHLEBOLITH IN THE ZYGOMATIC REGION: A CASE REPORT

Calcifications found on the orofacial region may turn out to be an intriguing diagnosis. In most cases, these radiopacities may be sialoliths, although other lesions must not be exempted, such as calcified lymph nodes and phlebolith. Phleboliths are calcified thrombi occurring mainly in hemangiomas or vascular malformations. Phleboliths are rare in the head/neck region, and their formation is thought to be as a result of vascular stasis, which induces thrombus formation and subsequent dystrophic calcification. They are usually oval, multiple, and asymptomatic. Radiographically, they present concentric laminations (onion peel appearance). This study aimed to report the case of a 42-year-old Latin American woman who complained of a mildly painful benign nodule in the right zygomatic region (infraorbital ridge). In the computed axial tomography scans, the images suggested a very calcified nodule. The nodule was biopsied and diagnosed as a phlebolith associated with an involuted hemangioma. During the late follow-up, no pain nor recurrence was reported.

DESMOPLASTIC FIBROMA IN ZYGOMATIC BONE

Desmoplastic fibroma represents a benign, locally aggressive myofibroblastic neoplasm and less than 1% of primary bone neoplasms. The regions of involvement are the mandible, femur, tibia, radius, humerus, and pelvic bones. A man attended the buccomaxillofacial surgery department reporting a nodule in the face. Physical examination revealed an increase in volume in the left zygomatic bone region, painless and with fibroelastic palpation. After a request for complementary exams, computed tomography showed an image of a lesion with about 20 mm of circumference and low density. Ultrasonography showed a hypoechoic image suggestive of an epidermoid cyst. The proposed treatment was the enucleation of the lesion under local anesthesia and sending for anatomopathologic analysis. The diagnosis was desmoplastic fibroma. The patient is in follow-up of 2 years without signs of relapse.

Clinical Accuracy of 3D-Planned Maxillary Positioning Using CAD/CAM-Generated Splints in Combination With Temporary Mandibular Fixation in Bimaxillary Orthognathic Surgery.

The aim of this study was to evaluate the accuracy of 3-dimensional (3D)-planned maxillary positioning by using computer-assisted design (CAD)/computer-assisted manufacturing (CAM) splints combined with temporary mandibular fixation in bimaxillary orthognathic surgery. In orthognathic surgery, customized splints work sufficiently well to transfer preoperative planning into the operation site for transverse und sagittal positioning of the maxilla. The vertical positioning is more difficult due to the non-fixed mandibular reference. Therefore, the combined use of CAD/CAM splints and temporary mandibular fixation to the zygomatic region was applied for transferring the 3D-planned maxillary position into the operation site from 2012 until 2015 in our hospital. In addition to the general accuracy, the precision should therefore be checked especially in the vertical plane compared to axial and sagittal plane. In this retrospective study, we calculated the deviation of 5 occlusal landmarks of the maxilla in 35 consecutive patients by fusing preoperative 3D planning images and postoperative computed tomography scans after bimaxillary surgery. The overall median deviation of maxillary positioning between plan and surgical result was 0.99 mm. The accuracy of left-right positioning was median 0.96 mm. Anterior-posterior positioning of the maxilla showed a median accuracy of 0.94 mm. Just slightly higher values were determined for the upward-downward positioning (median 1.06 mm). This demonstrates the predictability of maxillary positioning by using CAD/CAM splints in combination with temporary mandibular fixation in all 3 axes.

Fibroma desmoplásico em arco zigomático: relato de caso raro

O fibroma desmoplásico é um tumor osteogênico benigno muito raro, composto por fibroblastos difusos e abundantes fibras de colágeno. É localmente agressivo e apresenta alta taxa de recorrência, sendo assim, seu tratamento pode ser um desafio e diversas estratégias têm sido descritas como forma de evitar sua recidiva. Desse modo, o objetivo deste relato foi apresentar o curso clínico e tratamento de um paciente com diagnóstico de fibroma desmoplásico em região de arco zigomático esquerdo. Foi descrito um caso de um paciente de 37 anos de idade, cuja queixa era de aumento de volume indolor em face com aproximadamente seis meses de evolução. O exame físico evidenciou-se uma massa firme, sólida e bem delimitada em região temporal do arco zigomático esquerdo, que foi submetida a excisão cirúrgica. Os achados histológicos da lesão incluíram células fusiformes envolvidas por deposição de colágeno intersticial difusa com ausência de revestimento mucoso superficial, compatível com fibroma desmoplásico. O paciente segue com 2 anos e 6 meses de pós-operatório, não apresentando sinais de recidiva da lesão.

Cryptococcal osteomyelitis of the Zygomatic bone: a case report

BackgroundDisseminated cryptococcosis is a well-characterized complication in immunocompromised patients with cryptococcal pneumonia or meningitis; however, isolated cryptococcal osteomyelitis is a rare entity that occurs in approximately 5% of patients with cryptococcosis. Cryptococcal osteomyelitis in the head and neck region is extremely rare. To the best of our knowledge, no cases of cryptococcal osteomyelitis affecting only the zygomatic bone have been reported to date.Case presentationA 78-year-old man without other comorbidities presented with progressive swelling of the right cheek along with pain and trismus. Clinical examination revealed a tender swelling in the right zygomatic region; the maximal mandibular opening was about 2 cm. Laboratory data showed mildly elevated inflammatory indices (C-reactive protein: 0.45 mg/dL; erythrocyte sedimentation rate: 35 mm/h). Computed tomography showed a 30-mm-diameter lesion at the right zygomatic arch. A part of the lesion has extended to the subcutaneous area of the cheeks with signs of bone destruction and surrounding contrast effects. Histopathological examination of fine-needle aspirate and needle biopsy showed cryptococcus. Furthermore, culture of the aspirate showed growth of Cryptococcus neoformans. No evidence of any other site involvement was observed. Therefore, the patient was diagnosed with isolated cryptococcal osteomyelitis and was initiated on fluconazole therapy. The treatment was effective, and all symptoms were resolved in 4 weeks. Fluconazole therapy was stopped after 6 months. There are no signs of recurrence as of 15-month follow-up. The patient has no cosmetic abnormalities or sequelae.ConclusionsFine-needle aspiration cytology, needle biopsy, and fungal culture were useful for definitive diagnosis. Immunocompetent patients with isolated osteomyelitis may be cured with oral fluconazole alone.

Morphological Classification of the Zygomatic Regions in Young Chinese Han Males and Females Based on a Simulated Moiré Pattern.

The complex curved contours of the zygomatic regions are difficult to analyze. Therefore, a better evaluation medium must be developed. We aimed to examine and summarize the morphological characteristics of the zygomatic region by using a moiré pattern map and computer algorithm. In this cross-sectional study, we collected three-dimensional images of the facial contours of 251 Han Chinese youth and established a morphological moiré map database. Clustering analysis using a computer algorithm was applied to obtain the zygomatic morphologies for classification. Aesthetic evaluation was performed to summarize the characteristics of the zygomatic types and provide reference for the preoperative morphological design of the midface. Zygomatic regions were morphologically classified into five types. Each type had its typical feature in the moiré pattern map. The moiré stripes in the left zygomatic region formed an "Ω" shape outward and downward in type 1, and they tended to be diagonal like "\\\" in type 2, smoothly curved like ")))" in type 3, vertical like "|||" in type 4, and diagonal like "///" in type 5. The aesthetic evaluation outcome indicated that the integrally flat zygoma (type 4) was more aesthetically pleasing among males, and the integrally prominent zygoma (type 3) was more aesthetically pleasing among females. Five morphological contour types of the zygoma were classified among the Chinese Han males and females based on the simulated moiré pattern. This morphological classification would aid in preparing a guide for clinical diagnosis and surgical planning.

Frequency and location of the zygomaticofacial foramen and its clinical importance in the placement of zygomatic implants.

Anatomical knowledge of the zygomatic region is important, because the zygomatic nerve and its branches may suffer lesions during surgical procedures in the periorbital region. The position and frequency of zygomaticofacial foramina (ZFF) may vary between individuals, and between one side and the other in the same individual. In the present study, we analysed the presence and location of ZFF, as well as the distance between them and the orbital cavity, in macerated skulls of adult individuals. We examined 287 macerated skulls, of individuals of both sexes, analysing the frequency and location of ZFF and the distance from the ZFF to the margin of the orbital cavity (OC). Zygomaticofacial foramina are very frequent structures which tend to appear singly. They are generally located in the temporal process of the zygomatic bone, but in many cases, they may be located in the mid portion of the bone. They also tend to appear at the same distance from the OC when left and right sides are compared. Sex was an important factor in determining differences in ZFF; the distance from the ZFF to the margin of the OC was greater in males than in females. Sex, age, side and skin colour did not affect the frequency and location of the ZFF. We consider that the mid portion of the zygomatic bone is the safest place to anchor zygomatic implants (ZI), since ZFF are less frequently located there than in the temporal process of the zygomatic bone.

Facial soft tissue thickness in Yangtze River delta Han population: Accurate assessment and comparative analysis utilizing Cone-Beam CT.

Facial approximation plays a vital role in personal identification when other methods cannot be applied, and the study on facial soft tissue thickness (FSTT) is important to allow more accurate facial approximation. The Cone-Beam CT (CBCT) is considered to be an accurate approach in assessing FSTT, however only few studies have assessed the FSTT norms by CBCT in Chinese populations. The aim of this study was to (1) establish forensic measurement approach on a 3D model reconstructed by CBCT image; (2) obtain FSTT norms from the adults of Yangtze River delta Han population; (3) determine the impacts of sex, age, BMI as well as malocclusion type on FSTT and (4) form a FSTT database through CBCT. A total of 60 facial landmarks were primarily established from 3D reconstructed models from CBCT images of 424 healthy Han adults (130 males and 294 females) aged from 21 to 50years in Yangtze River delta region and measurements were carried out. The multivariate analysis of variance test and multiple linear regressions test showed that the FSTT values on most landmarks were significantly different between sexes and BMI, and males showed greater values, expect for the landmarks distributed in malarzygomatic areas. Simultaneously, BMI mostly affected the landmarks located in zygomatic region. Besides, only a few landmarks were influenced by age. Interestingly, several periodontal landmarks were influenced by malocclusion types, thus the impact of malocclusion types on FSTT requires attention. Finally, the validation analysis suggested that measurement approach is an important factor for FSTT.

Anthropometric Research of Metric Characters in Zygomatic Complex Region.

To get and analyze the metric data of zygomatic region for the plasty of zygoma. A total of 108 dry skulls in Chinese Han population were randomly collected and measured. The metrical data were divided into 4 parts, including the relative position of contour height of zygomatic bone, the relative prominence of zygomatic bone, the relative prominence of zygomatic arch, and the angle of the zygomatic bone and arch. The measurements in the 4 parts showed significantly difference between male and female (P < 0.05). For relative position of contour height of zygomatic bone group, the data of male is significantly bigger than female (P < 0.05). For relative prominence of zygomatic bone/zygomatic arch group, zygoma/zygomatic arch of male significantly protruded more than female (P < 0.05). The location of male zygoma is more protruding than female. The female zygoma is squarer than male and marginal process is helpful in zygomatic plasty. These studies show and analyze the metric data of zygomatic region in Chinese Han population for the plasty of zygoma. These different characters between males and females could be helpful in zygomatic plasty of Chinese Han population based on this research.

A Comparison of 3D Facial Features in a Population from Zimbabwe and United States.

Objectives The purpose of this study was to determine the differences in three-dimensional (3D) facial features in a population from Zimbabwe and the United States. In addition, this study seeks to establish an average facial template of each population allowing clinicians to treat patients according to their cultural esthetic perceptions. Materials and Methods Three hundred one subjects from Zimbabwe and the United States were carefully selected and recruited for the study. Each subject presented with a normal facial profile, no asymmetries, and normal body mass index. The 3D images were captured using the 3dMD cameras. All images were further separated into male and female groups of the respective populations and imported to a dedicated software for analysis. Statistical Analysis The 3D facial images were constructed using Rapidform 6 software to recreate a composite facial average for each group representing a male and female average 3D face of Zimbabwean (Zim) and United States origin. Results The linear measurements showed that the maximum average distance between the Zim-M and Zim-F was 1.24 mm and the minimum distance between the African American (AA)-M and AA-F was 0.24 mm. This was the absolute distance. When the signed linear measurements were taken into consideration, the maximum average distance between Zim-F and AA-M was 1.22 mm and the least average distance between the Zim-M and AA-M was 0.22 mm. The absolute color histograms showed greatest similarity between the Zim-M and AA-M at 58% and the Zim-F had a 25 and 27% similarity with the AA-F and Zim-M, respectively. Conclusion The Zim-F showed the most variable features with a broader face, prominent forehead, and retruded alar base compared with their male counterparts and the Zim-M showed a wider prominent malar/zygomatic region, and prominent lateral supraorbital regions. There was a high similarity of 58% between the Zim-M and the AA-M, with the Zim-M showing a more protrusive superciliary arches, and a lateral zygomatic region tapering to the root of the nose.

Microcomputed tomography cortical bone evaluation for craniofacial implantology

Introduction. Good implant stability is one of the most important factors for successful implant therapy. This precondition is important for all kinds of implants, oral and extra-oral, i.e. craniofacial implants as well. One of the most important factors for satisfactory implant stability is the bone quality, particularly of the cortical bone, which is determined by its microarchitectural parameters. The aim of this paper was to assess cortical bone microarchitectural parameters in the targeted regions for craniofacial implant placement. Methods. Bone quality on targeted locations was determined by the micro-CT method on a cadaver model. The target places for implant placement were the periorbital, the perinasal, and the periauricular region. Microarchitectural parameters included cortical thickness (Ct.Th.), cortical porosity (Ct.Po.), pore diameter (Po.Dm.), and pore separation (Po.Sp.). Results. The smallest Ct.Po. (4.1%) and the largest Po.Sp. (0.5 mm) were determined in glabella. The maximum Ct.Th. (2.7 mm) as well as Po.Dm. (0.2 mm) were found in the zygomatic region. The mastoid part of the temporal bone showed the smallest Ct.Th. (1.2 mm) and Po.Sp. (0.3 mm). The highest Ct.Po. was in the perinasal region (8.5%). Conclusion. The bone quality measured through microarchitectural parameters was good in all the regions of interest for the disk- and screw-shape extra-oral implant anchorage.

Ultrasonography for long-term evaluation of hyaluronic acid filler in the face: A technical report of 180 days of follow-up.

PurposeIn this study, we used ultrasonography to monitor the use of hyaluronic acid (HA) as a filler in the face for esthetic reasons. We monitored changes in the filler shape, distribution, and relationship with adjacent anatomical structures over a 180-day period.Materials and MethodsTwo patients each received an ultrasound-guided injection of HA, with different products and application sites for each patient. In 1 patient, the injection was administered in the angle of the mandible, while in the other, it was administered in the zygomatic region. The injection sites were monitored via ultrasonography at 24 hours, 30 days, and 180 days, at which times the imaging characteristics of the filler were observed. All injections were performed by the same professional, as were the ultrasound exams, which were conducted using the same equipment.ResultsIn both cases, the HA fillers were visualized using ultrasound at all time points. Some differences were observed between the cases in the images and the distribution of the pockets of filler. In 1 case, the filler appeared as a dark hypoechoic region with well-defined contours, and the material was observed to have moved posteriorly by the 180-day mark. In the other case, the material appeared hyperechoic relative to the previous case and presented no noticeable changes in its anteroposterior distribution over time.ConclusionBased on these 2 cases, ultrasonography can be a complementary tool used to monitor facial fillers over the long term, allowing for the dynamic observation of different fillers.

Assessment of dentofacial widths in adults with anterior open bite.

Anterior open bite is a complex condition involving a combination of various dental and skeletal components in three dimensions. The data on the differences and changes in the transverse relation in individuals with anterior open bite are limited. To assess the dental arch widths in individuals with anterior open bite using study casts and facial widths using frontal cephalogram and to compare these widths with that of individuals without anterior open bite. Eighty adults [40 with and 40 without anterior open bite, mean (standard deviation) age = 20.68 years] were selected. The study group was divided into skeletal (n = 19) and dental (n = 21) open bite groups according to Jarabak's ratio. Posteroanterior cephalograms and study casts were analyzed. The mean width of zygomatic arch (112.18 mm) and condylar region (100.55 mm) in the control group was significantly higher (P < 0.05). The mean gonial width in the skeletal open bite group (81.143 mm) was significantly (P < 0.05) lesser than the dental open bite group (84.842). The maxillary intercanine width for the skeletal open bite group (36.48 mm) was significantly (P < 0.01) higher than that of the dental open bite group (34.26 mm). A transverse deficiency was seen in in the zygomatic and condylar regions in adults with anterior open bite. Individuals with a skeletal open bite showed a narrow gonial and wider maxillary intercanine width compared with individuals with dental open bite.

Histological verification of autofluorescence borders of periorbital skin tumors

To compare histological borders of periorbital skin tumors with their autofluorescence borders built from the analysis of non-induced protoporphyrin IX autofluorescence. The study group included 8 patients with skin tumors of the eyelids, periorbital region, eyebrow and zygomatic regions aged 54-88 years. The tumors varied in size from 2 to 8 mm and all displayed signs of basal cell carcinoma (BCC). At admission, all the patients underwent non-induced autofluorescence diagnosis. The images were processed with the «CancerPlot» program. During radio excision, the autofluorescent border of each neoplasm was marked with a surgical incision of about 5 mm long and 2 mm deep. Upon pathomorphological examination, solid BCC was identified in 7 cases. The remaining case was senile keratosis. All reference incisions were located in healthy tissues not farther than 1 mm from the tumor (or keratosis locus, correspondingly). By the example of facial BCC, an evident correlation was established between histological borders of the tumor and its native (non-induced) protoporphyrin IX autofluorescence.

Primary tuberculosis of zygomatic bone: A rare case report

Tubercular osteomyelitis of zygomatic bone is extremely rare. Here we have reported a rarest case of primary tuberculosis (TB) of zygomatic bone in a 20 year male who presented with discharging sinus over right zygomatic region. Anti-tubercular chemotherapy given and patient improved well.

Differentiation between maxillary and malar midface position within the facial profile.

AimsTo define midfacial position differentiating maxillary and zygomatic regions and to evaluate the corresponding cephalometric characteristics discerning midfacial flatness and fullness.Material and MethodsA total of 183 pretreatment lateral cephalometric radiographs of non-growing orthodontic patients (age 25.98 ± 8.43 years) screened at our university orthodontic clinic. The lateral cephalographs of the orthodontic patients were stratified in four groups: flat, normal toward flat, normal toward full, full,according to distances from nasion and sella to points J and G (NJ, SJ, NG and SG). J is the midpoint of the distance connecting orbitale to point A, and G the center of the triangle connecting orbit, key ridge and pterygomaxillary fissure. Statistics included the Kendall tau-b test for best associations among measurements.ResultsAll measurements were statistically significantly different between flat and full groups. The highest associations were between NJ and SJ (τb = 0.71; p < 0.001) and NG and SG (τb = 0.70; p < 0.001). Flat midfaces were characterized by canting of the cranial base and palatal plane, hyperdivergent pattern and maxillary retrognathism. The opposite was true for fuller midfaces.ConclusionMidface skeletal location was assessed differentially in the naso-maxillary and malo-zygomatic structures differentially. Craniofacial characteristics were identified according to this stratification, indicating the potential for application in facial diagnosis and need for testing on 3D cone-beam computed tomography images.

Gender Differences in the Clinical Presentation of Cluster Headache: A Role for Sexual Hormones?

Introduction: Cluster Headache (CH) is a well-characterized primary headache that mostly affects men, although a progressive decrease in the male-to-female ratio has occurred over time. Available, but partly discordant, data on gender-related differences in CH suggest a more marked overlapping with migraine features in female subjects. The aim of this study is to carefully evaluate the female/male distribution of the typical migraine-associated symptoms and of other features of the disease in a large and well-characterized clinical population of CH subjects.Materials and Methods: We enrolled consecutive CH patients regularly followed at the tertiary Headache Science Center of the IRCCS Mondino Foundation of Pavia (Italy) who attended the Center for a CH bout between September 2016 and October 2018. The subjects were requested to fill in a semi-structured questionnaire focused on the presence of migraine-associated symptoms, familiarity for migraine and, for women, the relationship of CH onset with the reproductive events of their life. These data were compared and integrated with those recorded over time in our clinical database, including demographics and clinical characteristics. The primary outcome was the gender distribution of subjects who satisfied ICHD-III criterion D for migraine-associated symptoms. The secondary outcomes were represented by the gender distribution of individual migraine-associated symptoms and of other disease features included in the questionnaire and/or in the clinical database.Results: Data from 163 males (mean age 41.46 ± 10.37) and 87 females suffering of CH (mean age 42.24 ± 11.95) were analyzed. We did not find a different distribution between sexes as regards the primary outcome measure (F 73.6%, M 65.6%, p = 0.200). However, when we analyzed the occurrence of individual symptoms, nausea and osmophobia were reported more frequently by women (p = 0.048, p = 0.037, respectively). Ptosis and nasal congestion were predominant in females (p = 0.017 and p = 0.01, respectively), while enlarged temporal artery was more frequently reported by men (p = 0.001). Distribution of pain across the head tended to be larger in women, extending more frequently to the zygomatic (p = 0.050), parietal (p = 0.049), and frontal (p = 0.037) regions. Women had a longer mean attack duration (p = 0.004) than men. In CH women the onset of disease often corresponded with moments of important changes in the levels of sexual hormones (menarche, post-partum, menopause). Concomitant thyroid diseases and psychiatric disorders were observed more frequently in women than in men, while snoring and smoking habit was reported by a higher percentage of men than women.Conclusion: We confirmed the presence of distinct gender-related differences in CH and added some novel information that lends credibility to the hypothesis of a closer phenotypical similarity between CH and migraine in the female sex. These observations are relevant for advancing our knowledge on CH pathophysiology, as well as for a more refined diagnostic framing and improved management of the disease.

557 A case of acquired dermal melanocytosis associated with Imatinib mesylate treatment

Imatinib mesylate is a tyrosine kinase inhibitor (TKI) that regulates cell growth, thereby inhibiting cancer cell proliferation. It has been used to treat various neoplasms such as chronic myeloid leukemia (CML). The most common side effect in skin is hypopigmentation. However, hyperpigmentation has also been rarely reported. A 48-year-old woman diagnosed as chronic myeloid leukemia presented with bluish to grayish macules and patches on face, shoulder, and buttock. She had got a treatment of CML with imatinib mesylate for 9 years. She complained hyperpigmentation on face 3 years after the imatinib mesylate treatment. Additionally, the patient reported diffuse bluish to brownish hyperpigmentation similar to Mongolian spot on the upper trunk and buttock appearing about 2 years ago. Histopathologic examination revealed brownish pigmentation of melanin in dermis with dendritic and stellate-shaped dermal melanocytes. In immunohistochemistry, the cells were positive for S-100, Melan-A, and HMB-45. Based on these pathologic findings considering with temporal relationship between the treatment and the clinical manifestations, the diagnosis of an imatinib-induced acquired dermal melanocytosis was made. Imatinib mesylate induces KIT and its ligand stem cell factor (SCF) which inhibits the production of melanin from melanocytes, leading to hypopigmentation. However, some theories postulated it could have different target effects on melanocytes, suggesting melanin production of immature melanocytes could be promoted by imatinib mesylate. In our case, the patient showed hyperpigmentation on typical locations of congenital nevi such as Mongolian spots and nevus of Ito rather than usual locations of the acquired dermal melanocytosis including forehead and zygomatic region. Herein, we report a case of acquired dermal melanocytosis induced by imatinib mesylate, which suggests that immature melanocytes are predominantly distributed in specific areas.