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Dive into the research topics where Michael K. Yoon is active.

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Featured researches published by Michael K. Yoon.


British Journal of Ophthalmology | 2011

Giant cell arteritis in Asians: a comparative study

Luciano de Sousa Pereira; Michael K. Yoon; Thomas N. Hwang; Jenny E. Hong; Kathyrn Ray; Travis C. Porco; Timothy J. McCulley

Background Giant cell arteritis (GCA) is a common systemic vasculitis, with a presumed Caucasian predominance. The occurrence of GCA in Asians has rarely been addressed. This study aims to assess the incidence of giant cell arteritis in Asians. Methods In this retrospective review, the self-reported ethnicities of patients with biopsy-proven GCA at the University of California–San Francisco (UCSF) were recorded. Ethnic distribution of the patient population served by UCSF was estimated from an age- and sex-matched control group. The odds ratio for each ethnicity (Asian and Caucasian) was determined and compared using Fishers exact test and logistic regression analysis. Results The ethnic distribution of the 38 patients with positive temporal artery biopsies were as follows: Caucasian n=31 (81.6%), Asian n=1 (2.6%) and other n=6 (15.8%). The ethnic distribution of the patient population served by UCSF was as follows: Caucasian 42%, Asian 28% and other 30%. The difference in the proportion of GCA in Asians and Caucasians was statistically significant (OR 0.049 (95% CI 0.0065 to 0.374), p=0.0036). Conclusions In our patient population, GCA was seen 20 times less frequently in Asian than Caucasian patients. Although this difference is significantly different (p=0.036), given the small sample size and wide CI this should be viewed as a rough estimate.


American Journal of Ophthalmology | 2003

A new mutation (Leu569Arg) within Exon 13 of the TGFBI (BIGH3) gene causes lattice corneal dystrophy type I

John F. Warren; Richard L. Abbott; Michael K. Yoon; J. Brooks Crawford; William H. Spencer; Todd P. Margolis

PURPOSE To describe an American family with lattice corneal dystrophy type I, which associates with a novel mutation, Leu569Arg, of the TGFBI (BIGH3) gene. DESIGN Experimental study. METHODS Genomic DNA was extracted from buccal epithelial cells of four affected members of an American family with lattice corneal dystrophy type I. All 17 exons of the TGFBI gene were evaluated by PCR amplification and direct sequencing. Clinical and histologic data were also collected. RESULTS Three generations of this family have been positively diagnosed with lattice corneal dystrophy, indicating autosomal dominant inheritance. We identified a heterozygous point mutation that associates with the disease phenotype. The single base-pair substitution (T1753G) results in an amino acid substitution (Leu569Arg) in exon 13 of the TGFBI gene. CONCLUSIONS Substitution of arginine for leucine at position 569 of the TGFBI gene results in a form of lattice corneal dystrophy that is phenotypically similar to other genetically distinct forms of type I disease. This is the first report of disease correlated with changes in exon 13 of the TGFBI gene.


British Journal of Ophthalmology | 2004

A novel arginine substitution mutation in 1A domain and a novel 27 bp insertion mutation in 2B domain of keratin 12 gene associated with Meesmann’s corneal dystrophy

Michael K. Yoon; John F. Warren; Douglas S. Holsclaw; David C. Gritz; Todd P. Margolis

Aim: To determine the disease causing gene defects in two patients with Meesmann’s corneal dystrophy. Methods: Mutational analysis of domains 1A and 2B of the keratin 3 (K3) and keratin 12 (K12) genes from two patients with Meesmann’s corneal dystrophy was performed by polymerase chain reaction amplification and direct sequencing. Results: Novel mutations of the K12 gene were identified in both patients. In one patient a heterozygous point mutation (429A→C = Arg135Ser) was found in the 1A domain of the K12 gene. This mutation was confirmed by restriction digestion. In the second patient a heterozygous 27 bp duplication was found inserted in the 2B domain at nucleotide position 1222 (1222ins27) of the K12 gene. This mutation was confirmed by gel electrophoresis. The mutations were not present in unaffected controls. Conclusion: Novel K12 mutations were linked to Meesmann’s corneal dystrophy in two different patients. A missense mutation replacing a highly conserved arginine residue in the beginning of the helix initiation motif was found in one patient, and an insertion mutation, consisting of a duplication of 27 nucleotides, was found before the helix termination motif in the other.


British Journal of Ophthalmology | 2016

Invasive fungal disease of the sinus and orbit: a comparison between mucormycosis and Aspergillus

Danielle Trief; Stacey T. Gray; Frederick A. Jakobiec; Marlene L. Durand; Aaron Fay; Suzanne K. Freitag; Nahyoung Grace Lee; Daniel R. Lefebvre; Eric H. Holbrook; Benjamin S. Bleier; Peter M. Sadow; Alia Rashid; Chhabra N; Michael K. Yoon

Background/aims Invasive fungal infections of the head and neck are rare life-threatening infections where prompt diagnosis and intervention is critical for survival. The aim of this study is to determine the clinical characteristics and outcomes of invasive fungal disease of the sinus and orbit, and to compare mucormycosis and Aspergillus infection. Methods A retrospective review was conducted from a single tertiary care eye and ear hospital over 20 years (1994–2014). Twenty-four patients with a confirmed pathological diagnosis of invasive fungal disease of the sinus and/or orbit were identified and their medical records were reviewed. The main outcome measures were type of fungus, location of disease, mortality and visual outcome. Results Patients with orbital involvement had a higher mortality and higher likelihood of mucormycosis infection compared with those with sinus-only disease (78.6% vs 20%, p=0.01; 86% vs 30%, p=0.01, respectively). Patients with mucormycosis had a higher mortality (71%) than patients with Aspergillus (29%); however, this was not statistically significant (p=0.16). All patients with orbital involvement and/or mucormycosis infections were immunosuppressed or had inadequately controlled diabetes, and had a cranial neuropathy or ocular motility dysfunction. All five post-transplant patients with orbital infections died, while the two transplant patients with sinus infections survived. Conclusions Patients with orbital fungal infections are more likely to be infected with mucormycosis compared with Aspergillus and have a higher mortality compared with infections sparing the orbit. History of transplant portends a dismal prognosis in orbital infections. Invasive fungal disease should be considered in any immunocompromised patient presenting with a new cranial neuropathy or ocular motility abnormality.


Saudi Journal of Ophthalmology | 2012

Infantile hemangiomas: A review

Alison B. Callahan; Michael K. Yoon

Infantile hemangiomas (IH) are the most common eyelid and orbital tumors of childhood. Although they are considered benign lesions that have a generally self-limited course, in the periocular region, they have the potential to cause amblyopia, strabismus, and severe disfigurement. The decision for treatment can be a source of anxiety for patients, parents, and physicians alike. There are numerous treatment modalities, including emerging therapies that may make treatment safer and more effective than ever before. This review discusses our current understanding of this disease, its management, and future therapies.


Current Opinion in Ophthalmology | 2015

Current trends in the management of thyroid eye disease.

Rohini Rao; Peter W. MacIntosh; Michael K. Yoon; Daniel R. Lefebvre

Purpose of review The present review summarizes the body of literature concerning the medical and surgical treatment of thyroid eye disease (TED) from 1 January 2014 through 30 March 2015. Recent findings Corticosteroids continue to be the primary medical therapy for TED. Recent research has offered insight into potential differences between oral corticosteroid and intravenous corticosteroid treatment regimens in terms of efficacy and side-effect profiles. Steroid-sparing medications, for example, rituximab and others, are an area of active study. There has been renewed interest in the role of radiation therapy as a nonmedical treatment for TED with some promising data. The use of balanced orbital decompression techniques have become popular, although the data regarding postoperative diplopia are mixed, and ‘fat decompression’ offers an alternative or an augmentation to bony decompression. Stereotactic image guidance is a useful adjunct to orbital decompression surgery. Summary TED continues to be a difficult condition for the patient to cope with and for the clinician to treat, and recent research builds on the present foundation of knowledge and treatments, but unfortunately does not offer paradigm-shifting information at the present time.


American Journal of Ophthalmology | 2013

Canaliculops: clinicopathologic features and treatment with marsupialization.

Michael K. Yoon; Frederick A. Jakobiec; Pia R. Mendoza

PURPOSE To report the features of the rare and under-recognized condition of canaliculops (or canaliculocele) of the eyelid, which is a dilation of the canaliculus, and to evaluate treatment with marsupialization. DESIGN Retrospective interventional case series. METHODS The records of 2 patients with canaliculops from the Massachusetts Eye and Ear Infirmary were reviewed. Data collected included clinical history, surgical technique, histopathologic analysis, and comparative immunohistochemical analysis of a range of cytokeratins in normal conjunctival epithelium, normal canalicular epithelium, and canaliculops epithelium. RESULTS Two women, 53 and 66 years of age, experienced chronic, noninflammatory, painless medial eyelid and eyelid margin fluctuant swelling after earlier trauma or eyelid surgery. The external mass was accompanied by a whitish opalescent or bluish discoloration of a palpebral surface bulge. Biopsy revealed multilaminar (up to 12 cells thick), nonkeratinizing, tightly packed small squamous epithelial cells that surmounted a highly regimented basal layer with a picket fence arrangement. No goblet cells or subepithelial inflammation were present. Immunohistochemistry revealed only superficial CK7 immunostaining and positive patchy suprabasilar CK17 staining in the canaliculops epithelium, contrasting with their full-thickness positivity and negativity, respectively, in normal conjunctival epithelium. Marsupialization achieved resolution of the condition in each patient. CONCLUSIONS An improved awareness of the normal canalicular epithelial structure and its immunohistochemical features can definitively separate canaliculops from conjunctival cysts. Previous treatment of canaliculops has involved complete excisions. Canaliculops may, however, be effectively treated with less invasive marsupialization while obtaining an adequate biopsy specimen for histopathologic diagnosis.


Journal of Neuro-ophthalmology | 2010

Acquired enophthalmos in lupus erythematosus profundus

Tina Y. Kao; Michael K. Yoon; Timothy J. McCulley; Beth S. Ruben; Thomas N. Hwang

Lupus erythematosus profundus (LEP) is an uncommon subtype of lupus erythematosus. A 76-year old man presented with inflammation of the eyelids and underlying orbital soft tissue. A biopsy disclosed inflammation and atrophy of the orbital fat consistent with LEP. Systemic corticosteroid treatment produced resolution of the inflammation. but as the edema subsided, enophthalmos became apparent. LEP should be considered in patients with a characteristic rash and orbital inflammation and may cause acquired enophthalmos.


Ophthalmic Plastic and Reconstructive Surgery | 2013

Secondary tarsoconjunctival graft: A modification to the cutler-beard procedure

Michael K. Yoon; Timothy J. McCulley

Purpose: The Cutler-Beard procedure is a commonly used technique to reconstruct large upper eyelid defects. Eyelid retraction and entropion are common complications. To prevent these problems, the authors modified the traditional Cutler-Beard procedure with secondary placement of an autologous tarsoconjunctival graft. Methods: This is a retrospective review of 2 patients with large upper eyelid defects necessitating upper eyelid reconstruction. The initial stage is unaltered. At the time of flap division, a tarsoconjunctival graft from the contralateral upper eyelid is sutured to the posterior surface of the newly constructed upper eyelid. Two patients underwent this procedure, and follow up was 4 and 23 months, respectively. Patients developed no postoperative complications, including entropion or retraction. Conclusions: This modification to the Cutler-Beard operation is a technically simple procedure that can restore a more anatomically correct eyelid and can prevent subsequent entropion or retraction. This technique is unique, offering 3 major advances: first, placing the graft at the second surgical stage; second, replacing the tarsus and conjunctiva with like tissue; and third, preserving a lip of conjunctiva to cover the edge of the newly reconstructed upper eyelid.


Ophthalmic Plastic and Reconstructive Surgery | 2009

Adult orbital trapdoor fracture.

C. Kum; Timothy J. McCulley; Michael K. Yoon; Thomas N. Hwang

Trapdoor fractures occur almost exclusively in the pediatric population. The authors describe an adult with an entrapped inferior rectus muscle sheath in a trapdoor fracture. A 37-year-old man presented with persistent diplopia 3 weeks after blunt right orbital trauma. The only abnormal findings on clinical examination were limited vertical ductions. No bony defect or displacement was evident on CT. However, several small pockets of air were visible adjacent to the inferior rectus muscle. On surgical exploration, a linear nondisplaced orbital floor fracture was confirmed, and the entrapped inferior rectus muscle was released. One month postoperatively, extraocular motility had improved with no diplopia in primary or reading positions. This case demonstrates that trapdoor fractures can occur in adults and should be considered when suggestive findings are encountered. Clinicians should be aware of this because timely diagnosis and treatment might achieve more favorable outcomes.

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Frederick A. Jakobiec

Massachusetts Eye and Ear Infirmary

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Suzanne K. Freitag

Massachusetts Eye and Ear Infirmary

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Anna M. Stagner

Massachusetts Eye and Ear Infirmary

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Daniel R. Lefebvre

Massachusetts Eye and Ear Infirmary

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Alia Rashid

Massachusetts Eye and Ear Infirmary

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Seanna Grob

Massachusetts Eye and Ear Infirmary

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Natalie Wolkow

Massachusetts Eye and Ear Infirmary

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