Notes on Presumed ocular histoplasmosis syndrome (POHS)
• affects all ages with no sex bias.
• The characteristic triad of Presumed ocular histoplasmosis syndrome:
1- peripapillary atrophy
2- multiple atrophic ‘histo-spots’ around the posterior pole with pigment clumping, and serous or haemorrhagic disciform detachment due to (CNV), usually associated with a macular ‘histo-spot’.
3- Linear streaks of chorioretinal atrophy are sometimes seen.
• Vitreous cells are absent.( no vitritis)
• Usually asymptomatic until CNV develops.
• The diagnosis is clinical but order FFA if CNV is suspected.
• Focal argon laser is appropriate for juxta- and extrafoveal CNVs.
• Oral steroids are of no benefit.
• Photodynamic therapy is unproven.
• the CNV is type II, may benefit from surgical removal.
• The role of anti-VEGF agents has yet to be fully determined.( further studies required)
• Offer an Amsler chart to monitor the other eye.
Presumed ocular histoplasmosis syndrome power point presentations: Histoplasmosis
1. INSTITUTE OF HEALTH TECHNOLOGY, DHAKA Department of Laboratory Medicine BSc in Health Technology (Laboratory)- 1st Year MYCOLOGY Lecture No. 06 (Deep Mycoses – Histoplasmosis) By Sk. MIZANUR RAHMAN Lecturer, Mycology MS in Biotechnology & Genetic Engineering (UODA) MS in Microbiology (SU)
2. Outline of Histoplasmosis • Characteristics • Pathogenesis • Histoplasmosis –Pulmonary –Disseminated • Lab Diagnosis 2
3. Histoplasmosis Characteristics • Member of the phylum Ascomycota • Worldwide distribution • Naturally found in fecal-contaminated soils • Birds and bats appear to be reservoirs • Etiologic agent of histoplasmosis
4. Characteristics (cont.) • Dimorphic fungus – Sexual multi-cellular saprophytic mycelia – Asexual single-celled parasitic yeast • Mycelial form is most commonly found in the environment • Heterothallic species • Tightly coiled septate hyphae (A) • Globose cleistothecia (C) • Pear-shaped asci (E) • Smooth, hyaline, spherical ascospores (F) A C E F 4
5. Characteristics (cont.) • Yeast form is the infectious agent in humans • Form asexual macro- and microconidia – Also borne by hyphae in the mycelial form (B) • Conidia germinate via non/polar budding • Yeast cells have white, thin-walled, oval bodies (A) A B 5
6. Histoplasmosis-Types • 2 major forms of histoplasmosis – Pulmonary and disseminated • Pulmonary histoplasmosis occurs when microconidia or mycelial fragments are inhaled – Form lesions in the hilar and/or mediastinal nodes – Many types of pulmonary histoplasmosis • Asymptomatic pulmonary histoplasmosis • Acute pulmonary histoplasmosis • Mediastinal granuloma • Fibrosing mediastinitis • Chronic cavitary pulmonary histoplasmosis 6
7. Disseminated Histoplasmosis • Disseminated histoplasmosis – Occurs primarily in immunocompromised individuals – In healthy individuals, H. capsulatum is similar to tuberculosis • While the infection is usually resolved, the fungus is still present • Constantly kept in check by T lymphocytes – In immunocompromised individuals, H. capsulatum is able to spread from the lungs into other organs – Patients display fever, malaise, and occasionally petechiae or skin lesions (cutaneous histoplasmosis) – Tests often reveal mucous membrane ulcerations, simultaneous enlargement of the liver and spleen, and enlarged lymph nodes 7
8. Disseminated Histoplasmosis (cont.) –Diagnosis is performed by demonstrating the presence of the fungus in extrapulmonary tissue • Blood cultures, bronchoscopy, BAL, ID, CF, and positive antigen tests are commonly performed –Elevated levels of lactate dehydrogenase and ferritin in AIDS patients 8
9. HISTOPLASMOSIS Pathogenesis Respiratory Infections inhale yeast form spores macrophages macrophases in lung ingest yeast Lymph nodes Liver Spleen Adrenal glands Intestine Bone Marrow Proliferation halted by onset of acquired CMI at 10-14 d. Vasculitis, tissue necrosis, caseating granulomata. Killing by macrophages, healing, calcification 9
10. Histoplasmosis Clinical • Chronic pulmonary histoplasmosis (1/100,000) – pre-existing structural lung defect, i.e. COPD, emphysema – chronic pneumonia or infection in cavities, increased sputum – reactivation or reinfection – apical infection, may be cavitary • Mediastinal granulomatosis and fibrosis – fibrosis, traction, occlusion of mediastinal structure • Histoplasmoma – Fibrocaseous nodule – Concentric caseation and calcification • Presumed ocular histoplasmosis syndrome – choroiditis – active or inactive • may result in visual loss due to macular involvement 10
Presumed ocular histoplasmosis syndrome Videos:
Dr. Isernhagen — “Ocular Histoplasmosis”
Presumed ocular histoplasmosis syndromePresumed ocular histoplasmosis syndrome (POHS)
