Rhinosporidiosis is an infection caused by Rhinosporidium seeberi. Classification
This organism was previously considered to be a fungus, and rhinosporidiosis is classified as a fungal disease under ICD-10. It is now considered to be a protist classified under Mesomycetozoea.Authors of detailed studies have revealed superficial similarities between Dermocystidium and Rhinosporidium when using light microscopy, but substantial morphological differences between the groups exist.There is some evidence that DNA extracted from purified uncontaminated round bodies (Rhinosporidium seeberi) is of cyanobacterial origin. Pathophysiology
Rhinosporidiosis is a granulomatous disease affecting the mucous membrane of nasopharynx, oropharynx, conjunctiva, rectum and external genitalia. Though the floor of the nose and inferior turbinate are the most common sites, the lesions may appear elsewhere too. Traumatic inoculation from one site to others is common. Laryngeal rhinosporidiosis, too, has been described and may be due to inoculation from the nose during endotracheal intubation. After inoculation, the organism replicates locally, resulting in hyperplasia of host tissue and localised immune response.
The highest incidence in the United States of America is in American boys of school age.There are three type of tinea capitis, microsporosis, trichophytosis, and favus; these are based on the causative microorganism, and the nature of the symptoms. In microsporosis, the lesion is a small red papule around a hair shaft that later becomes scaly; eventually the hairs break off 1–3 mm above the scalp. This disease used to be caused primarily by Microsporum audouinii, but in Europe, M. canis is more frequently the causative fungus. The source of this fungus is typically sick cats and kittens; it may be spread through person to person contact, or by sharing contaminated brushes and combs. In the United States, Trichophytosis is usually caused by Trichophyton tonsurans, while T. violaceum is more common in Eastern Europe, Africa, and India. This fungus causes dry, non-inflammatory patches that tend to be angular in shape. When the hairs break off at the opening of the follicle, black dots remain. Favus is caused by T. schoenleinii, and is endemic in South Africa and the Middle East. It is characterized by a number of yellowish, circular, cup-shaped crusts (scutula) grouped in patches like a piece of honeycomb, each about the size of a split pea, with a hair projecting in the center. These increase in size and become crusted over, so that the characteristic lesion can only be seen around the edge of the scab. Pathophysiology
From the site of inoculation, the fungus grows down into the stratum corneum, where it invades keratin.