Clinical and Experimental Dermatology 1992; 17 (Suppl. 1): 6-7.
Clinical manifestations of onychomycosis N.ZAIAS Diseases of the Skin and Skin Cancer, Miami Beach, Florida, USA
The invasion of the nail unit by fungus is termed onychomycosis. Clinical types of onychomycosis are defined by the mode of invasion of the nail unit by the fungus and this can be divided into four types. (a) Distal subungual onychomycosis The fungus, usually a dermatophyte, first invades the hyponychium and then progresses to affect the underside of the distal free-edge of the nail plate. (b) White superficial onychomycosis The fungus only invades the superficial surface of the nail plate and produces white 'islands' of infection on the nail plate. (c) Proximal subungual onychomycosis The nail plate is invaded proximally through the glabrous skin via the lower portion of the nail plate. The invasion is usually secondary to proximal nailfold candidiasis or dermatophytosis. (d) Onychomycosis associated with chronic mucocutaneous candidiasis The nail plate is distally invaded through its entire thickness by the fungus.
Distal subungual onychomycosis This clinical type of onychomycosis is most commonly seen. Distal subungual onychomycosis primarily involves the nail-bed epidermis and, secondarily, the most distal and lateral aspects of the nail plate. The process usually starts with a fungal infection or dermatophytosis of the plantar and palmar surface of the feet and/or hands. Plantar tinea pedis may first make its appearance in the teens and is commonly referred to as 'athlete's foot'. As the patients grow older, susceptible individuals who have a strong family history of the same disease begin to develop distal subungual onychomycosis. It has been calculated that between 3 and 10% of the world's population of 14-year-olds have distal subungual onychomycosis. Unfortunately there is little data from prospective studies to support these figures. Observations of approximately 600 randomly studied patients show that onychomycosis of the distal subungual type is extremely Correspondence: Dr N.Zaias, Diseases of the Skin and Skin Cancer, 1680 Michigan Avenue, Suite 900, Miami Beach, FL-3139 USA.
prevalent, and by the age of approximately 60 years as many as 20-30% of the population have this disease. However, transmissibility of organisms does not seem to play a significant part in determining the prevalence of tinea pedis and distal subungual onychomycosis. Sultzberger conducted a survey among married couples, one of whom had either plantar tinea pedis or distal subungual onychomycosis, and noted a lack of transmission despite close contact (M.Sulzberger et al., pers. comm.) Finally, dermatophytosis of the plantar type or onychomycosis tend to be incurable diseases in many patients. Elimination of the active stage of tinea pedis or subungual onychomycosis may relieve the patient of signs and symptoms of the disease for a time until they stop taking antifungal medication. Unfortunately relapses are extremely common and well documented in both diseases. The evolution of distal subungual onychomycosis is as follows: Early invasion of the fungus is primarily through the plantar skin into the hyponychial epidermis and secondarily into the nail-bed epidermis, resulting in thickening of the stratum corneum beneath the nail plate causing a slight elevation of the nail plate from the nail bed. In this particular nidus a number of different micro-organisms can develop, which in themselves may be capable of destroying the nail plate, therefore making the underside of the nail plate more accessible to invasion by the offending fungus. The commonest fungus—Trichophyton rubrum—has been shown by Zaias''^ in previous experiments to be only poorly capable of destroying nail-plate tissue compared to Trichophyton mentagrophytes which is active in destroying nail tissue. The bacteria, Pseudomonas aeruginosa, is also extremely successful in nail-plate destruction. As the disease progresses, more material accumulates and clinically some areas develop a dense white appearance typical of a dermatophyte infection of the inferior surface of the nail and its bed. The nail plate per se is rarely involved and, even though many reports have claimed that it becomes discoloured and crumbly, it is usually not affected in early disease. A study of this disease shows that fungal elements or hyphae are similar to those seen in glabrous skin and quite different from the fungal elements found in other fungal infections of the nail to be described below.
CLINICAL MANIFESTATIONS OF ONYCHOMYCOSIS Ninety-nine per cent of the aetiological agents that Fusarium and Acremonium have also been described. This produce distal subungual onychomycosis are members of form of superficial nail-plate invasion is easily treated the genera Trichophyton, Epidermophyton and Micros- with topical antifungals or topical antimicrobial agents porum. The most common organism producing this that penetrate a few cells from the surface of the nail plate. disease is Trichophyton rubrum. However, each geographic region of the world may have a specific dermatoProximal subungual onychomycosis phyte and therefore almost all dermatophyte fungi have been reported to produce distal subungual onychomy- When this form of onychomycosis is caused by dermatocosis. In addition, a very small percentage (less than 1%) phytes the proximal and subungual nail plate is invaded. of distal subungual onychomycosis is produced by a The presence of proximal subungual onychomycosis due group of non-dermatophyte fungi which include the to dermatophytes is now recognized to be a marker for genera Aspergillus, Acremonium, Fusarium and Scopular- immunodeficient patients. The most common organism iopsis. These specific fungi do not produce a clinical is Trichophyton ruhrum and, although this disease is very syndrome that involves plantar tinea pedis, and usually rare in normal individuals, it is not so uncommon in only the large toe nail of either one or both feet is affected. patients with immunodeficiency syndrome. Another interesting and upcoming non-dermatophyte fungus is Hendersonula toruloidea, also believed to be a Cbronic mucocutaneous candidiasis form of Scytalidium. This agent produces the same clinical picture as the dermatophyte fungi that cause The last form of onychomycosis follows invasion by the plantar tinea pedis, tinea palmaris, tinea manuum and yeast Candida alhicans of the entire thickness of the nail onychomycosis, all identical to dermatophyte infection. It plate in patients who have chronic mucocutaneous wasfirstdescribed by Gentles and Evans^ in Scotland and candidiasis. In this form the host-parasite relationship is later reported elsewhere in the world. The organism is again unique, in that the yeast Candida alhicans produces extremely sensitive to cycloheximide and resistant to large numbers of hyphae much like they would see in most antifungal agents that are used today such as aggressive oropharyngeal candidiasis rather than the griseofulvin, miconazole, intraconazole, fluconazole and yeast forms that dominate in other forms of cutaneous other agents. This organism may pose a problem at a candidosis. Here the nail plate, bed and nail fold may be future date as new agents are developed that have a good affected by the infection. antifungal effect against the dermatophytes, but not against Hendersonula. References White superficial onychomycosis White superficial onychomycosis only involves the toe nails, and the most common organism is Trichophyton mentagrophytes. Members of the genera Aspergillus,
1 Zaias N. Onychomycosis. Archives of Dermatotogy 1972; 105: 263274. 2 Zaias N. The Nait in Heatth and Disease. New York: Spectrum Publications, 1980. 3 Gentles JC, Evans GV. Infection of the feet and nails with Hendersonuta torutoidea. Sabouraudia 1970; 8: 72-75.
Clinical manifestations of onychomycosis N.ZAIAS Diseases of the Skin and Skin Cancer, Miami Beach, Florida, USA
The invasion of the nail unit by fungus is termed onychomycosis. Clinical types of onychomycosis are defined by the mode of invasion of the nail unit by the fungus and this can be divided into four types. (a) Distal subungual onychomycosis The fungus, usually a dermatophyte, first invades the hyponychium and then progresses to affect the underside of the distal free-edge of the nail plate. (b) White superficial onychomycosis The fungus only invades the superficial surface of the nail plate and produces white 'islands' of infection on the nail plate. (c) Proximal subungual onychomycosis The nail plate is invaded proximally through the glabrous skin via the lower portion of the nail plate. The invasion is usually secondary to proximal nailfold candidiasis or dermatophytosis. (d) Onychomycosis associated with chronic mucocutaneous candidiasis The nail plate is distally invaded through its entire thickness by the fungus.
Distal subungual onychomycosis This clinical type of onychomycosis is most commonly seen. Distal subungual onychomycosis primarily involves the nail-bed epidermis and, secondarily, the most distal and lateral aspects of the nail plate. The process usually starts with a fungal infection or dermatophytosis of the plantar and palmar surface of the feet and/or hands. Plantar tinea pedis may first make its appearance in the teens and is commonly referred to as 'athlete's foot'. As the patients grow older, susceptible individuals who have a strong family history of the same disease begin to develop distal subungual onychomycosis. It has been calculated that between 3 and 10% of the world's population of 14-year-olds have distal subungual onychomycosis. Unfortunately there is little data from prospective studies to support these figures. Observations of approximately 600 randomly studied patients show that onychomycosis of the distal subungual type is extremely Correspondence: Dr N.Zaias, Diseases of the Skin and Skin Cancer, 1680 Michigan Avenue, Suite 900, Miami Beach, FL-3139 USA.
prevalent, and by the age of approximately 60 years as many as 20-30% of the population have this disease. However, transmissibility of organisms does not seem to play a significant part in determining the prevalence of tinea pedis and distal subungual onychomycosis. Sultzberger conducted a survey among married couples, one of whom had either plantar tinea pedis or distal subungual onychomycosis, and noted a lack of transmission despite close contact (M.Sulzberger et al., pers. comm.) Finally, dermatophytosis of the plantar type or onychomycosis tend to be incurable diseases in many patients. Elimination of the active stage of tinea pedis or subungual onychomycosis may relieve the patient of signs and symptoms of the disease for a time until they stop taking antifungal medication. Unfortunately relapses are extremely common and well documented in both diseases. The evolution of distal subungual onychomycosis is as follows: Early invasion of the fungus is primarily through the plantar skin into the hyponychial epidermis and secondarily into the nail-bed epidermis, resulting in thickening of the stratum corneum beneath the nail plate causing a slight elevation of the nail plate from the nail bed. In this particular nidus a number of different micro-organisms can develop, which in themselves may be capable of destroying the nail plate, therefore making the underside of the nail plate more accessible to invasion by the offending fungus. The commonest fungus—Trichophyton rubrum—has been shown by Zaias''^ in previous experiments to be only poorly capable of destroying nail-plate tissue compared to Trichophyton mentagrophytes which is active in destroying nail tissue. The bacteria, Pseudomonas aeruginosa, is also extremely successful in nail-plate destruction. As the disease progresses, more material accumulates and clinically some areas develop a dense white appearance typical of a dermatophyte infection of the inferior surface of the nail and its bed. The nail plate per se is rarely involved and, even though many reports have claimed that it becomes discoloured and crumbly, it is usually not affected in early disease. A study of this disease shows that fungal elements or hyphae are similar to those seen in glabrous skin and quite different from the fungal elements found in other fungal infections of the nail to be described below.
CLINICAL MANIFESTATIONS OF ONYCHOMYCOSIS Ninety-nine per cent of the aetiological agents that Fusarium and Acremonium have also been described. This produce distal subungual onychomycosis are members of form of superficial nail-plate invasion is easily treated the genera Trichophyton, Epidermophyton and Micros- with topical antifungals or topical antimicrobial agents porum. The most common organism producing this that penetrate a few cells from the surface of the nail plate. disease is Trichophyton rubrum. However, each geographic region of the world may have a specific dermatoProximal subungual onychomycosis phyte and therefore almost all dermatophyte fungi have been reported to produce distal subungual onychomy- When this form of onychomycosis is caused by dermatocosis. In addition, a very small percentage (less than 1%) phytes the proximal and subungual nail plate is invaded. of distal subungual onychomycosis is produced by a The presence of proximal subungual onychomycosis due group of non-dermatophyte fungi which include the to dermatophytes is now recognized to be a marker for genera Aspergillus, Acremonium, Fusarium and Scopular- immunodeficient patients. The most common organism iopsis. These specific fungi do not produce a clinical is Trichophyton ruhrum and, although this disease is very syndrome that involves plantar tinea pedis, and usually rare in normal individuals, it is not so uncommon in only the large toe nail of either one or both feet is affected. patients with immunodeficiency syndrome. Another interesting and upcoming non-dermatophyte fungus is Hendersonula toruloidea, also believed to be a Cbronic mucocutaneous candidiasis form of Scytalidium. This agent produces the same clinical picture as the dermatophyte fungi that cause The last form of onychomycosis follows invasion by the plantar tinea pedis, tinea palmaris, tinea manuum and yeast Candida alhicans of the entire thickness of the nail onychomycosis, all identical to dermatophyte infection. It plate in patients who have chronic mucocutaneous wasfirstdescribed by Gentles and Evans^ in Scotland and candidiasis. In this form the host-parasite relationship is later reported elsewhere in the world. The organism is again unique, in that the yeast Candida alhicans produces extremely sensitive to cycloheximide and resistant to large numbers of hyphae much like they would see in most antifungal agents that are used today such as aggressive oropharyngeal candidiasis rather than the griseofulvin, miconazole, intraconazole, fluconazole and yeast forms that dominate in other forms of cutaneous other agents. This organism may pose a problem at a candidosis. Here the nail plate, bed and nail fold may be future date as new agents are developed that have a good affected by the infection. antifungal effect against the dermatophytes, but not against Hendersonula. References White superficial onychomycosis White superficial onychomycosis only involves the toe nails, and the most common organism is Trichophyton mentagrophytes. Members of the genera Aspergillus,
1 Zaias N. Onychomycosis. Archives of Dermatotogy 1972; 105: 263274. 2 Zaias N. The Nait in Heatth and Disease. New York: Spectrum Publications, 1980. 3 Gentles JC, Evans GV. Infection of the feet and nails with Hendersonuta torutoidea. Sabouraudia 1970; 8: 72-75.
