Nail is produced by the normal nail bed: a controversy resolved

Does the Nail Bed Regenerate?

BACKGROUND

The regenerative potential of the nail bed after trauma remains controversial.

METHODS

We performed a retrospective review of 51 patients who underwent nail bed reconstruction with 2 techniques (direct flow island flap or a Tranquilli-Leali "Atasoy" flap) due to trauma involving the nail bed complex. These 2 flaps were used to support the loss of distal substance and to allow the regeneration of the nail bed. Outcomes were analyzed for at least 18 months. There were 34 men (66.7%), and the average age was 16.1 years. Most patients (56.9%) had crush injuries. The little (16) and index (14) fingers were the most affected. Twenty-seven were children (range: 4-11) with an average age of 7.4 ± 1.9 years. The middle finger was the most affected (29.2%).

RESULTS

The outcomes were good to excellent in 41 operated patients (80.4%). Hook nail was absent in 84.3% of the patients. Most patients (98%) did not develop necrosis. Children had an excellent/good outcome rate of 85.2%, while in adults, the rate was 75% of cases (P = .485).

CONCLUSION

The direct flow island flap is superior in terms of outcome, regardless of age, sex, affected finger, dominant hand, type of trauma, and injury zone. In cases where there was a correct reconstruction of the hyponychium, there was regeneration of the nail bed.

Hepatitis B virus DNA in the fingernails and hair of children with acute hepatitis B

Hepatitis B virus (HBV) DNA is detectable in the nails and hair of patients with chronic HBV infection. However, it remains unclear whether HBV DNA can be detectable in the nails and hair of patients with acute HBV infection. We encountered two cases of children with acute HBV infection. HBV DNA in the nails and hair from the two children was evaluated by real-time PCR. To clarify the characteristics of HBV DNA, full-length HBV genome sequencing and phylogenetic tree analysis were performed. The levels of serum HBV DNA in children of cases 1 and 2 at day 0 were 7.6 Log IU/mL and 7.4 Log IU/mL, respectively. Nail HBV DNA was detected in both children (case 1: 4.6 Log IU/mL at day 0, case 2: 5.5 Log IU/mL at day 14). Moreover, hair HBV DNA was detectable in case 2 (4.0 Log IU/mL at day 14). Serum HBV DNA became undetectable within approximately 3-4 months after the first hospital visit. After the resolution of HBV viremia, nail and hair HBV DNA became undetectable. The sequence analysis of serum, nail and hair HBV DNA showed the same HBV genotype in each case (case1: genotype C, case 2: genotype A). In case 1, 3 nucleotides were different in the full-genome HBV sequence between the serum and nails. In case 2, the full-genome HBV sequences were identical among the serum, nails and hair. In conclusion, HBV DNA was detectable in nails and hair of children with acute HBV infection.

Significance of Surgery to Correct Anatomical Alterations in Pincer Nails

Background

Pincer nail deformity and its causes can pose a therapeutic challenge. Ill-fitting shoes and subungual exostosis of the toes may be attributed to pincer nail formation. However, in some cases, the causes of pincer nail deformity could not be determined. The role of mechanobiology in nail configuration and deformities has rarely been considered.

Objective

The present study investigated the effectiveness of surgical procedures to correct pincer nail deformity, in terms of anatomical changes measured by radiographs.

Methods

Two surgical procedures, nail bed widening with matrixectomy or a dermal graft, were used on 30 nails in 20 patients with pincer deformity. Changes in the width, height, and curvature indices were assessed. Radiographs were obtained to evaluate the presence of osteophytes and measure the interphalangeal angle in terms of mechanobiology in nail configuration.

Results

Preoperative and postoperative assessment results revealed marked improvement objectively and subjectively. The mean width index was greater after surgery than that before surgery (84.4% vs. 64.8%). Both mean height and curvature indices were smaller after surgery than before preoperative (23.0% vs. 76.7% and 1.3% vs. 2.2%, respectively).

Conclusion

Nail bed widening with matrixectomy, which corrects anatomical alterations in pincer nails, is suggested to be suitable for patients with pincer nail deformity.

Wearable Nail Deformation Sensing for Behavioral and Biomechanical Monitoring and Human-Computer Interaction

The dynamics of the human fingertip enable haptic sensing and the ability to manipulate objects in the environment. Here we describe a wearable strain sensor, associated electronics, and software to detect and interpret the kinematics of deformation in human fingernails. Differential forces exerted by fingertip pulp, rugged connections to the musculoskeletal system and physical contact with the free edge of the nail plate itself cause fingernail deformation. We quantify nail warpage on the order of microns in the longitudinal and lateral axes with a set of strain gauges attached to the nail. The wearable device transmits raw deformation data to an off-finger device for interpretation. Simple motions, gestures, finger-writing, grip strength, and activation time, as well as more complex idioms consisting of multiple grips, are identified and quantified. We demonstrate the use of this technology as a human-computer interface, clinical feature generator, and means to characterize workplace tasks.

Risk Factors and Frequency of Ingrown Nails in Adult Diabetic Patients

The present study evaluated the properties of nails, frequency of ingrown nails in patients with type 2 diabetes mellitus (DM), risk factors for developing ingrown nails, and effect of diabetic polyneuropathy and vasculopathy on the development and outcome of ingrown nails. Our 6-month epidemiologic prospective study included 300 patients with type 2 DM attending a DM outpatient clinic for routine examinations. The general characteristics and foot changes of the study population were investigated. Diabetic polyneuropathy and vasculopathy were evaluated using a biothesiometer, monofilament tests, and arterial Doppler ultrasonography. The frequency of ingrown nails was 13.6%. Multivariate analysis with logistic regression showed that body mass index (odds ratio [OR] 1.077, 95% confidence interval [CI] 1.007 to 1.15; p = .03), previous trauma (OR 2.828, 95% CI 1.017 to 7,867, p = .042), a weak dorsalis pedis pulse (OR 2.72, 95% CI 1.17 to 6.30, p = .02), trimming type (OR 2.3, 95 CI 1.06 to 4.98), p = .35), onychogryphosis (OR 9.036, 95% CI 2.34 to 34.87, p = .001), and subungual hyperkeratosis (OR 4.3, 95% CI 1.99 to 9.3, p = .001) were predictive variables for ingrown nails in our population. The incidence of onychomycosis was significantly greater in patients with ingrown nails (p = .032) than in patients without ingrown nails. The nail curvature ratio was greater in the patients with ingrown nails than in the group with normal nails. Arterial Doppler ultrasound examinations showed peripheral arterial disease in 19 patients (46.9%) with ingrown nails. The prevalence of ingrown nails was greater in the patients with DM than in the healthy population. Our results indicate that nail type, nail morphology, and diabetic vasculopathy affect the formation and evolution of ingrown nails.

Nail anatomy

The nail unit comprises the nail plate, the surrounding soft tissues, and their vasculature and innervation based upon the distal phalanx. The nail plate is a laminated keratinized structure lying on the nail matrix (15-25%), the nail bed with its distal onychodermal band (75-85%), and the hyponychium at its free edge. The distal part of the matrix, the lunula characterized by its half-moon shape, can be observed in some digits. The nail plate is embedded by the proximal and lateral folds. From the proximal nail fold, the cuticle (also known as the eponychium), adheres to the superficial surface of the proximal nail plate. The nail unit possesses a complex and abundant vascular network to ensure adequate blood supply. Finally, both the periungual soft tissues and the nail folds are innervated. The shapes, structure, and inter-relationships of these tissues are factors in the way nails present with disease and how we understand and manage those diseases. In particular, an understanding of the surgical anatomy is important for those undertaking diagnostic or curative operations on the nail. With this knowledge, the most appropriate surgery can be planned and the patient can be provided with accurate and clear guidance to enable informed consent.

Clinical Evidence for the Relationship between Nail Configuration and Mechanical Forces

Summary:

Mechanobiology is an emerging field of science that focuses on the way physical forces and changes in cell or tissue mechanics contribute to development, physiology, and disease. As nails are always exposed to physical stimulation, mechanical forces may have a particularly pronounced effect on nail configuration and could be involved in the development of nail deformities. However, the role of mechanobiology in nail configuration and deformities has rarely been assessed. This review describes what is currently understood regarding the effect of mechanical force on nail configuration and deformities. On the basis of these observations, we hypothesize that nails have an automatic curvature function that allows them to adapt to the daily upward mechanical forces. Under normal conditions, the upward daily mechanical force and the automatic curvature force are well balanced. However, an imbalance between these 2 forces may cause nail deformation. For example, pincer nails may be caused by the absence of upward mechanical forces or a genetic propensity increase in the automatic curvature force, whereas koilonychias may occur when the upward mechanical force exceeds the automatic curvature force, thereby causing the nail to curve outward. This hypothesis is a new concept that could aid the development of innovative methods to prevent and treat nail deformities.

Benefits of an ungual prosthesis in traumatology and reconstructive surgery of the nail

Lesions of the nail apparatus can leave esthetic and sometimes functional sequelae. Many sequelae are the result of incorrect growth of the nail plate. During the acute phase, in the absence of a nail plate, the nail bed may keratinize or form a pyogenic granuloma, compromising harmonious regrowth of the nail plate. The ideal is to reinsert the plate if it is available, but if it has been lost, an ungual prosthesis must be inserted to act as a temporary implantable splint. This implant must have the same shape and structure as the nail plate. Many ideas have been used in the past, including suture pack, infusion tubing, or x-ray film. However, these techniques are no longer acceptable, as, in many countries, all types of implants require a documented recorded identification or "traceability." The implants we use are packed individually in sterile packaging. They are therefore immediately available in traumatology departments treating Hand Emergencies. These prostheses are also very useful in reconstructive surgery of the digit in the hand and feet, particularly when the nail bed has to be reconstructed. In this case, the implant is used to flatten the nail bed, whether it is sutured, grafted, or reconstructed with flaps, during the slow regrowth of the nail plate. The author reports his experience in emergency or secondary repair of the nail complex.

Nail bed defect covered with labial mucosa graft after subungal glomus tumor removal

The nail bed is an important part of the nail unit. It supports the nail plate, but does not regenerate itself. The labial mucosa and the nail bed both lack a granular layer. Because the keratinization of the nail bed can cause poor nail adhesion, harvesting graft from nonkeratinized sites is preferred. Furthermore, harvesting graft from labial mucosa is convenient in surgical approach. Therefore, the labial mucosa is more eligible for covering the nail bed defect than other graft methods. In this report, a 46-year-old female patient suffered from a subungal glomus tumor of the right fourth fingernail bed for 10 years. After the nail plate was removed, complete excision of the tumor was performed, and a labial mucosa graft was used to cover the defect. Eight months after the operation, the tumor had not reoccurred and no nail deformity was observed. This outcome demonstrates that our procedure is a good surgical option for treatment of nail bed defects.

Nail biology and nail science

The nail plate is the permanent product of the nail matrix. Its normal appearance and growth depend on the integrity of several components: the surrounding tissues or perionychium and the bony phalanx that are contributing to the nail apparatus or nail unit. The nail is inserted proximally in an invagination practically parallel to the upper surface of the skin and laterally in the lateral nail grooves. This pocket-like invagination has a roof, the proximal nail fold and a floor, the matrix from which the nail is derived. The germinal matrix forms the bulk of the nail plate. The proximal element forms the superficial third of the nail whereas the distal element provides its inferior two-thirds. The ventral surface of the proximal nail fold adheres closely to the nail for a short distance and forms a gradually desquamating tissue, the cuticle, made of the stratum corneum of both the dorsal and the ventral side of the proximal nail fold. The cuticle seals and therefore protects the ungual cul-de-sac. The nail plate is bordered by the proximal nail fold which is continuous with the similarly structured lateral nail fold on each side. The nail bed extends from the lunula to the hyponychium. It presents with parallel longitudinal rete ridges. This area, by contrast to the matrix has a firm attachment to the nail plate and nail avulsion produces a denudation of the nail bed. Colourless, but translucent, the highly vascular connective tissue containing glomus organs transmits a pink colour through the nail. Among its multiple functions, the nail provides counterpressure to the pulp that is essential to the tactile sensation involving the fingers and to the prevention of the hypertrophy of the distal wall tissue, produced after nail loss of the great toe nail.

Arsenic microdistribution and speciation in toenail clippings of children living in a historic gold mining area

Arsenic is naturally associated with gold mineralisation and elevated in some soils and mine waste around historical gold mining activity in Victoria, Australia. To explore uptake, arsenic concentrations in children's toenail clippings and household soils were measured, and the microdistribution and speciation of arsenic in situ in toenail clipping thin sections investigated using synchrotron-based X-ray microprobe techniques. The ability to differentiate exogenous arsenic was explored by investigating surface contamination on cleaned clippings using depth profiling, and direct diffusion of arsenic into incubated clippings. Total arsenic concentrations ranged from 0.15 to 2.1 microg/g (n=29) in clipping samples and from 3.3 to 130 microg/g (n=22) in household soils, with significant correlation between transformed arsenic concentrations (Pearson's r=0.42, P=0.023) when household soil was treated as independent. In clipping thin sections (n=2), X-ray fluorescence (XRF) mapping showed discrete layering of arsenic consistent with nail structure, and irregular arsenic incorporation along the nail growth axis. Arsenic concentrations were heterogeneous at 10x10 microm microprobe spot locations investigated (<0.1 to 13.3 microg/g). X-ray absorption near-edge structure (XANES) spectra suggested the presence of two distinct arsenic species: a lower oxidation state species, possibly with mixed sulphur and methyl coordination (denoted As(approximately III)(-S, -CH3)); and a higher oxidation state species (denoted As(approximately V)(-O)). Depth profiling suggested that surface contamination was unlikely (n=4), and XRF and XANES analyses of thin sections of clippings incubated in dry or wet mine waste, or untreated, suggested direct diffusion of arsenic occurred under moist conditions. These findings suggest that arsenic in soil contributes to some systemic absorption associated with periodic exposures among children resident in areas of historic gold mining activity in Victoria, Australia. Future studies are required to ascertain if adverse health effects are associated with current levels of arsenic uptake.

Morphologic study of normal, ingrown, and pincer nails

BACKGROUND

Pincer nail has been confused with ingrown nail for decades.

OBJECTIVE

The objectives were to analyze the circumferential length of pincer nail and the relationship between nail deformity and the underlying distal phalangeal shape.

METHODS

The circumferential length of 53 pincer nails was determined at successive 5-mm intervals of the nail plate. Sixty great toes, including normal (n=20), ingrown (n=20), and pincer nails (n=20), were assessed with respect to body height, body weight, body mass index, nail height, nail width index, and nail height index. Nail angle and height of osteophyte were measured.

RESULTS

Despite the presence or absence of overcurvature, the circumferential length displayed nearly identical values across the proximal to distal range of the nail. In the pincer nail group, only the correlation between the width and height indices was statistically significant; 50%, 80%, and 100% of cases were confirmed based on osteophyte presence in normal, ingrown, and pincer nails.

CONCLUSION

The findings suggest that the mechanical cause may be associated with the over curved nail, which is affected by nail bed contraction. Results may support the hypothesis that an osteophyte of the distal phalanx may not be a cause of, but rather a result of, an overcurving deformity.

Treatment of nail bed defects with hard palate mucosal grafts

BACKGROUND

Nail bed defects produce a nail plate dystrophy that is permanent and presents important cosmetic problems. To correct the defect, we used a hard palate mucosal graft. This is a procedure with encouraging outcomes for nail bed scars.

OBJECTIVE

To show our initial experience with the hard palate mucosal graft technique for correcting nail dystrophy or permanent onycholysis secondary to a nail bed scar.

METHODS

This was a prospective, longitudinal, descriptive, observational study. We included five patients with a traumatic nail bed scar and one patient with congenital dystrophy. Seven nails were treated using a hard palate mucosal graft.

RESULTS

All repaired nails had a good outcome, with excellent growth and improvement in nail dystrophy. The patients had surgical recovery in 2 weeks and tolerable pain.

CONCLUSIONS

This is a relatively easy procedure for experienced surgeons to correct nail dystrophy secondary to a nail bed scar, with good to excellent results.

Expression of hair keratins in the adult nail unit: an immunohistochemical analysis of the onychogenesis in the proximal nail fold, matrix and nail bed

BACKGROUND

Recently, the expression profiles of the members of the complex hair keratin family have been determined in the human anagen hair follicle. In contrast, the details of hair keratin expression in the human nail unit are poorly known.

OBJECTIVES

In order to fill this gap, we have performed an immunohistochemical study of the adult human nail unit by means of specific antibodies against nine hair keratins of both types (hHa2, hHb2, hHa5, hHb5, hHa1, hHb1, hHb6, hHa4 and hHa8) as well as three epithelial keratins (K5, K17 and K10).

METHODS

Formalin-fixed paraffin sections of adult nails were examined using monoclonal and polyclonal keratin antibodies, respectively. Longitudinal as well as transverse sections were investigated.

RESULTS

Our study revealed two types of epithelial tissue compartments in the nail unit. The first comprised the eponychium and hyponychium and the nail bed, which expressed only epithelial keratins. While keratins K5, K17 (basal) and K10 (suprabasal) were found in the orthokeratinizing eponychium and hyponychium, throughout, the nail bed epithelium expressed only K5 and K17. The second type comprised the apical and ventral matrix which exhibited a mixed pattern of epithelial and hair keratin expression. Thus, K5 and K17 were expressed in the entire multilayered basal cell compartment of the apical and ventral matrix; however, in the latter, K5 and K17 also occurred in the lowermost layers of the overlying keratogenous zone. The hair matrix keratin hHb5, but not its type II partner hHa5, was seen in the entire keratogenous zone of the apical and ventral matrix, but was also located in the uppermost cell layers of the basal compartment of the ventral matrix, where it overlapped with K5 and K17. Similar to their sequential expression in the hair follicle cortex, hair keratins hHa1, hHb1, hHb6 and hHa4 were consecutively expressed in the keratogenous zone of both the ventral and, albeit less distinctly, apical matrix, with hHa1 initiating in the lowermost cell layers. The expression of hHa8 in only single cortex cells of the hair follicle was also preserved in cells of the keratogenous zone. In the region of the so-called dorsal matrix, we observed two histologically and histochemically distinct types of epithelia: (i) a dominant type, histologically similar to the eponychium and an associated K5, K17 and K10 keratin pattern which clearly extended into the apical matrix, and (ii) a minor type, histologically resembling the postulated dorsal matrix without a granular layer and a cuticle, and exhibiting extended K5 expression as well as hair keratin expression in superficial cells.

CONCLUSIONS

The coexpression of hHb5 with K5 and K17 in the uppermost cell layers of the basal compartment and the lowermost layers of the keratogenous zone of the ventral matrix prompts us to designate this region the prekeratogenous zone of the ventral matrix. The two alternating types of histology and keratin expression in the dorsal matrix identify this region as a transitional zone between the eponychium and the apical matrix. Finally, our data clearly show that the ventral matrix is the main source of the nail plate. In addition, the mixed scenario of hair and epithelial keratins, including demonstrable amounts of K10, in superficial cells of the apical matrix, lends support to the notion that the dorsal portion of the nail is generated by the apical matrix.

Modulation of linear nail growth to treat diseases of the nail

Diseases affecting the nail can cause significant distress and interfere with an individual's self-esteem, personal relationships, and professional life. Often, hand and foot function is adversely affected. Certain diseases are characterized by accelerated nail growth while others show a decrease. In this review, drugs known to influence the growth rate of nails are examined, highlighting their potential use as adjunctive therapy in the treatment of nail disease. This approach, described recently in the context of the yellow nail syndrome,(1) may be extended to other common disorders such as nail psoriasis, brittle nails, and onychomycosis.

Subsídios para o estudo histopatológico das lesões ungueais

FUNDAMENTOS: Os autores apresentam ampla revisão sobre os fundamentos da biópsia da unidade ungueal, fornecendo bases teóricas sobre anatomia, histologia e histopatologia. Abordam, detalhadamente, as indicações e os objetivos da biópsia da unidade ungueal e as várias técnicas disponíveis. OBJETIVOS: Definir os locais adequados da biópsia do aparelho ungueal para as diferentes doenças da unha, comparar duas formas de amaciamento da lâmina ungueal, uma utilizando KOH a 20%, outra, solução aquosa de Tween 40 a 10%, e estabelecer uma rotina para o processamento do material de biópsia. MÉTODOS: O grupo de estudo constou de 11 pacientes com doença ungueal, que procuraram o ambulatório de Dermatologia do HUPE/UERJ para esclarecimento diagnóstico. Foi realizado o total de 12 biópsias. RESULTADOS: Não houve diferença na dificuldade técnica, em incluir ou cortar o material, consoante ao método de amaciamento utilizado, nem prejuízo citológico ou histológico ao exame histopatológico. CONCLUSÕES: Os autores concluíram que biópsia ungueal é procedimento seguro e eficaz para esclarecer o diagnóstico das doenças ungueais quando o exame clínico ou outras técnicas falharam. Também é importante, para quem deseja realizar o procedimento, o conhecimento adequado da anatomia dessa região.

Acquired periungual fibrokeratoma with accessory germinal matrix

Five cases of acquired periungual fibrokeratoma involving the proximal nail fold were treated surgically. Clinically, all five patients regained normal nail contours postoperatively, but one patient developed a local recurrence 1 year after operation. Histologically, an accessory germinal matrix was observed at the distal end of the lesion in all five cases. Change in pressure around the lesion seemed to have induced the formation of this accessory germinal matrix.

Hard palate mucosal grafts for defects of the nail bed

The authors present 2 children in whom a hard palate mucosal graft was used for a defect of the nail bed after resecting subungual exostosis. After the tumor was resected with the overriding nail bed, hard palate mucosa without periosteum was grafted to the nail bed defect. In both patients the graft took completely, and within 2 weeks after the operation the patients were able to enjoy activities of daily life, including athletic movement, without any symptoms. Nail growth was uneventful and was complete in 4 or 5 months after the operation without any complications. The authors think that a hard palate mucosal graft is a valid choice for a defect of the nail bed, and the mucosa does not need to be harvested with periosteum. The grafting of hard palate mucosa without periosteum to a defect of the nail bed contributes to a shorter healing time, resulting in a reduction in the period of restriction of movement in activities of daily life, and this is a great advantage in children.

A nonsense mutation in MSX1 causes Witkop syndrome

Witkop syndrome, also known as tooth and nail syndrome (TNS), is a rare autosomal dominant disorder. Affected individuals have nail dysplasia and several congenitally missing teeth. To identify the gene responsible for TNS, we used candidate-gene linkage analysis in a three-generation family affected by the disorder. We found linkage between TNS and polymorphic markers surrounding the MSX1 locus. Direct sequencing and restriction-enzyme analysis revealed that a heterozygous stop mutation in the homeodomain of MSX1 cosegregated with the phenotype. In addition, histological analysis of Msx1-knockout mice, combined with a finding of Msx1 expression in mesenchyme of developing nail beds, revealed that not only was tooth development disrupted in these mice, but nail development was affected as well. Nail plates in Msx1-null mice were defective and were thinner than those of their wild-type littermates. The resemblance between the tooth and nail phenotype in the human family and that of Msx1-knockout mice strongly supports the conclusions that a nonsense mutation in MSX1 causes TNS and that Msx1 is critical for both tooth and nail development.

Drugs in nails: physiology, pharmacokinetics and forensic toxicology

In recent years, drug analysis in keratinised matrices, such as hair and nails, has received considerable attention because of several advantages over drug testing methodologies employing body fluids, such as urine or serum. For example, keratinic matrices, such as finger- and toenails, can accumulate drugs during long term exposure. Drugs are incorporated into nails by a double mechanism: (i) deposition into the root of the growing nail via the blood flow in the nail matrix; and (ii) incorporation via the nail bed during growth from the lunula to the beginning of the free margin. Together, these account for a wide retrospective window of drug detection. Nails can provide a good forensic matrix for the detection of drugs of abuse. Indeed, the international literature has reported the use of nail analysis in postmortem detection of drugs of abuse, drug testing in the workplace and drug screening to detect prenatal exposure, even though further studies are needed for correct interpretation of the data obtained. Another application of drug analysis in nails consists of the possibility of detecting the presence of an antimycotic at the site of action during antifungal therapy for patients with onychomycosis. When available, this evidence has permitted drug treatment of a shorter duration and reduced toxicity. However, so far the potential of drug monitoring in nails still lacks harmonisation and validation of analytical methodologies and a better comprehension of the possible correlation between drug concentrations in the matrix and period of exposure.

Keratin expression in the normal nail unit: markers of regional differentiation

Differentiation within the nail unit was examined using a range of antikeratin monoclonal antibodies including the recently described antibody LHTric-1, specific to the acidic hair-type keratin Ha1. Keratinocytes of the nail matrix, nail bed and the digit pulp were characterized by different patterns of keratin expression. Nail matrix was the sole site of expression of Ha1, which colocalized in suprabasal matrix epidermis with epidermal keratins K1 and K10. Small amounts of K17 were found at the apex of the matrix in some cases. K6 and K16 were found where the epidermal surface folds forwards to become the ventral aspect of the proximal nail fold. The nail bed was distinguished by the absence of hair-type keratin Ha1 and the absence of markers of cornified epidermis and mucosal differentiation K1/K10 and K4/K13, respectively, while K6, K16 and K17 were detected. The basal keratin conformation marker, LH6, was expressed suprabasally throughout the nail bed. This complement of keratins exists in the nail bed in the absence of notable proliferative activity, and suggests a state of minimally developed differentiation which may be afforded by the physical or biological properties of the overlying nail. Keratins, K6, K16 and K17 were all found in the digit pulp in limited amounts, possibly in association with the epidermal component of the eccrine duct. The simple epithelial keratins, K7, K8 and K18, were found in small amounts in the specimens from younger individuals, mainly in epibasal cells of the apex of the matrix and in putative Merkel cells.

Current management of onychomycosis. An overview

Until recently pedal onychomycosis, particularly when it affected several nails or involved a large nail plate area, was often regarded as untreatable. The advent of new therapies such as itraconazole, terbinafine, and fluconazole has been a significant and welcome addition to the armamentarium of therapies at the disposal of the physician. These drugs appear in the nail plate within days of starting oral therapy, being taken up by both the nail matrix and the nail bed. The duration required for effective therapy has been reduced, while the efficacy rates and cost-effectiveness have increased compared with the older treatments, such as griseofulvin. Some of the newer agents appear to have a wider spectrum of activity. Thus far, the newer agent have exhibited a low risk to benefit ratio. I may be possible to combine oral therapies with topical and surgical treatments, thereby further increasing efficacy rates and the cost-effectiveness while decreasing adverse effects and duration of oral therapy.

Early events in the invasion of the human nail plate by Trichophyton mentagrophytes

A new in vitro model for the study of nail invasion by dermatophyte fungi was developed. The dermatophyte Trichophyton mentagrophytes, and fragments of finger-nails and toe-nails were used. Arthroconidia were inoculated on the ventral surface of the nails. After 6 h, adherence and germination of arthroconidia was observed. By 16 h, small germ tubes with side branches were evident. At about 24 h, micro-colonies had become established. At 48 h, a mycelium had formed, and at about 72 h most of the nail fragment was covered with fungal growth. Nail penetration occurred from the ventral surface through the intercellular spaces, and with longer incubation all three layers were invaded by arthroconidia growing through channels. Nail invasion occurred in the absence of added nutrients. Dermatophyte fungi appeared to invade the nail by a combination of mechanical and chemical factors. The model provides a substrate to study the pharmacokinetics and bioavailability of new antifungal agents in situ.

Antifungal agents: an overview. Part II

The recent introduction of a new generation of antifungal drugs promises to alter significantly therapy for both systemic and superficial mycoses, in particular, onychomycosis. This article presents an in-depth review of the azoles (the triazoles itraconazole and fluconazole), the allylamines (naftifine and terbinafine), and the morpholine derivative amorolfine.

Ligamentary structure of the base of the nail

The authors report the results of 115 dissections of the base of the distal phalanx of fingers and toes. In 85% of cases including hypoplastic supernumerary digits, there is a connective ligament-like structure. It is a dorsal expansion of the lateral ligament of the distal inter-phalangeal joint arising from the intermediate phalanx and ending in the matrix and the lunula. This ligament may have a role in biomechanical strains on the nail. It can explain some dystrophic nails associated with some malpositioned joints in fingers or toes.

Determinants of nail thickness and length

The determinants of final nail thickness and length at its point of detachment at the onychodermal band were studied in 20 normal great toe-nails, removed after injury, by correlating measurements of nail thickness, taken at six anatomical points, with length of nail and its lunular (matrical) and ventral nail components. Final nail thickness at the onychodermal band was related to initial thickness of the proximal matrix, and independently to the lengths of the lunula and ventral nail, but not to final nail length. There was an increase in nail thickness with age, particularly in the first two decades; this appeared not to be due to a decrease in frictional loss of nail.

Fingernail creatinine as a predictor of prior renal function

When a patient presents with renal failure, it is often difficult to ascertain whether the individual is suffering from acute or chronic renal failure. Fingernail creatinine might help to differentiate between the two. To test this possibility, the relationship between the fingernail creatinine and the serum creatinine obtained concurrently or 1 or more months previously was examined in 22 normal adults, nine patients with acute renal failure, seven patients with chronic renal failure not undergoing dialysis, 16 maintenance hemodialysis patients, and 33 patients with a functioning renal transplant who had been transplanted 0.2 to 3.9 months (n = 21) or 4.3 to 33 months previously (n = 12). Fingernail creatinine was significantly greater than normal in the patients with chronic renal failure, patients undergoing maintenance hemodialysis, and patients who had a functioning renal transplant implanted 0.2 to 3.9 months previously. In contrast, fingernail creatinine was not different from normal in the patients with acute renal failure and in patients who had a functioning renal transplant placed 4.3 to 33 months previously. In the maintenance hemodialysis patients, fingernail creatinine showed the strongest correlation with the serum creatinine obtained between 5 and 10 months previously, with the highest correlation at 9 months. In the renal transplant recipients, the fingernail creatinine decreased to normal or near normal values within approximately 90 to 120 days after transplantation. These findings indicate that fingernail creatinine may reflect the serum creatinine values several months previously. The fingernail creatinine may help to identify whether patients have recent onset as compared with longstanding renal failure.

Continuous formation of nail along the bed

To resolve the problem of whether nail is formed continuously along the length of the nail bed as well as by the germinal matrix, nail thickness was measured at six anatomical points along the length of 20 normal big toe-nails removed after injury. Nail water content was constant at 9-10% along the nail length, and the nails did not shrink with dehydration. Approximately 79% of nail thickness was contributed by the nail matrix, and 21% by the nail bed. The rate of nail production was constant at 0.13 mm/mm along the lunula and 0.027 mm/mm along the whole bed from the distal lunula to the point of separation at the onychodermal band; the fractional change in linear growth and thickness showed less variation than absolute change. The continuous production of nail by the bed provides a simple biological solution to the problem of attachment of a continuously moving plate. It provides a source of entry of drugs into the distal nail plate, and a rationale for the use of much shorter courses of antifungal drugs than previously believed possible.

Surgical anatomy of the nail unit

A gross anatomic exploration of the nail unit was performed. The characteristic gross components of the nail unit and its relationship to the digital anatomy are described and presented in detail. Each segment of the nail unit is illustrated both photographically and with artistic illustration. It is our intention that through a simple gross dissection the nail structural unit may be better understood.