Diagnosis of human scabies by epidermal shave biopsy

Approach to the so-called "Invisible Dermatosis": When Subtle Histopathological Findings Guide Diagnosis

ABSTRACT

Invisible dermatosis is a concept that can be applied either to clinical or histopathological findings. We will focus on the dermatopathological aspect of this invisible dermatosis that can be seen as dermatosis with subtle histopathological findings that are mandatory to known to stablish the diagnosis. With a proper approach facing in depth the different skin layers from stratum corneum to subcutaneous tissue combined with some especial stains, special investigations and mostly a proper clinicopathological correlation, the problem of missing out a diagnosis can be decreased. We will review the general aspects for diagnosis and the peculiar findings of an in-depth review of them because it is important to note that minor changes on a skin biopsy do not mean it is disease free. We will review classic clues, we will add some new useful ones, and we will also provide a guide on the special stains helpful, such as periodic acid-Schiff when facing fungi, orcein-Giemsa and van Gieson when altered elastic fibers are suspected, or Pearl and Masson Fontana when an altered skin pigmentation is suspected.

Diagnosis and treatment of scabies: a practical guide

Scabies is a common, highly pruritic infestation of the skin caused by Sarcoptes scabiei var. Hominis. It is a very contagious parasitosis with specific lesions, such as burrows, and nonspecific lesions, such as papules, vesicles and excoriations. The typical areas of the body it affects are finger webs, wrists, axillary folds, abdomen, buttocks, inframammary folds and, in men, the genitalia. It is characterized by intense nocturnal pruritus. Scabies is spread through close personal contact (relatives, sexual partners, schoolchildren, chronically ill patients and crowded communities). Definitive diagnosis is made when the scabies mites or their eggs or fecal pellets can be identified on a light microscope. New techniques for diagnosis include the use of the epiluminiscence microscopy. The most common topical treatments for scabies include lindane and permethrin. Permethrin provides a greater margin of tolerability because of its low inherent toxicity and low percutaneous absorption. Oral ivermectin is the most recently developed treatment for scabies. A single oral dose of ivermectin 200 microg/kg of bodyweight is a well-tolerated and very effective treatment. It is especially indicated in crusted scabies, scabies in immunocompromised hosts and infestations in crowded communities. It is also useful as a simple treatment in the prophylaxis of close contacts.

The role of mast cells in treatment of scabies

OBJECTIVE

The purpose of this study was to recognize the role of mast cells in the pathogenesis of scabies.

METHODS

One hundred and fifty patients and 10 controls were included in the study. Group 1 included 20 patients without previous treatment. In group 2, 80 patients were treated with antiscabietic drugs. Group 3 had 50 patients who received an antiscabietic drug followed by 3 days of crotamiton. Diurnal and nocturnal skin biopsies were taken from group 1. In groups 2 and 3, the biopsies were taken after 2 weeks of treatment. Sections were cut and stained by hematoxylin and eosin and Giemsa stains.

RESULTS

Mast cells were increased in diurnal and nocturnal biopsies. Evident degranulation of mast cells was detected in nocturnal biopsies. The mast cell number decreased to half its pretreatment number in patients treated with antiscabietic drugs and to its normal number in patients treated with antiscabietic drugs followed by 3 days with crotamiton.

CONCLUSION

The number of mast cells are increased in scabietic lesions. This plays a role in the pathogenesis of the clinical and histologic picture of scabies. We recommend that an antiscabietic drug should be followed by 3 days of crotamiton in the treatment of scabies.

Scabies and lice

Scabies and pediculosis, two commonly encountered infestations both having an incidence that is on the rise, are discussed in detail in this article with special emphasis given to their symptomatology, pathogenesis, and treatment.

Scanning electron microscopy of the scabies burrow and its contents, with special reference to the Sarcoptes scabiei egg

An entire burrow of a female Sarcoptes scabiei (var. hominis) mite was examined by scanning electron microscopy during serial transverse sectioning. The elevated roof and the wall were composed of compacted corneocytes. The floor had a smooth surface except at the anterior end. Here it was made up of nucleated stratum granulosum cells, etched in appearance, presumably having been chewed by the mite. The female mite, the larvae, scybala, and eggs were also examined. The ultrastructure of the eggshell surface revealed it to have a distinctive geometric patterning. Cross-sectioning showed this shell or chorion to be composed of an outer layer of minute, closely packed penta- and hexahedrons resting on a thin inner homogenous layer. The polyhedric surface pattern was exactly replicated in the cement substance which attached the egg to the burrow floor. Observations were made on the embryonic positioning which permitted the larvae to emerge from the eggshells in a uniform manner.