Caterpillar bodies of porphyria cutanea tarda ultrastructurally represent a unique arrangement of colloid and basement membrane bodies

A Compendium of Specific Histopathological Bodies in Dermatology

The spectrum of histopathological variations of most of the Dermatological conditions is so wide and overlapping that even with our current vast knowledge of this discipline, it seems to be a tough task for clinicians as well as Dermatopathologists to arrive at a conclusive diagnosis in many cases. However, with the aid of special stains and advanced diagnostic techniques, some characteristic histopathologic features have been defined over the time, among which histopathological bodies or inclusion bodies serve as specific clues. With this perspective in view, an attempt has been made to collate and describe the well-known as well as the lesser-known histopathological bodies seen in various dermatological diseases. The underlying pathogenesis and ultramicroscopic features of these structures have also been outlined in brief.

Diagnostic histochemistry in non-neoplastic skin diseases

Non-neoplastic skin lesions comprise a sizable group of disorders with variable etiologies and clinical manifestations. They can be grouped into vesiculopustular dermatitides; spongiotic and psoriasiform diseases; lichenoid dermatitides; lymphoid infiltrates of the dermis; granulomatous processes; bullous disorders; vasculopathies; panniculitides; deposition disorders; and defects in maintenance of dermal connective tissue. The use of histochemical methods continues to be an indispensable adjunct to conventional microscopy in the further characterization of such lesions. This review considers that topic.

Cutaneous deposits

: The cutaneous deposition disorders are a group of unrelated conditions characterized by the accumulation of either endogenous or exogenous substances within the skin. These cutaneous deposits are substances that are not normal constituents of the skin and are laid down usually in the dermis, but also in the subcutis, in a variety of different circumstances. There are 5 broad categories of cutaneous deposits. The first group includes calcium salts, bone, and cartilage. The second category includes the hyaline deposits that may be seen in the dermis in several metabolic disorders, such as amyloidosis, gout, porphyria, and lipoid proteinosis. The third category includes various pigments, heavy metals, and complex drug pigments. The fourth category, cutaneous implants, includes substances that are inserted into the skin for cosmetic purposes. The fifth category includes miscellaneous substances, such as oxalate crystals and fiberglass. In this article, the authors review the clinicopathologic characteristics of cutaneous deposition diseases, classify the different types of cutaneous deposits, and identify all the histopathologic features that may assist in diagnosing the origin of a cutaneous deposit.

Cutaneous porphyrias part I: epidemiology, pathogenesis, presentation, diagnosis, and histopathology

The porphyrias are a group of disorders characterized by defects in the heme biosynthesis pathway. Many present with skin findings including photosensitivity, bullae, hypertrichosis, and scarring. Systemic symptoms may include abdominal pain, neuropsychiatric changes, anemia, and liver disease. With advances in DNA analysis, researchers are discovering the underlying genetic causes of the porphyrias, enabling family members to be tested for genetic mutations. Here we present a comprehensive review of porphyria focusing on those with cutaneous manifestations. In Part I, we have included the epidemiology, pathogenesis, presentation, diagnosis, and histopathology. Treatment and management options will be discussed in Part II.

The sensitivity and specificity of "caterpillar bodies" in the differential diagnosis of subepidermal blistering disorders

Caterpillar bodies are eosinophilic, elongated, segmented bodies located within the roofs of blisters and are considered to represent a specific histopathologic feature of porphyric bullous eruptions, including porphyria cutanea tarda and erythropoietic protoporphyria. The possibility that similar or identical bodies may be present in other disorders prompted further study exploring the specificity of caterpillar bodies in the differential diagnosis of subepidermal vesiculobullous disorders. Seventy-six cases exhibiting subepidermal clefting were reviewed by light microscopy. "Classic" caterpillar bodies were present in porphyria cutanea tarda (6 of 14) and 1 case representing either venous stasis-associated bulla or possibly bullosis diabeticorum. Caterpillar body-like clusters were present in porphyria cutanea tarda (5 of 14), erythropoietic protoporphyria (1 of 3), bullous pemphigoid (7 of 24), and junctional or dystrophic epidermolysis bullosa (3 of 5). In some cases, classic caterpillar body and caterpillar body-like clusters coexisted in a blister roof. Caterpillar bodies or caterpillar body-like clusters were not identified in any cases of dermatitis herpetiformis, linear IgA bullous dermatosis, bullous erythema multiforme, epidermolysis bullosa acquisita, or wound-healing reactions. In contrast to caterpillar bodies, caterpillar body-like clusters were negative for PAS or Type IV collagen stains. In conclusion, caterpillar bodies appear to represent a specific feature of porphyria cutanea tarda (specificity, 98%) but were present in less than half of those cases in this study (sensitivity, 43%). Caterpillar body-like clusters are less specific and may be present in porphyria cutanea tarda, erythropoietic protoporphyria, pseudoporphyria, bullous pemphigoid, epidermolysis bullosa, and epidermolysis bullosa acquisita.

Porphyria cutanea tarda

Porphyria cutanea tarda (PCT) is a metabolic disorder of haem biosynthesis caused by decreased activity of uroporphyrinogen decarboxylase. Porphyria cutanea tarda is manifest by fragility, erosions, bullae, milia and scars on sun-exposed skin. Excess porphyrins in the skin interact with light of approximately 400 nm-wavelength radiant energy, forming reactive oxygen species. Porphyria cutanea tarda is categorized as familial, acquired or toxic. Factors that may induce clinical expression of PCT in susceptible individuals include alcohol, oestrogen, iron, polyhalogenated compounds and viral infections. Porphyria cutanea tarda is associated with an increased incidence of the haemochromatosis gene. Treatments for PCT include withdrawal of aggravating factors, phlebotomy and oral antimalarial medications.