Lecture 3 Part 2 PDF

Impetigo Impetigo is a common superficial cutaneous infection with Staphylococcus that can occur at any age. It is typically most common in early childhood. Impetigo presents as a superficial ulcer with sticky, honey-colored crusting. The most common area involved in children is the face, especial...

Impetigo Impetigo is a common superficial cutaneous infection with Staphylococcus that can occur at any age. It is typically most common in early childhood. Impetigo presents as a superficial ulcer with sticky, honey-colored crusting. The most common area involved in children is the face, especially peri-oral areas (Figure 3.8). In this setting, impetigo can look very similar to herpes simplex, and a culture may be necessary to differentiate the two. The lesions are typically painful, but the patient should not have fever or be systemically ill. Occasional patients will present with blisters at the site of lesions, this is called bullous impetigo (Figure 3.9). Typical impetigo is usually caused by Staphylococcus aureus, and can be confirmed by swabbing the lesion and sending the swab for bacterial culture. Bullous impetigo is caused by strains of Staph aureus that produce an exfoliative toxin. This toxin is a protein which cleaves desmoglein type 1. Desmoglein type 1 is the major protein found in desmosomes in the superficial epidermis. When this protein is cleaved by the toxin, the keratinocytes are no longer able to adhere to each other, and this leads to a blister forming in the epidermis. In bullous impetigo, the toxin is released locally, leading to blister formation at the site of the infection. When impetigo is suspected, a bacterial culture should be taken. However, treatment should be initiated prior to the culture results becoming available. In mild cases, treatment with the topical antibiotic, mupirocin ointment, is sufficient. In more severe or widespread cases, including Staph Scalded Skin Syndrome, oral antibiotics with good Staph coverage, such as dicloxacillin or cephalexin should be used. Café-au-Lait Macule Café-au-lait macules are fairly common and are usually incidental findings unrelated to any underlying disease. They are more common in African-Americans than in Caucasians. Café-au-lait macules present as flat, sharply bordered homogenous brown macules (Figure 3.10). They may be present at birth, and new lesions may continue to appear for the first several years of life. If a patient has 5 café-au-lait macules over 5 mm in diameter, they should be thoroughly evaluated for neurofibromatosis. Infants with one or two café-au-lait macules are not at particular risk for neurofibromatosis. Infants with more than two café-au-lait macules should be observed, and if more macules develop, evaluation for neurofibromatosis should be considered. There is no need for treatment of the café-au-lait macules. Ash Leaf Macules Ash leaf macules are uncommon. Ash leaf macules are white, flat macules. They are usually oval shaped and measure 1-3 cm in diameter (Figure 3.11). They are often present at birth, but may develop throughout the first two years of life. Ash leaf macules can be a manifestation of tuberous sclerosis. Tuberous sclerosis should be suspected strongly in any child with multiple ash leaf macules and in any child with seizures or mental retardation and even one ash leaf macule. There is no need for treatment of the ash leaf macules, other than evaluation for possible tuberous sclerosis. Hemangioma Hemangiomas are very common, affecting up to 10-15% of infants. They typically appear within the first few weeks of life, but may be present at birth. They are more common in females than males, they are also more common in premature infants and in infants whose mothers underwent chorionic villus sampling. There are two major types of hemangiomas: superficial and deep Superficial hemangiomas are typically bright red with a pebbly surface (Figure 3.12) (Figure 3.13). They are sharply demarcated from the surrounding skin. They typically start as a small lesion that grows rapidly for up to one year, then stops growing and slowly shrinks until they disappear. 50% of hemangiomas disappear by age 5, and 90% disappear by age 9. Deep hemangiomas are usually slightly bluish in color (Figure 3.14). It is often difficult to tell the exact borders of a deep hemangioma. Mixed hemangiomas are also relatively common. These are combination lesions with a superficial hemangioma overlying a deep hemangioma. Superficial hemangiomas are divided into typical types and plaque types. The typical types are well defined, round, papules or nodules that typically have a greater height than width (see Figure 4.12). Plaque types are flat, slightly raised lesions that cover a large area and have a much greater width than height. Plaque type hemangiomas are frequently associated with other congenital anomalies (Figure 3.15). Superficial hemangiomas commonly ulcerate. This is thought to be the sequelae of rapid growth (Figure 3.16) (Figure 3.17). The pathogenesis of hemangiomas has become clearer in recent years. Hemangiomas express several proteins that are relatively specific for placental tissue. This, combined with the fact that hemangiomas grow for about 9 months, are more common in female infants, and are more common after chorionic villus sampling, has led to the hypothesis that hemangiomas represent a proliferation of placentally-derived angioblasts that implant in the developing fetus. Most hemangiomas require no treatment – they will spontaneously resolve. However, hemangiomas located next to critical structures (eye, mouth, genitals) can cause significant problems, and treatment to accelerate resolution should be considered. Common treatments include intralesional steroid injections, systemic steroids, and most recently, propranolol. Superficial hemangiomas commonly ulcerate. These ulcerations are very painful. They are commonly treated with antibiotic ointments and non-stick dressings, both of which help relieve pain and prevent infection. Consideration of oral antibiotics should be given if infection is suspected. Laser treatment can also speed resolution. Mastocytosis Mastocytosis is a relatively uncommon disorder. Most cases present in children. The two most common forms of cutaneous mastocytosis are solitary mastocytomas and urticaria pigmentosa. Urticaria pigmentosa is more common. In both forms, the hallmark lesion is a brown-yellow papule or nodule that will often develop a hive around it when it is rubbed. A solitary mastocytoma is a single lesion, while in urticaria pigmentosa, there are multiple, similar lesions (Figure 3.18), numbering from several lesions up to several thousand lesions. The red lesion in Figure 4.18 was rubbed, causing the mast cells to release their granules and leading to a hive-like lesion. This is called Darier’s sign. In adults, there are other forms of mastocytosis, including TMEP (telangiectasia macularis eruptive perstans) in which the lesions are flat, tan spots with telangiectasias. In rare cases, this disease can be systemic, with mast cells infiltrating and proliferating in multiple organs (liver, lungs, bone marrow, GI tract, etc.). Some cases are also associated with myelodysplastic syndromes or even with mast cell leukemia. Mastocytosis is a disease of abnormal mast cell proliferation, which make up individual lesions. There are several mechanisms that can lead to excessive mast cell proliferation. The most interesting and well described mechanism involves the c-kit gene, which encodes the protein KIT, a tyrosine kinase receptor. There are numerous c-kit mutations that lead to constitutive activation of KIT, which, in turn, promotes proliferation of mast cells and prevents apoptosis. Patients with c-kit mutations are more likely to have prolonged, extensive, systemic disease than patients without these mutations. Treatment of mastocytosis is directed at relieving symptoms causes by release of mast cell mediators, especially histamine. Thus, antihistamines are the mainstay, along with avoidance of known mast cell degranulators, such as opioids and alcohol. Other therapies include topical steroids and oral cromolyn sodium. The latter prevents mast cells from degranulating. Histiocytosis Histiocytoses are rare, but serious, diseases. They may present at birth or soon thereafter, or they may present later in childhood. Historically, histiocytoses have been divided into four variants: Letterer-Siwe disease, Hand- Schuller-Christian disease, Eosinophilic granuloma, and Hashimoto-Pritzker disease. Letterer-Siwe disease typically presents in the first year of life with pink papules, pustules, or vesicles in the scalp, retroauricular, and diaper areas. The lesions may become widespread (Figure 3.19). Petechiae and scale are frequently present. This is the most severe variant, and widespread systemic involvement frequently leads to a poor prognosis. The most commonly involved organs are the liver, spleen, lungs, lymph nodes, and bones. Hand-Schuller-Christian disease consists of the triad of diabetes insipidus, exophthalmos, and lytic bone lesions, caused by proliferation of histiocytes in the pituitary gland, orbit, and bone, respectively. It typically presents early in childhood, but after the first year of life. It is usually slowly progressive. Skin lesions are present in less than half of patients. Eosinophilic granuloma typically presents as a single, lytic bone lesion due to localized proliferation of histiocytes. Hashimoto-Pritzker disease is also called congenital self-healing reticulohistiocytosis. It presents in the first weeks or months of life, with widespread red, brown papules and nodules which crust over and involute within several months. The histiocytoses are felt to represent abnormal proliferations of Langerhans cells, which are normally professional antigen presenting cells of the skin. These cells are generally defined by the presence of both CD1a and Birbeck granules. Birbeck granules are specialized phagosomes involved in acquiring, processing, and presenting antigens. The pathogenesis of the histiocytoses is unknown. These diseases are generally classified as clonal neoplasms of histiocytes, but it is possible that the cause of proliferation is actually viral or immunologic, rather than due to autologous proliferation secondary to genetic mutations. Treatment is determined by the extent of disease. All patients should undergo a thorough, comprehensive evaluation for systemic involvement, focusing on the reticuloendothelial system, lungs, and skeletal systems. Patients with skin limited disease may be treated with topical steroids, topical chemotherapy, or ultraviolet light. Limited bone disease may be treated with radiation. Disseminated disease generally requires systemic chemotherapy.