NEET MDS Lessons
General Pathology
Lupus erythematosus
- chronic discoid lupus is primarily limited to the skin, while SLE can involve the skin and other systems.
- pathogenesis: light and other external agents plus deposition of DNA (planted antigen) and immune complexes in the basement membrane.
Histology:
- basal cells along the dermal-epidermal junction and hair shafts (reason for alopecia) are vacuolated (liquefactive degeneration)
- thickening of lamina densa as a reaction to injury.
- immunofluorescent studies reveal a band of immunofluorescence (band test) in involved skin of chronic discoid lupus or involved/uninvolved skin of SLE.
- lymphocytic infiltrate at the dermal-epidermal junction and papillary dermis.
Lichen planus is an itchy, violaceous, flat-topped papule highlighted by white dots or lines called Wickham's striae.
- lichen planus may occur in the oral mucosa, where it has a fine white net-like appearance.
- increased epidermal proliferation; ? immunologic; initiated by epidermal injury from drugs, viruses, or topical agents.
- characteristic histologic features include:
- hyperkeratosis
- absence of parakeratosis
- prominent stratum granulosum
- an irregular "saw toothed" accentuation of the rete pegs.
- dermal-epidermal junction obscured by a band-like infiltrate of lymphocytes.
- It is generally self-limiting and resolves spontaneously 1 to 2 years after onset; however, the oral lesions may persist for years.
Eosinophilia:
Causes
-Allergic disorders.
-Parasitic infection.
-Skin diseases.
-Pulmonary eosinophilia.
-Myeloproliferative lesions and Hodgkin's disease.
FUNGAL INFECTION
Histoplasmosis
A disease caused by Histoplasma capsulatum, causing primary pulmonary lesions and hematogenous dissemination.
Symptoms and Signs
The disease has three main forms. Acute primary histoplasmosis is usually asymptomatic
Progressive disseminated histoplasmosis follows hematogenous spread from the lungs that is not controlled by normal cell-mediated host defense mechanisms. Characteristically, generalized involvement of the reticuloendothelial system, with hepatosplenomegaly, lymphadenopathy, bone marrow involvement, and sometimes oral or GI ulcerations occurs, particularly in chronic cases
Progressive disseminated histoplasmosis is one of the defining opportunistic infections for AIDS.
Chronic cavitary histoplasmosis is characterized by pulmonary lesions that are often apical and resemble cavitary TB. The manifestations are worsening cough and dyspnea, progressing eventually to disabling respiratory dysfunction. Dissemination does not occur
Diagnosis
Culture of H. capsulatum from sputum, lymph nodes, bone marrow, liver biopsy, blood, urine, or oral ulcerations confirms the diagnosis
Peutz-Jeghers syndrome
1. Lesions appear as small, melanotic, and freckle-like. They can be found on the skin, oral mucosa, lips, feet, and hands.
2. May also present with intestinal polyps, which may develop into a gastrointestinal carcinoma.
3. Genetic transmission: autosomal dominant.