Aids and Insects

affected, and sometimes healing is associated with scar formation. Skin lesions are infrequent in mucous membrane pemphigoid. Similar oral lesions may be seen in other subepithelial disorders such as epidermolysis bulbosa, dermatitis herpetiformis, and linear IgA disease." Oral lesions are uncommon in bullous pemphigoid, but they are seen in most patients with pemphigus vulgaris, often preceding the appearance of skin bullae. The oral blisters of pemphigus rupture early on to leave painful and persistent irregular erosions. Biopsy of the oral mucosa for conventional histological examination and for direct immunostaining is frequently needed to distinguish these mucocutaneous disorders, particularly to exclude pemphigus,9 though exfolitive cytology is of little value. Erythema multiforme of the mucous membranes (Stevens-Johnson syndrome) mostly affects young men and is usually readily distinguished on clinical grounds: the presentation is often acute or recurrent, and bloodstained crusting of swollen lips may be a helpful diagnostic sign. Most infective mouth ulcers are caused by viral infections and are usually non-recurrent, scattered small round ulcers seen in a febrile child or young adult. Primary herpetic stomatitis is the most common viral cause of mouth ulcers. It presents with scattered vesicles and ulcers and a diffuse gingivitis. Recurrent intraoral herpes simplex virus infections are rare, though they may occur in immunocompromised patients'0 including those with AIDS." Other herpes virus infections such as chickenpox and infectious mononucleosis may be complicated by mouth ulcers, and there may be unilateral mouth ulcers in zoster of the mandibular or maxillary divisions of the trigeminal nerve. Enteroviruses may cause mouth ulcers in herpangina and in hand, foot, and mouth disease. Diagnosis of these infections is primarily clinical. Viral cultures are still the most sensitive method of diagnosing infection with herpes simplex virus, though this takes from two to four days and sometimes longer. The most rapid diagnostic technique is electron microscopy: this may take only minutes to perform and is very sensitive when intact vesicles are examined but much less so when lesions are at a later stage. Single serological assays are of little value in the diagnosis of acute herpes simplex virus infection, but seroconversion between acute and convalescent serum samples is diagnostic of primary infection.'2 Bacterial infections may cause mouth ulcers in tuberculosis and in all stages of syphilis, but fungal causes are rare in Britain. Culture, dark ground microscopy, and serology may be required to confirm a clinical suspicion of the chronic bacterial infections in groups at risk who have a chronic ulcer or ulcers or in those with ulcers of unusual appearance.