<unk>  can be of 2 types, low grade chronic<unk>  or high grade chronic<unk> . Low grade chronic<unk>  involves less than 10 villi containing lymphocytes. Low grade chronic<unk>  can be either focal or multifocal. Focal has involved villi on only one glass slide, while multifocal has involved villi on at least two slides. High grade chronic<unk>  has more than 10 inflamed villi per focus. High grade chronic<unk>  is differentiated into diffuse and patchy. The term patchy is used if less than 30% of distal villi are involved. The term diffuse is used if more than 30% of distal villi are involved.<unk>  has 2 prominent distinct patterns. Approximately 50% of the cases only involve the distal villi (mature intermediate and terminal villi) and do not involve the proximal stem villi, the anchoring villi embedded in the basal plate, and the chorionic plate. The second most common pattern (roughly 30% of<unk>  cases) involves the proximal stem villi (and possibly the chorionic plate) and the distal villi usually. This type of<unk>  is linked with foetal vascular obtrusive lesions (Obliterative Foetal Vasculopathy).<unk>  does not have specific clinical signs and symptoms suggesting diagnosis; but an analysis of the inflammatory filtrate can aid in diagnosis. The composition of inflammatory infiltrate in<unk>  on a cellular level is primarily macrophages and lymphocytes. The relative proportions of cells vary case by case. The lymphocytes present in<unk>  are predominantly CD8+ T-cells then CD4. There is usually a ratio of 0.1 to 0.5 for CD4/CD8. The macrophages present are mainly Mac387-, followed by CD68 and HAM56+. Class 2 major histocompatibility complex (MHC) antigens on macrophages are up-regulated at sites of<unk> . Neutrophils should not be present at sites of<unk> .<unk>  is a condition involving inflammation and not inflammation. High numbers of neutrophils are present in infectious<unk>  and not<unk> . Histopathology Histomorphologically,<unk>  is characterized by a lymphocytic infiltrate of the chorionic villi without a demonstrable cause. Plasma cells should be absent; the presence of plasma cells suggests an infective<unk> , e.g. CMV infection. Image:<unk>  - intermed mag. Intermed. mag. Image:<unk>  - high mag. High mag. Differential diagnosis<unk>  is often confused with infectious<unk> . They can be differentiated by the following characteristics: There are no signs of infection in either the mother or the infant with<unk> . Infectious villi there is both maternal and foetal infection.<unk>  is more common than infectious<unk> ; Infectious<unk>  is present in approximately 1–4 births per 1000 births.<unk>  is present in approximately 76–136 births per 1000 births.<unk>  occurs in the term placenta, in the late third trimester of pregnancy. Infectious<unk>  occurs at the early-third to late-second trimester of the pregnancy. Infectious<unk>  involves a greater part of the placenta (umbilical cord, chorionic plate, membranes) compared to<unk>  (terminal and stem villi). Histologically<unk>  is characterised with more lymphocytes present than infectious<unk> . Recurrence of infectious<unk>  is rare.<unk>  has a 10% to 15% recurrence rate.
Villitis of unknown etiology
Rhinitis medicamentosa
Mouth and genital ulcers with inflamed cartilage syndrome
Pyostomatitis vegetans
Tick-borne lymphadenopathy
Lymphedema–distichiasis syndrome
Treponematosis
Staphylococcal infection