AH is characterized by spontaneous hemorrhages in patients without prior history of hemophilia. Skin bleedings ranging from petechia to ecchymosis are common. Furthermore, most patients experience epistaxis, gastrointestinal hemorrhages provoking melena and/or hematochezia, and hematuria due to lesions of the urinary tract. Retroperitoneal hematoma has repeatedly been reported. Affected individuals are prone to soft tissue hematomas and muscle bleeds. While the latter is also typical of congenital hemophilia, the genetic disorder is generally associated with hemarthroses, but these are rarely observed in AH patients [2]. Muscle bleeds may lead to compartment syndrome. Fortunately, few patients sustain an intracranial hemorrhage [7], but the aforementioned bleedings may still cause life-threatening hemorrhagic shock. In less than 20% of patients, the bleeding diathesis is only registered upon trauma, childbirth or surgery [5]. On the other hand, patients may present with symptoms consistent with anemia, i.e., fatigue, headaches, palpitations, dyspnea, and cyanosis. Here, anemia is the result of occult hemorrhages. Symptoms may vary over time, hemorrhages aren't usually limited to a specific organ system, may become apparent after an episode of occult bleedings a vice versa. A minority of patients, about 6%, remains asymptomatic and the suspicion of coagulopathy arises from routine measurements of coagulation times and incidental detection of anomalies [3].

• Subcutaneous Bleeding

  This disorder is characterized by spontaneous and post-traumatic subcutaneous bleeds and massive mucosal hemorrhages. [ncbi.nlm.nih.gov]

• Easy Bruising

  This results in people bleeding longer after an injury, easy bruising, and an increased risk of bleeding inside joints or the brain. Those with a mild case of the disease may have symptoms only after an accident or during surgery. [play.google.com]

  He had not history of bleeding diathesis diagnosed in him or a family member and had no reported easy bruising or bleeding previously. He had no recent medication changes. [uscmedicine.blog]

  They may experience joint bleeds or easy bruising. [20] Mild haemophilia may only be discovered later, usually after an injury or a dental or surgical procedure. [en.wikipedia.org]

  These included knee hemarthrosis and psoas hematoma formation following minor trauma, prolonged bleeding after a minor dental procedure, and 2 years of easy bruising. [hematologyandoncology.net]

• Anemia

  Anemia is also common in AHA patients, but the cause of anemia is rarely reported. [journals.lww.com]

  Laboratory evaluations were done and showed mild anemia (HB=10.7 gr/Dl) and prolonged partial thrombin time (PTT=80 second). [austinpublishinggroup.com]

  A 79-year-old man was introduced from other hospital by cerebral infarction and severe anemia. His left thigh and leg were swollen with subcutaneous bleeding. Activated partial thromboplastin time was 99.4 seconds. [ncbi.nlm.nih.gov]

  The patient had developed worsening anemia for past few months and had needed three blood transfusions for symptomatic anemia within past 2 months. [tandfonline.com]

  His anemia worsened and his hemoglobin (Hb) level reached 6.3 g/dL, requiring red blood cell (RBC) transfusions for 5 d consecutively. [wjgnet.com]

• Ecchymosis

  After 10 weeks, he developed an ecchymosis of the right upper extremity, in the absence of past or family history of bleeding disorder. [ncbi.nlm.nih.gov]

  The patient manifested spontaneous ecchymosis (Fig. 1–3). [termedia.pl]

  Five months after delivery, the patient started noticing multiple ecchymosis, which started from the buttock with extension to the lower extremities, variable in size from 3 cm to about 6 cm, associated with on and off gum bleeding. [jahjournal.org]

  On hospital day 29, the symptoms of OHSS lessened and the patient gradually improved, but she developed gross haematuria and ecchymosis on her right leg. [academic.oup.com]

  Bleeding is mostly mucocutaneous or in soft tissues such as hematuria, gastrointestinal bleeding, ecchymosis or hematomas, as compared to hemarthrosis in younger patients with congenital hemophilia. [cureus.com]

• Fatigue

  On the other hand, patients may present with symptoms consistent with anemia, i.e., fatigue, headaches, palpitations, dyspnea, and cyanosis. Here, anemia is the result of occult hemorrhages. [symptoma.com]

  Symptoms of PSGN can include: dark, reddish-brown urine, swelling (edema), especially in the face, around the eyes, and in the hands and feet, decreased need to pee or decreased amount of urine, feeling tired due to low iron levels in the blood (fatigue [nccid.ca]

  He also reported a 2-year history of persistent and progressively worsening fatigue likely related to iron-deficiency anemia in the setting of occult gastrointestinal bleed and uncontrolled UC. [hematologyandoncology.net]

• Dyspnea

  On the other hand, patients may present with symptoms consistent with anemia, i.e., fatigue, headaches, palpitations, dyspnea, and cyanosis. Here, anemia is the result of occult hemorrhages. [symptoma.com]

  Herein, we report the case of an immunocompetent 4-year-old boy who presented with cough, intermittent fever, and dyspnea attributed to penicillin-intermediate-resistant S. viridans-related community-acquired pneumonia. [indianpediatrics.net]

  The most common symptom at the time of presentation was fever, followed by dyspnea. The initial symptom was stroke in 5 patients (3 ischemic and 2 hemorrhagic). In 7 patients, the usual cutaneous manifestations of endocarditis appeared. [revespcardiol.org]

• Hoarseness

  Cough, rhinorrhea, hoarseness, oral ulcers, and conjunctivitis are not typically seen in patients with group A strep pharyngitis and are therefore strongly suggestive of a viral etiology. [nccid.ca]

• Melena

  Additional symptoms may include epistaxis, gastrointestinal and/or urogenital bleeding, spontaneous bruising, melena, and hematuria. [orpha.net]

  Furthermore, most patients experience epistaxis, gastrointestinal hemorrhages provoking melena and/or hematochezia, and hematuria due to lesions of the urinary tract. Retroperitoneal hematoma has repeatedly been reported. [symptoma.com]

  Other manifestations include muscle hematoma, melena, and hematuria and gastrointestinal bleeding [1,2]. Similarly, our case had an 82-year-old male who presented with hematuria and dysuria. [cureus.com]

  As gastrointestinal bleeding (melena, due to multiple peptic ulcers) occurred one year earlier, treated with endoscopic haemostasis and blood transfusion, aspirin was stopped and substituted for clopidogrel. [hindawi.com]

  Other frequent manifestations of acquired hemophilia include melena, hematuria, and iatrogenic bleeding, particularly after attempts to insert intravenous (IV) lines. [emedicine.medscape.com]

• Abdominal Pain

  Go to: Abstract The author report a case involving a 60-year-old man with acquired hemophilia who presented with sudden-onset left abdominal pain and exhibited retroperitoneal hematoma and hemothorax. [pc.jksronline.org]

  Early signs and symptoms of necrotizing fasciitis include fever, severe pain and swelling, and redness at the wound site. Early signs and symptoms of STSS may include fever, dizziness, confusion, low blood pressure, rash and abdominal pain. [health.ny.gov]

  She had 2 artificial abortions, and one abdominal delivery without significant bleeding. Three days prior to the appearance of bleeding, she had been prescribed cephalosporin and proton pump inhibitors for 2 days due to abdominal pain and diarrhea. [journals.lww.com]

  Clinical course summary He developed acute abdominal pain with associated nausea. Blood tests revealed an amylase of 1641 units per liter (U/L) and he was diagnosed with pancreatitis. [bjuinternational.com]

  Abdominal pain, nausea, and vomiting might be present especially among children. [nccid.ca]

• Hematochezia

  A 33-month-old girl who presented with hematochezia and ecchymotic skin lesions was diagnosed with Mycoplasma pneumoniae pneumonia by serology and polymerase chain reaction. [ncbi.nlm.nih.gov]

  Furthermore, most patients experience epistaxis, gastrointestinal hemorrhages provoking melena and/or hematochezia, and hematuria due to lesions of the urinary tract. Retroperitoneal hematoma has repeatedly been reported. [symptoma.com]

• Rectal Bleeding

  This underlying immunologic disorder was therefore associated with AHA in this patient, in whom bleeding tendency had been triggered by NSAIDs. Case 3. A 87-year-old woman presented with persistent rectal bleeding and large ecchymoses. [hindawi.com]

• Bleeding Gums

  […] after your teeth and gums helps you avoid problems such as gum disease, which can cause bleeding. [nhs.uk]

• Hypertension

  Patient had a history of diabetes and hypertension for the past 3years for which he was taking oral hypoglycemics (glimepiride, glucophage) and anti-hypertensives (amlodipine). [medcraveonline.com]

  Case presentation A 60-year-old Sri Lankan woman with a background of longstanding hypothyroidism, diabetes mellitus, hypertension, hyperlipidaemia and bronchial asthma developed spontaneous cutaneous purpura and a limb-threatening intramuscular haematoma [jmedicalcasereports.biomedcentral.com]

  His past medical history included type 2 diabetes mellitus, arterial hypertension, prostatic hypertrophy, psoriasis, and arthrosis. At that time he was taking nonsteroidal anti-inflammatory drugs (NSAIDs) because of back pain. [hindawi.com]

  Case The patient is a 70 year old Hispanic female with a past medical history significant for hypertension, GERD, osteoarthritis, and poorly controlled asthma, including a hospitalization for an asthmatic exacerbation eight weeks prior to her diagnosis [omicsonline.org]

• Cyanosis

  On the other hand, patients may present with symptoms consistent with anemia, i.e., fatigue, headaches, palpitations, dyspnea, and cyanosis. Here, anemia is the result of occult hemorrhages. [symptoma.com]

• Palpitations

  On the other hand, patients may present with symptoms consistent with anemia, i.e., fatigue, headaches, palpitations, dyspnea, and cyanosis. Here, anemia is the result of occult hemorrhages. [symptoma.com]

• Tachycardia

  On admission, the comatose patient showed 180/min of tachycardia and unmeasurable blood pressure on the assist ventilation. Light reflex was prompt. The body temperature was 40.1 °C. [ann-clinmicrob.biomedcentral.com]

• Petechiae

  Platelet Coagulation Purpura Ecchymoses Petechiae 9. THE CLOTTING MECHANISM Collagen Tissue Thromboplastin aPTT PT X V VII XII XI IX VIII PROTHROMBIN THROMBIN FIBRINOGEN (I) (II) (III) FIBRIN 10. Look at Thrombin Time!!! 11. [slideshare.net]

  Patients with primary hemostatic disorders (platelets) tend to present with mucosal or cutaneous bleeding; epistaxis or gingival bleeding; petechiae, especially in dependent areas; immediate bleeding post-injury; and menorrhagia/metomenorrhoagia. [uscmedicine.blog]

  Aside from the extensive bruising of both hands, no other bruising, petechiae or sites of active bleeding were discovered, and there was no evidence of hemarthrosis. [cmaj.ca]

  Skin bleedings ranging from petechia to ecchymosis are common. Furthermore, most patients experience epistaxis, gastrointestinal hemorrhages provoking melena and/or hematochezia, and hematuria due to lesions of the urinary tract. [symptoma.com]

  At week 8 of antiviral therapy, he had an eczematous dermatologic reaction with pruritus and petechias, treated for a week with oral dexametasone, topic methylprednisolone and oral ebastine, with complete resolution. [scielo.isciii.es]

• Skin Bleeding

  Skin bleedings ranging from petechia to ecchymosis are common. Furthermore, most patients experience epistaxis, gastrointestinal hemorrhages provoking melena and/or hematochezia, and hematuria due to lesions of the urinary tract. [symptoma.com]

  Solutions of antifibrinolytic agents can be used topically to treat oral or skin bleeding. [onlinelibrary.wiley.com]

• Epistaxis

  Additional symptoms may include epistaxis, gastrointestinal and/or urogenital bleeding, spontaneous bruising, melena, and hematuria. [orpha.net]

  Furthermore, most patients experience epistaxis, gastrointestinal hemorrhages provoking melena and/or hematochezia, and hematuria due to lesions of the urinary tract. Retroperitoneal hematoma has repeatedly been reported. [symptoma.com]

  Specific symptoms may include nosebleeds (epistaxis), bruising throughout the body, solid swellings of congealed blood (hematomas), blood in the urine (hematuria), and gastrointestinal or urogenital bleeding. [hemophilianewstoday.com]

  Patients with primary hemostatic disorders (platelets) tend to present with mucosal or cutaneous bleeding; epistaxis or gingival bleeding; petechiae, especially in dependent areas; immediate bleeding post-injury; and menorrhagia/metomenorrhoagia. [uscmedicine.blog]

  Hemorrhagic complications include epistaxis, GI and urologic bleeding, retroperitoneal hematomas, compartment syndrome, prolonged postpartum bleeding, excessive posttraumatic or postoperative bleeding, subglottic or cerebral hemorrhage, and thrombocytopenia [emedicine.medscape.com]

• Hematuria

  KEYWORDS: Factor 8 deficiency, acquired [Supplementary Concept] ; Hematuria; Nephrolithiasis [ncbi.nlm.nih.gov]

  She developed obstructive renal failure due to hematuria, which was confirmed with ultrasonography and noncontrast CT (NCCT) of the abdomen. [ijccm.org]

  Keywords: Hemophilia, systemic lupus erythematosus, factor VIII, hematoma, autoimmune diseases, hematuria. [eurekaselect.com]

• Urogenital Bleeding

  Additional symptoms may include epistaxis, gastrointestinal and/or urogenital bleeding, spontaneous bruising, melena, and hematuria. [orpha.net]

  Specific symptoms may include nosebleeds (epistaxis), bruising throughout the body, solid swellings of congealed blood (hematomas), blood in the urine (hematuria), and gastrointestinal or urogenital bleeding. [hemophilianewstoday.com]

  Specific symptoms can include nosebleeds (epistaxis), bruising throughout the body, solid swellings of congealed blood (hematomas), blood in the urine (hematuria) and gastrointestinal or urogenital bleeding. [rarediseases.org]

  urogenital bleeds also occur.2 Often, bleeding episodes correspond with iatrogenic interventions that fail to respond to routine treatment. [hematologyandoncology.net]

• Intracranial Hemorrhage

  A 74-year-old man presented with life-threatening intracranial hemorrhage and prolonged activated partial thromboplastin time (APTT). [ncbi.nlm.nih.gov]

  Fortunately, few patients sustain an intracranial hemorrhage, but the aforementioned bleedings may still cause life-threatening hemorrhagic shock. [symptoma.com]

  Patients will typically present with subcutaneous bruising, mucosal and soft tissue bleeds such as intracranial hemorrhage, muscle bleeds and retroperitoneal hematoma [ 6 ]. [omicsonline.org]

  Severe intracranial hemorrhage in a newborn infant with transplacental transfer of an acquired factor VII:C inhibitor. J Pediat, Oct 1995; 127(4): 649-50. 33. Zeitler H, Ulrich-Merzenich G, Marquardt N, et al. [revistahematologia.com.ar]

• Headache

  Some signs of a blood clot may include pain, swelling, warmth, redness, or a lump in your legs or arms, chest pain, shortness of breath, or sudden severe headache and/or loss of consciousness or function Your healthcare provider should monitor you for [novosevenrt.com]

  Bleeding into a joint can result in permanent damage while bleeding in the brain can result in long term headaches, seizures, or a decreased level of consciousness. [play.google.com]

  Common symptoms include facial pain, headache, and fever following previous upper respiratory viral illness. [britannica.com]

  Headache that will not go away. Neck pain. Double vision. Vomiting. Convulsions or seizures. Get useful, helpful and relevant health + wellness information enews Cleveland Clinic is a non-profit academic medical center. [my.clevelandclinic.org]

Anamnestic data are of major importance in AH diagnosis since the clinical picture gives little clues as to the cause of an observed bleeding diathesis. In this line, AH may be suspected in the case of elder patients, possibly suffering from malignancies or another autoimmune disease, or in post-partal women without a family history of coagulopathies. In any case, coagulation times should be measured if a patient presents with hemophilia. AH may be associated with normal or prolonged activated partial thromboplastin time (APTT) and prothrombin time (PT). In detail, the distinct forms of AH typically present as follows [1]:

• Prolonged APTT, normal PT: consistent with inhibition of factors VIII, IX, XI, XII
• Prolonged APTT and PT: to be expected in case of an autoimmune response against factors II, V, X
• Normal APTT, altered PT: indicates acquired deficiency of factor VII

Contrary to congenital hemophilia due to deficiency of coagulation factors, mixing with normal plasma may appear to correct prolonged APTT and PT, but will eventually demonstrate the presence of a time-dependent inhibitor of the respective factor (non-linear inactivation pattern consistent with type 2 kinetics). This effect is more readily observable after an incubation of the mixture at 37 °C for one or two hours; analysis prior to incubation may lead to a false-negative result [8].

Of note, complexes formed by coagulation factors and autoantibodies may present residual activity. Thus, high titers aren't necessarily accompanied by the complete absence of coagulation factor activity. Both parameters are to be evaluated, though, to determine the subtype of AH in an approach often referred to as "Bethesda assay" and respective modifications [9].

Platelet counts are not usually altered.

• Activated Partial Thromboplastin Time Prolonged

  The laboratory revealed isolated activated partial thromboplastin time prolongation with low FVIII activity and a presence of FVIII inhibitor. She was diagnosed with acquired hemophilia A. [ncbi.nlm.nih.gov]

• Partial Thromboplastin Time Prolonged

  The laboratory revealed isolated activated partial thromboplastin time prolongation with low FVIII activity and a presence of FVIII inhibitor. She was diagnosed with acquired hemophilia A. [ncbi.nlm.nih.gov]

Patients presenting with severe hemorrhages require immediate attention to prevent complications from ischemia, blood loss, and pressure-induced tissue damage. This particularly applies in the case of an intracranial hemorrhage. To this end, bypassing agents like recombinant activated factor VII and plasma-derived activated prothrombin may be applied. These compounds allow the body to "skip" dysfunctional steps of the coagulation cascade and thus aid to control hemorrhages. Moreover, recombinant porcine factor VIII has recently been approved for therapy of AH-associated bleedings [10], but is currently considered a second-line option [11]. The latter also applies to desmopressin. Patients should be protected from trauma; elective surgery should be postponed until successful eradication of autoantibodies. It is recommended to carefully consider the benefits and risks of non-elective interventions.

Further therapeutic measures aim at curing the underlying disease, if known and feasible, suppressing the autoimmune response and eradicating the inhibitor of the coagulation cascade. With regards to the latter, treatment recommendations have been published for patients suffering from acquired hemophilia A [11]. First-line therapy consists of corticosteroids (e.g., prednisolone at a dose of 1 mg/kg/d) or a combination of corticosteroids with cyclophosphamide (at a dose of 1.5-2 mg/kg/d); no differences have been encountered in response to therapy and mortality of patients submitted to either regimen. If the patient fails to respond to this treatment, or if those drugs are contraindicated, rituximab may be administered. Immunosuppression has occasionally been achieved with alternative drugs like azathioprine or cyclosporin A, but these are no longer considered in treatment recommendations.

Recurrence after discontinuation of immunosuppressive therapy occurs in up to 20% of AH patients [4]. Therefore, regular follow-ups are highly recommended and should extend over more than one year. Patients who relapse may undergo renewed immunosuppressive treatment and may achieve a second complete remission or require long-term maintenance immunosuppression [12].

AH most frequently affects elder individuals suffering from comorbidities that may be related to considerable morbidity and mortality. Thus, survival times of these patients are generally limited to a few years, but death is not necessarily caused by hemorrhages and blood loss. In turn, AH may remain undiagnosed despite accounting for premature death. During a 2-year observational study realized in Wales, 9% of patients diagnosed with acquired hemophilia A died because of bleedings [4]. According to a retrospective study conducted in Europe, four-year survival rates of AH patients younger than 75 years amounted to 62%, while only 40% of elder individuals remained alive after that same time [5]. Besides young age, a patient's response to immunosuppressive therapy directly affected their prognosis. The aforecited study also included 42 cases of pregnancy-related AH; all of these patients survived.

AH is an autoimmune disease; the production of autoantibodies directed against coagulation factors provokes a deficiency of the respective factor and thus interrupts the coagulation cascade. Similar to other autoimmune disorders, the precise trigger of the immune response against endogenous proteins remains unknown. However, an underlying disease may be detected in up to half of AH patients, and the disease is frequently related with malignant neoplasms, infectious diseases, additional autoimmune disorders, drug intake or pregnancy [2]. Due to the low incidence of AH in the respective groups of patients, additional, as-of-yet unknown factors are likely to be involved in the pathogenesis of AH. To date, affected individuals have not yet been shown to be genetically predisposed for AH.

AH may be associated with the presence of antibodies against the following coagulation factors [1] [3]:

• Factors I, II, V, VII
• Factor VIII (acquired hemophilia A)
• Factor IX (acquired hemophilia B)
• Factor X, XI, XII, XIII
• Vitamin-K dependent proteins

The overall incidence of acquired hemophilia A in UK has been estimated to be 1.5 per million per year [4]. Under the assumption that acquired hemophilia A accounts for about half of all AH cases, an annual incidence of 3 per million inhabitants may be assumed for the latter. However, diagnosis of AH is a major challenge and most patients are elder people with comorbidities. Thus, incidence rates are likely to be underestimated.

A predilection for Blacks has been suggested [2]. With regards to gender and age, a biphasic pattern may be recognized: The median age at symptom onset is >70 years, and 57% of elder patients presenting with AH are males. However, about one in ten cases is related to pregnancy and post-partal appearance of autoantibodies in females with a median age of 34 years [5]. Of note, these data refer to acquired hemophilia A. Reliable epidemiological data regarding other forms of AH cannot be provided at this moment.

As has been indicated above, considerable knowledge gaps remain regarding the etiology and pathogenesis of AH. Both genetic and environmental factors may be involved in those processes, and it has been proposed that an aging immune system becomes increasingly susceptible to such influences [3]. In any case, the production of autoantibodies directed against coagulation factors implies a breakdown of immune tolerance. Because of distinct subsets of immune cells, namely CD4+ T helper cells, affect B cell mediated antibody release, it may be speculated that a dysfunctional regulation of antibody production was the result of T-cell anomalies [6].

Little is known about the pathophysiological relation between malignancies, infectious diseases, autoimmune disorders, pregnancy and the induction of an autoimmune response. However, tumor- or pathogen-derived antigens may trigger an immune response directed against degenerated cells or microorganisms, and in the case of cross-reactivity, produced antibodies may bind to endogenous structures. Although this theory seems plausible, epidemiological studies did not yet reveal a certain type of tumor or group of pathogens that would significantly increase a person's risk of developing AH.

No specific measures can be recommended to prevent AH.

Acquired hemophilia (AH) is a rare disorder of unknown etiology. Production of autoantibodies of immunoglobulin types G, A, or M, directed against coagulation factors causes a propensity to bleed that manifests in form of spontaneous hemorrhages, e.g., epistaxis, melena and hematochezia, hematuria, and possibly intracranial hemorrhage.

A myriad of coagulation factors comprises what is commonly known as the coagulation cascade, a complex network of biochemical reactions whose respective products are required for the next step towards fibrin production, platelet aggregation, and clot formation. Autoantibodies may be directed against any coagulation factor, but half of AH patients develops a bleeding diathesis due to an autoimmune-mediated deficiency of factor VIII [1] [2]. Because patients suffering from an inherited deficiency of factor VIII are diagnosed with hemophilia A, the respective form of AH is designated acquired hemophilia A. Similarly, an autoimmune response to factor IX triggers acquired hemophilia B.

The majority of AH patients are older than 70 years, and about half of them present with malignancies or apparently unrelated autoimmune disease. Still, the remaining half of cases cannot be ascribed to any primary disease and is thus deemed idiopathic. Of note, women of child-bearing age may also develop AH. Here, pregnancy-related factors seem to induce the respective autoimmune response. In neither case, precise triggers are not identified. Lack of anamnestic data indicating a cause of hemophilia complicates the diagnosis of AH. In fact, it is currently assumed that AH is largely underdiagnosed.

Hemophilia is diagnosed by means of standard measures like measurements of coagulation times. Identification of an individual type of AH requires a more thorough workup that may include the assessment of the activity of single coagulation factors and inhibitor kinetics. With regards to treatment, severe hemorrhages require immediate attention, but therapy aims at eradicating the autoantibodies and reestablishing the coagulation cascade.

Hemophilia is a medical term that refers to a bleeding tendency; hemophilia is provoked by disturbances of the coagulation cascade, a complex network of biochemical reactions whose respective products are required for the next step towards fibrin production, platelet aggregation, and clot formation. For instance, a determined coagulation factor may be activated and thereby become the catalyst of the activation of the next coagulation factor. Any interruption of that cascade, possibly due to a deficiency of a coagulation factor, renders the affected individual prone to hemorrhages.

People suffering from congenital hemophilia have inherited defective genes encoding for dysfunctional coagulation factors. In contrast, acquired hemophilia (AH) is the result of an autoimmune reaction, i.e., of the production of antibodies directed against endogenous structures and subsequent inhibition of any coagulation factor. To date, it is not known how this autoimmune response is triggered, but a considerable share of AH patients present with cancer, another autoimmune disease, or an infection. Moreover, pregnant women are susceptible to AH. Otherwise, AH is typically diagnosed in patients aged 70 years and older.

Treatment consists of the control of hemorrhages - they may manifest in form of cutaneous hemorrhages, hematomas, nosebleeds, bloody urine or feces, etc. - and in suppressing the autoimmune response. Most patients respond well to therapy, but primary diseases like cancer may be associated with a poor prognosis.

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