Paroxysmal nocturnal hemoglobinuria: A rare case of recurrent episodes of icterus

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired clonal disease of hematopoetic stem cell, without malignant potential. PNH is caused by a somatic mutation of genes on X chromosome, usually PIGA gene is involved. These genes are responsible for anchoring of several proteins such as CD55 and CD59 on the surface of blood cells. These mutations could lead to the production of deficient blood cells with a decreased or totally absent resistance to complement, which leads to the episodes of haemolysis. PNH is a potentially life threating disease associated with intravascular and frequently also with extravascular haemolysis, thromboembolic events, and in some cases with myelodysplastic syndrome (MDS) or aplastic anaemia AA (1).

The main mechanism in pathophysiology of PNH is a deficiency of CD55 and or CD59 on the surface of blood cells. The main purpose of these proteins is to inhibit complement activation on membrane surface. In the case of decreased or absent complement inhibition, the state of complement overactivation is achieved, which leads to intravascular haemolysis that gives rise to a leak of haemoglobin to circulation (2). Free haemoglobin has a toxic effect on endothelium, which precipitates thrombosis formation. The exact mechanism is a subject of an ongoing debate and research. The other pathophysiological mechanism in PNH is caused by free circulating fragments of activated complement which accumulate in reticuloendothelial system in spleen and liver. This leads to a further damage of these organs.

Patients usually manifest with nonspecific signs like fatigue, lethargy, dyspnoea, headaches, chest pain, abdominal pain, and odynophagia. Other symptoms are jaundice, haemoglobinuria, and thrombosis in atypical locations such as splanchnic veins, cranial venous sinuses, and skin veins (table number 1).

In laboratory tests we detected signs of intravascular haemolysis, iron deficiency, leukopenia, thrombocytopenia, rise of creatine, and hepatopathy (3). Indication for screening for paroxysmal nocturnal hemoglobinuria are shown in table number 2.

We recognize three main groups of PNH. A classic PNH where dominant clinical presentation is haemolysis and thrombosis with minimal bone marrow involvement. Patients with the classic form of PNH usually have significant PNH clone population. A subclinical PNH which is characterized by a lack of clinical symptoms and laboratory signs of haemolysis but there is a detectable population of PNH clone by flow cytometry. And the last group is PNH developed in context of other disease with bone marrow failure like myelodysplastic syndrome PNH/MDS or aplastic anaemia PNH/AA (4).

The therapeutic approach is mostly determined by a clinical form of disease. In case of the classic PNH, treatment is based on a target therapy and supportive care like B12, B9, and iron substitution. An important part of management of PNH is also prevention of complement stimulation by preventing infectious diseases with vaccinations and early antibiotics treatment (5). The most effective treatment is a target therapy with anti C5 monoclonal antibodies with eculizumab. This approach blocks out C5 part of complement cascade which leads to theprevention of MAC (membrane attacking complex) formation. This leads in averting further haemolysis in most patients with PNH (6). A small subgroup of patients is only a partial responder or no responder. This can happen either due to the resistance of C5 to eculizumab or dysregulation on C3 level of complement. These patients could benefit from antibodies targeted to C3, such as pegcetacoplan (7). Adverse effects of treatment with anti C5 antibodies include an increased risk of an infection, especially meningococcal infections. This is the reason why it is highly recommended for all patients on eculizumab to be vaccinated.

The main cause of mortality and morbidity in patients with PNH are thromboembolic events. In case of past thromboembolic event some authors do recommend lifelong anticoagulation therapy. There are no data comparing efficacy of low molecular heparin with direct oral anticoagulant or warfarin. In case of an acute thromboembolic event, the regular management according to location is recommended (8).

In this article we presented the case of a 27-year-old male with a medical history of recurrent attacks of haematuria, jaundice, and transitory elevations of liver enzymes.

The first episode that led to a hospitalization occurred in October 2019. The patient was hospitalized in Sweden with an attack of haematuria, jaundice, and elevations of liver enzymes. This attack was interpreted as a non-severe case of acute alcoholic hepatitis. Later that year the patient was re-hospitalized in Slovakia with yet another attack with a similar clinical manifestation. This time the clinical interpretation was a drug induced liver injury with an acute kidney injury. After discharge the patient was referred to a nephrologist and a gastroenterologist for further management.

In June 2020 the patient was once again hospitalized at department of Internal Gastroenterological Medicine with another attack. Main clinical manifestation was haematuria jaundice pain in the lumbar region. The patient did report recurrence of this pain usually followed by a period with dark coloured urine. Typically, this conditions spontaneously disappear in two to three days. Laboratory findings were dominated by normocytic normochromic anaemia, thrombocytopenia, hyperbilirubinemia, elevation of lactate dehydrogenase, and decrease of haptoglobin. For overall laboratory results see table number 3. Urine aseptic haematuria was detected but there was no detection of erythrocytes in microscopic analysis.

The differential diagnosis of haemolytic anaemia was initiated based on the clinical picture. Coombs tests were negative, blood schwab was without a presence of schistocytes or changes in shape of erythrocytes. ADAMTS 13 activity was examined to definitively rule out thrombotic thrombocytopenic purpura.There was no significant decrease in enzyme activity.

In the next step a flow cytometry was performed where a population of PNH cells was detected (see Fig. 1 and Fig. 2).

Fig 1

Fig 2

Due to the presence of thrombocytopenia in cooperation with haematologist we performed a bone marrow biopsy to rule out myeloblastic syndrome or aplastic anaemia. No specific signs of dyshaematopoesis were detected in the biopsy. During the hospitalization, Stafylococcus aureus was detected by a cultivation from nasopharyngeal schwab. This was interpreted as a precipitating factor for an attack of haemolysis, subsequently a target antibiotic therapy was initiated, and after a period of observation the patient was discharged. Afterward, the patient was referred for ambulatory care by a haematologist, where a therapy with eculizumab was started. On this therapy up to date there has been no major thromboembolic event or a need for hospitalization or hemosubstitution. In a periodical laboratory check, we observed a stable hemogram but oscillations in lactate dehydrogenases, bilirubin, and reticulocytes suggesting remaining inconsequential level of haemolysis (Tab 4). There was no significant shift in PNH population in a flow cytometry (Tab 5).

In our case report we focus on struggle and obstacles of diagnosis of PNH, especially if this disease is present in a patient with comorbidities masking the main symptoms of haemolysis. In our case it was morbus Gilbert. As described in our case report, this led to repeated misdiagnoses and quite significant prolongation in the diagnostic time.

PNH is a rare potentially life-threatening disease with a very low prevalence in population. Epidemiological data from United Kingdom suggest an incidence of 3.5 cases per million people. Because of broad clinical manifestation and inexperience of clinicians with PNH the time from the first manifestation to the diagnosis could be significantly prolonged as was seen in our case report. In some cases, the first manifestation could be severe thromboembolic event with possibly fatal consequences. The prognosis significantly varies for each subgroup. In general, five-year survival rate is 72% for all types of PNH (9).

The diagnosis is based on medical history, clinical manifestation of Coombs negative haemolytic anaemia, for definitive diagnosis flow cytometry is performed. This method can unarguably confirm the presence of PNH clone in peripheral blood (10). Furthermore, the size of individual clone population for granulocytes and erythrocytes can be count. This is quite useful since the size of erythrocyte PNH clone is often underestimated. This usually happens because of extensive haemolysis and hemosubstitution. In contrast, the population of polymorphonuclears is not influenced by the deficit in surface CD55/59, that is whypolymorphonuclears clone size corelates with the extension of the disease more precisely (11). The flow cytometry is a relatively widely available and cheap diagnostic tool and should be performed whenever PNH is suspected. The indication for flow cytometry could be found in table no 2. During the diagnosis the other cause of Coombs negative haemolytic anaemia should be considered (see table 6).

In the case of our patient, we observed severe prolongation from manifestation to the diagnosis of PNH. In the period before the initiation of eculizumab administration the patient had significantly increased the risk of development of severe haemolysis or thromboembolic events with potentially fatal consequences. For these reasons a prompt diagnosis and treatment is crucial in all cases of PNH.

PNH is a rare disease, with a broad spectrum of clinical manifestation and challenging differential diagnosis. Many clinicians struggle with prompt diagnosis of PNH. This could get even trickier if PNH developed in a context of other disease such as Gilbert disease. Due to the association of PNH with potentially life-threatening thromboembolic complications the early diagnosis and proper management is crucial for prognosis of each patient.