Left atrial thrombus complicates Mycoplasma pneumonia infection: Rare case reported

Approximately 10%-40% of pediatric community-acquired pneumonia cases are due to Mycoplasma pneumonia. Most of these cases are mild to moderate and confined to the lungs only but some may become severe with life-threatening extra-pulmonary complications such as arthritis, hepatitis, pericarditis, hemolytic anemia, central nervous system sequelae, and thrombosis .

Sagar Lad et al have reported a rare case of left atrial thrombus complicating M.Pneumoniae pneumonia in the latest issue of Journal of Pediatric Critical care.

A four year old girl presented with fever and cough in pre-covid era(December 2019) along with an episode of seizure. Parents gave history that child was unable to walk due to right knee pain and also noted discoloration of skin over right leg. Past history was not significant for any illness.

At admission to hospital, she was conscious with GCS of 13 but was febrile, tachypnoiec and hypoxemic. Upon systemic examination there was moderate respiratory distress with decreased air entry and crepitations on right side. Neurological examination revealed grade 2 power in right lower limb and with normal findings in other limbs. Right lower limb appeared pale ,cold with feeble right dorsalis pedis and popliteal artery pulsations.

Chest Xray findings were notable for right middle and lower lobe consolidation with synpneumonic effusion. Blood investigations were suggestive of anemia(Hb: 9.2 g/dL,TLC: 7500/cu.mm [N70% L21%],Plt: 2,80,000/cu.mm) ,raised C reactive protein (CRP) 49 mg/L. A cold agglutinin test and direct Coombs' test were positive. Prothrombin time, international normalized ratio, APTT Activated Partial Thromboplastin Time (PTTK), Protein C and S, antithrombin III and Factor V Leiden mutation, and lupus anticoagulant were normal ruling out inherited coagulation disorder. M. pneumoniae IgM antibody was strongly positive (73.15U/ml) along with positive Anti phospholipid IgG antibodies (20.109 U/ml).

Right lower limb Doppler was notable for a thrombus in the distal superficial femoral artery. A well-defined 20 mm × 16 mm × 7 mm thrombus arising from the right inferior pulmonary vein with extension into the left atrium with base attached to interatrial septum was seen on two dimensional (2 D) echocardiogram (ECHO) and later on confirmed by cardiac magnetic resonance imaging (MRI).

With the above findings child was confirmed as Mycoplasma pneumonia with thrombus and was trated with IV antibiotics(ceftriaxone and vancomycin), Low molecular weight heparin(LMWH) and other supportive measures. Child gradually improved and child was able to walk. Check Doppler done after 15 days showed resolution of thrombus and child was given 3 weeks course of subcutaneous LMWH. At 3 months of followup antiphospholipid antibodies were negative and repeat 2D-ECHO did not show any thombus.

Thrombus in the cerebral arteries is common, but thrombus in the left atrium extending to the pulmonary vein is very rare. In this case ,the child's prothrombotic state was due to the transient antiphospholipid antibodies induced by the M. pneumoniae infection. The "molecular mimicry" and immunomodulations may be responsible for the generation of anti-phospholipid antibodies in Mycoplasma pneumoniae infections.

Authors conclude-" Mycoplasma infections have the high possibility of triggering autoimmune responses hence Antiphospholipid antibodies which are common have to screened in Mycoplasma infection to plan management strategies."

Source-Journal of Pediatric Critical care