¿What is *Mycoplasma pneumoniae*?

Mycoplasma pneumoniae is a
bacterial organism
that, unlike other
bacteria, lacks a cell wall. This pathogen is responsible for causing
Unlike other respiratory tract infections.

Transmission and Incubation of Mycoplasma Infection

The infection spreads through contact with droplets released from the upper and lower respiratory tracts of infected individuals. The incubation period
incubation period usually ranges from one to three weeks. M. pneumoniae is a frequent cause of community-acquired pneumonia worldwide. It is important to note that immunity developed after a mycoplasma infection tends to be short-lived, allowing for the possibility of
or develop
recurrent infections.

Common Symptoms and Possible Complications of Mycoplasma Infection

In many situations, the infection caused by M. pneumoniae can be
asymptomatic, or manifest only with nonspecific symptoms such as headache,
fever low-grade fever, dry cough, and
general malaise. Upon respiratory examination, this is usually normal, although scattered crackles or wheezing may be heard when auscultating the chest. Nevertheless, this bacterium can progress to cause pneumonia, a potentially serious lung infection.

Additionally, M. pneumoniae has the capacity to trigger complications in other organ systems. This occurs either through direct invasion by the
organism or as a response by the immune system to the infection. Frequently, these secondary complications can be more severe than the
primary respiratory infection.

Below is a table detailing some of the conditions associated with mycoplasma infections according to the affected organ system:

Organ system	Symptoms and diseases caused by mycoplasma.
Respiratory system	Pharyngitis Dry or mildly productive cough Wheezing, especially in children and if there is a history of asthma Pneumonia
Nervous system	Encephalitis Meningitis aseptic Cerebellar ataxia Myelitis transverse leukonychia Sjögren's Guillain-Barré syndrome
Liver	B Virus, which is believed to be caused by inflammation T-cell undetectable. Slightly abnormal blood tests for liver function are commonly observed.
Heart	Myocarditis Pericarditis and pericardial effusion
Blood system	Anemia hemolytic Hemolytic anemia present in 60% of cases; it is generally mild but can worsen in people with sickle cell anemia. It is possible to detect cold agglutinins.
Musculoskeletal	Transient arthritis, which may be the most prominent manifestation in adults.

Currently, there is no definitive cure for dyskeratosis congenita. Clinical management focuses mainly on supporting bone marrow function, as this is the main cause of mortality:	Musculoskeletal
Musculoskeletal system	Muscle and joint aches are frequent. Polyarthritis is rare; it is thought to be due to the immune response. M. pneumoniae has been isolated from joint fluid in some cases.
Gastrointestinal system	Nausea and vomiting Furthermore, this dual strategy may mitigate the toxicity associated with each drug when administered alone, notably reducing skin side effects induced by dabrafenib. pathway, offers the potential benefit of preventing or delaying acquired resistance arising from the reactivation of this pathway.

Skin Rashes Associated with *M. pneumoniae* Infection M. pneumoniae

Skin rashes affect up to one-third of patients with *M. pneumoniae* respiratory tract infection. M. pneumoniae.

The An exanthem or toxic erythema The most common rash is a nonspecific exanthem, where short-lived red patches appear on the trunk and extremities. These areas of An exanthem or toxic erythema erythema erythema disappear on their own and do not require specific treatment.

Rashes including vesicles and bullae, petechiae (small purple spots due to subcutaneous bleeding), and urticaria (hive-like reactions) have also been described vesicles y can be detected, associated with the presence of crusts and, which facilitates clear visualization of the petechiae hives in association with *M. pneumoniae* infection. M. pneumoniae.

Mycoplasma bullae

Mycoplasma bullae

Erythema Multiforme

M. pneumoniae can occasionally cause bullous erythema multiforme (EM) bullous (). Typically, several distinctive features are observed in these cases.

• Presence of lesions Presence of raised, reddish, target-shaped lesions, which have three distinct zones, including a central blister bulla (blister).
• The rash usually starts on the extremities before spreading to the trunk.
• Mucositis manifestations are frequent: mucositis: conjunctivitis and ulcerations on the lips (stomatitis)stomatitis) and genital area.

Atypical erythema multiforme due to mycoplasma

Atypical erythema multiforme due to mycoplasma

Target lesions associated with mycoplasma infection

Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis Associated with Mycoplasma

Stevens-Johnson Syndrome / Toxic Epidermal Necrolysis

Stevens-Johnson syndrome (SJS) and its more severe counterpart, toxic epidermal necrolysis (TEN), are now recognized as manifestations of a rare, acute, severe skin reaction. This condition is characterized by extensive loss of the superficial layers of the skin and mucous membranes.

Standard classification distinguishes SJS when skin sloughing affects less than 10% of the body surface area (BSA). TEN is diagnosed when this loss exceeds 30% of the BSA, while the term "overlap" is used when sloughing is between 10% and 30%. The most common etiology for most of these cases lies in adverse drug reactions.

However, *Mycoplasma pneumoniae* is identified as the most frequent infectious cause of SJS, especially in pediatric and adolescent populations. A recent retrospective analysis of SJS cases at a major US clinic over an eight-year period revealed that 22% of cases were linked to *M. pneumoniae* infection. The median age of this subgroup was 14 years, with a range observed between 10 and 36 years.

It is important to note that the association of *M. pneumoniae* with toxic epidermal necrolysis is significantly less frequent.

Mucositis Associated with Mycoplasma

Rarely, *M. pneumoniae* has been reported in association with isolated mucosal involvement, such as oral mucositis (stomatitis), conjunctivitis, and ulceration of the genital mucous membranes, in the absence of a significant skin rash. This clinical presentation has received various names, including 'Atypical Fuchs Syndrome' or 'Incomplete SJS'. However, it has been proposed that the most accurate term to describe this syndrome is 'mycoplasma-associated mucositis'. This clinical picture tends to manifest predominantly in children and young adults.

Mycoplasma Mucositis

Mycoplasma mucositis

Less Common Skin Signs Related to *M. pneumoniae*

*M. pneumoniae* infection has also been documented in conjunction with various other dermatological conditions, including:

• Erythema nodosum (reported in up to 8% of infected children).
• Kawasaki disease.
• Raynaud's phenomenon and chilblains.
• Leukocytoclastic vasculitis.
• Thrombotic thrombocytopenic purpura.
• Subcorneal pustular dermatosis.
• Sweet's syndrome.

Diagnosis of *M. pneumoniae* Infection

Clinical suspicion of an *M. pneumoniae* infection generally arises in patients presenting with a respiratory illness accompanied by any type of skin rash, with erythema multiforme being a particularly indicative pattern.

The fastest available diagnostic tool is the polymerase chain reaction (*M. pneumoniae* PCR) applied to a throat swab. This test offers notably high sensitivity and specificity, ranging between 78% and 100%.

Alternatively, mycoplasma serology (a blood test) allows for the detection of IgM and IgG antibodies, which appear approximately 7 to 10 days and 3 weeks after infection, respectively. The sensitivity and specificity of serological tests are lower than those of PCR (between 50% and 66%). However, this range can be improved if a second test is performed during the convalescent phase of the illness. Serological diagnosis is confirmed if a single titer greater than 1:32 is detected, or if a fourfold increase in the baseline IgG or IgM titer is evidenced by repeated testing. It should be noted that IgM titers tend to remain elevated for several weeks, while IgG levels remain high for many months following mycoplasma infection.

Findings revealed on chest X-rays during active *M. pneumoniae* infection are nonspecific. The most common finding is: