From the Guidelines

A rash in Mycoplasma pneumonia is a significant clinical finding, but its presence is not a reliable diagnostic criterion.

The presence of a rash in patients with Mycoplasma pneumonia can be an indicator of the disease, but it is not a specific or sensitive diagnostic criterion 1.
Mycoplasma pneumoniae infection can cause a range of extrapulmonary manifestations, including skin rashes, but these are not unique to this pathogen and can be seen in other infections as well 1.
The diagnosis of Mycoplasma pneumoniae infection is typically based on a combination of clinical, radiological, and laboratory findings, including serological tests and PCR 1.

Serological tests, such as IgM antibody detection, can be useful in diagnosing Mycoplasma pneumoniae infection, but they should not be relied upon as the sole diagnostic criterion 1.
A combination of IgM antibody detection and PCR may be the most sensitive approach to diagnosing Mycoplasma pneumoniae infections 1.
Clinical judgment and consideration of other diagnostic findings, such as radiological and laboratory results, are essential in diagnosing and managing patients with suspected Mycoplasma pneumoniae infection 1.

From the Research

A rash in Mycoplasma pneumonia can be a significant symptom, as it may indicate the presence of extrapulmonary complications, including mucocutaneous eruptions such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and erythema multiforme (EM) 2.
Mycoplasma pneumoniae-induced rash and mucositis (MIRM) is a recently described entity, characterized by prominent mucositis with or without a characteristic vesiculobullous and/or atypical targetoid eruption 3.
The presence of a rash in Mycoplasma pneumonia can also be associated with other symptoms, such as oral lesions, ocular lesions, and genital lesions, which can occur in approximately 25% of patients diagnosed with Mycoplasma pneumoniae infections 3.

MIRM is a distinct clinical entity from SJS and other related skin disorders, with a milder disease course and lower mortality rates 2, 3.
The diagnosis of MIRM is based on clinical presentation, laboratory tests, and imaging studies, and can be confirmed using IgM/IgG Mycoplasma antibody testing or PCR 3.
Treatment of MIRM typically involves supportive care, including pain management, intravenous hydration, and mucosal care, as well as systemic antibiotics in some cases 3, 4.

Patients with MIRM typically present with a wide range of symptoms, including cough, dyspnea, mucositis, conjunctivitis, and cutaneous rash 3, 4.
The diagnosis of MIRM can be challenging, as it may resemble other conditions, such as SJS or EM, and requires a thorough clinical evaluation and laboratory testing 2, 3.
The presence of bilateral otitis media and sinusitis, as described in one case report, can be an additional symptom of MIRM 4.