COVID-19

Introduction and epidemiology

COVID-19 (coronavirus disease 2019) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), an enveloped single-stranded RNA betacoronavirus that sparked a global pandemic in late 2019, with hundreds of millions to billions of cases worldwide to date. A wide variety of cutaneous manifestations have been reported in widely varying proportions and manifestations.

Transmission and incubation

• High-risk groups include elderly patients over 65 years old, immunocompromised patients, and those with comorbidities including diabetes mellitus, chronic kidney disease, cardiovascular disease, cancer, and obesity.

• Incubation ranges from 2 to 14 days, with an average onset of 4–5 days.

• Transmission occurs primarily via respiratory droplets.

Clinical features: Inflammatory patterns

Morbilliform or maculopapular eruptions represent the most prevalent morphology, accounting for 22% of cutaneous COVID-19 presentations in a 2020 international registry and up to 47% in a 2020 Spanish prospective series of 375 patients. (1, 2) These manifest as diffuse 2–5-mm symmetric erythematous macules and papules that coalesce into patches and thin plaques on trunk, proximal extremities, and flexural surfaces.

Urticarial lesions were reported in 16% of registry cases and appear as annular or polycyclic edematous wheals with central pallor and serpiginous borders, with onset occurring at the same time of COVID-19 symptoms and associated with pruritus. (1)

Vesicular eruptions are not as common and occur in up to 11% of registry patients. (1) Vesicular lesions present as either localized serous monomorphic vesicles < 1 cm on the trunk, often in a V-shaped distribution, or more commonly as diffuse eruption of monomorphic vesicles with a widespread distribution on the trunk and extremities. (3)

Clinical features: Pernio-like and vascular lesions

“COVID toes,” or pernio-like acral lesions, comprise about 18% of morphologies in the registry and present as tender, erythematous to violaceous 5–15 mm edematous plaques or nodules on dorsal fingers, toes, heels, and lateral feet. (1) The lesions are associated with painful burning/pruritus peaking 7–14 days post-respiratory symptoms.

Petechial / purpuric lesions are among the least commonly described cutaneous manifestations associated with COVID-19. They typically appear as less than 2 mm, non-blanching, red-brown hemorrhagic macules located diffusely, acrally, or on limbs and appear in cases with greater severity of infection. (4)

Livedo reticularis classically presents as reticular or lacy, non-blanching dusky erythematous to violaceous purpuric plaques on the lower legs, thighs, buttocks, and trunk. (2)

Clinical features: Mucocutaneous patterns

Oral manifestations include transient U-shaped lingual papillitis (“COVID tongue” ), painful aphthous ulcers on the buccal / labial mucosae, atrophic glossitis with patchy depapillation, and erosive mucositis. (7)

Complications and sequelae

Severe complications include distal ischemia resulting in tissue necrosis, necessitating consideration of thrombolytics. (8)

Systemic complications include hypoxic respiratory failure, in addition to potentially fatal events such as acute kidney injury, sudden cardiac death, or liver failure. (7)

Acute telogen effluvium (TE), self-limited diffuse hair shedding following a triggering event, is the most common post-COVID cutaneous manifestation. COVID-associated TE appears a median of 1.5 months following infection and lasts a shorter duration than typical TE cases, with resolution reported after approximately 2 months. (9)

Diagnosis

• Gold-standard diagnosis employs real-time reverse-transcriptase polymerase chain reaction (RT-PCR) detecting SARS-CoV-2 RNA on nasopharyngeal swabs.

  • Rapid antigen immunoassays offer point-of-care testing, though they are less sensitive than RT-PCR. (7)

  • Antibody tests assess immunity prior exposure to SARS-CoV-2.

• Additional supporting tests include chest imaging showing consolidation, as well as laboratory values showing lymphopenia and elevated CRP, D-dimer, LDH, troponin, and ferritin.

Patient management and treatment (10)

Management includes medications for the treatment of COVID-19 itself, including nirmatrelvir / ritonavir, remdesivir, or molnupiravir for high-risk patients.

Though there are no standard treatments for the cutaneous manifestations, some studies have recommended topical corticosteroids for inflammation, oral antihistamines for urticaria / pruritus, and NSAIDs for pain, with varied results.

Prevention

Vaccination options include mRNA vaccines (BNT162b2 Pfizer, mRNA-1273 Moderna). In 2024–2025, COVID-19 vaccines demonstrated 33% effectiveness against emergency department or urgent care visits among adults aged 18 years or older; 45–46% vaccine effectiveness against hospitalizations among immunocompetent adults aged 65 years or older; and 40% vaccine effectiveness against hospitalizations among immunocompromised adults aged 65 years or older, compared with individuals with not receiving a 2024–2025 vaccine dose. (11)