From the Guidelines

Absence epilepsy is a type of generalized epilepsy that does not typically present with generalized tonic-clonic (GTC) seizures.

Generalized seizures are categorized into motor (e.g., tonic-clonic) and nonmotor (e.g., absence) seizures 1.
Absence seizures are a type of nonmotor generalized seizure, characterized by a brief loss of consciousness without a warning sign or post-ictal phase 1.
Generalized tonic-clonic (GTC) seizures, on the other hand, are a type of motor generalized seizure, characterized by both tonic and clonic phases 1.

The International League Against Epilepsy (ILAE) classifies seizures as focal onset, generalized onset, or unknown onset 1.
Generalized seizures rapidly affect both hemispheres and both sides of the body, even when caused by a "focal" lesion 1.
The classification of seizures is important for etiologic diagnosis, appropriate treatment, and accurate prognostication 1.

Absence epilepsy typically presents with absence seizures, which are characterized by a brief loss of consciousness without a warning sign or post-ictal phase 1.
GTC seizures are not typically associated with absence epilepsy, but rather with other types of generalized epilepsy 1.

From the Research

Absence epilepsy is a type of epilepsy characterized by brief, sudden lapses in consciousness, often accompanied by a blank stare and sometimes minor physical movements 2, 3.
Generalized tonic-clonic (GTC) seizures, also known as grand mal seizures, are a type of seizure that affects the entire brain and can cause convulsions and loss of consciousness 3, 4.
Studies have shown that GTC seizures can occur in patients with absence epilepsy, although the frequency and risk factors for this are not fully understood 2, 4, 5.

Family history of epilepsy has been identified as a potential risk factor for GTC seizures in absence epilepsy 2, 6.
Photosensitivity, or sensitivity to light, has also been linked to an increased risk of GTC seizures in some patients with absence epilepsy 2, 6.
The use of certain antiepileptic drugs, such as ethosuximide, has been studied in relation to the risk of GTC seizures in absence epilepsy, with some studies suggesting that it may not increase the risk 2, 4.

Patients with absence epilepsy who experience GTC seizures may have similar clinical features and outcomes to those without GTC seizures, although some studies suggest that the presence of GTC seizures may be associated with a slightly higher risk of treatment failure 4, 5.
The onset age of GTC seizures in absence epilepsy can vary, with some studies suggesting that it may occur later in the course of the disease 4.
Treatment outcomes for patients with absence epilepsy and GTC seizures are generally favorable, although some patients may experience recurrent seizures or require adjustments to their treatment regimen 3, 5.