Diagnosis involves testing and evaluation during which it is determined if the scores/performance are "substantially below" developmental expectations and if they "significantly" interfere with academic achievement, social interactions, and daily living. This assessment may also determine if the characteristic is deviant or delayed. Therefore, it may be possible for an individual to have communication challenges but not meet the criteria of being "substantially below" criteria of the DSM IV-TR. The DSM diagnoses do not comprise a complete list of all communication disorders, for example, auditory processing disorder is not classified under the DSM or ICD-10. The following diagnoses are included as communication disorders:

Expressive language disorder – characterized by difficulty expressing oneself beyond simple sentences and a limited vocabulary. Individuals can better understand than use language; they may have a lot to say, but have more difficulty organizing and retrieving the words than expected for their developmental stage. Mixed receptive-expressive language disorder – problems comprehending the commands of others. Stuttering – a speech disorder characterized by a break in fluency, where sounds, syllables, or words may be repeated or prolonged. Phonological disorder – a speech sound disorder characterized by problems in making patterns of sound errors (e.g., "dat" for "that"). Communication disorder NOS (not otherwise specified) – the DSM-IV diagnosis in which disorders that do not meet the specific criteria for the disorder listed above may be classified. DSM-5
The DSM-5 diagnoses for communication disorders completely rework the ones stated above.
Nasu–Hakola disease also known as polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy is a rare disease characterised by early-onset dementia and multifocal bone cysts. It is caused by autosomal recessive loss of function mutations in either the TREM2 or TYROBP gene that are found most frequently in the Finnish and Japanese populations. Signs and symptoms
Four stages are recognised in this condition. The first (latent stage) show no symptoms or signs. This stage typically lasts up to the early 20s. This is followed by the osseous stage. This is characterised by recurrent bone pain usually affecting the long bones of the limbs. This is usually followed by pathological fractures of these bones. The third stage (early neurological) is marked by the onset of symptoms typical of a frontal lobe syndrome (euphoria, lack of concentration, loss of judgment and social inhibitions) with memory loss. Epilepsy may occur. This stage usually has its onset in the late 20s and early 30s. The final stage is characterised by severe dementia and paralysis. Death usually occurs in the late 40s or early 50s. Genetics
This condition has been associated with mutations in the TYRO protein tyrosine kinase binding protein (TYROBP) gene and in the triggering receptor expressed on myeloid cells 2 (TREM2) gene. TYROBP is located on the long arm of chromosome 19 (19q13.12) and TREM2 is located on short arm of chromosome 6 (6p21.1). Pathopysiology
This is not understood but appears to involve the microglia. Diagnosis
This syndrome may be suspected on clinical grounds.