The quadriceps are relatively spared, and remain strong until the late stages of disease, which is the reason IBM2 is often referred to as Quadriceps Sparing Myopathy (QSM). Signs and symptoms
Some early signs of HIBMs includes:

Difficulty walking on heels, and difficulty running;
Weak index finger;
Frequent loss of balance. On muscle biopsy, the typical finding includes inclusion bodies, rimmed vacuoles and accumulation of aberrant proteins similar to those found in senile plaques of Alzheimers disease (amyloid beta, hyperphosphorylated tau, amongst others)

Genetics
The different forms have different mutations and inheritance patterns. See the detailed descriptions for details

Mechanisms
The exact mechanisms of these diseases are not well understood. GNE/MNK a key enzyme in the sialic acid biosynthetic pathway, and loss-of-function mutations in GNE/MNK may lead to a lack of sialic acid, which in turn could affect sialoglycoproteins. GNE knockout mice show problems similar to people with IBM and in people with IBM dystroglycan has been found to lack sialic acid. However, the part of the dystroglycan that is important in muscle function does not seem to be affected. Another protein, neural cell adhesion molecule is under-sialyated in people with IBM, but as of 2016 it had no known role in muscle function. Diagnosis
The most useful information for accurate diagnosis is the symptoms and weakness pattern. If the quadriceps are spared but the hamstrings and iliopsoas are severely affected in a person between ages of 20 - 40, it is very likely HIBM will be at the top of the differential diagnosis.
Inclusion body myopathy with early-onset Paget disease and frontotemporal dementia (IBMPFD), now more commonly referred to as multisystem proteinopathy (MSP), is an autosomal dominant condition caused by mutations in VCP, HNRPA2B1 or HNRNPA1; it is a multisystem degenerative disorder that can affect muscle, bone, and/or the central nervous system.The condition now called Desmin-related myofibrillar myopathy (also called myofibrillar myopathy-1) was formerly known as inclusion body myopathy 1 (IBM1).More types of HIMBs, linked to other genes, may be identified in the future. Treatment
Treatment is palliative, not curative (as of 2009).Treatment options for lower limb weakness such as foot drop can be through the use of Ankle Foot Orthoses (AFOs) which can be designed or selected by an Orthotist based upon clinical need of the individual. Sometimes tuning of rigid AFOs can enhance knee stability. Prognosis
A 2009 review noted that muscle weakness usually begins after age 20 and after 20–30 years, the person usually requires a wheel chair for mobility. There was no mention of increased mortality. Research
Because lack of sialic acid appears to be part of the pathology of IBM caused by GNE mutations, clinical trials with sialic acid supplements, and with a precursor of sialic acid, N-Acetylmannosamine,  have been conducted, and as of 2016 further trials were planned. History
Hereditary inclusion body myopathy (IBM) constitutes a unique group of neuromuscular disorders characterized by adult-onset slowly progressive distal and proximal weakness, and a typical muscle pathology including rimmed vacuoles and filamentous inclusions.