Prolidase deficiency

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Prolidase deficiency is a disorder that causes a wide variety of symptoms. The disorder typically becomes apparent during infancy. Affected individuals may have enlargement of the spleen (splenomegaly); in some cases, both the spleen and liver are enlarged (hepatosplenomegaly). Diarrhea, vomiting, and dehydration may also occur. People with prolidase deficiency are susceptible to severe infections of the skin or ears, or potentially life-threatening respiratory tract infections. Some individuals with prolidase deficiency have chronic lung disease.

Characteristic facial features in people with prolidase deficiency include prominent eyes that are widely spaced (hypertelorism), a high forehead, a flat bridge of the nose, and a very small lower jaw and chin (micrognathia). Affected children may experience delayed development, and about 75 percent of people with prolidase deficiency have intellectual disability that may range from mild to severe.

People with prolidase deficiency often develop skin lesions, especially on their hands, feet, lower legs, and face. The severity of the skin involvement, which usually begins during childhood, may range from a mild rash to severe skin ulcers. Skin ulcers, especially on the legs, may not heal completely, resulting in complications including infection and amputation.

The severity of symptoms in prolidase deficiency varies greatly among affected individuals. Some people with this disorder do not have any symptoms. In these individuals the condition can be detected by laboratory tests such as newborn screening tests or tests offered to relatives of affected individuals.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Prolidase deficiency is caused by mutations in the PEPD gene. This gene provides instructions for making the enzyme prolidase, also called peptidase D. Prolidase helps divide certain dipeptides, which are molecules composed of two protein building blocks (amino acids). Specifically, prolidase divides dipeptides containing the amino acids proline or hydroxyproline. By freeing these amino acids, prolidase helps make them available for use in producing proteins that the body needs.

Prolidase is also involved in the final step of the breakdown of some proteins obtained through the diet and proteins that are no longer needed in the body. Prolidase is particularly important in the breakdown of collagens, a family of proteins that are rich in proline and hydroxyproline. Collagens are an important part of the extracellular matrix, which is the lattice of proteins and other molecules outside the cell. The extracellular matrix strengthens and supports connective tissues, such as skin, bone, cartilage, tendons, and ligaments. Collagen breakdown occurs during the maintenance (remodeling) of the extracellular matrix.

PEPD gene mutations that cause prolidase deficiency result in the loss of prolidase enzyme activity. It is not well understood how the absence of prolidase activity causes the various signs and symptoms of prolidase deficiency. Researchers have suggested that accumulation of dipeptides that have not been broken down may lead to cell death. When cells die, their contents are released into the surrounding tissue, which could cause inflammation and lead to the skin problems seen in prolidase deficiency. Impaired collagen breakdown during remodeling of the extracellular matrix may also contribute to the skin problems. The intellectual disability that occurs in prolidase deficiency might result from problems in processing neuropeptides, which are brain signaling proteins that are rich in proline. It is unclear how absence of prolidase activity results in the other features of prolidase deficiency.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Prolidase deficiency is a rare disorder. Approximately 70 individuals with this disorder have been documented in the medical literature, and researchers have estimated that the condition occurs in approximately 1 in 1 million to 1 in 2 million newborns. It is more common in certain areas in northern Israel, both among members of a religious minority called the Druze and in nearby Arab Moslem populations.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Abnormal facial shape · Very frequent (99-80%)

An abnormal morphology (form) of the face or its components.

Abnormality of the hip bone · Very frequent (99-80%)

An abnormality of the hip bone.

Abnormality of the immune system · Very frequent (99-80%)

An abnormality of the immune system.

Abnormality of the middle ear · Very frequent (99-80%)

An abnormality of the middle ear.

Carious teeth · Very frequent (99-80%)

Caries is a multifactorial bacterial infection affecting the structure of the tooth. This term has been used to describe the presence of more than expected dental caries.

Cutaneous photosensitivity · Very frequent (99-80%)

An increased sensitivity of the skin to light. Photosensitivity may result in a rash upon exposure to the sun (which is known as photodermatosis). Photosensitivity can be diagnosed by phototests in which light is shone on small areas of skin.

Depressed nasal bridge · Very frequent (99-80%)

Posterior positioning of the nasal root in relation to the overall facial profile for age.

Dry skin · Very frequent (99-80%)

Skin characterized by the lack of natural or normal moisture.

Other findings in the same source

From: Orphanet

Additional reported features include Erythema (Very frequent (99-80%)); Hearing impairment (Very frequent (99-80%)); Hyperkeratosis (Very frequent (99-80%)); Palmoplantar keratoderma (Very frequent (99-80%)); Papule (Very frequent (99-80%)); Pruritus (Very frequent (99-80%)); Recurrent respiratory infections (Very frequent (99-80%)); Skin ulcer (Very frequent (99-80%)); Thin skin (Very frequent (99-80%)); Aplasia/Hypoplasia of the skin (Very frequent (99-80%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Prolidase deficiency is Metabolic Medicine, with a metabolic specialist / clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with metabolic specialist / clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Is a biochemical or molecular result needed to clarify the diagnosis?
• Does this condition require an individual plan for illness or reduced food intake?
• Should nutrition advice come from a specialist metabolic dietitian?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Prolidase deficiency. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.