Infants with SCN have frequent infections: 50% have a significant infection within 1 month, most others by 6 months. Their etiology is usually bacterial, especially staphylococcal, and they commonly involve abscesses, both cutaneous and of internal organs, pneumonia, mastoiditis (inflammation of the mastoid process), and sepsis. All of these are life-threatening for infants.

Kostmann syndrome is a group of diseases that affect myelopoiesis, causing a congenital form of neutropenia (severe congenital neutropenia [SCN]), usually without other physical malformations. SCN manifests in infancy with life-threatening bacterial infections.

Most cases of SCN respond to treatment with granulocyte colony-stimulating factor (filgrastim), which increases the neutrophil count and decreases the severity and frequency of infections. Although this treatment has significantly improved survival, people with SCN are at risk of long-term complications such as hematopoietic clonal disorders (myelodysplastic syndrome, acute myeloid leukemia).

Kostmann disease (SCN3), the initial subtype recognized, was clinically described in 1956. This type has an autosomal recessive inheritance pattern, whereas the most common subtype of Kostmann syndrome, SCN1, shows autosomal dominant inheritance.

In addition to the symptoms associated with immunodeficiency, such as depletion of T-cells, decline of lymphocyte activity, and an abrupt proliferation of both benign and opportunistic infections — PNP-deficiency is often characterized by the development of autoimmune disorders. lupus erythematosus, autoimmune hemolytic anemia, and idiopathic thrombocytopenic purpura have been reported with PNP-deficiency.

Neurological symptoms, such as developmental decline, hypotonia, and mental retardation have also been reported.

Sarcosinemia (SAR), also called hypersarcosinemia and SARDH deficiency, is a rare autosomal recessive metabolic disorder characterized by an increased concentration of sarcosine in blood plasma and urine ("sarcosinuria"). It can result from an inborn error of sarcosine metabolism, or from severe folate deficiency related to the folate requirement for the conversion of sarcosine to glycine. It is thought to be a relatively benign condition.

The disorder is relatively benign, although it causes an increased incidence of periodontal infections, and can under rare circumstances lead to gangrene.

Myomatous erythrocytosis syndrome describes an excessive erythrocyte (red blood cells) production, occurring in about 0.5% of individuals affected by uterine leiomyomas (fibroids). This syndrome is believed to be caused by increased erythropoietin (EPO) production by the kidneys or by the leiomyomas themselves.

Acatalasia (also called acatalasemia, or Takahara's disease) is an autosomal recessive peroxisomal disorder caused by low levels of the enzyme catalase.

The four men and two women were all diagnosed at middle age. The symptoms were slowly and steadily progressive. Telangiectasias developed over the face, trunk and arms. Increased serum erythropoietin levels, eventually exceeding 5000 mU /ml, preceded the intrapulmonary shunting and the development of hypoxemia. Sampling of the perinephric fluid revealed a clear, serous fluid with low levels of protein, few leukocytes and no cholesterol or triglycerides. An IgG monoclonal gammopathy was implicated in the four patients tested (with an associated kappa light chain in all three patients tested). Spontaneous venous thromboses occurred in three patients, two of whom also had spontaneous intracranial bleeding in the absence of blood vessels malformations.

Since then more patients with the syndrome have been reported.

TEMPI Syndrome is a novel orphan disease where the person share five characteristics from which the acronym is derived: telangiectasias, elevated erythropoietin and erythrocytosis, monoclonal gammopathy, perinephric fluid collection, and intrapulmonary shunting.

HIES often appears early in life with recurrent staphylococcal and candidal infections, pneumonias, and eczematoid skin.

- Autosomal dominant Hyper-IgE Syndrome caused by STAT3 defects, called Job Syndrome, have characteristic facial, dental, and skeletal abnormalities. Patients with STAT3 HIES may have either delay of or failure in shedding of primary teeth. The characteristic facial features are usually set by age 16. These include facial asymmetry, a prominent forehead, deep-set eyes, a broad nasal bridge, a wide, fleshy nasal tip, and mild prognathism. Additionally, facial skin is rough with prominent pores. Finally, some patients with STAT3 HIES have scoliosis, as well as bones that fracture easily.

- Autosomal recessive

Hyperlysinemia is an autosomal recessive metabolic disorder characterized by an abnormal increase of lysine in the blood, but appears to be benign. It is caused by mutations in "AASS", which encodes α-aminoadipic semialdehyde synthase.

Hyperlysinemia is associated with ectopia lentis (a displacement or malposition of the eye's crystalline lens) in humans.

It is characterized by recurrent "cold" staphylococcal infections, unusual eczema-like skin rashes, severe lung infections that result in pneumatoceles (balloon-like lesions that may be filled with air or pus or scar tissue) and very high concentrations of the serum antibody IgE. Inheritance can be autosomal dominant or autosomal recessive. Many patients with autosomal dominant STAT3 hyper-IgE syndrome have characteristic facial and dental abnormalities, fail to lose their primary teeth, and have two sets of teeth simultaneously.

Nakajo syndrome, also called nodular erythema with digital changes, is a rare autosomal recessive congenital disorder first reported in 1939 by A. Nakajo in the offspring of consanguineous (blood relative) parents. The syndrome can be characterized by erythema (reddened skin), loss of body fat in the upper part of the body, and disproportionately large eyes, ears, nose, lips, and fingers.

Purine nucleoside phosphorylase deficiency, often called PNP-deficiency, is a rare autosomal recessive metabolic disorder which results in immunodeficiency.

Presenting in infancy, symptoms include lack of appetite, vomiting, dehydration, hypotonia and failure to thrive.

EEM syndrome exhibits a combination of prominent symptoms and features. These include: ectodermal dysplasia (systemic malformations of ectodermal tissues), ectrodactyly ("lobster claw" deformity in the hands and feet), macular dystrophy (a progressive eye disease), syndactyly (webbed fingers or toes), hypotrichosis (a type of hair-loss), and dental abnormalities (hypodontia).

Most patients with APRT deficiency have repeated episodes of kidney stones that are not detected by a conventional x-ray study. However, all stones are easily detected by other medical imaging methods such as ultrasound or computerized tomography (CT) scan. A minority of patients develop symptoms of kidney failure. Kidney stones are often associated with severe loin or abdominal pain. Symptoms associated with kidney failure are largely nonspecific such as increased fatigue and weakness, poor appetite, and weight loss. Children with the disease may have similar symptoms as adults. In young children, APRT deficiency can cause reddish-brown diaper spots.

Cystathioninuria, also called cystathionase deficiency, is an autosomal recessive metabolic disorder that results in an excess of cystathionine in the urine. It is associated with a congenital dysfunction of the enzyme cystathionase, or acquired deficiency of vitamin B which is essential for the function of this enzyme. The latter is usually related to an overall deficiency of all the B-complex vitamins.

An inherited disorder associated with the deposition of a steroid known as cholestanol in the brain and other tissues and with elevated levels of cholesterol in plasma but with normal total cholesterol level; it is characterized by progressive cerebellar ataxia beginning after puberty and by juvenile cataracts, juvenile or infantile onset chronic diarrhea, childhood neurological deficit, and tendineous or tuberous xanthomas.

Symptoms of congenital Type III Galactosemia are apparent from birth, but vary in severity depending on whether the peripheral or generalized disease form is present. Symptoms may include:

- Infantile jaundice

- Infantile hypotonia

- Dysmorphic features

- Sensorineural hearing loss

- Impaired growth

- Cognitive deficiencies

- Depletion of cerebellar Purkinje cells

- Ovarian failure (POI) and hypertrophic hypergonadism

- Liver failure

- Renal failure

- Splenomegaly

- Cataracts

Studies of Type III galactosemia symptoms are mostly descriptive, and precise pathogenic mechanisms remain unknown. This is largely due to a lack of functional animal models of classic galactosemia. The recent development of a "Drosophila melanogaster" GALE mutant exhibiting galactosemic symptoms may yield a promising future animal model.

Cerebrotendineous xanthomatosis or cerebrotendinous xanthomatosis (CTX), also called cerebral cholesterosis, is an autosomal recessive form of xanthomatosis. It falls within a group of genetic disorders called the leukodystrophies.

Acheiropodia (ACHP), also known as Horn-Kolb Syndrome, Acheiropody and Aleijadinhos (Brazilian type), is an autosomal recessive disorder that results in hemimelia, a lack of formation of the distal extremities.

This is a congenital defect which consists of bilateral amputations of the distal upper and lower extremities, as well as aplasia of the hands and feet. It was first discovered and is prevalent almost exclusively in Brazil.

EEM syndrome (or Ectodermal dysplasia, Ectrodactyly and Macular dystrophy syndrome) is an autosomal recessive congenital malformation disorder affecting tissues associated with the ectoderm (skin, hair, nails, teeth), and also the hands, feet and eyes.

Aminolevulinic acid dehydratase deficiency porphyria (also known as "Doss porphyria", and "plumboporphyria") is a neuropsychiatric condition, disease can present during early childhood (as well as in adulthood) with acute neurologic symptoms that resemble those encountered in acute intermittent porphyria. The condition is extremely rare, with fewer than 10 cases ever reported.

ALA dehydratase deficiency is a rare cause of hepatic porphyria. It is an autosomal recessive disorder that results from inappropriately low levels of the enzyme ALA dehydratase (ALAD, also called porphobilinogen synthase), which is required for normal heme synthesis.

Polycythemia (also known as polycythaemia or polyglobulia) is a disease state in which the hematocrit (the volume percentage of red blood cells in the blood) is elevated.

It can be due to an increase in the number of red blood cells ("absolute polycythemia") or to a decrease in the volume of plasma ("relative polycythemia"). Polycythemia is sometimes called erythrocytosis, but the terms are not synonymous, because polycythemia refers to any increase in red blood cells, whereas erythrocytosis only refers to a documented increase of red cell mass.

The emergency treatment of polycythemia (e.g., in hyperviscosity or thrombosis) is by phlebotomy (removal of blood from the circulation). Depending on the underlying cause, phlebotomy may also be used on a regular basis to reduce the hematocrit. Cytostatics such as busulfan and hydroxyurea are sometimes used for long-term management of polycythemia.